Airway / Intubation / Ventilation

Airway / Breathing / Ventilation

Posted by Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2021-01-05

Securing an open airway is fundamental in all emergency medical activities in the care of severely ill patients. Oxygen deficiency due to obstructed airway is the single most important anesthetic-related cause of severe injury or perioperative death. It usually occurs in a patient who is not breathing and is unable to ventilate. This is a situation that anyone working with emergency care can get into. A pre-devised action plan and access to relevant emergency equipment and intubation equipment is necessary to avoid serious incidents of insufficient airway control on an anesthetized or unconscious patient. Intubating the patient is about creating and securing the open airway.

The easiest way to create a open airway on an unconscious person is primarily to place the patient in the forward position with the upper arm’s hand under the chin. This mode is often used on patients after anesthesia during a wake-up phase or after termination of ventilator treatment, e.g. after extubation after cardiac arrest. When initiating an anesthesia, the patient is usually placed in the usual flat back position (supine) in order to best manage the airway and to be able to intubate in the easiest way. If the airway is obstructed by the back of the tongue, an oropharyngeal airway (OPA/”Guedel”) or nasopharyngeal airway (NPA) may establish an open airway. Manually, the airway may be cleared by a chin lift, a head tilt backwards and by a solid jaw thrust. Manual ventilation with bag and mask is the basis for all airway management of unconscious or anesthetized patient.


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There are a number of different models of these aids as shown below in slide shows. However, a nasopharyngeal airway (NPA) may irritate the posterior pharynx and provoke nausea, vomiting and laryngospasm if it is deprived of an overly awake or insufficiently anesthetized patient. When properly placed on a sufficiently anesthetized patient, it can be a good help for establishing a open airway. Open airway devices should therefore only be deployed when the patient is sufficiently anesthetized or relatively deeply unconscious. A nasopharyngeal airway (NPA) is usually tolerated at a higher degree of alertness but may also irritate the posterior pharynx, insertion of the NPA must always be preceded by proper gel instillation in the nasopharynx to avoid nasal bleeding. Blood and mucus in the nasopharynx should always be avoided and disposed of when handling and establishing the airway.

In order for an intubation attempt to be optimal, reasonable experience with the procedure, a well-functioning laryngoscope, best choice of laryngoscope blade, type and size and conductor, optimal patient placement, adequate muscle relaxation and optimal positioning of the larynx is required. Under good conditions, an intubation is usually not difficult, but nevertheless, a difficult intubation may appear unexpectedly. With the patient in the supine position, height of the headend, well-trained patient, well-oxygenated and fully muscle relaxant, the best conditions for a successful intubation are achieved.

Bag valve mask (Ambu bag)

Manual bag and mask ventilation is a basic skill for all airway management that can be difficult to perform properly. All airway management during anesthesia or emergency care with respiratory failure basically starts with manual ventilation with bag and mask. This ventilation can be performed with self-expanding or non-self-expanding breathing bags.

Self-expanding breathing bags, also called Ambu bag, Bag valve mask, Resuscitator, Ruben’s bag, Ruben’s balloon or Bag and mask, can be used with or without oxygen supply and therefore does not require the connection of a ventilator or anesthetic device. An Ambu bag is often used in pre-hospital setting and in emergency rooms and in many other contexts where emergency ventilation is necessary without a mechanical ventilator. Bag and mask can be used anywhere without access to other medical equipment. If possible, oxygen is connected via a simple rubber or plastic hose and in order to obtain higher oxygen concentration in the inhalation air, a so-called reservoir bag is connected to the Ambu bag, as shown in the pictures.

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Most often, pure oxygen is used in the gas flow. Normal oxygen flow with a breathing bag is 5-10 liters of oxygen per minute. It easily happens that the flow of oxygen exceeds 10 liters per minute in the breathing bag, but this can cause difficulties in compressing the bag and cause stress in the staff in an emergency situation. Therefore, no more than 10 liters of oxygen per minute should be given.

The breathing bag is usually made of silicone rubber with two valves, one at each end. Closest to the patient is one pressure release valve and at the other end an intake or reservoir valve, please see picture for description. These valves are opened and closed synchronously with the air flow for the air to move in the right direction, in and out during breathing. Some breathing bags are also provided with a pressure relief valve, especially when using smaller bags for pediatric use. Breathing bag for neonatal use, “neovent” is entirely based on the principle of intermittent occlusion of a valve in a breathing mask without a breathing bag.

To be able to ventilate with a manual ventilator, the patient must be ventilated via a tightly closed breathing mask. These are available in many different models and sizes. The flexibility or softness of the mask varies between different models. Nowadays, these masks are usually transparent and “semi-soft” so it is possible to see the patient’s lip color or any foam or respiratory mucus in the mouth or nose. A soft breathing mask can be difficult to hold tightly to the patient’s face, but it is usually just a matter of habit. The grip should be firm but yet gentle creating a jaw thrust. Vigorous beard growth or nasogastric tubes can make it difficult to keep a face mask tight.

For adults, a mask of size 4 (medium) or 5 (large) is usually used. For smaller adults, size 3 (small) can also be used. Controlled manual ventilation is usually easier if a smaller breathing mask is used. A smaller sized mask is easier to get tightly sealed than a large mask. To make the manual ventilation work, the mask must be tightly closed, the gas flow must be adequate (neither too high or too low) so that sufficiently large tidal volumes can be delivered. Small tidal volumes less than 400 ml can often provide adequate minute ventilation if compensated with higher frequency (> 15 breaths/minute). The advantage of smaller tidal volumes is that lower pressure can be applied which reduces the risk of blowing air into the stomach, which in turn can cause regurgitation of gastric contents with the risk of pulmonary aspiration.

Respiratory ventilation must be adequate. About 300-400 ml in tidal volume with a frequency of 15-20 is usually sufficient but in some cases both larger tidal volumes and higher frequency are needed. If the patient is spontaneously breathing, it is important to synchronize ventilation with the patient so that the controlled ventilation assists the patient’s own breathing, ie you can add a small tidal volume at the end of each breath the patient himself takes. The worse the patient breathes the more you need to take over in controlled breathing. If it is not possible to synchronize breathing with the patient and the airway is threatened, it is usually good to muscle relax the patient and take over completely on controlled ventilation via intubation and endotracheal tube or laryngeal mask.

If you insert a Guedel airway device (oropharyngeal airway – OPA) in the mouth when the patient falls asleep, this may mean that it is necessary to step up one size in the breathing mask. You can make this change while introducing the Guedel airway. Some breathing masks are fitted with a double mask to be able to extract excess anesthetic gases with active suction during inhalation anesthesia. The system thereby becomes more environmentally friendly for the staff, but it is somewhat clumsy and is increasingly not used. Other masks are fitted with plastic hooks in a ring to be able to fix the mask with rubber bands during mask anesthesia, but this is now very rarely used and has largely been replaced by laryngeal mask anesthesia (LMA).

Non-self-expanding breathing bag is usually used in circle airway systems connected to an anesthetic machine or a ventilator. To expand this bag, air hoses are usually used in a circle system via an outflow valve, often called the adjustable pressure limiting valve (APL), also called the Berner valve. The APL valve regulates the resistance of flow in the breathing bag while also acting as an excess valve where anesthesia gases can exit via an active suctioning. The air flow is set with gas rotameters physically or electronically depending on the equipment. The usual flow rate for ventilation with non-self-expanding breathing balloon is initially 8-10 l/min but even lower flows can be used.

Oropharyngeal airway (“Guedel airway”) and Nasopharyngeal airway (NPA)

Oropharyngeal airways (OPA:s/“Guedel airway”) and nasopharyngeal airways (NPA:s) are available in a variety of models and sizes. Both have the purpose of facilitating the creation of open airway on unconscious, anesthetized or drowsy patients which can create good conditions for manual ventilation with bag and mask. The airways are usually placed with the patient in a supine position. Guedel airways are inserted through the mouth past the tongue. The purpose is to open up the occlusion between the back of the tongue and pharynx, the tongue base should be raised forward upwards which is facilitated by a jaw thrust.


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When inserting an OPA, it is important that the OPA is of the correct size and that the patient is sufficiently anesthetized/awake to accept an OPA. If the OPA is too small, this may risk pressing down the tongue base against the pharynx instead of lifting it. If the patient is insufficiently anesthetized, an OPA can provoke a vomiting reflex, trigger cough and, in the worst case, a laryngospasm. The Guedel airway can thus compromise rather than facilitate the establishment of open airway, but properly handled by skilled staff it is usually an excellent tool. An OPA should not be inserted on an insufficiently anesthetized patient and in the case of insufficiently established open airway upon initiation of anesthesia, it may be necessary to first deepen anesthesia before an OPA is inserted.

When positioning an OPA, it is important that the distal end descends properly past the tongue base. To achieve this, you raise the lower jaw either by lifting from below (“jaw thrust”) or by pulling up the mandible with a powerful jaw pull, you can grab the teeth in the lower jaw if they are not too fragile. Some OPAs have a central air duct which facilitates ventilation and which can allow for suctioning in the rear pharynx, but suction is usually clumsy and difficult to perform through the OPA.

During awakening, the OPA is removed when the patient has intact swallowing reflexes. In the lateral position, a patient who wakes up after an inhalation anesthesia can accept an OPA for a quite long time. If the patient spits out the OPA or removes it by his own hand, the patient is usually without the need for an OPA to clear the airway.

Nasopharyngeal airways (NPA) are a good alternative to OPA:s to create open airway on a sleepy or unconscious patient. The advantage of a nasopharyngeal airway compared to the OPA is that it teases less in the posterior pharynx and does not provoke as easily coughing, vomiting reflexes or triggers laryngospasm. The NPA is therefore better suited than OPA’s on a patient who is not awake but not quite as deep as is required to accept an OPA.

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A nasopharyngeal airway also opens the posterior part of the tongue toward the pharynx and more often creates open airway, especially in patients with robust jaw or thick throat. However, it is not always the case that a nasopharyngeal airway reaches properly down behind the tongue base. Neither an OPA nor a nasopharyngeal airway is therefore a guarantee of an open airway. The disadvantage of a nasal tube is instead a certain risk of nasal bleeding during the passage through the nostril. However, this risk can be avoided by lubricating properly both on the nasopharyngeal airway and the nostril. It is usually not enough to just lubricate the NPA, you also need gel into the nostrils to get good conditions. Excess gel can be removed by suctioning through the nasal tube when inserted. Avoid overly rigid or sharp nasopharyngeal airways (NPA) that may damage the nasal septum and cause troublesome nasal bleeding. Modern NPA:s are softly cut at the end to be gentle to the nasal septum. The cut means that they are not as suitable for insertion into both nostrils but are adapted to either the right or left nostril.

Laryngeal mask airway (LMA)

Laryngeal masks are one kind of supraglottic airway (SGA) device placed deep in the throat behind the tongue during general anesthesia and thereby creating open airway. A laryngeal mask can be used for general anesthesia with spontaneous breathing, assisted breathing or controlled ventilation. With controlled pressure ventilation, there is a small risk that air not only goes down into the lungs during anesthesia but also down into the stomach, which is why laryngeal mask ventilation is best suited for spontaneous breathing. It still works well with controlled ventilation, but it is important to avoid excessive high pressures to reduce the risk of inflating the stomach, which increases the risk of pulmonary aspiration. The time factor also plays a role, previously a “rule of thumb” was used not to choose procedures longer than one hour for laryngeal mask ventilation, but with modern and better laryngeal masks and good respiratory monitoring, longer procedures can also be performed with good safety. Patients at high risk for regurgitation and aspiration should not be anesthetized with a laryngeal mask but intubated.

Laryngeal masks are available in many different models and in different materials, both with and without a cuff. They are available in many different sizes and are well suited for both adults and children. In day care surgery anesthesia and many other procedures, laryngeal mask anesthesia is often standard practice when the patient is to be anesthetized in the supine position. In the lateral and abdominal positions, you can be ventilated with a laryngeal mask, but this can present difficulties with the airways. In addition, in case of hassle, it is difficult to change from laryngeal mask to intubation with a patient in the abdominal position or lateral position.

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Laryngeal mask ventilation is inappropriate when the patient’s head is dressed and inaccessible during surgery. High aspiration risk is a contraindication as is laparoscopic surgery. High body weight is a relative contraindication, at a BMI over 40 other airway management should be chosen, usually intubation.

The laryngeal mask can be inserted with the help of a guide or manually with the help of the fingers, usually you only use your own hands and fingers. It is easier if the mask is lubricated with some form of lubricant before. The actual technique for inserting a laryngeal mask is quickly learned during normal anesthesia practice. The patient should sleep well and be relaxed in the arms, shoulders and jaw. The mouth should be easy to open. With the mouth open, under adequate anesthesia, the laryngeal mask is passed down through the mouth behind the tongue in an arcuate line. It can be easier if you lift the mandibel in a jaw thrust. It is important that the tip of the mask in this step does not flip forward down the throat. The risk of this is greater with cuffed masks than uncuffed, which is why the latter are often preferable. If the tip of the mask folds incorrectly, this can be corrected with a forefinger deep in the patient’s throat. Larynx masks with a cuff should be inserted  with the cuff unfilled or “half-filled”. On laryngeal masks with a cuff, the cuff is filled with air after it has been placed correctly deep down in the larynx until you get a resilient resistance but not “rock hard”. Usually the cuff pressure is not measured in a laryngeal mask, but it is usually between 30 and 60 cm H2O. The pressure should not exceed 60 cm H2O. Once the mask is in place, check that you can easily ventilate the patient and that you return adequate volumes of air. You should not have any leakage or have any leaking sound from the mask (“murmurs”). The breathing curve (capnography curve – end-tidal CO2) in the monitoring screen must be well filled and must not have a sawtooth pattern during ventilation. If the airway is unsatisfactory it might be a good idea to change type of LMA, for instance from a cuffed LMA to an uncuffed type of mask (“Igel”) or to intubate the patient.

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After completion of anesthesia, the mask is removed immediately after the patient has opened his eyes and makes contact. It is important not to force the mask out at the end so that there is no risk of any loose teeth dislocating. Some discomfort in the throat (as in a cold) may persist for a few days in the patient after a laryngeal mask anesthesia.

Predictors for difficult laryngeal mask use

  • Limited jaw opening capacity
  • Supra- or extraglottic pathology (radiation, large heavy scarring)
  • Glottic or subglottic pathology (laryngeal stenosis, etc.)
  • Limited flexion in the cervical spine
  • Cricoid pressure
  • Elevated BMI (> 35), obese patients
  • “Bad teeth”
  • Change of body position and operating table with turns during operation
  • Low lung compliance may require higher inspiratory pressures with risk of air leakage


Laryngoscopes have been used for many years in anesthesia to be able to visualize the larynx and intubate the patient with an ET-tube. A laryngoscope consists of a handle, a laryngoscope blade and a light source, usually fiber optic via a rechargeable battery. The use of traditional laryngoscope with direct insight has been standard in anesthesia practice for several decades during regular intubation. The laryngoscope provides direct insight into the larynx, unlike video laryngoscopes, which in some contexts can be advantageous, for example when bleeding in the throat or to be able to clean or remove mucuos, blood or foreign objects. The laryngoscope is usually made of metal but is also available in plastic. Metallic laryngoscope gives a reasonable weight in the hand during intubation which creates good conditions for steady maneuvers in the throat with a firm touch.

The laryngoscope consists of a handle and a blade that is removable. The light source is located on the underside of the front end of the blade. All anesthesia personnel must be well acquainted with how this is assembled and disassembled. The handle is available in a standard version and in a shorter variant that is suitable for intubation of a patient with a short distance between the chest and chin tip. The handle has a rechargeable battery and the blade has a light source with fiber optics that gives a strong and clear light. Older laryngoscope models lacked fiber optics and gave significantly worse light than today’s laryngoscope. When not in use, the laryngoscope is usually located in a charging station. Such a laryngoscope charging station should be available inside all operating rooms and all intensive care units. There is usually room for two laryngoscopes and there you often have a laryngoscope with a normal blade and one with a long blade.

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The laryngoscope blade is available in several different models and sizes, both curved blades (Macintosh) and straight blades (Miller). By default, curved blades are used. The blade is bent in a longitudinal segment to provide space for the tongue which is moved to the side during intubation. There are also laryngoscope blades with a tiltable end “flexible tip” to create more space and better visibility deep down in the throat of difficult-to-intubate patients (McCoy). The bending of the laryngoscope blade is usually to the left, so it is best to hold the laryngoscope in the left hand and enter the mouth from the right corner during intubation. The tongue is then deviated slightly to the left so that the blade ends up centrally in the mouth and the distal end down into the larynx where the tip is inserted above the epiglottis. Laryngoscope blades are available in sizes between 0–5. Some hospitals name the blades by numerical size, but the most common in clinical practice is to talk about size number 4 as “normal blade/regular blade”, size number 5 as long blade and size number 3 as short blade. Size number 4 is standard for most anesthetics as a starting point. Long blades are usually chosen for intubation of heavy men with a rough neck.

For intubation of children, shorter blades (size 0–2) and smaller laryngoscopes are regularly used. For neonatal children, it may be beneficial to use a straight blade during intubation over a curved blade. Laryngoscope and laryngoscope blades are available in a variety of models and designs. Some are named after the manufacturer such as Miller (straight blade) and Macintosh (curved blade).

Endotracheal tube (ET tube)

Endotracheal tubes (ETT) are referred to in everyday speech during anesthesia practice simply as “ET tubes“. These are used to be able to ventilate anesthetized or sedated patients with positive pressure ventilation. This is made possible by an inflatable “cuff” (balloon) at the distal end of the tube which is inflated with air via a separate pilot line (plastic hose). The inflated cuff prevents backward leakage of air outside the tube, thereby allowing controlled pressure ventilation and the use of PEEP. At the proximal end of the cuff tube is a valve that allows the cuff to remain inflated in the trachea (pilot valve). The cuff is inflated with 5 – 10 ml of air after intubation, in some exceptional cases with water. The material and appearance of the cuff vary, but there is an idea that the pressure in the cuff should not be too high to avoid ischemia and mucosal damage in the trachea. Normally the pressure in the cuff is set at 20 – 30 cm H2O. The pressure should not exceed 30 cm H2O. Normally the pressure in the cuff is checked with a so-called cuff pressure gauge that can also regulate the pressure. The cuff also prevents saliva and stomach contents from passing down into the lungs.

The tube enables controlled pressure ventilation, prevents aspiration and ensures an open airway. Tubes are available in a number of different models and sizes. The tube is slightly curved to follow the anatomy of the pharynx and is usually made of transparent PVC plastic or opaque silicone rubber. The transparent variant softens when heated, which can be utilized for nasal intubation, for example. The curvature and shape of the tube vary according to the procedure to be performed. For most anesthetics, standard tubes with only slight curvature are used, while for certain ear, nose and throat procedures or plastic surgery, special tubes can be used with strong curvature or with a gooseneck appearance, see pictures below. The end of the tube is usually cut with the distal opening to the left, which means that you should choose the right nostril so as not to traumatize the nasal septum with the risk of nosebleeds during nasal intubation. In addition to a hole in the end of the tube, some tubes also have a side hole for air passage (Murphy’s eye). This side hole reduces the risk of ventilation being blocked if the end of the tube gets stuck in the tracheal mucosa or against a wall.

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The length and thickness of the tubes vary. An ordinary standard tube is usually 27 cm long. Common sizes for adults are the 6th, 7th or 8th tube. The dimensions specified refer to the inner diameter (ID) in millimeter of the tube. The 7’s tube works well as standard tube for most adult patients (7 mm in inner diameter ID). The 6’s tube can be chosen for small adults or teenagers. The 8’s tube can be chosen for heavy patients, mostly men.

Recomended sizes of Endotracheal Tubes for Children.

Tube position (cm in the corner of the mouth) = Patient length (cm)/10 + 5. Nasal tube: + 20%
Age03 months1 year5 years9 years12 years14 years> 15 years
Weight3 kg5 kg10 kg20 kg30 kg40 kg50 kg> 50 kg
Endotracheal tube inner diameter (mm)33.5456777

Just proximal to the cuff, there are usually one or two black lines that facilitate the placement of the tube during intubation. If there are 2 lines, position the tube so that one line is placed below the vocal cords and one above. If the tube has only one line, this is placed at vocal cord level or just above. The tube is usually placed with a certain measuring distance stated as which centimeter mark is in the corner of the mouth. The distal end of the tube should normally be 4 cm above the carina in the trachea. This occurs in most adults if the tube is fixed at 21 – 23 cm in the corner of the mouth. Deeper than 23 cm in the corner of the mouth is rarely needed, there is only a risk that the patient will be “right intubated”, i.e. that the tube goes down into the right main bronchus and the left lung is thereby underventilated. The tube is fixed in the corner of the mouth with tape. There are several different techniques for fixation. In anesthesia where the patient’s head is dressed or where the patient is turned in the abdominal position, it is more important to have a firm fixation of the tube, e.g. a 3-tongue wide semi-flexible tape x 2. For standard anesthetics where the head and face are accessible, simpler taping may be sufficient. A functioning good ventilation is always checked after fixation of the tube before starting surgery.

Endotracheal tube stylets and other guides for intubation

A normal intubation without complicating factors can be handled without a guide in the ET tube, but if the patient is difficult to intubate, intubation is facilitated if you have a guide in place. The guide’s function is primarily to create rigidity, improved mobility and better controllability during movements in the throat with the tube. The ET tube, which is normally flexible, is given greater stability with a guide in it, even if you encounter soft parts and tight passages. The guide is usually removed when the distal end of the tube has passed the vocal cords.

There are several different types of guides for different occasions and different tubes. When intubating with a video laryngoscope with indirect visibility, it is an advantage to have a completely rigid guide, for example a so-called “Hyperangulated Glidescope Stylet“. This gives the opportunity to pass through the throat even if you thorn against soft parts on the way down to the vocal cords and trachea. When doing an intubation with video laryngoscopy and a steel stylet it is helpful if an assistant presses down the larynx during the procedure from the outside on the front of the throat.

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Standard guides have a soft atraumatic tip so as not to damage the mucous membrane if it protrudes the trachea first. Standard guides are semi-rigid (semi-flexible) so that they can be reshaped and modified to the correct shape before starting intubation, for example a “gooseneck shape”. The distal end of the guide should not protrude from the tube but lie just inside.

Other guides such as elastic Bougie are so long that you can insert the guide first and then thread the tube over the guide when the guide has already passed the vocal cords. Oxygen can also be given through the guide so that the patient can be oxygenated continuously. This long guide can also be used for risky or doubtful extubations from a respiratory point of view, for example in patients with swelling in the throat. The guide can then be left behind after extubation so that there is an opportunity for rapid reintubation if the patient has difficulties with the airway after the extubation. Prior to this variant of extubation, the patient may be anesthetized in the trachea by inhalation of a nebulised anesthetic, eg lidocaine 40 mg/ml 2.5 ml. ET tubes and guide may need to be lubricated before intubation with some form of lubricating solution.

Videolaryngoscope (various models)

There are several different video laryngoscopes that facilitate the implementation of a difficult intubation. There are 2 fundamentally different types of video laryngoscope, a variant with a small screen that sits directly on the handle of the laryngoscope and another variant that has a video screen standing next to it on a stand connected to the laryngoscope. The image can also be displayed on TV screens in the operating room or in the room where you are in. With a picture on a video screen next to it, you get a larger and sharper image compared to a small screen on top of the laryngoscope. The small laryngoscope is easy to take with you, for example, to an emergency room in the care of acute trauma cases.

Compared with conventional laryngoscopy, video laryngoscopy provides good insight into the larynx even on difficult airway patients who are deep in the throat or have a highly positioned vocal cord, with a Mallampati grade 3-4. The insertion of the tube during the intubation are a little different compared to conventional intubation, it requires some habit that one should master the technology. In video laryngoscopy, it is natural and standardized to intubate with a stylet in the tube, preferably a completely rigid steel conductor of the type “Hyperangulated Glidescope Stylet“. It is essential that you choose the right type of blade for video laryngoscopy and the right fitting stylet. Most video laryngoscopes are equipped with 3 different types of blades, a short blade, a long blade and a long and extra curved blade, a so-called “D-blade”. For patients with Mallampati grade 3-4, it is usually best with the D-blade. In this type of intubation, it is an advantage if an assistant can press down the larynx a little from the outside on the throat. The other two blades are more like a normal laryngoscope blade.

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Posted by Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2021-01-08

An intubation is done to ensure the airway and to be able to ventilate the patient in a controlled manner, thereby ensuring adequate oxygenation and elimination of carbon dioxide of the blood. During the induction of anesthesia the patient can be ventilated manually using bag and mask and after intubation by an endotracheal tube (ET tube). Bag and mask are used initially for ventilation followed by intubation after adequate administration of analgesics, hypnotics and muscle relaxation under strict control.

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To be able to use positive pressure ventilation the endotracheal tube is provided with an inflatable cuff that occludes the tube against the tracheal wall and allows open air passage through the tube. The cuff is usually inflated with 5-10 ml of air. In small children, uncuffed tubes can be used as the trachea is so narrow that you can ventilate without a cuff. Normally, one may ventilate the lungs manually with a positive pressure of about 20 cm H2O in each breath. The respirator can ventilate the patient with lower pressure if the lungs are healthy, about 8-14 cm H2O in each breath.

In order for an intubation attempt to be optimal, it is necessary with reasonable experience within the staff and optimal ventilation conditions, such as a well-functioning laryngoscope, best choice of laryngoscope blade, type and size, a suitable tube guide, optimal patient placement, adequate muscle relaxation and optimal positioning of the larynx. The patient should normally be well anesthetized and muscle relaxed when intubating the trachea. Normally, the patient is intubated orally by the mouth and the ET tube is fixed using adhesive tape to the cheek with the distal end of the tube positioned at about 4 cm above carina. In emergency situations such as acute cardiac arrest, one may need to intubate in suboptimal conditions without any muscle relaxant or sedative drugs given. In some circumstances one may need to intubate without being able to anesthetize the patient deeply as with difficult airway management during spontaneous breathing. Then one often chooses to intubate nasally instead of orally during moderate sedation with application of local anesthesia (topical anesthesia) in nasopharynx and larynx. However, “regular” intubations are normally done orally with well-anesthetized and muscle-relaxed patient.

Intubation – Practical advice

The patient is most easily intubated in the supine position with a slightly heightened head end (30 degrees) with back tilt. After preoxygenation via mask over mouth and nose during spontaneous breathing, the patient is anesthetized and muscle relaxed. Breathing is controlled first via mask ventilation and open airway is secured by a steady lift of the lower jaw until a substantial underbite “jaw thrust”. If the tongue still obstructs the airway, you can insert a Guedel airway or a nasofaryngeal airway to be able to optimize ventilation conditions. When the patient is well-anesthetized and muscle-relaxed, a laryngoscope is inserted in the mouth from the right corner towards the center where the laryngoscope blade lift the tongue base in the direction of the handle. One can use a traditional laryngoscope in metal or plastic (metal is standard) with fiber optics or a video laryngoscope. Video laryngoscope has either a small screen connected directly to the laryngoscope or a standalone screen beside it. In traditional laryngoscopy, direct insight into the larynx is used, while video technology uses indirect vision via a screen.

It is important that the laryngoscope blade is inserted deep into the throat. Then, firmly raise the tongue and lower jaw forwards upwards in the direction of the shaft with a slight bend backwards of the laryngoscope (not too strong bend but a strong lift) while checking that one does not strike the front teeth in the upper jaw. With this powerful lift you can inspect the larynx and find the vocal cords and the entrance to the trachea. Then you can insert the ET tube. The tip of the laryngoscopic blade is inserted above the epiglottis (in vallecula) whereby the epiglottis moves forward upward in the lifting one performs. One should not normally catch epiglottis with the laryngoscope blade but the epiglottis is being lifted upwards in any case. When you see the vocal cords, one can usually simply insert an ET tube between the vocal cords into the trachea. It is essential to be able to see and identify the vocal cord opening during the intubation.

To be able to insert the tube, it may be necessary to slightly twist the ET tube clockwise when passing the vocal cord opening. The tube is inserted approximately 8-10 cm below the vocal cords of an adult. An ideal position of the tube is that the distal end of the tube is approximately 4 cm above the carina. At 8-10 cm from the end, on most tubes, there are 1-2 marking lines, the distal black line should be positioned below the vocal cords and the proximal line immediately above the vocal cords. In adults, the tube is fixed with a marking of 21-24 cm in the corner of the mouth in normal cases, here tape is attached around the tube for fixation to the cheek. In order to get more control of movements of the tube during intubation, a flexible guide can be used in the tube which is removed as soon as the tube has passed the vocal cords.

  • Bilderesultat for anesthesia mask ventilation
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When the ET tube is in place you inflate the cuff and check that the tube is correctly positioned by checking and verifying:

  1. Fog in the tube back and forth during breathing (can also be heard and felt).
  2. Listen with stethoscope and hear breathing sounds from both lungs during manual ventilation. Listen in at least 4 different positions.
  3. Verify with capnometry that respiration works through a normal carbon dioxide elimination curve.

In doubtful cases, the position of the tube can be verified by bronchoscopy or X-ray examination. However, you do not have too much time to verify the tube position of the anesthetized patient. Capnometry and bronchoscopy are the safest methods. When in doubt, take it out and start all over again.

When the location is verified, the tube is secured by either:

  • Fixture with some form of adhesive tape
  • Cotton band tied around the tube
  • In rare cases, the tube can be fixed by suturing (eg in craniofacial surgery) but usually only tracheal cannulae are fixed by suturing

In the event of an emergency operation, the surgeon is notified when the tube is fixed and the airway is secured.

Fiberoptic intubation

By Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2020-09-25

Fiberoptic intubation, ie intubation using bronchoscopy, is a method of intubation that every anaesthesiologist should be well acquainted with. Fiberoptic intubation is a technique in which a flexible endoscope with an endotracheal tube mounted along its length is passed through the glottis. The endotracheal tube is then pushed down the endoscope into the trachea, and the endoscope is withdrawn. The method is not routinely used for anesthesia but is used regularly when it has been possible to identify a difficult airway. Fiber intubation is usually performed with the patient in a semi-awake state with spontaneous breathing maintained during sedation. It is rarely performed with the patient fully anesthetized to better maintain airway and spontaneous breathing. The procedure is therefore often called “awake fiber intubation”.

Fiberoptic intubation is normally performed by lowering a tube endotracheally over the fiber bronchoscope when the fiber bronchoscope is lowered into the larynx past the vocal cords into the trachea. There are several different techniques for performing a fiber intubation presented here. Normally this is done electively, ie when you have been able to predict a difficult intubation with a difficult airway and are reluctant to muscle relax the patient to be able to maintain spontaneous breathing continuously and not risk having a patient with a difficult airway who stops breathing and can lose the airway completely. Fiber intubation may in some cases be necessary in acute situations when it is not possible to intubate orally in the usual way, but it can be extremely difficult and complicated in situations where the patient does not breathe or has plenty of blood or secretions in the airways. Fiber intubation is therefore primarily suitable for elective cases where the intubation is performed calmly and quietly according to a predetermined plan.

Indications for fiber intubation

  • Known difficult intubation case
  • Anatomical anomalies in the pharynx
  • Small mouth opening
  • Trismus, inability to open the mouth
  • Stridor
  • Tumor in the throat or abscess that compresses or displaces the vocal cord entrance
  • Trauma with fractures in the neck region
  • Previous radiation treatment with scarring on the neck
  • Patient who looks obviously difficult to intubate, for example a so-called bull’s neck or short and wide neck
  • Dense fracture or other fracture of the cervical column

Before starting your planned fiber intubation, it is essential to be well prepared and to go through your planned intubation with an anesthesia nurse, operating room nurse and other staff who will assist. In some high-risk cases, an ENT doctor or surgeon may need to be present prepared to perform an acute coniotomy or acute tracheotomy. A fiberoptic intubation of, for example, a patient with acute epiglottitis or stridorous breathing always needs to have a plan A and a plan B in case plan A fails. In such a case, it may be a good idea to apply local anesthesia with adrenaline subcutaneously on the throat before starting the fiber intubation in case you need to proceed with acute coniotomy. In acute coniotomy, bleeding in the incision is usually the most difficult complication and the use of adrenergics in local anesthetics is a good method to prevent bleeding.

In addition to the usual oral premedication, fiberoptic intubation is usually performed with the patient well sedated, for example with continuous infusion of remifentanil. The usual oral premedication can be given as usual, for example with Paracetamol 1 g + Oxycodone 10 mg to an adult normal weight patient. Thereafter, it may be appropriate to allow the patient to inhale local anesthetics with an oxygen mask and nebulizer, eg 2 ml lidocaine (Xylocain) 40 mg/ml for 5 minutes to anesthetize the airways while administering an anticholinergic intravenously (Glycopyrrone) 0.2 mg iv or Atropin 0.5 mg to counteract excessive mucus secretion in the pharynx. Blood and mucus are the worst opponents of fiber intubation and can cause the intubation to fail.

Without mucus and blood in the throat and with a well-functioning sedation, a fiber intubation is relatively easy to perform technically, but with a lot of mucus and blood it is all the more difficult. The patient is placed in a supine position, preferably with the head end raised. The nostril to be used for nasal fiber intubation should be gelled before starting intravenous sedation. You can administer some kind of gel, for example Instillagel about 2 ml which the patient himself actively sniffs in through the nostril so that the entire mucous membrane in the epipharynx down to the throat becomes soft and easy to glide. The bronchoscope needs to be lubricated before the bronchoscopy, for example with Dimethicone oil or silicone on the outside. The tube to be inserted can be lubricated on the inside with, for example, saliva substitute. It is essential that the tube and bronchoscope are dimensioned for each other and can slide against each other. A fiber bronchoscope that is 5 or 5.5 mm requires at least the 7th tube size to get through. For the 6th tube size, a bronchoscope that is 4 mm fits, while the 5.5 mm bronchoscope is too large.

Then you start with intravenous sedation. Moderately heavy sedation is the A and O for “awake” fiber intubation. There are several different possibilities for a suitable sedation. The goal is for the patient to maintain respiration and oxygen saturation and not experience too much discomfort from the intubation itself. Continuous infusion with propofol can be difficult to adjust properly and may quickly lead to too deep anesthesia and is not recommended. However, a small bolus dose of propofol (20 mg) can be given for methods 1B and 2B when the tube is passed down through the nose, which can be uncomfortable. Once the tube enters the trachea, this is usually irritating to the respiratory tract and the sedation can then be deepened immediately after the tube is in place and you move from sedation to anesthesia. This is usually done by giving a bolus dose of propofol.

Sedation and other practical steps during fiber intubation

  • Intravenous anticholinergic (Glycopyrrone 0.2 mg or Atropine 0.5 mg) should be given 30 minutes before to counteract mucus secretion
  • Decongestant nasal drops in both nasal openings
  • Lubricate the bronchoscope and tube with the correct lubricant
  • If necessary, place a tube in a bottle of hot water for 5 minutes to soften the tube (applies only to transparent tubes)
  • Lidoocaine 40 mg/ml, 2 ml is nebulised in inhalation for surface anesthesia of the airways 5-15 minutes before intubation
  • Give oxygen by a nasal catheter in the “wrong nostril” throughout the intubation.
  • Gel in the nose, about 2-3 ml as a lubricant
  • Connect suction to the fiber bronchoscope
  • Attach the tube without the connector with a piece of tape high up on the bronchoscope for methods 1 A and 2 A.
  • Midazolam 1-2 mg i v +
  • An opioid of some kind:
    • Fentanyl 50-100 μg or
    • Alfentanil 500-1000 μg or
    • Remifentanil by infusion
      • TCI 1-2 ng/ml
      • TIVA 0.05-0.25 μg/kg/min
        or alternatively
  • Ketamine 50-100 mg iv v b
  • Propofol in continuous infusion or in small bolus doses
  • Cricoid anesthesia. With a thin cannula, the upper part of the trachea can be anesthetized with eg 3 ml lidocaine 10 mg/ml by transmembrane injection (through the cricoid membrane).

Sedation should be given so that the patient is well sedated with maintained spontaneous breathing and free airway throughout the procedure. It is advisable that one and the same person has full attention to the sedation and the patient’s status during the fiber bronchoscopy (anesthesia nurse). Oral fiberoptic intubation is suitable, for example, for anesthesia of a patient with a cervical spine injury. To be able to perform oral fiber intubation, a special type of oropharyngeal airway tube is required that can keep the tongue and tongue base away and at the same time allow passage of the fiber bronchoscope (eg Glenn’s oropharyngeal airway). This technique usually requires full anesthesia and may be suitable for a patient who, after induction of anesthesia, proves to be very difficult to intubate. These cases are now solved primarily by oral intubation with a video laryngoscope.

Fiberoptic intubation can be performed in several different ways as follows

1 With the anesthesiologist intubating standing above the head end

You stand in the same place as during normal intubation.

  • A. Bronchoscopy is performed through the nose, through the oropharynx and into the trachea before lowering the tube.
  • B. The endotracheal tube in the oropharynx is first lowered through the nose in heavy sedation before bronchoscopy through the tube, through the oropharynx and into the trachea.

2 With the anesthesiologist intubating standing below the head end next to the patient face to face with the patient

  • A. Bronchoscopy is performed through the nose, through the oropharynx and into the trachea before lowering the tube.
  • B. The endotracheal tube in the oropharynx is first lowered through the nose in heavy sedation before bronchoscopy through the tube, through the oropharynx and into the trachea.

3. Oral fiberoptic intubation under anesthesia

  • You first insert a special oropharyngeal airway tube tube behind the tongue, after which you perform bronchoscopy through the mouth, through the oropharynx and into the trachea before inserting the tube.

Method 1 A

The anesthesiologist is standing above the head end. Bronchoscopy is performed through the nose down to the carina before lowering the tube that is first attached to the bronchoscope.

You stand in the same place as during normal intubation. A short anesthesiologist may sometimes need to stand on a stool. An advantage is that you are used to standing in this place at the beginning of anesthesia. From here, if necessary, you can easily ventilate the patient by hand with a breathing bag and mask and you experience that you can control the airway in the same position as you are usually used to. It is close to the anesthesia machine and a short distance to anesthesia equipment and suction. “Everything is within reach”. The tube is first attached with a piece of tape high up on the bronchoscope while identifying the vocal cord opening.

  • Fiberoptic intubation

You first go down through the nose, pass the conchas, enter the oropharynx, pass the base of the tongue and can then identify the vocal cord opening. You then pass the vocal cord opening and go down into the trachea so you can clearly see the cartilage rings and carina. A suitable stop is about 4 cm above the carina. The tube is then pulled down through the nose with a gentle but firm hand. When the tube is to pass the vocal cords, you can get a notch that is often solved by turning the bronchoscope and tube 90 degrees to the right. After that, the tube can usually pass the vocal cords. After this, the bronchoscope is removed while observing that the tube end is at a distance of about 4 cm from the carina.

Advantage: May be easier in complicated anatomical cases to find the vocal cord opening. Excludes the risk that the tube is positioned too far down in the pharynx from the beginning, which can create difficult angles.

Disadvantage: The bronchoscope needs to go to some extent in an S-shaped arc similar to a gooseneck. Easy to get mucus or blood on the bronchoscope that makes visibility difficult or impossible. Mucus in the nose can obscure the view, unlike method B. Movements with the bronchoscope in the throat can irritate the cough or vomiting reflex. When the tube is to be pushed down through the nose, it can be crowded and difficult to get the tube down past the conchs. It is not known whether the tube will be able to pass through the nose before the vocal cord opening has been found.

Method 1 B

The anesthesiologist is standing above the head end. The tube is first lowered through the nasal opening before bronchoscopy is started.

Advantage: If the tube is pulled down through the nasal opening before you start bronchoscopy, the bronchoscopy itself will usually be easier and faster. Many times you find the vocal cord opening directly in front of the bronchoscope when you come out of the tube in the pharynx. This is often the fastest and easiest method and you can avoid prolonged fiber intubation. It is less troublesome for the patents when the bronchoscope passes through the nose through the tube than without a tube in place in the nose.

Disadvantage: There is a certain risk of nosebleeds when you first pull the tube down through the nasal opening, some force may be needed. Nasal bleeding can be prevented with nasal drops and gel. In addition, only a soft tube should be used. A clear endotracheal tube can be softened before intubation by allowing it to stand for 5 minutes in hot water (45-50 g for 5 minutes). The tube thereby becomes soft and compressible. It is important that the tube is soft with this method, the walls should be able to be pressed together against each other. There is a risk of placing the tube too far in the pharynx through the nose so that the angle into the trachea becomes too steep (S-shaped). Then it can be difficult to find the vocal cord opening and the problem is usually solved by backing up the tube a few centimeters during an ongoing bronchoscopy. The tube should pass the conchs of the nose down into the pharynx before the bronchoscopy but must then never be brought down too far, which complicates intubation.

Method 2 A

The anesthesiologist is standing below the head end. You stand next to the patient’s side face to face with the patient. The advantage is that the bronchoscope gets an even curvature through the nose down into the trachea during the bronchoscopy. An advantage is that you are in the right place if you need a coniotomy or acute tracheotomy patient.

  • To enjoy all the functionality in this e-learning session, please enable JavaScript in your web browser. When difficulty with mask ventilation, laryngoscopy or mask ventilation is likely, careful consideration should be given to securing the airway awake. The ...
  • Fiberoptic intubation

One can easily perceive the anatomy as “upside down” through the bronchoscope and the right becomes left, but this is mostly a habit. A disadvantage is that you are wrong if you need to ventilate the patient manually with a mask and a breathing bag.

Bronchoscopy is performed before the tube is pulled down and the vocal cords are passed before the tube is lowered through the nasopharynx. The tube is attached with a piece of tape high up on the bronchoscope while identifying the vocal cord opening.

Advantage: Less risk of nosebleeds compared to method B. May be easier in complicated anatomical cases to find the vocal cord opening. Excludes the risk of the tube being lowered too far from the beginning. Allows greater movement in the pharynx compared to method B.

Disadvantage: Easy to get mucus or blood on the bronchoscope which makes it difficult or impossible to see. The bronchoscope can tear into the nasal mucosa, it has sharper edges than the tube. Mucus in the nose can obscure the view, unlike method B. Movements with the bronchoscope in the throat can irritate the cough or vomiting reflex. When the tube is to be brought down through the nose, it can be crowded and difficult to get the tube down through the nose. It is not known whether the tube will be able to pass through the nose before the vocal cord opening has been found. You need to move to the head end if you are to take over breathing manually.

Method 2 B

The anesthesiologist stands below the head end near the armpit. The tube is lowered through the nasal opening before bronchoscopy.

Advantage: If the tube is passed down through the nasal opening before bronchoscopy, the bronchoscopy itself will usually be easier. Many times you find the vocal cord opening directly in front of the bronchoscope when you come out of the tube in the oropharynx. This is often the fastest and easiest method and you can avoid prolonged fiber intubation. It is less troublesome for the patents when the bronchoscope passes through the nose through the tube than without a tube in place in the nose.

Disadvantage: There is a certain risk of nosebleeds when you first pull the tube down through the nasal opening. Nasal bleeding can be prevented with nasal drops and gel. In addition, you should only work with a soft tube. A clear endotracheal tube can be softened immediately before intubation by allowing it to stand for 5 minutes in hot water (45-50 degrees for 5 minutes). The tube thereby becomes soft and compressible. It is important that the tube is soft for this method, the walls must be able to be compressed completely. Risk of laying the tube too far in the pharynx so that the angle into the trachea becomes too S-shaped. The tube should pass the conchs in the nose but must then never be brought down too far, which complicates intubation.

Method 3

Oral fiber intubation

You first insert a special laryngeal tube behind the tongue, after which you perform bronchoscopy through the mouth, through the oropharynx and into the trachea before lowering the tube. Suitable for example for patients with a fracture in the neck that is located in the skull where you want to avoid cough reflexes and sudden movements in the cervical spine in connection with intubation. The patient is anesthetized as usual in a flat supine position intravenously and muscle relaxed. Then a special oropharyngeal airway (eg Glenn’s oropharyngeal airway tube) is placed which allows fiber intubation. The tube is threaded over the fiber bronchoscope and when the tube has passed the vocal cord opening, the oropharyngeal airway tube is removed and the tube is lowered over the bronchoscope into the trachea. It can be easier if an assistant makes a jaw lift during intubation by lifting under the mandible forward upwards.

The procedure is relatively simple if the pharyngeal tube can create a free airway and allow passage of the bronchoscope. It is important with a working lubricant so that the bronchoscope does not get stuck in the oropharyngeal airway tube. You should lubricate the bronchoscope on the outside (silicone or similar, but not xylocaine gel) and the tube on the inside, eg with saline replacement spray. The patient can be ventilated manually before intubation.

Intubation using the flexible fiberoptic bronchoscope. | Download Scientific Diagram

Management of difficult airways

Posted by Per Nellgård, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2020-09-25

Creating and maintaining an open and safe airway is always the primary aim in all anesthesia practice and intensive care. Failure to secure the free airway is both dangerous to the patient and may cause anxiety for the anesthetist. The situation “cannot intubate and cannot ventilate” is luckily very unusual (about 1/10 000 intubations). Often the airway accounts for about 30% of the very serious incidents associated with anesthesia (death and serious brain injury). What is dangerous is hypoxia not “lack of tube”. Failure of intubation constitutes approximately 10% of all intubations, and is between 0.13-0.3% of all intubations. In the Fourth National Audit Project (NAP 4 – UK) 184 cases of major adverse airway events were recorded among 2.9 million anesthesia. In order to avoid these situations it is important to make a careful preoperative assessment of cases of difficult airways and to prepare for the right equipment and sufficient expertise for anesthesia.

Feel free to learn SFAI’s airway algorithm, at or below on the Anesthesia Guide. Learn where the airway trolley is located in the operating department and what it contains and how to use different airway devices.

Assessment of difficult-to-intubate patient

Risk parametersGreen
Mallampati class 0–40 and 123 and 4
Thyromental distance (TMD)> 7 cm6–7 cm< 6 cm
Mouth opening ability> 4 cm2–4 cm< 2 cm
Cormack & Lehane grade I-IVIIIIII and IV
Mallampati is used to predict how easy or severe an endotracheal intubation can be expected to be. The test includes a visual assessment of the distance from the tongue base to the palate. This value is final valued according to Cormack & Lehane, which is a classification system that describes what was noted during intubation. Thyromental distance is the distance between the upper part of the thyroid cartilage and the tip of the chin and helps to predict intubation difficulties.

All operating departments should have access to some type of video laryngoscopes. Video laryngoscopes have meant that many difficult airways can now be better managed and intubated with reasonable risks. In most cases, video laryngoscopes can reduce Cormac & Lehane’s rating by up to 2 grades, such as from C & L grade 4 to grade 2. However, video laryngoscopes do not solve all problems, and in the really difficult cases, flexible bronchoscopes are still needed and the ability to use them. Feel free to introduce an “airway hall” one day a week on a regular basis where you can train with varied airway equipment so that everyone gets good skills. Work in team and apply current airway algorithm.

  • Bilderesultat for anesthesia laryngoscope

In order for an intubation trial to be optimal, reasonable experience of the intubator, well-functioning laryngoscope, best choice of laryngoscope leaflets, type and size and conductor, optimal patient setup, adequate muscle relaxation and optimal positioning of larynx are required. Under good conditions, an intubation is usually not difficult, yet a difficult intubation may appear unexpectedly. With the patient positioned on their back, upheld head end, well- anesthetized patient, well oxygenated and fully muscle relaxed are the best conditions for successful intubation. Severe laryngoscopy occurs when no part of the laryngeal entrance can be visualized in optimal laryngoscopy (Cormack Lehane Grade III-IV). Severe intubation is also present when correct tubing has not been achieved despite three optimal intubation tests or within 10 minutes of intubation. Strong man with short, stiff throat and bullet nose is a typical hard-intubated patient. In case of sudden unexpectedly severe intubation, it may be best to awake the patient and reboot from the beginning, for example, through vigorous fiber intubation. Always avoid excessive mucus or bleeding in the nose and throat.

Tests for evaluation of difficult intubation

  • Mallampati test
  • Thyreomental distance
  • Ability to open mouth
  • Neck movement

Risk factors for difficult intubation

  • Small mouth
  • Short neck, “Bull’s neck”
  • Large or loose teeth
  • Bleeding or vomiting in the pharynx
  • Inability to open mouth or gape
  • Anatomical anomalies in the oral cavity or pharynx
  • Swelling in the oral cavity, tongue, throat or throat
  • Male gender
  • Mallampati level III or IV
  • Sleep apnea syndrome
  • Beard
  • Age> 55 years
  • Adipositas, BMI> 26
  • Tumors, infections, bleeding in the oral cavity or in the pharynx
  • Earlier radiation to the head and neck region
  • Stridor
  • Foreign body in the pharynx or in the upper respiratory tract
  • Large trauma in the head or neck region
  • Subcutaneous emphysema on the throat
  • Horseshoe-shape of the maxilla

Difficult airways can be categorized as

  1. Difficult mask ventilation (about 5%)
  2. Difficult ventilation with laryngeal mask (LMA / SGAD)
  3. Difficult laryngoscopy
  4. Difficult intubation (2-5-10%, in the ICU up to 20%)
  5. Difficult airways for surgical intervention

Assessment of the airways

Different airway tests are used to find those with difficult airways. A high sensitivity test means that most people are identified with “difficult” airways. A high specificity test means that most people with an “easy” airway can be ruled out.

Some of the most common assessment methods of the airway are as follows:

  • Modified Mallampati (Class 0-4)
  • Thyromental distance (<6 cm, 6-7 cm & > 7 cm) (TM)
  • Sternomental distance (<11 cm, 11-12.5 cm> 12.5 cm) (SM)
  • Wilson sum test
  • LEMON-law
  • Upper lip bite test (ULBT)
  • Gap capacity (<2 cm, 2-4 cm> 4 cm)

No test alone is good enough, but the combination of Mallampati and thyromental distance seems best, even better when combined with long experience and good judgement. Patients with Mallampati Class 0 (when looking at the upper edge of epiglottis) are almost always easily intubated, if there is no other larynx or tracheal pathology.

Risk patients for pronounced hypoxia

  • Unstable angina pectoris
  • Severe CNS pathology incl. severe carotid stenosis
  • Severe lung disease (COPD, fibrosis, etc.)
  • High BMI (lower oxygen reserves in the lungs)
  • High metabolism: sepsis / pregnant
  • Lowered alertness, unconscious patient
  • Aspiration of gastric contents
  • Acute fall with injury or swelling of the airways

On these patients, the airway must be secured in a “good” way with maintained oxygenation throughout the intubation. This means that you are more liberal in maintaining spontaneous breathing, avoiding apnea and choosing a “safer” method, such as tracheostomy in local anesthesia, intubation with flexible bronchoscope or intubation with video laryngoscopes in local anesthesia and possibly light sedation.

Predictors for difficult mask ventilation

  • High BMI or high body weight.
  • High age
  • Male sex
  • Limited subluxability of the lower jaw.
  • Short thyromental distance.
  • Modified Mallampati Class 3-4.
  • Beard (can be removed!)
  • Toothlessness
  • Snorers or OSAS
  • Previous radiation to the throat.

Predictors for difficult laryngeal mask use

  • Limited gap capability
  • Supra- or extraglottic pathology (radiation, large tonsils)
  • Glottic or subglottic pathology (larynx stenosis, etc.)
  • Limited flexion of the throat
  • Cricoid pressure
  • Male sex
  • Increased BMI (> 35)
  • “Bad teeth”
  • Position changes during operation.
  • Low lung compliance may require higher inspirational pressure with a risk of air leakage.
  • Patients with Mallampati grade 1-2 appears to be more difficult to get a good fit on LMA without leakage compared to Mallampati grade 3-4.

Predictors for difficult laryngoscopy

  • Limited gap capability (<4 cm).
  • Limited subluxability of the mandible (ULBT 2-3).
  • Narrow, often high, hard palate.
  • Short thyromental (<6-7 cm) and sternomental distance (<12 cm).
  • Modified Mallampati Class 3-4.
  • Indurations of buccal cavity.
  • Limited extension of the head and upper throat.
  • Increased circumference of the neck = High power measure (> 45 cm).

Predictors for difficult video laryngoscopy

  • Cormac-Lahane grade 3-4 in direct laryngoscopy.
  • Abnormal throat anatomy: radiation damage, scars inside the throat, thick throat and pathology in the throat.
  • Limited subluxability of the mandible.
  • Short distance between sternum and thyroid gland (larynx)

Predictors for difficult cricothyrotomy

  • Difficulties to identify the cricothyroid membranes
  • Female sex
  • Children before puberty (<8-12 years).
  • Thick or fat throat.
  • Local pathology (inflammation, radiation, tumor, etc.)
  • Difficulties to access the trachea through the front of the throat
  • Fixed neck back with motion limitation
  • Cervical spine fracture

How to handle difficult intubations

A successful intubation is based on the following factors:

  • Oxygenation, is it satisfactory?
  • The ventilation (via mask or LMA) is it functioning properly?
  • Is there any risk of regurgitation or aspiration?
  • Is there any other help available nearby, and how fast may you be assisted?
  • Is there any other (known) airway equipment nearby? Respiratory utilities!
  • Application of airway guidelines for difficult intubation. Predicting difficulties – and be prepared!
  • “Never fail to prepare for failure”
  • Tell us about your “Back-up plan” – so your employees know and understand.
  • Do not use technology or equipment that you are not used to.
  • “Learn to swim by swimming” – but train in the shallow part of the pool. Intubation should be good for the patient – not your “ego”
  • The patient does not die of failed intubation without oxygen deficiency!
  • It is important to know your own limitations.
  • One has to know when to end further intubation attempts – and how to handle the continuation.

In case of failure, consider to:

  1. Wake up the patient
  2. Laryngeal mask
  3. Alternative techniques
  4. Emerged surgical airway (Knife, Leader & Tube)

Keep in mind that the first intubation attempt is your best attempt. Limit the number of intubation attempts to three or four.

Procedure for difficult airways (non-acute)

Planned anesthesias on patients with known difficult airways should not cause any major problems if you prepare well with equipment and competence. Tracheostomy in local anesthesia “is always right” in the case of very difficult airways. Alternatively number two, should use flexible bronchoscopes in local anesthesia with or without sedation. Suitable patients for “awake intubation” can be;

Patients with recognized severe/very difficult airways

  • Various syndromes like Pierre-Robin, Treacher-Collins, Crouzon, Goldenhaar, etc. (There are about 70 different rare syndromes with airway problems)
  • Different storage diseases such as Hunters and Hurler’s syndrome.
  • Reduced gap capabilities (definitively those below <2 cm gap and relatively those with 2-3.5 cm).
  • Upper respiratory tract infections such as epiglottitis, oral bone marrow, harder mononucleosis and necklaces, etc.
  • Tumors et al. In the tongue, hypopharynx and larynx. Radiation-treated patients in oropharynx.
  • Vallecula cyst
  • Foreign body
  • Larynx and tracheal stenosis
  • Others with known difficult airway
  • Patients with increased risk of vomiting and aspiration.
  • Patients recently eaten/patients with gastroparesis.
  • Patients with pronounced and severe reflux problems.
  • Patients with elevated intraabdominal pressure / volume, such as Ileus, later part of pregnancy, big tumors, etc.
  • Trauma and patients receiving large doses of opiates.
  • Patients with nausea.

Procedure for difficult airways (acute)

  • Should this be done on call? Is there time for the consultant on call, and possibly ENT doctors to join in and assist?
  • Make a plan for this patient and communicate the plan and gather enough skills.
  • Use a difficult airway trolley, but use the equipment and methods you are familiar with.
  • Preoxygenate properly. Continue with oxygen supply.
  • Optimal body position, preferably the “Sniffing position.”
  • Consider elevated Head End and Cricoid Pressure (Release this if it is difficult).
  • If there’s enough time and skills, consider intubation with flexible bronchoscopes.
  • Otherwise, plan for video laryngoscopy and guide wire.
  • If there’s little to no space, a long tube sized number five often works well.
  • Use a good laryngeal mask if it is not possible to intubate initially. A “good” laryngeal mask has: two lumens, one for V-probe / guide wire and high sealing pressure, can be intubated through flexible bronchoscopes.
  • Consider early surgical airway (cricothyrotomy, PCT or surgical tracheostomy).
  • Consider the possibility of transtracheal ventilation with Ventrain through a 2 mm needle / cannula. You can ventilate 5-7 l / min with I / E 1: 1. Ventrain is new, cheap and not to say the least a life saving device in the airway equipment arsenal!
  • There are methods that we do not recommend, but that can solve an acute situation such as Retrograde intubation, blind nasal intubation and digital intubation, i.e. You feel your fingers in your throat and guide the tube.
  • Afterwards, always document what has been difficult and how to best solve the situation.

Intubation utilities

Various laryngoscopes, in addition to standard sheets with fiber optics include; Macintosh-alike blades for example In C-Mac, McGrath S3, and Glidescope Titan.

Macintosh-alike bladesC-Mac, McGrath S3, och Glidescope Titan
Advantages: Easy to use
Easy to see
Easy to intubate
Easy to use a guidewire
Low pressure against teeth.
Disadvantages:Difficult insight at very anteriorly high-seated larynx.
Heavily curved bladeC-Mac D-blade, McGrath S5, Glidescope
Advantages: Good insight at very anteriorly high-seated larynx
May be more difficult to intubate, despite good insight
Disadvantages:Slightly difficult technique. You must have a leader with the same curvature as the blade
Blade with a channel for an endotracheal tubeAirtraq, Pentax AWS, Kings Vision
Advantages: The tube slides protected in a channel
Once placed correctly, it is easy to intubate
Airtraq can send the image via the Internet to a "consultant"
Disadvantages:They may feel a bit "plastic"
They have been coarser (from Pentax AWS and difficult to get through the oropharynx
You have to go around epiglottis, which is sometimes difficult

Video laryngoscopy

There are several types of video laryngoscopes and each group has its advantages and disadvantages, as seen in the picture down below. Video laryngoscopy is the method of the future, and within 10 years, these are probably standard equipment in each and every operating theater.

Categories of video laryngoscopes

Acute coniotomy

Coniotomy (also called emergency tracheotomy) is an acute surgical incision through the skin and cricothyroid membrane (Ligamentum cricothyroideum medianum) down to the trachea with the aim of creating an open airway. The cricothyroide membrane is a connective tissue membrane between the thyroid cartilage (cartilago thyroidea) and ring cartilage (cartilago cricoidea). Coniotomy is a last life-saving measure when all other means of creating a free airway have failed and it is not possible to wait for the extra time it takes to perform a tracheotomy. A coniotomy is a temporary solution and is therefore often accompanied by a tracheotomy.

Predictors of severe coniotomy

  • Difficulty identifying cricothyroid membrane
  • Female gender
  • Children before puberty (< 8-12 years)
  • Thick, short or massive throat
  • Local pathology (inflammation, radiation, tumor, etc.)
  • Difficulty accessing the trachea through the front of the throat
  • Obesity
  • Fixed cervical spine with restriction of movement
  • Cervical spine fracture

Relatert bilde

Percutaneous tracheostomy

To be updated

Triage before tracheotomy

Risk parametersGreenYellowRed
BMI< 3030–35> 35
Neck mobility> 30º10-30º< 10º
Collar size< 45 cm45–50 cm> 50 cm
Bleeding diseaseNoYes
AnticoagulantsNoOnly ASAYes
PT (INR)INR < 1,3INR 1,3–1,5INR > 1,5
Platelets (109/l)> 150–35050–150< 50
APTt<40 sec40–60 sec>60 sec
Oxygenation problemsNoNO with oxygenYes
Difficult to intubateNoNO with video laryngo /
INR = international norm ratio; indicates patient coagulation time / normal coagulation time. PT (INR) is not a test but a way to answer the analysis. PT (prothrombin complex) measures factor II, VII and X. APTt (Activated Partial Thromboplastin Time) measures factor XII, XI, X, IX, VIII, V, prothrombin and fibrinogen.

Mechanical ventilation

By Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital

Updated 2020-09-25

Patients, who cannot breathe satisfactorily due to lung disease or other lung damage, can be treated with a ventilator that ventilates the lungs mechanically. Normal breathing is done by establishing a negative pressure , air is sucked into the lungs using the breathing muscles meanwhile in controlled ventilation air is blown into the lungs by means of an positive pressure. The ventilator’s compressed air is normally located on the backside of the ventilatory system. A precision valve controls the flow of gas to the patient. The most common basic settings of the ventilator’s system are volume controlled ventilation (VC/VCV, 20-1500 ml/breath) or pressure controlled ventilation (PC/PCV, 5-60 cm H2O in inhalation pressure). Putting the patient on the ventilator relieves the breathing work, but unfortunately, it is possible to add additional injuries to already sick or injured lungs due to pressure injuries (so-called ventilator induced lung injury), atelectasis, pneumothorax or infections.

Mechanical ventilation in ARDS is almost always required, as people with acute respiratory distress syndrome are by definition severely hypoxemic. Minimizing any additional damage while maintaining adequate gas exchange (“compatible with life”) is the central goal of mechanical ventilation in ARDS and acute lung injury, its less-severe form.

Therefore, in order to minimize the risk of damage due to treatment on a ventilator, it is desirable to adjust the ventilator settings for each individual patient and to minimize the amount of burden to the lung tissue. Controlled ventilation means major changes in lung volume changes and airway pressure. The gas exchange in the lungs is affected by both ventilation and circulation. Common causes of breathing failure are pulmonary edema, pneumonia, sepsis, atelectases, severe COPD or asthma. Other causes may be severe trauma, lung contusions, skeletal trauma, stroke, drug overdose, poisoning, unclear unconsciousness, or conceited and exhausted patient. Mechanical ventilation is usually done with a ventilator. Either the patient is intubated endotracheally (invasive ventilation) or the ventilation is performed with the help of a tight facial mask, non-invasive ventilation (NIV). A tube or breathing mask is connected to the ventilator hose system and its ventilation gases.

Mechanical ventilation is usually instituted with volume controlled ventilation (VC/VCV) or pressure controlled ventilation (PC/PCV). Volume controlled ventilation means that the given volume in each breath is predetermined and pressure controlled ventilation means that the given pressure in each breath is predetermined. Volume controlled ventilation always provides a constant flow in the inspired air, while in pressure controlled ventilation, a decelerating flow is obtained. Pressure controlled ventilation favors gas distribution and produces lower peak pressure compared to volume controlled ventilation. Volume controlled ventilation provides a smaller risk of hypoventilation and may be beneficial to ARDS. You always want to minimize the ventilation treatment time.

Ventilator treatment

Ventilator settingsHealthy lungModerate pulmonary failureSevere pulmonary failure
Tidal volume ml/kg< 6 - 8< 6 - 8< 6 - 8
Respiratory rate15 - 2015 - 2015 - 30
I:E quote1:21:2 - 1:11:1 - (2:1)
PEEP cm H200 - 55 - 1010 - 20
Oxygen fraction %< 4040 - 6040 - 100
Lung recruitement-YesYes, at an early stage

Adjustments of the ventilatory settings

By Vitus Krumbholz, Senior Physician in Anesthesia & Intensive Care, Sahlgrenska University Hospital.

Updated 2018-12-21

It is important to remember that normal breathing is a physiological masterpiece. A large diffusion surface in the lungs in a relatively small cavity interacts with an effective muscle engine and partly with the blood flow in the small circulation. The combination mainly regulates oxygenation as well as elimination of carbon dioxide. Breath is centrally controlled by efferent and afferent neurophysiological pathways that can react and adjust the respiratory momentarily as needed. Ventilation and perfusion are a finely tuned system that is the result of an evolution for millions of years. Ventilation in the ventilator, on the other hand, is not that but depends entirely on our settings in a mechanical ventilator under positive pressure ventilation.

Today’s mechanical ventilation is a rather clumsy imitation of natural breathing, even though it is the foundation of modern intensive care.

Volume controlled ventilation (VC)

In the simplest case of volume controlled ventilation (VC), where the patient does not breathe by themselves, the ventilator ensures oxygenation and carbon dioxide elimination with sustained volume but with variable insufflation pressure. Respiratory treatment means high pressure ventilation of the lungs while normal breathing is a form of negative pressure ventilation. It is the positive pressure that in various ways damages the lungs during prolonged respiratory treatment. The goal of the modern ventilator treatment is therefore to limit the barotrauma. A limited barotrauma is only possible as long as we stay within safety margins regarding time volume, peak pressure and transpulmonary driving pressure

With assisted ventilation (ASB/PS/CPAP), the patients manages to breathe by themselves, which requires increased attention and adaptation of the ventilator settings to an individual and dynamic need. The most widely used form of assisted ventilation is likely to be pressure-assisted ventilation, so-called PS/CPAP. Other assisted ventilation modes such as NAVA, APRV, PAV are available but are used to a lesser extent. However, most of all ICU patients with a respiratory time over a day will spend some time with PS/CPAP.

Adjustable ventilatory settings in the PS/CPAP mode

  1. Trigger sensitivity
  2. PEEP
  3. Pressure support (= pressure over PEEP)
  4. Inspiratory rising time
  5. Cycling off

Pressure-assisted ventilation (PA)

The inspiratory rise time defines the time from when the breath is triggered to when maximum inhalation flow is achieved. Cycling-off airflow threshold describes the point where inhalation changes to exhalation as a percentage of maximum inhalation flow.

Trigger sensitivity

In pressure support ventilation/CPAP, the ventilator uses a pneumatic trigger that is either flow or pressure based. During flow-based triggering, the ventilator feels of an inhalation attempt through a measured reversal in the exhalation flow. In order to register and, above all, measure the reversal, the ventilator uses a so-called bias flow. This means that during expiration the ventilator exerts an airflow of 2 l / min that runs parallel to the expiratory flow. This is to obtain a constant “baseline” that is measurable and neither individual nor varied as a physiological exhalation. When the patient initiates a breath, this bias flow is reduced relative to the patient’s inspiration. The change in airflow that occurs triggers an assisted breath when it passes the predetermined trigger value. A similar default setting in PS / CPAP could be 1.4 l/min. A reduced value means increased sensitivity and a faster response time that can increase patient comfort, the patient can therefor be able to trigger each breath more easily. One should be aware of the risk of auto-triggering at very low trigger sensitivity, for example by movements or leaks in the breathing circle, which increases the more we lower the bar. This can create a dyssynchrony breathing pattern which in turn, in addition to stressing the patient, also increases the risk of ventilation-induced lung damage.

When a pressure-based trigger occurs it initiates a breath when the patient through a breathing attempt creates an under pressure under the preset PEEP. The principle is “simple” and works in most ventilators. The disadvantage is that it usually increases respiratory response time and can be stressful for the patient with increased respiratory effort, compared to flow-based triggering. The risk of self-triggering breathing appears to be less in pressure-based trigger setting even with low threshold. However, with a high trigger value, you can really challenge the patient or even prevent breathes from being triggered at all. Excessive triggering causes spontaneous breathing and can thus be perceived as unpleasant to the patient.

There are very few scientific studies of different trigger settings valued against clinical outcomes. Flow-based triggering seems to be a more modern and smarter variant. The recommendation could thus be to not change the predetermined flow trigger if there is no obvious clinical triggering problem.


The basic idea for the setting of PEEP is simple, to always maintain an intra-alveolar pressure above zero cm H2O to prevent end-expiratory collapse of the lung tissue. The goal is, hypothetically, a global (= the entire lung), constant (= throughout the breathing cycle) and persistent (throughout the treatment period) ventilation/perfusion ratio (V/Q) as close as possible. It is therefore about finding the right PEEP level that is neither too low nor too high, a so-called optimal PEEP. Too low PEEP can increase the risk of shunt development, dynamic recruitment/derecruitment that leads to “shearing stress” and atelectic trauma, which in turn increases the risk of lung damage and ARDS development. Excessive PEEP may increase the risk of end-time over-distension of the lungs with increased dead-space, which in turn may create a need for increased driving pressure (> 15-20 cm H2O). The best method for finding the right PEEP level under controlled ventilation is debatable, no conclusive data yet. In addition, several methods are relatively difficult in practice.

A fundamental problem with all PEEP methodologies is that an instantaneous improvement in lung mechanics or gas exchange does not necessarily mean an improvement over time. Existing ventilator-induced pulmonary damage and ARDS, the benefit or damage of a given change may sometimes be assessed only after several days of treatment. It should also be borne in mind that all pressure measured in respiratory treatment is measured as global measurements. The patient’s lung, on the other hand, is exposed to different pressures in different parts, while elasticity, resilience and atelectic tendency also vary in different parts of the lung.

What happens under assisted ventilation is that the inspirational pressure that the lung is actually exposed to, the transpulmonary pressure can not yet be measured easily, but method development is ongoing. In addition, the supported ventilation is patient controlled and therefore varied in both volume and dynamics. This makes it more difficult or even impossible to draw conclusions of most measurement methods that have been used for bedside purposes. In other words, in terms of PEEP and PA/CPAP, we have relatively little benefit from measuring:

  • Static compliance
  • Lowest infliction point
  • Lowest shunt
  • Lowest dead space fraction

Although oesophageal balloon manometry appears to be a good method of measuring transpulmonary pressure with high clinical potential to control respiratory treatment, it does not seem to have become enough of a regular procedure for finding the right PEEP level under assisted ventilation.

Electrical Impendance Tomography (EIT) appears as a practical, more promising and useful method of PEEP adjustment, both in controlled and assisted ventilation. But despite the fact that the technology itself is not new and that it has been used successfully in several clinical studies, it is far from a routine use.

In summary, regarding PEEP, there is not much substantial evidence that could help us find the right level. Usually, in clinical practice one can study the ventilator trend image with changes in dynamic compliance over the past 24 hours. For example, recurring impairments may be related to repositioning of an otherwise painless and stressed patient may result in increased atelectic tendency. The patient’s condition would most likely improve with increased PEEP. At low dynamic compliance with high pressure requirements for adequate tidal volumes, as well as a patient who needs to use accessory breathing muscles, possibly lowering of PEEP may lead to immediate improvement. Regardless of the way in which we adjust PEEP, we should follow and evaluate changes in dynamic breathing measurements over time along with the clinical picture.

Pressure Support

When switching from pressure controlled ventilation (alternatively VCPS) to pressure-assisted ventilation, the support level (PS over PEEP, “driving pressure”) can usually be reduced. This occurs when the patient in question begins to contribute to the breathing through a diaphragm contraction. In pressure-assisted ventilation, the pressure during the inspiration phase is constant while the flow decreases. As long as PS is set to a value where the patient is not dependent of pressure support, the patient can determine their own tidal volume (TV). On the other hand, if we underestimate the value to a level where the patient can no longer compensate by their own effort, TV will decrease in relation to the pressure support. As a general goal for adjustment of PS, ​​one should aim for a breathing rate below 30/min and a tidal volume below 6 ml/kg (IBW). Furthermore, one should seek breathing without auxiliary breathing muscles with a “calm” and relaxed patient. The assessment of the last point is obviously difficult, as there is usually a lot more in addition to the respiratory treatment that may stress the patient.

Weaning from mechanical ventilation

By Vitus Krumbholz, Senior Physician in Anesthesia & Intensive Care, Sahlgrenska University Hospital.

Updated 2018-12-21

As with pressure controlled ventilation, it is essential to keep the inflation pressure under 20 cm H2O. Regarding the support level (where we achieve adequate tidal volumes), it is not necessarily the level the patient may be in need of. The goal during weaning may be the maximum practice effect with minimal effort. A protocol-controlled weaning with structured escalation of support and ultimately extubation has been shown to provide more respiratory-free days. Because respiratory treatment and weaning is usually controlled by doctors on the basis of individual decisions, standardized weaning protocols are lacking at most clinics. A pragmatic advice is to regularly evaluate and possibly lower PS until the patient needs to increase the breathing work. Signs of increased breathing work may be an increased respiratory rate or visible efforts of auxiliary respiratory muscles, most often in m. sternocleidomastoideus.

Another possibility is, of course, to talk to the patient, who is usually communicable during the weaning phase, and ask the patient when breathing efforts starts to feel exhausting. The level of support we choose is just over the effort threshold. However, the patient should never “wear out” in the ventilator at risk of becoming fatigue. Extubation of an exhausted patient is contraindicated. Acceptance of 5 over 5 in negative pressure/PEEP with FiO2 under 0.3 is considered a safe level to extubate. Even at higher pressure levels the patient can be extubated in some cases. It is always a clear advantage if the patient is communicable and calm during extubation. One should always avoid “crash extubation”.

Rising time

The pressure set or airflow that assists the patient during inhalation (pressure over PEEP in PS/CPAP mode) is not at the peak of the beginning but gradually increases after the breath has been triggered. Increase speed is set with inspiratory rise time.

Pressure support ventilation (PS)

A shortening of the inspirational rise time (A + B) leads to a reduced inspiration time without a major change in tidal volume (VT) by a left shift of the inspiration curve. An increased inspiration termination (C + D) reduces both breathing time and VT through previous cycling-off.


The default setting of the rise time in PS/CPAP is 0.15 sec. A decrease in inspiratory rise time affects, at least in theory, not the tidal volume. This is only theoretical speaking because an inadequate shortening of the rise time can cause premature interruption of the occurrence of occasional double breath (double triggering). This is due to too high resistance in the breathing circle caused by secretion or the patient’s “flow in excess” (see curve A below). Double breaths do not necessarily imply a requirement for increased inspirational rise time, but must always be related to the clinical situation. An extension of inspirational rise time may be beneficial in an ARDS-diseased patient with the atelectic tendency, as it creates time for an adequate redistribution of tidal volume between alveoli with different time constants. However, too long rise time can lead to a sense of breathlessness and increased breathing work. This can be seen by a concave deflection of the inspiratory pressure curve (curve C below).

Pressure Assisted ventilation

PA is an example of dyssynchronism due to inadequate inspirational rise time. (A)The figure shows short inspirational rise time (0.0 sec) with early pressure peak during the inspiration phase as signs of “flow in excess of demand” or obstruction in the airways or in the tube. (B) Shows normal breathing curve. (C) Shows a long inspirational rise time (0.5 sec) with concave deformation of the curve during flow increase as a sign of “demand in excess of flow” with consistently increased breathing work.

Generally speaking, a brief inspirational rise time (shortened inhalation in relation to exhalation time) benefits primarily the obstructive patient (asthma, COPD), and that an extension may sometimes be used for patients with atelectric tendency at slow respiratory rate.

Inspiration finish

The airflow during inhalation begins to decrease as soon as the predetermined pressure level is reached. When the flow is below a certain level, expressed as a percentage of the max flow, the inspiration merges intto expiration. The predetermined value is 30%. If we increase the value by changing the inspiration end, thus shortening the patient’s breath and vice versa.

Pressure-assisted ventilation (PA) increase inspiration termination to 50% (C) with consecutive reduced tidal volume (VT). Image (D) shows attempts to VT compensation by reducing inspiration termination to 30% as well as shortened inspiratory rise time to 0.0 sec.

The purpose is obvious to affect the I:E relationship. To give the obstructive patient more time to breathe out and reduce the risk of auto-PEEP (increased inspiration termination, preferably in combination with shortened inspiratory rise time) or increase the inspiration time for the low-compliance atelectic-restricted restrictive patient with a low compliance (reduced inspiration termination with possible prolongation of inspirational rise time ). Double breath can express the need for further lowering of inspiration termination.

In summary

Fine adjustments in the ventilatory settings allow us to optimize the respiratory treatment for the individual patient. Although there are alternatives to PA/CPAP (Pressure Assist/CPAP), this breathing mode can generally be considered the most effective weaning pattern. Default settings in PA/CPAP should be the basis of the respiratory setting, but adjustments may be required in consideration of the specific lung pathology and change during different phases of the weaning procedure.

In order to achieve effective respiratory treatment, active attendance with relevant adjustments of respiratory settings and some acceptance of the “trial and error”-principle requires consideration of lung physiological principles and continuous monitoring of respiration and patient’s overall clinical picture. Several different measurement methods exist to find optimal ventilatory settings, but basic clinical examination supplemented with ultrasound examination, frequent blood gas analyzes, and common chest x-rays are usually sufficient to optimize ventilation. Computer tomography scanning or magnetic camera pictures will increase the understanding of the patient’s lung disease and should be performed relatively liberally in intensive care patients.

Ventilatory treatment in respiratory failure and ARDS

Francesca Campoccia Jalde, Chief Physician
TIVA Solna, Perioperative Medicine and Intensive Care
Karolinska University Hospital, Stockholm

Johan Petersson, Chief Physician
IVA Solna, Perioperative Medicine and Intensive Care
Karolinska University Hospital, Stockholm

Updated 2021-02-25

Definition of ARDS

  • Acute pulmonary failure (≤ 7 days)
  • Pulmonary failure is not entirely explained by heart failure
  • Bilateral infiltrates (X-ray/CT/ultrasound)
  • PaO2/FiO< 40 kPa despite PEEP 5 cm H2O

Grading of ARDS

ARDS PFI (kPa) =
FiO2 with PaO2 10
(SpO2 ≈ 95 %)
FiO2 with PaO2 8
(SpO2 ≈ 90 %)
Mild 40.0-26.6 25 %21 %
Moderate26.6-13.3 37 %30 %
Severe≤ 13.3 75 %60 %

General recommendations

  • Avoid positive fluid balance if possible, increasingly important with increasing degree of ARDS
  • With the increasing degree of ARDS, there is an increased need for hemodynamic evaluation (Cardiac echo – UCG) and special measures if right chamber failure occurs.
  • Ensure adequate diagnosis and treatment of the etiology, infection diagnosis and treatment of infection.
  • Sedation rate is selected for patient comfort, avoid excessive breathing work (if PS) and avoid patient – ventilator dyssynchrony
  • Prophylaxis regarding DVT, stress ulcer, VAP and pressure ulcers

Decision support at early ARDS

ClassificationActionsTreatment goals
PFI 26.7-40 kPa
Favorable body position
If not intubated: High flow halter ≥ 40 L/min alt. NIV with PEEP ≥ 6, TU ≤ 5.
If intubated: Often TU/CPAP: PEEP ≥ 8, TV ≤ 8 ml/kg
Initiate adequate antimicrobial therapy
Avoid positive fluid balance if possible
Target: SpO 2 : 92-95%, PaO 2 : 9-10 RR < 7
Treatment aims for
• Reduce heavy breathing work
• Avoid large tidal volumes
• Minimize patient/ventilator dyssynchronies
If not better in NIV ≤ 2 h ➔ possible intubation
Moderate ARDS
PFI 26.7-13.3 kPa
Frequent need for intubation, especially if PFI < 20:
• Usually PEEP 10-14
• Dimensions TV: ≤ 6 ml/kg PBW
• Most often controlled ventilation
• Ventilating pressure: if PS: 8-14, if PC: ≤ 15
• If heavy breathing drive / large TV, increase sedation
In PFI <20: abdominal position 16-20 h/day (unless contraindicated)
Target: SpO 2 90-94%, PaO2 8-10,
At PC: pH > 7.25 PaCO2: ≤ 7(-8)
In case of negative PFI trend despite adequate treatment, consider and manage as severe ARDS.
Aim also as in the action box on the left.
Severe ARDS
PFI <13.3 kPa
Invasive ventilation in controlled mode (PC)
TV ≤ 6 ml/kg PBW TK over PEEP: ≤ 15
Ptop <30,
Usually PEEP 12-18, titrated (Note compliance and hemodynamics)
RR determines MV (target pH > 7.25, PCO2 <7-8)
Unless contraindicated:
• Abdominal position 16-20 h/day
Sedation to comfort and knocked out self-breathing
• Neuromuscular blockade of severe dysynchrony
Cardiac echo for hemodynamic assessment
• ECMO contact in case of continued negative trend (PFI <10)
Target: SpO 2 88-94%, PaO2 7.5-10
pH > 7.25 PaCO2: ≤ 7-8
• Avoid self-breathing
• If possible, negative fluid balance
• Caution when recruiting with a ventilator, but try in case of sudden deterioration and as a rescue measure
• Hemodynamic optimization, right ventricular relief

In ARDS, one often, but not always, sees a correlation between the degree of oxygenation problems (lower PaO2/FiO2) and lower compliance. This is due to large lung parts that are not gas-filled/ventilated. When a small part of the lungs is ventilated, compliance becomes low and the blood flow through unventilated parts becomes an intrapulmonary shunt, which in turn explains hypoxemia which responds poorly to increased FiO2. This pathophysiology often, but not always, shows improved oxygenation and compliance with increased PEEP and after lung recruitment with high airway pressures. The mechanism is then that lung parts that were not previously gas-filled/ventilated are opened, which in turn means that larger parts of the lung are ventilated, which gives better compliance and less shunt. This is the logic when the need for increased FiOis linked to the use of higher PEEP (PEEP-FiOtables). In recent time, there has been an intense discussion about whether COVID-19 caused ARDS in a systematic way differs from other ARDS, e.g. caused by pneumonia. In several, relatively large, patient materials, however, it has been difficult to demonstrate clinically significant differences for e.g. compliance.

At the same time, it is relatively common with the combination of severe ARDS (low PaO2/FiO2 ratio) and relatively high (almost normal) compliance, but this also occurs in ARDS of an etiology other than COVID-19. For all patients with ARDS, regardless of etiology, the choice of treatment, e.g. ventilator settings, continuously adjusted to the current situation. An example of this is when major oxygenation problems (low PaO2/FiO2) are associated with well-preserved, almost normal, compliance. Preserved compliance indicates that low PaO2/FiOis not explained by lung parts without ventilation, which in turn means that there are poorer conditions for higher PEEP to improve gas exchange or compliance. Well-preserved compliance and the absence of larger lung parts that are not gas-filled/ventilated are well compatible with the most common X-ray findings in COVID-19 pneumonia: infiltrates of the groundglass type and the absence of larger consolidated lung parts.

The oxygenation problem in this situation has instead been suggested to be due to V/Q mismatch in combination with inhibited hypoxic vasoconstriction. It is in this situation that slightly lower PEEP and slightly higher tidal volumes become reasonable. High PEEP can impair gas exchange through several mechanisms, especially CO2 elimination. This is not specific to COVID-19 patients but it becomes particularly important as it seems more common that PEEP does not open unventilated lung sections. The deterioration of gas exchange with increased PEEP becomes more pronounced if the patient is at the same time relatively hypovolemic. With preserved lung compliance, PEEP has a greater effect on preload than with ARDS with reduced compliance. Impaired cardiac output due to high PEEP and relative hypovolemia has been suggested to contribute to acute renal failure in COVID-19 patients. In other patients with COVID-19 pneumonia, a pathophysiology is described that is more typical of “normal” ARDS: decreased compliance and shunt due to lung parts that are not gas-filled/ventilated combined with improved gas exchange with increased PEEP/lung recruitment. In this situation, the indication to limit the tidal volume and to try higher PEEP is strengthened.

The discussion about ARDS of different types is likely to continue. Regardless of this, the overall experience seems to suggest greater restrictiveness with higher PEEP and acceptance for higher tidal volumes than with non-COVID-19 ARDS, but also that there may be patients/situations where the pathophysiology is more similar to “normal” ARDS.

Respiratory failure and ventilator treatment in ARDS (Covid-19)

Patients cared for outside ICU

  • O2 supply with target SpO2 92-96%; in patients with COPD or risk of CO2 retention target SpO2 88-92% 1.
  • When O2 supply, including reservoir oxygen mask supply, is insufficient, high flow via nasal mask (HFNC, “Optiflow”) is recommended.
  • When HFNC is not sufficient, CPAP with pressure ≤ 10 cm H2O can be tested.
  • Experience has shown that COVID-19 patients who are completely dependent on NIV, ie. can not maintain sufficient gas exchange without NIV, often continues to deteriorate. This can lead to the need for acute intubation, which means increased risks for the patient and increased risk of spreading the infection. For patients with less pronounced lung failure, NIV can be an alternative that is used for a longer period of time, possibly alternating with HFNC. In the same way, NIV can be used for patients where intensive care is not relevant but is avoided if you have switched to palliative care.
  • HFNC, CPAP and NIV entail a risk of aerosol formation and the spread of infection, which strengthens the indication for protective equipment. Compared to CPAP/NIV, HFNC can bring an advantage through less need to be very close to the patient.
  • HFNC and NIV should not be used for transportation within the hospital, reservoir mask is used instead.
  • Mobilization, cough relief and changes in position are important to prevent and treat impaired lung function. It has proven particularly effective with prone positioning or abdominal position, with or without other respiratory support such as HFNC, NIV or CPAP.

Potential indications for intensive care

  • PaO2/FiO< 20 kPa or deterioration with need for increasing FiO(O2%), SpO2 <93% with O2 ≥ 10 L/min by mask.
  • Rising PCO2 (> 6.0 kPa), especially if pH <7.30.
  • Increased respiratory work and/or respiratory rate (RR) > 30/min. Ask the patient if it has gotten better or worse with breathing over time
  • When NIV is used for patients due to that oxygen on the reservoir mask or HFNC is insufficient treatment and the patient continues to deteriorate or that the patient has not improved within 1-2 hours after starting treatment.
  • Affected level of consciousness
  • Hypotension, oliguria, elevated and rising β-Lactate, echocardiography with pronounced right and/or left failure.
  • Before ICU contact is made, in the normal case, ev. treatment limitations have been discussed in the care unit even before these indications exist, see above. If the patient meets any ICU indication, ICU contact should be made in parallel with this discussion. The responsibility for this lies primarily with the responsible doctor in the department where the patient is cared for.


The intubation procedure is linked to an increased risk of infection of the staff, especially for the intubator and a risk of circulatory/respiratory collapse. COVID-19 patients may appear relatively unaffected despite significant hypoxia and high respiratory rate. They can deteriorate very quickly and then have a very hard time recovering after intubation. It is therefore a strong recommendation not to wait too long with intubation. Intubation of COVID-19 patients always involves an increased risk of spreading the infection. For procedure and checklist, see special guideline,

Recommendations regarding ventilatory treatment

Humidification/filters – mucus stagnation and “tube oclusion” are relatively common, active humidification with conventional equipment is a pre-selection. If active humidification is not used, passive humidification with HME with filter function is provided. Always use filters at the ventilator inlet expiration. All changes of filters/hoses are made with the ventilator in standby. Auto-PEEP and patient-ventilator dyssynchrony may be due to filters that need to be replaced – especially if the patient has active humidification and/or inhalations. Testing of new tubes can be skipped in aggrement with the responsible physician.

Closed suction system – always used with Covid 19.

Tidal volume/Drive pressure – generally adjust tidal volume up to 8 ml/kg PBW is accepted if driving pressure ≤ 15 cm H2O and plateau pressure ≤ 30 cm H2O. Larger tidal volume/driving pressure is accepted when reduction is impossible or requires measures that are deemed to worsen the situation such as increased sedation, need for relaxation or reduced gas exchange.

PEEP – selected individually, if good compliance often 6-12 cm H2O even at higher FiO2. Try higher PEEP for lower compliance and low PaO2/FiO2. Re-evaluate high PEEP by reduction with 2 cm H2O and follow-up of tidal volume, compliance and gas exchange. Note that compliance can only be assessed with controlled ventilation.

SpO2/PaO2 – target values:

  • Controlled ventilation: SpO88-94%, PaO7,5-9,5 kPa
  • Assisted ventilation: SpO92-94% PaO8,5-9,5 kPa

PaCO2 – up to 8.0 kPa is generally accepted. Higher PaCO2 can be accepted if pH > 7.20 with simultaneous reasonable breathing drive. Higher PaCO2 can also be accepted if the ventilation otherwise leads to excessive tidal volumes/drive pressure or significant auto-PEEP.

Pulmonary recruitment – early consideration of low PaO2/FIO2 and low compliance, especially of sudden deterioration. Exclude bronchial intubation, secretion/threatening tube obstruction, pneumothorax. Do not repeat recruitment if previous recruitment has not had an effect.

Patient-ventilator dyssynchrony – managed primarily with adjustment of ventilator settings and increased sedation, secondarily with intermittent muscle relaxants or infusion to be reconsidered after 12-24 hours.

Abdominal position (prone positioning)  treatment – recommended if PaO2/FIO2 < 20 kPa and even in case of PCO2 problems, aim for at least 16 h/day, daily turn over with 4-6 h in supine position.

Weaning – slow improvement and risk of “setbacks”. Regular training begins relatively late in the process and only at lower ventilatory settings than is otherwise usual.

Humidification/use of filters in the ventilatory circuit (“hoses”) in case of suspected or secured COVID-19

Balance between the risk of spreading the infection and what is optimal for the patient.

  • Make a patient- and situation based choice between active and passive humidification. Active humidification is preferable. Indication for active humidification is particularly present in case of pronounced hypercapnea with the need to eliminate dead space or in case of thick/dry mucus secretions. Dry/thick secretions can cause tube obstruction or auto-PEEP. If active humidification is not possible, one can consider e.g. acetylcysteine ​​inhalations but then via a “closed” nebulization system.
  • Passive humidification is regulated primarily with HME (moisture-heat exchanger) which also has a filter function. This advice should be placed as close to the tube as possible, but the closed suction system must be placed between the tube and the HME/filter.
  • If HME with filter function is missing, another HME is used which is supplemented with filters at the ventilator’s inspiration output.
  • There should always be a filter on the exhalation input on the ventilator.
  • If active humidification is used, the HME/filter at the tube should not be used, however, there should be a filter at the ventilator’s inspiration outlet.
  • For all filter changes, hose changes and the like, the tube must be clamped briefly and the ventilator put in Stand-By before disconnections are made. The ventilator will not start until you have ensured that everything is connected again. For tracheotomized patients, this is done in the same way but without clamping.

Invasive ventilation

  • With pressure control ventilation, driving pressure is selected for the desired tidal volume, then RR is adjusted to the desired minute ventilation and an acceptable PaCO2, but avoiding auto-PEEP.
  • Accept tidal volume approximately 8 ml/kg PBW (predicted body weight) if the driving pressure ≤ 15 cm H2O (driving pressure = pressure over PEEP, the ventilating pressure). Aim gradually towards lower tidal volume/kg PBW if the driving pressure is higher.
  • Note that the driving pressure can really only be assessed with controlled ventilation. For pressure-assisted ventilation, the proposal is to accept tidal volumes up to 8 ml/kg PBW, provided that the support is a maximum of 14 cm H2O and the patient does not “struggle” much with inhalation himself. If this cannot be achieved, controlled ventilation or other measures to reduce respiratory work are proposed, e.g. increased sedation.
  • Note that reducing pressure support to reduce tidal volume often has little effect but may lead to increased respiratory work. It is therefore rarely appropriate with pressure support < 8-10 cm H2O. At high tidal volumes, it may be appropriate to increase the pressure support if the patient has a large respiratory work. The result is often unchanged tidal volume but with reduced breathing work. The alternative is to switch to controlled ventilation.
  • Larger tidal volume/driving pressure is accepted when reduction is impossible or where the alternative is measures that are judged to worsen the situation, such as deeper sedation, need for muscle relaxation, impaired gas exchange, pronounced patient-ventilator dysynchrony.
  • The goal is peak pressure ≤ 30 cm H2O and driving pressure ≤ 15 cm H2O. Always aim for the lowest possible driving pressure.
  • FiO2 with target SpO2 at 88-94%, and 92-94% for pressure assisted ventilation.
  • PEEP is selected individually, often at levels of 6-12 cm H2O. Lower PEEP is often chosen than with other conditions of ARDS, especially if the patient has high compliance (> compliance 30 ml/cm H2O).
  • When high FIO2 is needed, ie. moderate-severe ARDS, higher PEEP can be tried, especially at low compliance. If higher PEEP does not lead to improved gas exchange or improved compliance, or if increased PEEP leads to hemodynamic deterioration, return to lower PEEP. In the same way, PEEP > 8-10 cm H2O should be re-examined at least daily, but first inquire about the effect of previous attempts of reduction. Changes are made in steps of 2 cm H2O.
  • Hypercapnéa due to difficult CO2 elimination is accentuated by high PEEP, especially in relative hypovolemia. Consider giving volume and reducing PEEP, a lower PEEP may be better overall even if it means that FIO2 must be increased.
  • Consider early lung recruitment with increased PEEP and increased airway pressure if the patient has low PaO2/FIO2 and low compliance (< 20 ml/cm H2O) but recruit with increased caution in case of hypovolemia/haemodynamic instability. Do not repeat recruitment attempts if they have not previously had any effect
  • Patient-Ventilator Dysynchrony – When the patient is difficult to ventilate and does not follow the ventilator (“breathing against”), it is handled with increased sedation (incl. increased opiate dose). If this is not enough, repeated doses of muscle relaxation or infusion for up to 24-48 hours may be tried.
  • In the event of a very severe gas exchange disturbance, caution is recommended when switching from assisted to controlled ventilation. There is a risk that this shift may cause respiratory collapse. The solution can then be a quick return to spontaneous breathing with assisted ventilation e.g. with reversal of drugs.

Avoid aerosol formation by not disconnecting the ventilator hoses/tube as far as possible. This recommendation also aims to avoid derecryption (atelectasis formation).

  • Use closed suction system
  • Avoid inhalation therapy except in case of strong indication
  • Minimize the number of bronchoscopies. Bronchoscopy is performed for diagnosis and in case of imminent risk of tube obstruction. Use muscle relaxants during bronchoscopy, but with readiness for reversal (see comment in the section on patient-ventilator dyssynchrony above). Blind protected brush is an alternative for diagnostics.
  • If disconnection is unavoidable, put the ventilator in Stand-By and clamp the tube with a peang. Consider sedation bolus before doing this. Switch to active ventilation only when all hoses are connected.

Abdominal position (prone position) treatment at least 16 h/day is recommended if PaO2/FIO2 < 20 kPa in the supine position. Abdominal position in COVID-19 ARDS often has a favorable effect and can therefore be tested at higher PaO2/FIO2, e.g. in case of gradual deterioration of oxygenation or when the problem is more hypercapne than hypoxemia. If “true abdominal position” is difficult to achieve, prone side position is an option. In both cases, small adjustments should be made so that pressure points and the position of the head/neck change regularly.

Other ventilation methods: There are no studies that have shown clear advantages of using other ventilation methods than pressure control and pressure support. In the current situation with very varying experience and competence of both doctors and nursing staff, it is recommended that one refrains from using ventilation modes that are not used in ordinary cases. I.e. use only Pressure control and Pressure support ventilation mode. Pressure controlled ventilation with controlled tidal volumes e.g. VCPS may be used in special cases where stable PaCO2 levels are required.


If the patient has well-functioning controlled ventilation, you should not be in a hurry to switch to pressure support. Wait for PaO2/FIO2 ≥ 33 kPa (approximately equivalent to SpO2 95% at FIO2 0.3) and that the patient does not breathe with excessive tidal volumes (e g > 10 ml/kg PBW) with assisted ventilation. For the same reason, PEEP should not be reduced to < 6 cm H2O until a relatively late stage in the process. Pronounced impaired oxygenation at turns indicates that the patient is not ready for extubation. Experience so far is that patients with COVID-19 ARDS require at least 10-14 days of intensive care. During intensive care, the patient should be considered infectious. Extubation should be done at a later stage of the process, ie. in a situation where the need for continued respiratory support after extubation is judged to be low.

Extubation: Several centers have reported airway obstruction after extubation, it is unclear if and why this may be more common in COVID-19 than other pneumonia/ARDS. Secretion and mucus stagnation problems are common after extubation, they are treated in the usual way with cough relief and mobilization. In selected cases, tracheotomy may probably allow less risk of reintubation and a faster termination of intensive care, but this presupposes that the patient can be discharged to care units with the right skills and staffing.

Refractory hypoxemia/hypercapnea: Possible measures are recruitment, abdominal position, optimizing PEEP (may mean lowering of PEEP), minimizing device dead space, hemodynamic assessment/optimization (excluding hypovolemia as a cause of impaired CO2 elimination), deepened sedation, neuromuscular blockade fever, acceptance of spontaneous breathing/assisted ventilation despite greater tidal volumes/airway pressure than desired, inhalation of vasodilators (there are positive experiences from inhalation of ileoprost and milrinone), consultation with ECMO. A high frequency of pulmonary embolism in COVID-19 patients has been described, which strengthens the indication for diagnosis in this regard.

ECMO: Consider contact with ECMO unit if the patient does not improve with the previously mentioned measures and severe hypoxemia persists (eg PaO2/FiO2 < 10 kPa) and no contraindications are present. The indication for ECMO may change during the epidemic.

Tracheotomy: Use protective equipment, use muscle relaxants to avoid coughing, feel free to cover the face/tube with a plastic cloth, put the ventilator on standby when the tube is backed up and the trachea should be incised. Make sure that all hoses are connected and that the needle is cupped before restarting the ventilator. See link for description of ARDS at COVID-19 and references.

Respiratory treatment graphics

Click on the image to download the PDF file


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  2. Tran K, Cimon K, Severn M, Pessoa-Silva CL, Conly J. Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review. PLoS One. 2012;7(4):e35797.
  3. Peng PWH, Ho PL, Hota SS. Outbreak of a new coronavirus: what anaesthetists should know. Br J Anaesth. 2020;124(5):497-501.
  4. Hui DS, Chow BK, Lo T, Tsang OTY, Ko FW, Ng SS, et al. Exhaled air dispersion during high-flow nasal cannula therapy versus CPAP via different masks. Eur Respir J. 2019;53(4).
  5. Murthy S, Gomersall CD, Fowler RA. Care for Critically Ill Patients With COVID-19. JAMA. 2020;323(15):1499-500.
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By Per Nellgård and Kai Knudsen Senior Physicians in Anesthesia & Intensive Care, Sahlgrenska University Hospital.

Updated 2020-09-25

Extubation is removal of the endotracheal tube which is performed after anesthesia or intensive care. The tube is removed when the patient is capable of breathing himself without being exhausted or without risk of desaturation. Extubation of an exhausted patient is contraindicated. Acceptance of 5 over 5 in pressure support/PEEP with FiO2 under 0.3 is considered a safe level to extubate from. Even higher pressure levels can be extubated in some cases. It is always a clear advantage if the patient is communicable and calm during extubation. One should avoid “crash extubation”.

Criteria for extubation

  • Spontaneous eye opening
  • Facial grimace
  • Patient movement other than coughing
  • Conjugate gaze
  • Purposeful movement
  • End tidal anesthetic less than:
    • Sevoflurane: 0.2%
    • Isoflurane: 0.15%
    • Desflurane: 1.0%
  • Oxygen saturation greater than 97%
  • Positive laryngeal stimulation test
  • Tidal volume greater than 5 ml/kg

Evaluate the patient’s ability to spontaneously breathe before extubation

  • Can the patient have supported ventilation in the ventilator?
  • Are there acceptable values for TU, PEEP 10, FiO2 <40%?
  • Are blood gases acceptable with SaO> 95%, PaO> 10 kPa, PaCO2 < 6 kPa?
  • Reduce to extubation settings with PEEP 5-7 and TU 5-7

Extubation criteria

  • Alertness RLS < 3 ?
  • Swallowing ability, coughing ability?
  • Manages PEEP 5-7 and PS 5-7 or spontaneous breathing through the tube > 30 min?

Evaluation after extubation

  • Free airway, as expected after extubation?
  • Pulse, blood pressure, respiratory rate, blood gases?

Consider the following:

  • A pilot must plan both start (Intubation) and landing (extubation).
  • Extubation is always elective (if not accidental).
  • NAP4 shows that 23% of severe airway-related events occur during extubation.
  • The most common complications of extubation are: hypertension, tachycardia, elevated intracranial and intraocular pressure, etc.
  • Common problems: Inadequate oxygenation and ventilation. Inability to protect the respiratory tract and to get mucus out of the airways.
  • During extubation, plans must be made on before hand, preparing for a failing extubation scenario.
  • During extubation, one must assess whether reintubation can be easy or difficult.
  • Reintubation under optimum conditions differs greatly from acute reintubation with hypoxic patients.
  • Consider laryngeal mask as a possible “bridge” in extubation.
  • Consider the “Airway Exchange Catheter”.

When giving patients anesthesia, one can often choose between general anesthesia or alternatively any type of regional block, central or peripheral in combination with sedation for the surgical procedure. It may seem tempting to choose regional anesthesia for patients with difficult airways, but then one has to choose a method that “works safely”, for example spinal anesthesia. If a blockade discontinues during operation and you are urgently forced to anesthetize a patient with a difficult airway you can quickly get into serious problems.

APRV – Airway Pressure Release Ventilation

By Alexander Ille and Noémi Szabó-Némedi, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2020-07-01

Spontaneous breathing at two different levels of pressure that are regulated independent of each other in self-controlled breathing. APRV improves alveolar ventilation and increases functional residual capacity (FRC) while keeping the airway open. APRV provides CPAP at two different levels at complete spontaneous breathing. APRV is used in the treatment of both moderate and severe pulmonary failure. APRV is available in ventilators from Dräger.

Simplified, APRV is a respirator breathing mode that allows spontaneous self-breathing with a high CPAP resistance that is varied with short pressure drops in the breathing cycle to improve the total carbon dioxide elimination from the lungs.

APRV can be used as:

  • An alternative ventilation mode in cases where conventional ventilation strategies have not achieved the expected effect
  • A possible alternative to abdominal position in severe lung failure
  • An alternative lung recruitment method


  • Hypoxic respiratory failure (Type 1) with high PEEP requirement (≥ 12 cm H2O) and low P/F ratio (≤ 26.7)
    • lower indication threshold in case of clear clinical deterioration
  • Potentially recruitable low lung compliance
  • Dyssynchrony in respiration with conventional respirator settings due to high or varying respiratory rate


All contraindications are relative and must be evaluated carefully in each case

  • Obstructive pulmonary disease (COPD, asthma with expiratory time constant > 0.8 s)
  • Right heart failure
  • Severe hypovolemia
  • High intracranial pressure

Initial settings

  • Phigh in most cases between 25-30 cm H2O
    • As a basis, one can calculate the average of Pmean and Ptop of the previous conventional respirator setting
  • Plow (marked as “PEEP”): 0 cm H2O or minimum value allowed by the respirator
  • Thigh: 4 sec
  • Tlow: 0.4 sec
  • I:E 10:1 (should not be considered as fixed)
  • All PS (pressure support): 0 cm H2O

Adjustment of settings

    1. Evaluate release volumes (the tidal volume measured during release periods) and adjust Tlow to achieve release volumes of 6-8 ml/kgABW. Decrease Tlow in 0.05 s steps to reduce the release volume or increase Tlow in the same step to get a higher release volume.
    2. Before raising the Tlow , the pressure and flow curve must be examined to avoid derecruitement that would occur with too long Tlow.
    3. The shift from low to high pressure must take place at an exhalation flow that corresponds to approximately 50-75% of the peak flow. Below 50% of the peak flow, auto-PEEP is dropped and consequently the risk of derecruitement increases. If you cannot reach the desired release volumes without having a dangerous flow reduction, you should increase Phigh by 2 cm H2O per step.
    4. Check a blood gas within half an hour.
    5. If the patient retains carbon dioxide, optimize sedation to get better spontaneous breathing work. You must reduce Thigh by 0.5 s step to increase the frequency of release periods. Then to maintain Pmean remember to raise Phigh by 1-2 cm H2O steps.
    6. To raise PaO2 increase Phigh in 2 cm H2O steps. If PaCO2 value allows it, you can extend Thigh as well. Unreasonably long Thigh (> 5 s) will probably not provide further oxygenation improvement and at the same time it may be uncomfortable for the patient.
    7. Evaluate the patient’s respiratory work. When there is an obvious high breathing effort, you must try to reduce Thigh by 0.05 s steps and try to adjust Phigh (either decrease or increase by 2 cm H2O) to find the optimal value. Check that the release volumes are large enough. Carefully deepen the sedation so as not to completely lose spontaneous breathing. If the patient, despite all efforts, fights the respirator, switch back to a conventional mode.


If there is an improvement in the whole clinical picture (FiO2 ˂ 50%, calm spontaneous breathing (10-25/min RR) in a slightly sedated patient (RASS -1/-2), start by lowering Phigh in steps of 2 cm. At less than 20 cm H2O of Phigh, Thigh can be extended by 0.5-1 s steps at 4-8 hour intervals. The goal is to bring the patient close to a real CPAP treatment.

Theoretical background

APRV mode differs conceptually from other ventilation methods and is based on the idea of slowly recruiting and keeping the lungs open. The long high pressure allows the alveoli to fill up in a balanced way and thus reduces heterogeneity in the filling of the lungs. The patient’s preserved spontaneous breathing during Phigh improves the V/Q coupling and mimics the physiological intrathoracic pressure changes with all their beneficial hemodynamic effects. With lower peak pressures, fewer iatrogenic injuries occur. Usually after a few hours of setting with APRV, the blood gas values make it possible to reduce FiO2 due to. slow recruitment, it also means that you have to spend enough time on the patient’s ventilator setting to get significant effects from the APRV treatment.


  1. Fredericks AS, Bunker MP, Gliga LA, et al. Airway Pressure Release Ventilation: A Review of the Evidence, Theoretical Benefits, and Alternative Titration Strategies. Clin Med Insights Circ Respir Pulm Med. Published 2020 Feb 5.
  2. Farkas J IBCC chapter: Guide to APRV for COVID-19, April 8, 2020,
  3. van der Zee P, Gommers D. Recruitment Maneuvers and Higher PEEP, the So-Called Open Lung Concept, in Patients with ARDS. Crit Care. 2019; 23 (1): 73. Published 2019 Mar 9.
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  5. Ehab G Daoud, Hany L Farag, Robert L Chatburn: Airway Pressure Release Ventilation: What Do We Know? Respiratory Care Feb 2012, 57 (2) 282-292
APRV settings in the ventilator
TV:6-8 ml/kg
RR:10-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-10 cm H2O
CPAP5-15 cm H2O
ASB8-15 cm H2O

BiPaP – Biphasic Positive Airway Pressure

Pressure controlled ventilation with room for spontaneous breathing throughout the entire breathing cycle. Adjustable pressure support in two positions. You set the pressure level in both CPAP breathing and supported breathing (ASB). BiPaP improves alveolar ventilation and increases functional residual capacity (FRC) while keeping the airway open. BiPaP is used in the treatment of both mild, moderate and severe pulmonary failure.

BiPAP-Assist (with SB): Pressure Controlled Assisted Ventilation

BiPAPNormal settings in the ventilator
ASB:3-10 cm H2O
TV:6-8 ml/kg
RR:10-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-10 cm H2O
CPAP:3-7 cm H2O

IPPV – Intermittent Positive Pressure Ventilation

IPPV keeps the lungs expanded by constantly blowing a volume of air into them. Constant volume is given in both controlled mode and assisted. The positive pressure can be controlled by stimulation of the patient’s own spontaneous inspiration or through complete mechanical ventilation. Access to the patient’s lungs occurs either by intubation or breathing mask. IPPV includes CPV (Continuous Positive Pressure Ventilation), PLV (Pressure-Reduced Ventilation), Auto-flow (Automatic Control of Inspiration Flow) and IRV (inversed ratio ventilation). IPPV is used primarily in the treatment of mild or moderate pulmonary failure.

IPPVIntermittent Positive Pressure Ventilation
ASB:3-12 cm H2O
TV:6-8 ml/kg
RR:10-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-10 cm H2O
CPAP:3-15 cm H2O

MMV – Mandatory Minute Ventilation

MMV provides spontaneous breathing with automatic adjustment of the compulsory respiration to the patient’s need for volume. Access to the patient’s lungs is through intubation or breathing mask. Possibility of pressure-reduced ventilation and auto-flow (automatic control of inspiration flow). MMV is used primarily in the treatment of mild or moderate pulmonary failure.

MMV - Mandatory Minute Ventilation Normal settings
ASB:3-12 cm H2O
TV:6-8 ml/kg
RR:10-20 breaths/minute
TU:5-15 cm H2O
PEEP:5-10 cm H2O
CPAP:3-15 cm H2O

NAVA – Neurally Adjusted Ventilatory Assist

NAVA controls ventilation by capturing the electrical impulses in the patient’s diaphragm via an esophageal catheter (Edi).

There are three main settings in NAVA; NAVA level, PEEP and O2 concentration all of which must be set before starting. What is needed besides the SERVO-in ventilator is the NAVA software, an Edi module and an Edi catheter. The Edi catheter is placed in the esophagus as a common ventricular probe. NAVA provides good synchronization between patient and ventilator and reduces the discomfort of the ventilator treatment. NAVA provides possibilities for lung protection treatment by avoiding giving too much or too little respiratory support. Optimal synchronization favors spontaneous breathing. The Edi signal can be used as a support in deciding whether to weigh the ventilation treatment. The Edi signal can be used as a surveillance parameter because it provides information which allows ventilation to be “ventilator controlled”, the desired volume of time, fan settings, and can provide information about sedation and exhaustion from the ventilator. The Edi catheter is available in sizes between 6 and 16 Fr. The catheter can also be used to give an esophagus discharge on ECG. The Edi signal is obtained as a peak value and a valley value. When the patient triggers a breath, gas flows with a variable pressure proportional to the patient’s Edi. The highest possible pressure is 5 cm H2O lower than the preset upper pressure limit. Edi trigger can be set between 0.1 – 2 μV. Set a lower trigger level if no breath is given while there is a sufficient Edi signal. Increase the Edi trigger level if there is a sufficient Edi signal. Increase Edi Trigger Level if too many breaths are caused due to noise in the signal. The trigger is displayed with a symbol and a color mark on the curve.

There are four basic settings in NAVA: NAVA level, PEEP, O2 konc. and Edi triggers. In the ventilator, set the NAVA level (cmH2O / μV), PEEP (cm H2O), oxygen concentration (%) and Trigger Edi (μV). The basic setting of Trigger Edi is 0.5 μV (0.1 – 2 μV). Pressure support sets the trigger sensitivity, inspirational cycle (off), and pressure support over PEEP.

NAVA Peak = NAVA level x (Edi peak – Edi min) + PEEP. Estimated NAVA peak appears in the ventilator display.

NAVA-modeNormal settings in NAVA-mode
NAVA level1,5-2,0 cm H2O/μV
Trigger Edi0.5 μV
PEEP:5-10 cm H2O

PCV – Pressure Controlled Ventilation

Controlled breathing, patients does not need to breathe by themselves. The ventilator provides breaths with a constant predetermined pressure with decelerating flow for a predetermined inspiration time and with preset secondary frequency. The ventilator always gives a decelerating flow in the breathing air. Provides lower peak pressure compared to volume controlled ventilation. Reduces the risk of pressure in the lung tissue and may be beneficial to ARDS. In pressure controlled ventilation the top pressure is equal to the plateau pressure. Pressure-oriented operating modes maintain a constant set of pressure under inspiration (pressure control, pressure support). PC is used primarily in the treatment of moderate or severe pulmonary failure.

PC - Pressure Controlled VentilationNormal settings
PS:5-15 cm H2O
TV:6-8 ml/kg
RR:12-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-15 cm H2O

PEEP – Positive End-Expiratory Pressure

Increased resistance in exhalation of intubated patient via a valve connected to the ventilator. PEEP provides recruitment of the lung tissue and increases oxygenation. Airway pressure is not allowed to fall back to atmospheric pressure at the end of exspiration. PEEP is usually used in combination with any of the aforementioned ventilation methods. Provides a basic setting in all ventilation modes of the ventilator. The PEEP valve controls the exhalation valve via power steering. Used primarily in lung edema or atelectases.

PEEP can lead to impaired venous reflux and impaired hemodynamics as a consequence of blood pressure drop. May also lead to increased brain swelling and should be limited when increased intracranial pressure. Best effect in extrapulmonary causes of breathing failure such as obesity or heart failure. Has the best effect early in the course of severe lung disease. Normal levels of PEEP are 5-10 cm H2O, at ARDS higher resistance may be required as 10-20 cm H2O. Has more effect on diffuse infiltrates than located. At high PEEP, the lung can be overdispersed and damaged, with the risk of pneumothorax in pronounced cases. At high PEEP that gives rise to PCO2, the lung is overexpressed by poorer gas yield

PEEP-level: 3-20 cm H2O.

Positive End-Expiratory Pressure (PEEP)

Ventilator settingsHealthy lungModerate pulmonary failureSevere pulmonary failure
Tidal volume ml/kg< 6-8< 6-8< 6-8
Respiratory rate15-2015-2015-30
I:E quote1:21:2-1:11:1 - (2:1)
PEEP cm H200-55-1010-20
Oxygen fraction %< 4040-6040-100
Lung recruitement (RM)-YesYes, at an early stage

PS – Pressure Supported Ventilation

Assumes spontaneous breathing and that the patient triggers every breath himself. The ventilator provides breath with a preset pressure that is constant throughout the inspiration time. All breaths are patient-triggered. Provides a decelerating flow in inspired air. Gives the top pressure you set. Reduces the risk of high pressure in the lung tissues and may be beneficial to ARDS. In pressurized ventilation the top pressure is equal to the plateau pressure. Used primarily during respiratory training and good spontaneous breathing. Pressure-oriented operating modes maintain a constant set pressure level during the inspiration (pressure control, pressure support). TU is used in the treatment of mild, moderate and severe pulmonary failure.

PS - Pressure Support Ventilation.Normala settings
PS:5-15 cm H2O
TV:6-8 ml/kg
RR:12-20 breaths/minute
TU:5-15 cm H2O
PEEP:5-10 cm H2O

SIMV – Synchronized Intermittent Mandatory Ventilation

Partially controlled breathing where the patient does not need to breathe himself. SIMV is a mixture of controlling and assisting ventilation modes. SIMV provides a guaranteed amount of predetermined breaths per minute. It also allows spontaneous breathing in-between the breaths. Thus, under the application of SIMV, both the patient’s assisted spontaneous breathing and the ventilator’s mandatory controlled breath are permitted. The breaths that the patient draws themselves is given either with deaccelerating or constant flow, that is volume controlled or pressure controlled breaths. SIMV is used primarily during weaning from the ventilator and good spontaneous breathing, usually in a transitional phase for spontaneous breathing. It can also be used for patients who do not enjoy volume controlled or pressure controlled ventilation. These patients have access to pressure reduction, ventilation and auto-flow (automatic control of inspiration flow). SIMV is used in the treatment of both moderate and severe pulmonary failure. Used for irregular breathing, during weaning or when the patient is about to breath by themselves

SIMV ASB (Assisted Spontaneous Breathing)

SIMV - modeNormal settings
ASB:3-12 cm H2O
TV:6-8 ml/kg
RR:5-10 breaths/minute
PS:5-15 cm H2O
PEEP:5-10 cm H2O
CPAP:3-7 cm H2O

VC – Volume Controlled Ventilation

Controlled predetermined respiration, patients does not need to breathe by themselves. The volume of each breath is predetermined. Always provides a constant flow in the breathing air. Provides higher peak pressure in the inhalation (final inspiratory) compared with pressure controlled ventilation. It reduces the risk of hypoventilation. In volume controlled ventilation, the peak pressure is higher than the plateau pressure. VC is used primarily in the treatment of mild or moderate pulmonary failure. In flow / volume-oriented breathing mode, a constant inspiration volume is maintained. In these breathing modes, additional flow can be triggered upon request under inspiration. Additional breaths can be triggered between the regular ones if the set trigger criterion is met.

VC - Volume Controlled VentilationNormal Settings
VC:5-15 cm H2O
TV:6-8 ml/kg
RR:12-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-15 cm H2O

VCPC – Volume Controlled Pressure Control

Controlled breathing, patients does not need to breathe by themselves. This mode of ventilation provides a decelerating flow in the inspired air. Gives sometimes higher peak pressure compared to pressure controlled ventilation. It also reduces the risk of hypoventilation, as well as controlling the pressure level so that the tidal volume is constant. Adjust the pressure to give the lowest possible pressure. VCPC is used in the treatment of mild, moderate and severe pulmonary failure.

VCPS - Volume Controlled Pressure SupportNormal Settings
PC:5-15 cm H2O
TV:6-8 ml/kg
RR:12-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-15 cm H2O

Lung recruitement (RM)

By Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2018-12-21

These maneuvers (RM) are rarely effective later than 48 hours after the onset of ARDS and can also cause serious damage. In all pulmonary recruitment, circulation and pulse oximetric saturation should be carefully monitored. Lung recruitment has the best effect early in the course of respiratory collapse and development of acute pulmonary failure.

Method 1

Insufflate an air oxygen mixture in the lung to an airway pressure of 40-50 cm H2O for 20-30 seconds. Continue to ventilate in the usual way, but initially keep a PEEP of 15-20 cm H2O. The manoeuvre can be repeated again after a few minutes if the oxygenation does not improve. During and after insufflation, use as low oxygen content in the respiratory gas as possible to minimize the development of absorption electrolysis. The PEEP level can then be slowly reduced if the arterial saturation is maintained. The above can either be achieved by allowing the ventilator to prolong the lung long-lasting by placing the ventilator on CPAP respiration (continuous positive airway pressure) at a total pressure of 40-50 cm H2O or by prolonging the inspiration time under pressure controlled ventilation and adjusting the ventilator to total peak pressure becomes 40-50 cm H2O. You can also manually perform the same maneuver using a breathing balloon with a plugged-in manometer. It is extremely important that the airway pressure is maintained at least at the PEEP level after maneuvering and not allowed to fall to zero or to be negative. Therefore, avoid if possible airway suction at this stage.

Method 2

The lungs insufflates frequently with an airway pressure of 40-50 cm H2O over a period of 5-10 minutes. This is accomplished by setting the ventilator at a low respiratory rate (10 / min), a long inspiration time (50 percent), a 20cm H2O PEEP and a total peak pressure (including PEEP) of 40-50 cm H2O and ventilating with these settings For 5-10 minutes. Thereafter, the ventilator is set to the settings indicated under Method 1.

CPAP – Continuous Positive Airway Pressure

By Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2018-12-21

Increased resistance to breath. Requires spontaneous breathing and that the patient triggers every breath. Can be done with the patient in the ventilator or with a closed breathing mask with a pressure valve. Can be combined with pressure-sustained breaths in a BiPAP system or CPAP with ASB. A pressure in addition to the atmospheric pressure is maintained throughout the breathing cycle (exspiration + inspiration + paustid). CPAP facilitates inhalation but exacerbates exhalation. The term CPAP is usually used for patients with spontaneous breathing.

The CPAP system provides high airflows (80-100 l/min) with constant pressure and flow through mask ventilation. The system can, to some extent, compensate for losses during malfunctioning mask ventilation. Provides recruitment of the lung tissue and increases oxygenation. Used primarily for sustained respiratory pressure in case of pulmonary edema or atelectasis. CPAP can be dangerous in case of insufficient breathing power. The advantage is that the airway is kept open and that the FRC increases, which facilitates breathing. CPAP is stressful for the patient in the long run and tires out the patient. In the case of pneumonia, it may lead to respiratory collapse. It is very effective against pulmonary edema.

Normala settings in CPAP
CPAP-level3-10 cm H2O


By Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2018-12-21

Optiflow is a type of respiratory support for patients with spontaneous breathing that allows airway breathing with resistance breathing without tight closing mask. Optiflow, therefore, provides many times better comfort and less effort for the patient than CPAP in tight-closing mask. Optiflow uses oxygen in a very high air flow, 20-60 L / min with active NHF nasal high flow. The system can be connected either by nasal grid or tracheal coupling. It enables comfortable and efficient delivery of up to 100% inhaled oxygen.


High oxygen demand almost always means dehydrated airways and poor secretion. Active oxygenation of oxygen can be used for spontaneous breathing when the oxygen demand is high but there is no need for positive pressure of CPAP or NIV. Active humidification thus allows high inhaled oxygen concentrations without dehydration of the respiratory tract. Gas flow rate greater than 20 liters / minute also creates a certain positive airway pressure (low), as well as a recovery of exhaled gas from the nose / throat which minimizes carbon dioxide recontamination. Preferred oxygen content is controlled by the gas blender.


This method can be used instead of oxygen mask when you want to avoid dehydration of the upper respiratory tract.  For instance, when switching between NIV and mask ventilation or for long-term oxygen demand. Gas flows up to 35 liters / minute can be tested without a physician’s recommendation. Higher flow rates are only used after approval by the responsible physician. Exercise from non-invasive respiratory treatment may be as good with Optiflow as close-fitting mask (NIV).


• Unconsciousness• Carbon dioxide retention• Skull base fracture• Liqourrhoe, aka leakage of cerebrospinal fluid• Nose fracture• Nose blood in the family• Thrombocytopenia <85• Nasal strictures• Recently performed surgery in the nose region Practical instructions Material• Mixer / flowmeter• Humidifier Fisher & Paykel• Hose set with hose and humid chamber• Gas connection to the humid chamber• Sterile water• Optiflow nasal prong• Optiflow tracheal connection

1. Connect the mixer / flowmeter to air and oxygen outlet. 2. Bring out the hose and connect the humidity chamber to sterile water. 3. Place the blue breathing hose on one outlet of the humid chamber and the adapter on the other. Yellow-labeled cable now only warms the inspiration hose. Blue-labeled cable measures the temperature of the inspirational hose. 4. Turn on humidifier 5. The humidifier should be on invasive ventilation, it can not be adjusted to an exact degree since it automatically adjusts; container 35.5 – 42o, airway 35 – 40o. It warns of low temp, <35.5o, and high temp, respectively> 41o. 6. Set the desired oxygen value (FiO2) to the mixer. 7. The flow from the mixer should be at least 20 liters / minute to provide the correct oxygen concentration. The maximum flow that can be set is 60 l / min. The aim of the high flow is to exceed the patient’s inhalation flow and therefore create a minimal dilution with room air. In this way, the patient will get the predetermined oxygen amount. 8. Connect Optiflow nasal grid / Optiflow tracheal coupling to the blue humidifier hose and connect to patient. Increase gas flow gradually at start-up until humidifier has approached operating temperature.

Optiflow via nasal prongs

Optilfow bild

Optiflow via tracheal connection

Active humidification via high flow Optiflow tracheal connection is a good alternative to patients with tracheostomy who breathes spontaneously though periodically, for example in ventilator weaning.The blue cup is cup-shaped to capture the original secretion. May be removed and cleaned with sterile water. The system is connected in the same way as described above.


A patient who has a speaking valve has an extremely limited ability to moisten the respiratory tract. By switching on Optiflow nasal prongs during the time the valve is used, the patient can achieve a good humidification with the help from oxygen gas. You can thus refrain from connecting oxygen through the valve.Replacement / CleaningApply sterile water by 1 time a day. Hoses / grim / tracheal connection are for one patient at a time and are changed once a week. Clean the halter with sterile water if necessary.


If the humidifier does not reach the predetermined temperature, empty if possible the condensate water at temperature probe and check that the hoses are warm. Make sure that the temperature probe is installed from above and properly pressed!LEDs show what triggered possible alarms. Tip: Hold the humidifier’s “silent alarm” button to read the temp on multiple measurement points.

Maquet/Siemens (Getinge) ventilators

By Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2018-12-21

Servo-I Maquet, Siemens Servo 300, Siemens Servo 900 C

Siemens has been incorporated by other companies, the Getinge Group and Maquet. Servo-I is made by Maquet.

Maquets and Siemens Servoventilators use controlled and supported breathing patterns.

Volume controlled ventilation (VC), Pressure controlled ventilation (PC), Volume controlled pressure support (VCPS), Pressurized ventilation (PV) and SIMV (Synchronized intermittent mandatory ventilation). The servo ventilator has Automode, improved volume support, new SIMV combinations (synchronized intermittent compulsory ventilation) and Open Lung Tool. The Siemens Servo 900 C has Volume Control Ventilation (VC) and Pressure Controlled Ventilation (PC) as the base. Servo-I (Maquet) has volume control pressure support (VCPS) as basic but equally good possibilities for VC and PC and several other breathing patterns. The ventilator can be used for accurate measurements of controlled, assisted ventilation or spontaneous breathing/CPAP.

Maquet/Siemens (Getinge) VentilatorsNormal Settings
PS:5-15 cm H2O
TV:6-8 ml/kg
RR:5-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-15 cm H2O
ASB:3-12 cm H2O
CPAP:3-10 cm H2O
Maquet/Siemens (Getinge) ventilators,Display Settings
Pulmonary Airway Pressure (Paw): Peak Pressure, Plateau Pressure, Airway mean pressure , PEEP
Minute volume (MV):Inspiratory MV, Expired MV, Spontaneous MV,
Tidal volume (VT): Inspired TV, Expired TV
Respiratory Rate (RR):RR , Spontaneous RR
Breathing Work (WOB):WOB in patient & ventilator, Shallow breathing index (SBI)
O2-concentration:Inhaled O2- Fraction (FiO2)
Time Measures:Inspiration-/Expiration (I:E), Inspiration-/tot. Respiratory time (TI/TTOT), Time constant (TC)
Lung mecanics: Respiratory restistance, Compliance (C) static (in the respiratory system), Dynamic elastanse (E)
Air temperature: 10-40 °C
Configuration of Curves:Airway Pressures vs Time, Flow vs time, Volume vs time, CO2 vs Time
Capnography: End-tidal CO2-conc. (etCO2), Minute elimination of CO2, Tidal CO2 elimination (VTCO2)
Trends: MV, TV, RR, PEEP, R, C, etCO2, Peak-, plateau & mean pressures
Loops:Paw vs Vol, Flow vs Vol.
Oxygen Saturation (SpO2):SpO2, Pulse

Datex-Ohmeda (GE Healthcare) ventilators

By Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.

Updated 2018-12-21

ADU – Aisys Carestation

Aisys has a variety of breathing modes to choose from. Volume Controlled Ventilation (VCV), Pressure Controlled Ventilation (PCV), Pressure Supported Ventilation (PSVPro (Pro = Protection)), SIMV (Synchronized Intermittent Mandatory Ventilation, SIMV-VC, SIMV PC), PCV-VG: Pressure-Controlled Ventilation With Volume Assurance and CPAP / PSV. Aisys has improved volume support and various new SIMV combinations (synchronized intermittent compulsory ventilation). Aisys have volume controlled ventilation (VCV) as a base but equally good possibilities for PC (PCV-VG) and other selective breathing patterns. The ventilator can be used for accurate measurements of controlled, assisted ventilation or spontaneous breathing/CPAP-PSV. The ventilator’s compressed air is located on the back of the respiratory system. A precision valve controls the flow of gas to the patient. Under inspiration, this gas flow closes the exhalation valve and pushes down the bellows. During expiration, a small flow exhalation membrane presses to apply a PEEP pressure.

ADU Carestation VentilatorsNormal Settings
PS:5-15 cm H2O
TV:6-8 ml/kg
RR:5-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-15 cm H2O
ASB:3-12 cm H2O
CPAP:3-10 cm H2O
ADU Aisys Carestation ventilatorDisplay Settings
Pulmonary Airway Pressure (Paw): Peak Pressure,"Plateau Pressure", Airway mean pressure , PEEP
Minute volume (MV):"Inspiratory MV ", Expired MV, Spontaneous MV
Tidal volume (VT): Inspired TV, Expired TV
Respiratory Rate (RR):"RR","Spontaneous RR "
Breathing Work (WOB):WOB in patient & ventilator, Shallow breathing index (SBI)
O2-concentration:Inhaled O2- Fraction (FiO2)
Time Measures:Inspiration-/Expiration (I:E), Inspiration-/tot. Respiratory time (TI/TTOT), Time constant (TC)
Lung mecanics: Respiratory restistance,"Compliance (C) static (in the respiratory system)", Dynamic elastanse (E)
Apnéa Time
Air temperature: 10-40°C
Configuration of Curves:"Airway Pressures vs Time ", Flow vs time,"Volume vs time ",CO2 vs Time
Capnography: End-tidal CO2-conc. (etCO2), Minute elimination of CO2, Tidal CO2 elimination (VTCO2),
Trends: MV, TV, RR, PEEP, R, C, etCO2, Peak-, plateau & mean pressures"
Loops: Paw vs Vol, Flow vs Vol.
Oxygen Saturation (SpO2):SpO2, Pulse,
You choose standard settings or "Paw-Manom, Loops, Big curves or Local"

Dräger ventilators

By Kai Knudsen, Senior Physician in Anesthesia & Intensive Care. Sahlgrenska University Hospital.
Updated 2018-12-21

Evita XL, Evita 4, Pulmovista

Dräger ventilators use several breathing patterns (breathing mode) such as: IPPV, BiPaP, BiPaP Assist, CPAP + ASB, SIMV, APRV, MMV.

Respiratory mode provides different types of assisted or controlled ventilation via mask or endotracheal tube. The fans have advanced breathing modes such as the “open breathing system” in Auto-Flow, APRV, and graphical support tools integrated in the display as default. Typically, the airway pressure in CPAP breaths and in assisted breaths (ASB) is usually set at 5-12 cm H2O.

Dräger Evita VentilatorsNormal Settings
PS:5-15 cm H2O
TV:6-8 ml/kg
RR:5-20 breaths/minute
PS:5-15 cm H2O
PEEP:5-15 cm H2O
ASB:3-12 cm H2O
CPAP:3-10 cm H2O
Dräger Evita VentilatorDisplay Settings
Pulmonary Airway Pressure (Paw):Peak Pressure, "Plateau Pressure ", Airway mean pressure , PEEP
Minute volume (MV):"Inspiratory MV ", Expired MV, Spontaneous MV, MV leakage
Tidal Volume (VT):Inspired TV,Expired TV, Assisted Spontaneuos TV (VTASB)
Respiratory Rate (RR):" RR ", "Spontaneous RR ", Obligatory RR,
Breathing Work (WOB):WOB in patient & ventilator, Shallow breathing index (SBI)
O2-concentration:Inspiratory O2- Fraction (FiO2)
Time Measures:Inspiration-/Expiration (I:E), Inspiration-/tot. Respiratory time (TI/TTOT), Time constant (TC)
Lung Mecanics:Respiratory restistance, "Compliance (C) static (in the respiratory system)", Dynamic elastanse (E)
Apnéa Time
Air temperature: 18-51°C
Configuration of Curves:"Airway Pressures vs Time ", Flow vs Time“ , "Volume vs Time ", CO2 vs Time
Capnography: End-tidal CO2-conc. (etCO2), Minute Elimination of CO2, Tidal CO2 Elimination (VTCO2)
Trends: "MV, TV, RR, PEEPi, R, C, etCO2, Peak-, plateau & mean pressures"
Loops:Paw vs Volume, Flow vs Volume
Oxygen Saturation (SpO2):SpO2, Pulse


Restrictive pulmonary disease

Lung fibrosis / Bronchiolitis / Interstitial pneumonia

Idiopathic interstitial pneumonia (IIP)

Is a group of several interstitial lung diseases.

IPF – Idiopathic pulmonary fibrosis

Previously, the diagnosis IFA (Idiopathic Fibrotating Alveolitis) has also been used. IPF is morphologically equivalent to UIP (“usual interstitial pneumonia”). Common symptoms are shortness of breath, fatigue and cough.

UIP/NSIP (Usual Interstitial Pneumonia – UIP)

The etiology is unknown. The disease responds poorly to treatment and has a poor prognosis. These patients usually need to be transplanted, both lungs being replaced. Lung transplantation has a 5-year mortality of about 70-75%.

  • UIP is also called cryptogenic fibrotizing alveolitis
  • Histological pattern is called common interstitial pneumonia
  • In order for the diagnosis of Idiopathic pulmonary fibrosis to be made, a specific histological pattern must be demonstrated, while other known causes of the pathology are excluded.
  • Other known causes of the pattern formation: asbestosis, collagen vascular diseases, etc.
  • Men are more commonly affected than women
  • Two thirds of patients are older than 60.
  • Leads to severe hypoxemia and cyanosis.

Morphology at UIP

  • One sees a specific histological pattern called interstitial pneumonia (UIP)
  • Macroscopically, the surface of the lung resembles cobblestones due to. scars in interlobular septa contracted.
  • The cut surface shows fibrosis (solid rubber-like white surfaces)
  • The lower lobes dominate the fibrosis
  • Microscopically, spotted interstitial fibrosis is seen, which varies in intensity and over time. A lot of fibroblasts occur initially, then more collagenous wounds that are not as cellular. The walls of the alveoli collapse. Cysts are formed that are lined with type-2 pneumocytes or bronchiolar epithelium (“honeycomb pattern”). The pulmonary arteries often change as a result of pulmonary hypertension with hyperplasia, intimate and media thickening.

Clinical picture

  • Insidious disease course with gradual deterioration of lung function. The patient develops unproductive cough and gradually more shortness of breath.
  • Dry or “velcro-like” inspirational rattles are common
  • Cyanosis, cor pulmonale, peripheral edema may occur later

Nonspecific interstitial pneumonia (NSIP – nonspecific interstitial pneumonia)

Dyspnoea and cough for several months are the most common symptoms. The diagnosis NSIP can be established when the patient has pneumonia with interstitial changes without another diagnosis either cellular or fibrous histopathological pattern. The cellular pattern means a better prognosis for the patient than the fibrous one.

  • NSIP shows a different histopathological pattern than that of idiopathic pulmonary fibrosis
  • NSIP has a better prognosis than idiopathic pulmonary fibrosis, so the diagnosis is important to make.


  • Cellular changes with mild to moderate chronic interstitial inflammation with lymphocytes and some plasma cells. You can see a uniform or spotted pattern.
  • Histopathologically, the fibrous changes are seen to have diffuse or patchy interstitial distribution in which all scars are equally obsolete (unlike the idiopathic pulmonary fibrosis which has the appearance of scars of different ages).
  • Fibroblast foci are usually absent.

BOOP, COP (Bronchiolitis Obliterans – Organizing Pneumonia)

Responds better to treatment. Treatment is given with steroids, cortisone. BOOP has a relatively good forecast.

Cryptogenic Organizing Pneumonia (COP / BOOP)

  • Also known as Bronchiolitis Obliterans Organizing Pneumonia (BOOP)
  • Cryptogen = unknown etiology
  • You see patchy consolidation (densification) of the airways. The infiltrates look the same as in a pneumonia, but have the peculiarity that they move with time. The symptoms are also the same.
  • The disease is often diagnosed in an infection ward where a patient with pneumonia does not respond to antibiotics.
  • Then a new lung X-ray is taken and you can see that the infiltrate has moved. Treatment is usually given with cortisone and the patient improves.
  • Polyparate plugs of loose connective tissue form in alveolar ducts, alveoli and bronchioles
  • The connective tissue is the same age everywhere
  • The lung architecture is intact
  • Some patients recover spontaneously, but most require treatment with oral steroids for 6 months or more.
  • This disease can also occur as a complication of infections or inflammatory damage to the lungs.


  • Non-cancerous diseases that occur due to inhalation of mineral dust, organic and inorganic particles as well as chemical fumes and vapors.
  • The most common mineral-induced pneumoconiosis is the result of inhalation of carbon dust, silica and asbestos.
  • These diseases are almost always work-related and were more common in the past.


  • The particles are most harmful if they get stuck in the bifurcations in the distal airways.
  • > 500 μm particles are too large to get out
  • < 0.5 μm large particles tend to act as gases and move in and out of the alveoli without depositing and causing any particular damage.
  • 15 μm particles are the most dangerous.
  • Carbon is quite inactive and large amounts must be deposited in the lungs to cause damage.
  • Silica, asbestos and beryllium are more reactive and lead to fibrous reactions at lower concentrations.
  • Most particles get stuck in the cilia and are brought up again by mucous mucus.
  • Some, however, get caught up in bifurcations and attract macrophages that endocyte them.
  • The more reactive particles then trigger the macrophages to release substances that initiate an inflammatory response with fibroblast proliferation and collagen deposition.
  • Some particles can reach the lymph nodes via drainage or inside migrating macrophages and thus initiate an immune response against components on the particles or their own proteins that have been modified by the particles.
  • Leads to strengthening and widening of the local reaction.
  • Tobacco smoking exacerbates the effects of all inhaled mineral dust. This is especially true for asbestos.

Coal worker pneumoconiosis

  • Occurs (mainly in the past) in coal workers due to the coal dust they breathe in during mining
  • Affects different patients differently: asymptomatic anthrax (cold dust lung): Pigment accumulation without visible cellular reaction.
  • Simple charcoal worker pneumoconiosis: accumulation of macrophages with little or no pulmonary dysfunction.
  • Complicated charcoal worker pneumoconiosis: Fibrosis is extensive and lung function is affected
  • The patient develops progressive massive fibrosis (PMF)
  • Wide range of clinical effects: from asymptomatic pigmentation to mild dysfunction to pulmonary dysfunction, pulmonary hypertension and cor pulmonale.
  • Fibrosis (PMF) tends to worsen without inhaling more carbon.
  • Coal mining dust contains a number of trace metals that can increase the harmful effects of coal in the dust.
  • No increased risk of bronchogenic carcinoma in coal workers compared to the standard population if smoking is taken into account as a risk factor. This distinguishes the carbon exposure from the silica and asbestos.


  • Most prevalent chronic occupational injury in the world.
  • Inhalation of crystalline silica: In the form of i.a. quartz, cristobalite, tridymite (quartz most common cause of silicosis of these)
  • Pathogenesis: the silicon particles are eaten by macrophages and activate them due to its reactivity. The macrophages release IL1, TNF, fibronectin, lipid mediators [PG, TX?], Free radicals, fibrogenic cytokines [PDGF, TGFβ?]
  • Silicon has a less toxic effect when mixed with other metals.
  • Miners who mine hematite ore may have more silicon in their lungs than some sick quartz-exposed workers, but still have a relatively mild disease due to. that the iron in the ore has a protective effect.
  • Silicosis is usually detected during routine X-ray examinations of asymptomatic workers exposed to silica fume.
  • Fine nodules are found in the upper lungs, but the effect on lung function is usually small or non-existent.
  • Symptoms appear later when the disease progresses to PMF. Then patients get pulmonary hypertension, cor pulmonale.
  • It takes a long time before you die of the disease, but the ability to work can be greatly reduced due to reduced lung function.
  • Silicon exposure increases the risk of tuberculosis, probably due to repression of cell-mediated immune systems and making it more difficult for macrophages to destroy phagocytic bacteria as a result of the silicon crystals they have eaten.
  • Silica crystals are carcinogenic.


  • Asbestos exposure causes parenchymal interstitial fibrosis (asbestosis), localized fibrous plaques or diffuse fibrosis in the pleura, pleural effusions (fluid in the pleura), bronchogenic carcinoma, laryngeal carcinoma, malignant pleural and peritoneal mesothelioma.
  • Whether or not the exposure makes the person ill is determined by the concentration, size, shape and solubility of the asbestos.
  • Serpentine asbestos is curly and flexible. It sticks more easily to the mucus of the upper respiratory tract and is transported out of the lungs. It is also more water-soluble and thus leaches out of the lung tissue if it is stuck further down.
  • Amphibole asbestos is the fiber straight, stiff and brittle. It is mostly pathogenic. The amphibole asbestos particles lie straight in the air stream and thus pass further down into the airways. They can penetrate the airway epithelium down there and enter the underlying connective tissue.
  • However, both forms can produce asbestosis and cancer.
  • Asbestos causes fibrosis by interacting with lung macrophages.
  • Asbestosis causes progressively worsening dyspnoea that occurs 1020 years after asbestos exposure. Usually patients also get productive cough (sputum is coughed up)
  • The disease can remain static or progress to heart failure, cor pulmonale and death.
  • Patients have a 5-fold increased risk of developing bronchogenic carcinoma.
  • Cigarette smoking in connection with asbestos exposure greatly increases the risk of developing this cancer, smoking + asbestos = 50 times increased risk of bronchial carcinoma.
  • The risk of malignant mesothelioma is 1000-fold increased (this cancer is very rare, 217 cases per 1,000,000 ordinary people).
  • Pleural plaque: White plaques that sit on visceral / parietal pleura at hilus height. Can also sit on the diaphragm. If they contain calcium, they are pathognomonic for asbestosis.

Drug-induced and radiation-induced lung disease

  • Both acute and chronic injuries to the lungs.
  • Bleomycin, a cancer drug, can cause pneumonitis and interstitial fibrosis due to direct toxicity of the drug and through the migration of inflammatory cells to the alveoli.
  • Amiodarone (Cordarone), an antiarrhythmic drug, can also cause interstitial fibrosis and pneumonitis.
  • Radiation therapy for lung cancer causes acute pneumonitis after 16 months in 20% of all treated patients. Causes fever and dyspnoea disproportionate to the amount of lung irradiated. May heal with corticosteroid therapy or turn into chronic radiation pneumonitis.

Granulomatous diseases


  • The most common idiopathic interstitial lung disease.
  • Sarcoidosis is a multisystem disease with an unknown etiology.
  • Characterized by non-caseous granuloma formation in many organs and tissues. In the lungs, granuloma formation occurs in the parenchyma and in the mediastinal glands.
  • Mycobacterial and fungal infections can also cause these granulomas, so the sarcoidosis diagnosis is made only when they have been ruled out.
  • Involvement of the lungs in many cases gives the main symptoms that cause the disease to be detected.


  • Acute: The acute sarcoidosis typically presents with bilateral angry arthritic arthritis, more often in women. The patient has a fever, low/no CRP and has a history of cough for a while.
  • Chronic: Uveitis/iritis. Prolonged cough.
  • Skin rash: Seen on skin involvement. Reddened rashes that tend to settle in old scars (after operations, for example), which then change shape. Biopsy shows granuloma. Erythema nodosum (tuberose).
  • Very varied course.
  • Completely asymptomatic in many individuals.
  • 2/3 of those who get symptoms get respiratory symptoms.
  • Shortness of breath, dry cough, vaguely substantial discomfort


  • Pulmonary X-ray: Shows bilateral hilus lymphoma. Unilateral lymphoma indicates TB / lymphoma / lung cancer.
  • Diagnosis is made when the non-caseous granulomas are found in a biopsy and all other known causes for their origin have been ruled out.
  • Serum ACE: Indicates disease activity.


  • Corticosteroids: 40 mg prednisolone in a phase-out schedule.
  • Methotrexate: The absolute indication for treatment is: Sarcoidosis + uveitis


  • 60-75% of affected individuals recover with minimal or no remaining damage. Those with acute onset disease have a better prognosis.
  • 20% get permanent lung dysfunction or visual impairment. The disease can also affect other organs (CNS, heart)
  • 10-15% succumb to progressive pulmonary fibrosis and cor pulmonale.

Allergic alveolitis (hypersensitivity pneumonia)

  • Called allergic alveolitis as it affects the alveoli unlike asthma which mainly affects the bronchi.
  • Immunologically mediated inflammatory disease: A mixture of type III (immune complex) and type IV (cell mediated) hypersensitivity.
  • Most commonly resulting from increased sensitivity to stale hay or other antigens inhaled in the workplace (agriculture).
  • The triggers are very different, but the syndromes that occur have similar clinical and pathological findings and probably very similar pathophysiology.
  • Examples of agents: Bacteria, fungi, animal proteins (pigeon, budgerigar, rats, pigs, cows), chemicals
  • Names after triggering agent: “Farmer’s lung, Birdfencer’s lung, Sawmill lung”.
  • Provides restrictive lung disease with reduced diffusion capacity, compliance and total lung volume.


  • Mottled mononuclear infiltrates of the lung interstitium
  • Interstitial non-caseous granulomas (as in sarcoidosis) are seen in 2/3 of cases.
  • In advanced chronic cases, diffuse interstitial fibrosis occurs.


  • Acute reaction 48 hours after exposure to the antigen: fever (39 degrees), dry cough, dyspnoea, myalgia, arthralgia
    If the exposure to the antigen disappears after the acute attack, the disease heals completely.
  • Chronic disease: If the antigen is not removed from the environment, the patient eventually develops chronic interstitial lung disease (diffuse interstitial changes in the lungs) but the acute more severe episodes after exposure.
  • Insidious chronic illness with productive cough, dyspnoea, fatigue, nausea and weight loss.


  • Rattle and ronki and possibly. cyanosis in acute form.
  • Precipitating antibodies to mold panel.


  • Cortisone in tapering in acute illness.
  • Remove the agent! If this is done, lung function can be completely restored. If there has been fibrosis, however, the disability is permanent. Eliminating an agent can in many cases mean a major life change. A farmer may have to stop working on his farm, for example.