# Comparative Analysis of Transverse and Longitudinal Ultrasound Techniques for Cricothyroid Membrane Identification in Anesthesiology Trainees

## TL;DR

This study compares two ultrasound methods for finding the cricothyroid membrane in trainee anesthesiologists, showing both are effective, with one being faster in obese patients.

## Contribution

The study introduces a comparative analysis of transverse and longitudinal ultrasound techniques for CTM identification by trainees, highlighting technique-specific performance in different body types.

## Key findings

- Transverse ultrasound was significantly faster in obese volunteers compared to the longitudinal approach.
- Both techniques achieved high success rates across all body types, with no significant difference overall.
- Brief training enabled trainees to successfully identify the CTM in over 96% of cases within 120 seconds.

## Abstract

Background and objectives

Cricothyrotomy is a life-saving procedure in "cannot intubate, cannot ventilate" scenarios, with accurate identification of the cricothyroid membrane (CTM) being critical to success. Palpation techniques are often unreliable, especially in obese patients. This study aimed to compare the time taken and success rates of transverse versus longitudinal ultrasound approaches for CTM identification by anesthesiology trainees in volunteers of varying body habitus.

Methods

In this prospective, randomized, crossover study, 55 novice anesthesiology residents received a brief training session, followed by ultrasound-guided CTM identification on slender, overweight, and obese male volunteers using both transverse and longitudinal techniques. Each attempt was timed and confirmed by an expert anesthesiologist. Statistical analyses included the Wilcoxon signed-rank test for time comparisons and the Cochran Q test for success rates, with a success threshold defined as CTM identification within 120 seconds.

Results

The transverse approach demonstrated similar identification times to the longitudinal approach in slender (64.5±46.5 sec vs. 67.7±46.8 sec) and overweight (76.4±54.7 sec vs. 67.7±46.8 sec) volunteers (p>0.05), but was significantly faster in obese volunteers (88.4±59 sec vs. 93.8±64.8 sec, p=0.011). Success rates within 120 seconds were high across all groups: 100% in slender, 98.2% in overweight, and 96.3% in obese volunteers, with no significant difference between techniques, though the transverse approach showed a slight advantage in obese subjects.

Conclusions

Both ultrasound techniques are effective for CTM identification by novice anesthesiology residents. The transverse approach offers a time advantage in obese patients. High success rates were achieved following brief training, supporting the integration of ultrasound into emergency airway management protocols, particularly for anticipated difficult airways.