Accuracy in Identifying the Cricothyroid Membrane, Dr. P. Lee

Paul Lee, DO

Article review

Accuracy of Identification of the Cricothyroid Membrane in Female Subjects Using Palpation: An Observational Study

The cricothyroid membrane (CTM) is the recommended site of access to the airway during cricothyroidotomy to provide emergency oxygenation. Despite the apparent simplicity of the technique, this rescue maneuver frequently fails to achieve its goals and complications are numerous. The reasons for this failure are unclear. We sought to determine the ability of physicians to correctly identify the CTM in female patients. Using fluorescent “invisible” ink, the physician was asked to mark the CTM with the patient in the supine neutral position and then with the head extended. The actual level was identified using ultrasound and the distance between the actual and estimated margin of the CTM was measured. A correct estimation was defined as a mark made between the upper and lower limits of the membrane and within 5 mm of midline. Participants were also asked to assess the ease of CTM palpation using a 10-cm visual analog scoring (VAS) scale. Fifty-six patients participated of whom 15 were obese. In the supine neutral neck position, the CTM was identified in 10/41 vs 0/15 (P = 0.048) in nonobese versus obese, respectively. Of the 46 incorrectly identified CTMs in this position, 24 were above (maximum 3 cm) and 22 below (maximum 3 cm) the actual level. Similar results were observed when the patients were placed with the neck in the extended position; the CTM was identified correctly in 12/41 vs 1/15 nonobese and obese patients, respectively. The range of values was also extensive; the estimation of the position of the membrane was as high as 2.5 cm above and 4 cm below the actual level, and up to 1.6 cm laterally. Participating doctors found palpation of the CTM subjectively more difficult in the obese than nonobese groups; VAS score for palpation difficulty was 5.25 ± 2.5 vs 3.3 ± 2.5, respectively, P = 0.005. Using multiple linear regression, VAS scores for palpation correlated negatively with increased patient height (P < 0.001) and greater thyromental distance (P = 0.006), and correlated positively with increased sternomental distance (P = 0.011) and neck circumference (P = 0.001). Misidentification of the CTM in female patients is common and its localization is less precise in those who are obese. This has implications for the likely success of invasive airway access via the CTM. Emergency cricothyroidotomy is a life-saving maneuver that may prevent death or permanent neurological injury in the event of difficult or failed airway management and is thus a core skill for anesthesiologists. Despite its crucial importance, it is a rare requirement in clinical practice. Consequently, individual clinical experience, even for experienced anesthesiologists, is infrequent and may in fact be a once-in-a-career event. Clearly, accurate anatomic localization of the cricothyroid membrane (CTM) is of critical importance before emergency cricothyroidotomy. Should the CTM be misidentified and the invasive airway device be misplaced, the consequences include continued hypoxia, airway trauma, esophageal penetration/perforation, and vascular and neural injury. The ability of clinicians to accurately identify the CTM has not been studied extensively. The purpose of this study was to determine the accuracy of clinical identification of the CTM using the traditional palpation technique. We hypothesized that the CTM would be more likely to be misidentified in obese patients than in normal weight patients on the basis that anatomical landmarks might be obscured