Comparison of Endoscopic and Ultrasonographic Measurements of the Subglottic Airway in Children

Abstract

Objective To compare measurements of the pediatric subglottis obtained by surgeon-performed ultrasound and endoscopy. Study Design Prospective observational comparison-of-methods study. Setting Tertiary care pediatric hospital. Subjects and Methods Thirty-one patients who underwent direct laryngoscopy from May 2017 to July 2018 were recruited. Transcervical ultrasound was used to visualize the vocal folds, subglottis, and cervical trachea. The anterior-posterior (AP) and transverse (TV) diameter of the subglottic space were measured endoscopically and via ultrasound by 2 independent evaluators. Measurements were compared for correlation, bias, and agreement. A clinically acceptable bias for subglottic diameter was assumed to be 0.5 mm or less. Results The median age of enrolled patients was 2.6 years (range, 4 months–13.3 years). Endoscopic subglottic AP and TV measurements ranged from 3.33 mm to 14.81 mm and from 4.44 mm to 11.65 mm, respectively, while ultrasonographic AP and TV measurements ranged from 4.57 mm to 9.85 mm and from 3.77 mm to 8.96 mm. Pearson coefficient showed strong a correlation for both endoscopic and ultrasound AP ( R = 0.8081, P < .0001) and TV ( R = 0.8796, P < .001) measurements of the subglottis. Bland-Altman plots revealed a bias (average discrepancy) for AP measurements of 0.22 mm and 0.11 mm for TV measurements. Conclusion Endoscopic and ultrasonography measurements of the pediatric subglottic airway were strongly correlated. The discrepancy between AP and TV measurements was less than 0.5 mm. Ultrasound of the subglottis may be an alternative to endoscopic assessment of the airway for measurement of the subglottic airway in children in select cases.