Written by Aaron Lacy
Anesthesiologists were more successful in identifying the cricothyroid membrane (CTM) when palpating upwards from the sternal notch compared to palpating down from the hyoid bone.
Why does this matter?
In a can’t oxygenate – can’t ventilate scenario, a surgical airway is needed. Accurately identifying the proper landmarks (the CTM) is a key component to the successful surgical airway. Studies show palpation techniques are not always accurate. If there was a new palpation technique that improved accuracy, it would be an easy step to take in helping secure a surgical airway.
Started from the bottom, now we’re here
Patients undergoing general anesthesia during elective procedures were randomized to two manual palpation techniques for identifying the CTM. The study designers chose to exclusively use female patients because identification of the CTM is more challenging than males. The first “conventional laryngeal handshake” method utilizes grasping the hyoid bone and subsequently moving in a caudal direction, next identifying the thyroid laminae, then the CTM. The second “modified upwards laryngeal handshake” involves grasping the trachea at the sternal notch and moving in a cranial direction until the cricoid cartilage is palpated, then subsequently identifying the CTM.
Confirmation of the CTM location was done using ultrasound. Patients randomized to the modified laryngeal handshake technique (n=99) were more likely to correctly identify the CTM than those randomized to the conventional laryngeal handshake technique (n=99) (84% vs 56%, OR 4.36, 95%CI 2.13 – 8.93, p < 0.001). Midline was also more likely to be correctly identified in the modified technique, and there was no difference in time taken to identify the CTM between techniques.
While POCUS is becoming the gold standard for identification of the CTM, it is not always practical or available in a can’t oxygenate – can’t ventilate scenario. While patients with past laryngeal surgery or anatomical abnormalities were excluded, the results of this are intriguing. I have always palpated from the top down, and I plan on trying this new technique next time I am in the cadaver lab to see how it goes.
Comparison of the Conventional Downward and Modified Upward Laryngeal Handshake Techniques to Identify the Cricothyroid Membrane: A Randomized, Comparative Study. Anesth Analg. 2021 Sep 13. doi: 10.1213/ANE.0000000000005744. Online ahead of print.