Background: Airway dimension measurements are an important component of treatment efficacy assessment and longitudinal follow-up in patients with subglottic stenosis (SGS) and tracheal stenosis. However, noninvasive, nonradioactive method is lack to assess the degree of stenosis.

Methods: In this study, volunteers and patients with a diagnosis of SGS underwent point-of-care ultrasonography (POCUS), CT and flexible bronchoscopy. Radiologist determined the anteroposterior and transverse diameters of the trachea on the CT image and calculated the mean value (CT-mean). Air column width (ACW) and anterior tracheal wall thickness (ATWT) were obtained from POCUS, and the diameter of the subglottic and cervical trachea calculated using the radius of curvature (CR) formula.

Results: A total of 123 volunteers without tracheal disease and 15 patients with SGS were enrolled. Both in control group and patients with SGS, there is a strong correlation between US-CR and CT-mean (r =0.96 and 0.98, P <0.001, respectively). The diameter of subglottic and cervical trachea assessed by US-CR is more accurate than the direct measurement of US-ACW. The intraobserver and interobserver repeatability of US-CR was excellent (all correlation coefficients > 0.95; P < 0.05). In patients with SGS, the degree of stenosis determined by US-ATWT correlate best with the CT-ATWT with coefficients of 0.98 (P<0.001), while a moderate correlation was observed between methods for ATWT (r = 0.65, P<0.001) in control group.

Conclusion: The airway dimension measured using POCUS based on the radius of the curvature is a reliable tool for assessing the subglottic and cervical tracheal diameters.