Learning Intubation: Head Position Effects Laryngeal View

When first learning intubation,  a beginner often concentrates on memorizing the key laryngeal anatomy. This is important of course. If you can’t recognize the vocal cords, you will not be able to successfully intubate. However, even more important to learning intubation is understanding how the larynx relates to the other structures in the head and neck. In order to intubate you must manipulate those other structures to bring the larynx into view.

A prior post, When Learning Intubation Is Hard, described in detail some of the most common barriers to learning to intubate. Here I will concentrate on helping you see how head position effects your ability to see the larynx.

Larynx Location In The Neck

To feel your own larynx, place your hand on the front of your neck, with thumb and forefinger on either side of the firm, roughly cylindrical shape in the midline.

Illustration showing Relationships thyroid and cricoid cartilage to cricothyroid membrane

Relationships thyroid and cricoid cartilage to cricothyroid membrane

The adult larynx lies opposite the 5th, 6th cervical vertebrae, as opposed to the infant larynx that lies opposite the 2nd, 3rd and 4th. The fact that the infant larynx is higher in the neck leads to greater risk of airway obstruction and a need to slightly alter technique during pediatric intubation. A link to how to intubate the pediatric patient is located at the end of this article. Here we will concentrate on the adult.

The larynx is located in front of the esophagus in the neck. The opening to the larynx, called the glottis, and the opening to the esophagus are immediately adjacent to each other. Misidentification of the esophagus as the glottic can lead to esophageal intubation.

Illustration showing how easy it is to insert a laryngoscope blade too deeply and hide the larynx during intubation of an infant or small child

It’s very easy  to insert the laryngoscope blade too deep, as in the right picture. If too deep you will not see recognizable anatomy because you are looking down the esophagus and hiding the larynx.

 

Photo of view during laryngoscopy, on the left the esophagus is seen "tented" to appear like the larynx, on the right the larynx.

If you insert your blade too deep you will hide the larynx underneath. This action also tents the esophagus and can made it mimic the glottic opening if you are not careful.

How The Larynx Relates To Other Structures

Look at this lateral Xray  of a head in neutral position. The outline of the epiglottis, the hyoid bone, the thyroid cartilage and the cricoid cartilage are easily identified. Notice the relationship of the larynx to the esophagus. The larynx lies in front of the esophagus but the opening to the larynx (the glottis) and the esophagus are right next to each other. Accidental esophageal intubation is a risk with every intubation.

Lateral view Xray showing the distinct outlines of the parts of the larynx and their relationship to the jaw, tongue and cervical spine.

Lateral view Xray showing the distinct outlines of the parts of the larynx and their relationship to the jaw, tongue and cervical spine.

Now imagine yourself intubating this patient. what would you have to do to bring the larynx into view? How deep would you have to insert a Macintosh blade to  place the tip in the vallecula? How deep would you need to insert a Miller blade to lift the epiglottis?

Here is a CT scan of another adult patient. Notice that in this second patient the larynx is located higher in the neck.

Normal CT side view showing relationship of laryngeal structures to external anatomy

Normal CT side view showing relationship of laryngeal structures to external anatomy

Whereas the epiglottis in the first patient is low behind the tongue, this patient’s epiglottis is higher. The depth of insertion and the strategy to lift the epiglottis will change from patient to patient. Straight blades often work better in patients with a larynx higher in he neck and this may be one of those patients.

How Does Neck Position Affect The Larynx During Intubation

Let’s look at a lateral Xray of our first patient, but now with his head tilted all the way back in full extension. Patients with respiratory distress, will often tilt their heads back. You can see that this position more fully opens the airway and decreases resistance to breathing.

lateral Xray of the neck in full extension showing how the relationship of the larynx changes with respect to the rest of the neck structures. Extension without placing the patient in the sniffing position will hide the larynx behind the tongue, or a so-called anterior larynx.

Lateral Xray of the neck in full extension showing how the relationship of the larynx changes with respect to the rest of the neck structures. Extension without placing the patient in the sniffing position will hide the larynx behind the tongue, or a so-called anterior larynx.

During intubation, we need to tilt the head back to bring the axis of the oral and pharyngeal axes into alignment. But if the patient is not in a good sniffing position,  with the head moved slightly forward  in addition to being tilted, the larynx may remain hidden behind the tongue during laryngoscopy.

Let me rotate this image to show you what I mean.

Lateral neck Xray showing how extreme head extension, without the sniffing position, can make visualization of the larynx difficult.

Lateral neck Xray showing how extreme head extension, without the sniffing position, can make visualization of the larynx difficult.

You can now see how anterior that larynx would look during laryngoscopy. Pushing down on the cricoid cartilage might help rescue a difficult intubation in a situation like this, but optimal head and neck positioning from the beginning would work better.

When getting ready to intubate, always glance at the side of your patient and assess whether the head and neck are in an optimal position before you start. If it’s not optimal, try to fix it. That several seconds can save you, and your patient, potential trauma.

Head Position Also Affects Laryngeal Opening

As long as we are looking at X-rays, let’s look at our first patient with his head flexed fully forward. When the head is flexed forward, the structures in the posterior pharynx and the tongue tend to obstruct the airway. You can test this by flexing your head forward as far onto your chest as you can. It becomes much harder to take a breath.

lateral Xray showing that With the head flexed fully forward onto the chest, the airway is almost fully obstructed. Visualization of the larynx wold be impossible.

With the head flexed fully forward onto the chest, the airway is almost fully obstructed. Visualization of the larynx would be impossible.

While no one would position a patient’s head this way for intubation, it’s common for novices to place too many pillows under the head trying to obtain a good sniffing position. If the head is too high, the patient, and the intubator, will not be able to tilt the head back.  In other words, our novice intubator, trying to maximize sniffing position, sabotages himself. Again, prior to intubation take a look to the side of your patient. Try to tilt the head back (or have the patient tilt their head back).

When learning to intubate, learn the anatomical relationships, not just laryngeal anatomy.  A good intubator understands that knowledge of how those structures move in relationship to each other gives you the power to manipulate that anatomy to give you the best possible view during intubation.

Please share with your fellow students. I’ve included a list with links below to previous posts on learning intubation to help you perfect your skills. Feel free to ask questions. Let me know if there are any topics that you would find helpful.

May The Force Be with You

Christine Whitten MD, author
Anyone Can Intubate, A Step By Step Guide
and
Pediatric Airway Management, A Step By Step guide

LINKS TO PRIOR DISCUSSIONS WITH MORE DETAILS OF HOW TO INTUBATE:

 

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