Role of ultrasonography in an impalpable tissue larynx model during a simulated front-of-neck access scenario: a randomized simulation study.

PURPOSE: A large vertical incision is recommended when performing front-of-neck access in patients with impalpable neck landmarks during a cannot intubate-cannot oxygenate (CICO) scenario. We investigated the impact of ultrasonography on vertical incision size of a front-of-neck access on an ultrasound-compatible impalpable porcine larynx model.

METHODS: Emergency medicine and anesthesia trainees were randomized to the Ultrasound (US, n = 21) and Non-Ultrasound (NUS, n = 21) groups. Within 1 week after a teaching session on airway ultrasound and Scalpel-Bougie-Tube (SBT) technique, participants were instructed to perform cricothyroidotomy on the model during a simulated cannot intubate-cannot oxygenate scenario. The primary outcome was a vertical size incision. Secondary outcomes were procedural completion time, horizontal size incision, tissue injury severity, and correct tube placement.

RESULTS: The ultrasound group performed a significantly smaller vertical incision [median (IQR), 35.0 (15, 40) vs 65.0 (52, 100) mm (95% CI) - 30.0 (- 55.1, - 4.9), p = 0.02] and took longer total time to complete the procedure [median (IQR), 200.5 (126, 267) vs 93.5 (71.0, 167.5) secs (95% CI) 91.0 (3.73, 178.3), p = 0.04]. Tissue injury severity and correct tube placement were similar between groups.

CONCLUSIONS: Ultrasound-guided identification of the cricothyroid membrane significantly reduced the recommended vertical incision size with similar success rates. However, there was an increased time when performing a Scalpel-Bougie-Tube cricothyroidotomy on an impalpable porcine larynx model by physicians in training. Ultrasonography should not be used in an emergency scenario of airway rescue. Its potential use to pre-mark the cricothyroid membrane should be considered in difficult airway management of impalpable neck.