Ultrasound for identifying the cricothyroid membrane prior to the anticipated difficult airway

Background: Prior to the anticipated difficult airway, the emergency physician commonly palpates the neck to identify the presumed location of the cricothyroid membrane (CTM). In the event of a “cannot-intubate, cannot‑oxygenate” airway, precise CTM localization is vital to the success of a cricothyrotomy and hence, the patient's survival. Objective: This narrative review will summarize the prospective studies evaluating CTM identification. It will demonstrate the inaccuracy of the classically used landmark palpation technique. It will then describe the use of ultrasound (US) as a superior tool for CTM identification, illustrate the technique itself, and propose its implementation in the pre-intubation checklist for the anticipated difficult airway. Discussion: Evidence demonstrates that physicians are not sufficiently accurate in palpating the CTM in both cadavers and volunteers in a stable non-emergent setting. In preparing for a real-time intubation, this fine motor task would be more difficult to achieve. Moreover, this particular patient group may often exhibit difficult airway features. US has been demonstrated to be superior for locating the CTM than landmark palpation across body habitus, gender, and failed airway simulations. This technique carries a short learning curve even without prior airway US experience, along with a high retention rate. An illustrative tutorial is provided. Conclusion: Emergency physicians may apply this US technique for CTM localization in preparation for an anticipated difficult airway. However, since this technique takes longer than landmark palpation, using US is not recommended once already in the midst of a failed airway situation.