Airway Anatomy

I’m going to start this post with a story; you’ll understand the point in a minute.  When I was about six, I asked my dad why he took the family car to the mechanic instead of fixing it himself.  My dad responded that his father (my grandpa) had once taught him that “there are things you should learn how to do, and become an expert at.  And then there are things that you should learn to write a check for.”  I’ve always remembered that, and for this reason I take my car to a good shop, I take my taxes to an accountant each year, and I prefer craft beer over mass-produced stuff.

Airway management is not one of those things that we should leave to others.  As medical providers we must be experts at airway management.  For this reason, I’m going to spend the next several posts discussing some techniques, some equipment, and some skills that will hopefully be helpful.

First, however, we’re going to spend some time talking about airway anatomy.  It’s easier to understand how to change a car’s oil if you understand how all the parts fit together; medicine is the same.

Surface Anatomy:

Let’s take a few moments and look at the face.  Full disclosure; I don’t remember or use all of the formal terms in my daily practice.  However, there are a few that are helpful to remember.

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  • Nasal Bone:  The hard, bony surface between the eyes.  This is the bone that people talk about breaking when they break their nose.  Why It’s Important:  It’s also one of the landmarks used to properly place a bag-valve-mask (BVM) or microshield CPR mask during artificial ventilation.  Additionally, broken noses bleed like crazy, which can cause airway obstruction and vomiting.
  • Anterior Nares:  These are generally called “the nostrils.”  Why It’s Important:  We spend a lot of time attempting to maintain patency of the trachea, but we frequently overlook checking the nostrils for obstructions and blood.  Additionally, if we’re unable to open the patient’s mouth for any of a number of reasons, we can ventilate and oxygenate the patient through the nose.  Finally, placing a nasopharyngeal airway (NPA, a common airway adjunct) depends choosing the properly sized device based on the size of the nares.
  • Angle of the Jaw:  The angle of the jaw is located on either side of the face directly below the ears, at the point where the lower jaw (mandible) curves upwards to join the skull at the temporomandibular joint.  Why It’s Important:  If we suspect spinal injury and want to perform a jaw thrust maneuver to open the patient’s airway, the angle of the jaw is what we press forward on to move the patient’s jaw forward and open the airway without compromising the cervical spine.  Additionally, the “point” is an important measuring point which we use to correctly size nasal airways, oral airways, and suction catheters.
  • Lips:  Fatty/muscular tissue surrounding the mouth.  Why It’s Important:  Lips have a lot of blood flow and nerve endings, and the skin is very sensitive and easily damaged.  When injured, lips bleed a lot, which can cause airway obstruction and vomiting.  If you’re inserting airway adjuncts, suction catheters, or (if you’re an advanced level provider) attempting to intubate the patient, take care not to damage the lips.
  • Mental Protuberance:  This is generally called “the chin.”  Why It’s Important:  We use the point of the chin to life the jaw/head forward and up when performing a head tilt-chin lift maneuver.  Additionally, the small depression between the bony point of the chin and the lower lip is where we place the lower edge of a BVM mask or CPR microshield.  Finally, as you attempt to figure out why the patient is acting the way they are, make sure you stroke your own mental protuberance; it makes you look wise.
  • Thyroid Cartilage:  We generally call this the “Adam’s Apple,” and it tends to be far more prominent in skinny men.  However, folks of all gender have a thyroid cartilage.  It can be felt by running your fingers firmly down the midline of the neck; about half-way down, you should feel a “ridgy” feeling bulge.  Why It’s Important:  This is more for advanced providers (doctors, PAs, and paramedics, I’m looking at you).  When it comes to airway management, the final option when nothing else works is a surgical cricothyrotomy, or passing a tube into the trachea after making a surgical opening through the cricothyroid membrane.  Additionally, pressing down on the thyroid cartilage or manipulating it from side to side can aid in the placement of endotracheal tubes.

Internal Anatomy

Now that we understand some of the important surface anatomy landmarks, we can take some time to get to know the internal structures of the airway.  We generally divide the airway into two parts, called the upper and lower airways.   The upper airway is composed of the nasopharynx (nostrils and their air passages), the orophyaryx (the mouth and the back of the throat) and the larynx (the airway from the back of the mouth to the vocal cords).  The lower airway is composed of trachea starting at the vocal cords and continues to the small air passages in the lungs.  Generally, when we talk about airway management we’re talking about techniques for keeping the upper airway open.  Therefore, for the purposes of today’s post, we’re going to talk about the structures of the upper airway and save the lower airway for another day.

The Nasopharynx:  The nasopharynx is the most superior (“uppermost”) part of the upper airway, and is generally thought to stretch from the nostrils to the end of the nasal cavity.  The nasopharynx serves several major purposes:

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  • Air Flow:  Air enters through the nares, travels through the nasal cavities, and joins the oropharynx through two small openings in the back of the mouth.  The two nasal cavities (one for each nostril) are separated from each other by a wall of tissue called the nasal septum.  They are separated from the mouth by a floor of bone and soft tissue called the hard and soft palates, and from the brain by the bone of the brain case.
  • Filtering Air:  As the air flows into the nostrils, hairs in the nasal cavities filter out large dust particles, and slow the influx of air so that smaller particles get dropped and trapped by sticky mucus.  The mucus and dust migrate to the back of the nasal cavity, and are eventually swallowed so the body can get rid it.
  • Warming and Humidifying:  Bony ridges along the walls of the nasal cavity called concha (named this because they resemble conch shells) cause the inflowing air to become turbulent, which causes it to slow down.  This in turn causes any remaining dust to drop out, and also allows the inflowing air to be warmed and humidified to body temperature.

Mouth and Oropharynx:  Inferior to (“below”) the nasophyaryx is the oral cavity, which we generally just call the mouth, and the oropharynx.  The mouth consists of the lips, gums and teeth, and first 2/3rds of the tongue.  The oropharynx contains the back of the throat, the last 1/3rd of the tongue, the soft palate, and the tonsils.

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  • Nom Nom Nom…:  The teeth allow food to be sliced into manageable sizes, and then ground into a pulp which can be swallowed.  Teeth also assist in modifying the flow of air from the mouth, which allows specific sounds to be formed.  From an airway management perspective, teeth which have been knocked loose can very easily become airway obstructions.
  • The Tongue:  The tongue is a muscle which moves food around the mouth so it can be evenly chewed and then swallowed, allows us to taste, and also changes the flow of air so we can make specific sounds while speaking or singing.  The tongue is also the most frequent airway obstruction encountered by responders.  While it’s impossible to swallow the tongue down into the esophagus, the tongue can flop to the back of the mouth in unconscious or sleeping patients, and fully or partially obstruct the flow of air into the trachea.
  • The Palates:  The roof of the mouth is made of two parts, the hard and soft palates.  The hard palate is at the front of the mouth, and consists of a plate of bone covered in soft tissue.  If you place the tip of your tongue firmly against the roof of your mouth, and slide it back towards the back of your throat you will be able to feel the point at which the bone ends and the soft palate, made of just soft tissue, begins.  It’s important to remember that the soft palate can be fragile, especially when inserting hard airway adjuncts into the mouth.
  • Back of the Throat:  At the back of the mouth, the nasal cavity joints with the oral cavity behind the uvula, which can only be described as “the dangly thing in the back of the throat.”  Food, water, and air all pass through this area towards the openings of the epiglottis and trachea.  Think of this area as a busy crossroads; when managing airway, be sure to check this area for objects, food, or fluids which could obstruct airflow, and remove them.

The Larynx:  The most inferior (“the lowest”) part of the upper airway.  The larynx, or “laryngopharynx” if you want to be technical, stretches from the back of the mouth to the openings of the esophagus and trachea.  It has the interesting distinction of being part of both the respiratory and digestive systems.

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  • Trachea:  The trachea is the passage which conducts air to the lungs.  It’s a semi-rigid structure, with its wall supported by “C” shaped cartilage rings.  A muscular wall separates the trachea from the esophagus.  The only full cartilage ring is the cricoid cartilage just below the vocal cords.
  • Epiglottis:  The epiglottis is a flap of tissue which covers the glottic opening (the opening of the trachea; “epi” means “above,” so the “epiglottis” is “above the glottis”), and prevents food and fluids from entering the airway when swallowing.  The notch just superior (“above”) the epiglottis is the vallecula, and is an important landmark for those of you (docs, PAs, and medics, I’m looking at you again) who intubate and use Mac blades.
  • Yak Yak Yak…:  Inferior to (“below”) the epiglottis, within the trachea itself, are the vocal cords, which look more like thin flaps of tissue instead of strings.  When air is pushed up through the vocal cords from the lungs, the cords vibrate and make sound, which we interpret as speech or singing.
  • Thyroid Cartilage and Cricothyroid Membrane:  We spoke briefly about the thyroid cartilage earlier.  In this picture, you can see how the trachea runs through the thyroid cartilage, which wraps around it.  When a surgical cricothyrotomy is performed, a small incision is made between the bottom of the thyroid cartilage and the cricoid cartilage, and a tube is passed into the trachea.  WFRs and WEMTs aren’t taught this skill, but it’s good to be aware of what more advanced providers may have to do.
  • Get In My Belly:  The esophagus is a muscular tube which lies between the trachea and the cervical spine and thoracic spine.  When food and fluids are swallowed, the epiglottis covers the trachea, and the food and fluids are directed into the esophagus.  The esophagus is not supported by tracheal rings, which allows it to stretch to accommodate different sized food.  The esophagus does not have a flap which covers it; if the patient is lying on his or her back and is unable to protect his or her airway, a real concern is stomach contents seeping back up the esophagus and being pulled into the trachea when the patient inhales.  This is called aspiration.

In the coming posts, we’ll use this foundation in anatomy to help explain some specific airway management techniques.

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