Learning Curve Analysis of Conventional and Point-of-Care Transcutaneous Laryngeal Ultrasonography

Vocal fold (VF) palsy is a significant complication of thyroid surgery, traditionally assessed using laryngoscopy. However, transcutaneous laryngeal ultrasonography (TLUSG) has emerged as a noninvasive and accessible alternative for VF evaluation. Despite increasing evidence of its diagnostic reliability, data on the learning curve of TLUSG-particularly among novice examiners and in Caucasian populations-remain limited. This study aimed to define the learning curve for TLUSG using both conventional ultrasonography (CUS) and point-of-care ultrasonography (POCUS) devices in medical students without prior ultrasound experience.

A prospective cohort study was conducted at the Medical University of Gdansk between January and August 2022 including patients undergoing thyroidectomy. Six medical students performed TLUSG on each patient using POCUS followed by CUS devices. Direct flexible or videostrobolaryngoscopy served as the reference standard. The diagnostic indices, including sensitivity, specificity, positive predictive value, and negative predictive value were determined based on laryngoscopic results. Learning curves were evaluated by applying cumulative sum (CUSUM) along with piecewise linear segmented regression analysis for continuous (time to visualization, time to complete examination) and learning curve CUSUM (LC-CUSUM) analysis for categorical (diagnostic accuracy) outcomes.

Among 120 TLUSG examinations, overall VF visualization rate was 94.9%. Based on the segmented regression analysis, the learning phase for time to visualization and time to complete examination was until 7th and 5th examination for POCUS and until 24th and 16th examination for CUS, respectively. According to LC-CUSUM analysis, trainees became proficient at accurately assessing VF between their 7th and 15th examination, with all trainees maintaining acceptable performance thereafter. Most trainees developed sufficient skill in performing TLUSG by their 15th attempt and acquired proficiency around the 25th examination.

TLUSG is a rapidly learnable, reliable, and reproducible tool for VF assessment, even among ultrasound-naÏve examiners. This study highlights the feasibility of incorporating TLUSG into perioperative and bedside workflows, potentially reducing reliance on routine laryngoscopy for VF assessment.