Practice of ultrasound-guided palpation of neck landmarks improves accuracy of external palpation of the cricothyroid membrane
BACKGROUND: Ultrasonography can accurately identify the cricothyroid membrane; however, its impact on the subsequent accuracy of external palpation is not known. In this study, we tested the ability of anesthesia participants to identify the midpoint of the cricothyroid membrane using external palpation with and without ultrasound (US)-guided practice. METHODS: Following institutional ethics approval and informed consent, anesthesia participants consisting of anesthesia residents, fellows, and practicing anesthesia assistants underwent didactic teaching on neck landmarks. The participants were then randomized to practice palpation of neck landmarks with US guidance (US group) or without ultrasonography (non-US [NUS] group). After the practice session, each participant identified the cricothyroid membrane using external palpation on the neck of 10 volunteers and marked the anticipated entry point for device insertion (palpation point [PT]). The midpoint of the cricothyroid membrane of each volunteer had been premarked with invisible ink using ultrasonography (US point) by a separate member of the research team. The primary outcome was the accuracy rate defined as the percentage of the attempts with the distance ≤5 mm measured from the PT to US point for the participant. The primary outcome was compared between NUS and US groups using Wilcoxon rank sum test. A mixed-effect logistic regression or mixed-effect linear model was also conducted for outcomes accounting for the clustering and adjusting for potential confounders. RESULTS: Fifteen anesthesia participants were randomized to US (n = 8) and NUS (n = 7) groups. A total of 80 and 61 attempts were performed by the US and NUS groups, respectively. The median accuracy rate in the US group was higher than the NUS group (65% vs 30%; P = .025), and the median PT-US distance in the US group was shorter than in the NUS group (4.0 vs 8.0 mm; P = .04). The adjusted mean PT-US distance in the US group was shorter compared to the NUS group (adjusted mean [95% CI], 3.6 [2.9-4.6] vs 6.8 [5.2-8.9] mm; P < .001). CONCLUSIONS: Anesthesia participants exposed to practice with US-guided palpation of the cricothyroid membrane location were better able to identify the cricothyroid membrane using only blind palpation than participants without US-guided practice. Practice with US-guided palpation of neck landmarks improves subsequent blind localization of the cricothyroid membrane using palpation alone. Copyright © 2018 International Anesthesia Research Society.