Airway anatomy – and how we make it worse

“The best position to kill a patient in, from an airway perspective, is flat on their back.”
-Rich Levitan – @airwaycam

This is one of the most important concepts in emergency airway management. Rich knowszTXey5ETB this better than anyone, having examined 20 cadaveric airways per month for the past 16 years in addition to clinical research. He coined the term “coffin position” to describe the detriment of having your patient supine. Cannot Oxygenate Face Flat in Neutral position. There are a few reasons this is true and it is important to understand them. Not only will it help improve patient outcomes but it will make you better at managing airways.

The Upper Airway
When we talk about airway management we are talking about the upper airway. Barring any severe trauma or pathophysiology, the airway south of the glottic opening is intrinsically patent. We are really only worried about the passageway above the glottis which is made up of soft tissues that do not have spontaneous patency. Normally, patency is maintained by muscles controlled consciously and unconsciously. But when patients are obtunded or sedated they lose the ability to maintain upper airway patency.

Untitled
Graphic: airwaycam.com
People do not maintain a perfectly straight posture. The neck curves forward which maintains the head in a slightly forward position. From an airway perspective, this helps keep the tongue and other soft tissue off of the posterior pharynx. You can easily see how this is effected when you stand flat against a wall. You will see that placing your head straight back against the wall causes discomfort. This shortens the thyromental distance leaving less room for the tongue and decrease mouth opening. Obviously you can still breath as you are able to maintain conscious control of your airway. But compromised patients lose this ability when they are positioned this way. Now, take the a patient and lay them flat on their back. Not only do you misalign the upper airway but the tongue and soft tissues fall back with gravity. These two mechanisms will undoubtedly cause partial or complete airway obstruction in obtunded patients.

Airway xray
Left: Ear-to-sternal notch, Middle: Neutral, Right: Hyperextended                    Graphic: Rich Levitan
The Lungs
Bad things happen to the lungs when a patient as lying flat. It becomes much more difficult to fully recruit lung tissue. This is due to a number of factors and is much more profound in obese patients. The abdominal contents are no longer held off the diaphragm by gravity. They move upward and often push on the diaphragm preventing it from contracting fully. This also decreases the amount of thoracic space the lungs have to expand in. The net result is decreased amounts of usable lung tissue, lower functional residual capacity, and more difficulty recruiting alveoli. In addition, the obese have weight from fat which puts pressure on the chest and abdomen preventing lung expansion and contributing to the abdominal component of supine positioning. Obese patients desaturate significantly faster than average sized patients, mainly for this reason.

The Stomach
RSI is a technique that was designed with the stomach in mind, not the lungs. This is very important as it highlights one of the most detrimental complications during airway management, regurgitation. Vomiting can be active or passive. In an RSI scenario it is often passive as paralytics are given to help prevent it. However, active or passive vomiting can occur at any time during the airway management process. It is further encouraged by poor bag-valve-mask technique which insufflates  the stomach with air. It is imperative to try to minimize the potential for regurgitation as much as possible.

Intubation
The end goal of any airway scenario is to secure the airway in the most appropriate means. This is frequently through endotracheal intubation. In the emergency setting, I believe the most frequently neglected aspect of this process is positioning. Proper patient positioning is probably THE MOST IMPORTANT factor that contributes to obtaining an adequate view of the cords. Not surprisingly, the worst position a patient can be in for this is flat on their back.

The Solution
All of the problems discussed above can be drastically improved by properly positioning your patient. This goes for ANY airway scenario whether you are setting up to intubate or doing procedural sedation. These techniques will work in the vast majority of patients.

6-1version2withline_1
Graphic: airwaycam.com
1. Place the patient in the ear-to-sternal notch position.

This method involves aligning the external auditory meatus with the sternal notch in the horizontal plane. If your patient is supine you are essentially elevating the head higher than the surface of the bed. This is to get the patient into the more natural airway position as was discussed earlier. It is easily accomplished by placing a pillow or towels under the occiput. Obese patients require more padding, or ramping. In kids, obtaining the position may require elevating the shoulders instead.

 

Ear-to-Sternal-Notch
Graphic: RebelEM.com
The benefits of this position are substantial. First, it helps lift the tongue off the posterior pharynx reducing airway obstruction. It also drastically improves glottic view when intubating by properly aligning the airway and creating a more direct pathway to the cords. Also, adding a jaw-thrust to this position will create maximal airway patency in any situation.

2. Sit your patient UP!

If you can only take one thing away from this post it is this: sit your patient up. This goes for any type of airway management and post-intubation situation. If the airway is at all compromised, sit them up. There are quite a few reasons to do this and really no downfalls.
In the upright position the lungs are able to expand more fully. This increases the functional residual capacity and improves oxygenation. This is the reason that intubated patients should usually be upright post-intubation; it will maximize their lung recruitment and ventilation. It also aids in oxygenation prior to intubation.
When patients are upright their tongues are not as prone to falling posterior. Combined with the ear-to-sternal notch position an upright patient will have a more spontaneously patent airway than a supine patient.
The upright position is likely to decrease the chances of regurgitation and aspiration. This is simple gravity but also is due to decreased pressure on the stomach and improved bag-valve-mask mechanics.
BVM use will be easier and more effective in the upright position. The airway is maintained more patent thus allowing better ventilation and less gastric insufflation.
Airway views during intubation are better with the patient sitting upright at 30 degrees or more. This is due to better alignment of airway structures and less force being required to displace the soft tissues.

3. Perform a jaw thrust

A jaw thrust is the most effective way of maintain airway patency non-invasively. Simply doing a head-tilt, chin lift does not completely displace the tongue from the posterior pharynx. If a patient is experiencing anatomical airway obstruction a jaw-thrust is likely to resolve it by lifting the tongue and creating a pathway for ventilation. It is important to maintain a jaw thrust in any patient being BVM ventilated, not controlling their own airway, and during the apneic period of RSI. When using apneic oxygenation (which should be used during any RSI) the airway must remain patent via jaw thrust during the apneic period.

The bottom line: patients with a compromised airway should be positioned upright in the ear-to-sternal notch position. Use a jaw thrust to resolve anatomical airway obstruction.

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References:

  1. Khandelwal, N, et al. “Head-Elevated Patient Positioning Decreases Complications of Emergent Tracheal Intubation in the Ward and Intensive Care Unit.” Anesthesia and Analgesia 122.4 (2016): 1101-107.
  2. Levitan, Richard. Fundamentals of Airway Management. 3rd ed. Irving: Emergency Medicine Residents Association, 2015. Print.
  3. Weingart, Scott, and Levitan, Richard. “Preoxygenation and Prevention of Desaturation During Emergency Airway Management.” Annals of Emergency Medicine (2011): 165-75.

 

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Airway anatomy – and how we make it worse

5 thoughts on “Airway anatomy – and how we make it worse

  1. Matt says:

    Thoughts on using this upright or 30 degree technique during CPR. I’ve see the advantages of sitting patients upright for many respiratory issues, but never considered it feasible to attempt any elevation during a full code.

    Like

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