The inaccuracy of using landmark techniques for cricothyroid membrane identification: a comparison of three techniques.

OBJECTIVES: Successful cricothyrotomy is predicated on accurate identification of the cricothyroid membrane (CTM) by palpation of superficial anatomy. However, recent research has indicated that accuracy of the identification of the CTM can be as low as 30%, even in the hands of skilled providers. To date, there are very little data to suggest how to best identify this critical landmark. The objective was to compare three different methods of identifying the CTM.

METHODS: A convenience sample of patients and physician volunteers who met inclusion criteria was consented. The patients were assessed by physician volunteers who were randomized to one of three methods for identifying the CTM (general palpation of landmarks vs. an approximation based on four finger widths vs. an estimation based on overlying skin creases of the neck). Volunteers would then mark the skin with an invisible but florescent pen. A single expert evaluator used ultrasound to identify the superior and inferior borders of the CTM. The variably colored florescent marks were then visualized with ultraviolet light and the accuracy of the various methods was recorded as the primary outcome. Additionally, the time it took to perform each technique was measured. Descriptive statistics and report 95% confidence intervals (CIs) are reported.

RESULTS: Fifty adult patients were enrolled, 52% were female, and mean body mass index was 28 kg/m(2) (95% CI = 26 to 29 kg/m(2) ). The general palpation method was successful 62% of the time (95% CI = 48% to 76%) and took an average of 14 seconds to perform (range = 5 to 45 seconds). In contrast, the four-finger technique was successful 46% of the time (95% CI = 32% to 60%) and took an average of 12 seconds to perform (range = 6 to 40 seconds). Finally, the neck crease method was successful 50% of the time (95% CI = 36% to 64%) and took an average of 11 seconds to perform (range = 5 to 15 seconds).

CONCLUSIONS: All three methods performed poorly overall. All three techniques might potentially be even less accurate in instances where the superficial anatomy is not palpable due to body habitus. These findings should alert clinicians to the significant risk of a misplaced cricothyrotomy and highlight the critical need for future research.