Accuracy of identifying the cricothyroid membrane by anesthesia trainees and staff in a Canadian institution.

Abstract

We sought to determine the rate of successful identification of the cricothyroid membrane by anesthesia residents and staff at a Canadian institution. In this prospective study, healthy adult volunteer subjects were positioned supine with their necks placed in neutral position. There were 12 subjects, half of whom were non-obese (body mass index < 30.0 kg·m(2)) and half of whom were obese. There were equal numbers of male and female subjects in each of the obese and non-obese groups. Anesthesia staff and resident participants were allowed to palpate multiple subjects but with only one attempt per subject. For each subject, ultrasonography was used to identify the superior and inferior borders of the cricothyroid membrane, which were then marked with "invisible" ink that could be made visible with ultraviolet light. The midline was also marked with invisible ink. Identification of the cricothyroid membrane was considered correct if the mark was between the superior and inferior borders and within 0.5 cm of the midline. Altogether, 61 participants palpated 12 subjects, resulting in 186 identifications. The success rates for the subgroups were as follows: non-obese men 72% (95% confidence interval [CI] 59 to 85%); obese men 39% (95% CI 26 to 54%); non-obese women 24% (95% CI 12 to 36%); obese women 35% (95% CI 21 to 49%). Success rates for correct identification of the cricothyroid membrane were poor in this Canadian institution.