Levitan, the “Laryngeal Handshake” and the “Cartilaginous Cage”
Pearls from Rich Levitan on surgical airways: Do the “Laryngeal Handshake” to identify airway anatomy and the Cricothyroid “Cartilaginous Cage” is protective
I had the amazing good fortune to be invited to one of the Practical Emergency Airway Management Courses in Baltimore, Maryland USA last week by Rich Levitan who runs the course and by Jim DuCanto who was a guest instructor. This course occurs 11 months every year and is in high demand with spaces filling up rapidly. Rich also has taken the course to Australia and the first course this year was sold out in record time. This is my second time at the course in two years and I was still discovering forgotten as well as new pearls.
Day 1 of the course was a full day with Rich Levitan on airway intricacies and day 2 was the airway cadaver lab. Each course has 20 participants, 20 cadavers and ample opportunity to practice direct laryngoscopy, various video laryngoscopy, bougie, supraglottic airways, flexible and stylet fiberoptics as well as open cricothyrotomy. The cadavers are preserved by arterial flushing with isopropyl alcohol and thus the tissues behave normally other than joints being a bit stiff. This simulates airways with high fluids, edema, limited mouth opening and limited neck movement.
I’ve collected miscellaneous pearls from the course here. Rich has an amazing way of developing sticky concepts that translate into practical airway solutions like NODESAT, epiglottoscopy/laryngoscopy/tube delivery and ear-to-sternal-notch positioning.
During the lab section on surgical airways, some take home points included the “Laryngeal Handshake” for accurate identification of the cricothyroid membrane and the concept of the protective “Cartilaginous Cage” when you are “stabbing” the airway at the cricothyroid membrane.
Correct identification of landmarks in the surgical airway is mission critical. Neck atlanto-occipital hyperextension also helps bring the airway to the surface and expose the anatomy. Staying in the midline where the airway is and “cutting to air (needling to air)” are absolute musts.
“Laryngeal Handshake” in surgical airways
Instead of just using the distal 1 cm of your index finger to find the cricothyroid membrane, it is much easier to identify the entire rhomboid shaped cartilaginous complex comprised of the hyoid-thyroid-cricoid. This is a large structure that can be distinguished from the trachea. In females, children and obese necks the laryngeal complex is easily identified compared to the traditional approach of finding the thyroid notch versus cricoid ring. Having a sense of where the hyoid-thyroid-cricoid allows you to identify the airway in the midline and also to know that the cricothyroid membrane is on the inferior part of this structure.
Standing on the right side of the patient, take all five fingers of your right hand, grab the neck for the laryngeal handshake: thumb on one side and four fingers on the other side just under the mandible. Feel the framework of the upper airway from top to bottom: hyoid will be up high on top, coming down is the broad flat laminae of the thyroid and then lowest is the cricoid. Movement of this hyoid-thyroid-cricoid complex side to side will define for you where the airway is and help distinguish between the larynx and the trachea.
Next stabilize the thyroid-cricoid with your left hand resting on the patient’s chin, and your thumb and fingers grasping the larynx to get a sense of the airway relation to midline. The most inferior prominence of the laryngeal complex palpated by your index finger will be the cricoid. The first soft spot palpated up is the cricothyroid membrane which can be tiny in children and variable size in adults. The airway anatomy is also much more reliably palpated through a vertical skin incision especially if there is much neck tissue or in small cricothyroid membranes.
“The Cartilaginous Cage”
If you cut into the neck south of the cricoid you run into potential badness. Lateral to the airway are the great vessels and the thyroid can be a bloody mess. The trachea has the soft membranous posterior wall where you can hit the esophagus.
Andy Neill has done an excellent anatomic review of the airway and has noted that the protective high back wall of the cricoid cartilage prevents your needle or scalpel from going beyond the airway when you enter the cricothyroid membrane. The average adult has an anterior cricoid ring measuring 5 mm high with the cricothyroid membrane being approximately 9 mm tall, and the posterior cricoid ring measures 30 mm tall. Rich Levitan notes that the cricothyroid area is a protected space not only posteriorly, but also laterally as the inferior cornua (horns) of the thyroid cartilage come down laterally to cover the cricoid cartilage and provide a natural lateral stopping point to a scalpel within the cricothyroid membrane.
Other important things to remember is to cut in the lower half of the membrane to avoid the superior running cricothyroid artery as well as staying away from the vocal cords. The cricothyrotomy also needs to be extended or dilated up to a 1cm incision, in order to accept a 6.0 endotracheal tube where the outer diameter is typically at least 8-9 mm. Ensure that there is adequate exposure and large enough cricothyrotomy in order to accurately identify it with your finger and to secure it with a trach hook +/- bougie prior to insertion of the airway. Too small a hole runs the risk of missing the airway on insertion and creation of false passages.
The other pearls discussed is to always practice and perform the procedure in the same way. We suggest always going with a vertical incision first in order to palpate and accurately identify landmarks before cutting/needling. Personal Protective Equipment from fluids is especially important when the airway is opened given that efforts at oxygenation and ventilation continue from above. Various other open surgical airway pearls are collected here.
“Laryngeal Manipulation” in laryngoscopy
Laryngeal movement is also able to identify airway anatomy during laryngoscopy as well. This is particularly useful when airway anatomy is distorted by various insults including trauma, blood and other fluids, edema, tumor, foreign body, and hematomas. Not only does external laryngeal manipulation move the laryngeal structure into view but you also get a sense of where the larynx should be in relation to the tip of the blade using bimanual laryngoscopy. In addition, laryngeal movement may allow you to identify the horizontal shaped epiglottis being lifted off the back of the pharyngeal wall out of a pool of fluid. Side to side laryngeal movement may also allow you to readily recognize the interarytenoid cleft and posterior cartilages.
Other subtle clues to identify distorted airways include vocal cord movement in the non-paralyzed patient and identifying air movement or bubbles out of the laryngeal inlet when the chest is compressed.
Use the “Laryngeal Handshake” to identify the cricothyroid membrane or to assist in laryngeal exposure during intubation. The “Cartilaginous Cage” is a protected space that provides a safety guard for cricothyrotomy in surgical airways.