The measurement of tracheal radius curvature for the assessment of subglottic stenosis by using point-of-care ultrasound

<bold>Background:</bold> Airway dimension measurements are an important component of treatment efficacy assessment and longitudinal follow-up in patients with subglottic stenosis (SGS). However, noninvasive, nonradioactive method is lack to assess the degree of stenosis. Point-of-care ultrasonography (POCUS) is a potential effective method for assessing the subglottic diameter and evaluating the abnormal airway. <bold>Methods:</bold> In this prospective, multicentre, observational study, volunteers and patients with a diagnosis of SGS underwent POCUS, CT and flexible bronchoscopy. A radiologist determined the anteroposterior and transverse diameters of the trachea on the CT image and calculated the mean value (CT-mean). The diameter of the subglottic and cervical trachea calculated using the radius of curvature (CR) formula. <bold>Results:</bold> A total of 123 volunteers without tracheal disease and 113 patients with SGS were enrolled in this study. Both in control group and patients with SGS, there is a strong correlation between US-CR and CT-mean (r =0.96 and 0.94, P <0.001, respectively). The intraobserver and interobserver repeatability of US-CR was excellent (all correlation coefficients > 0.95; P < 0.05). <bold>Interpretation:</bold> The airway dimension measured using POCUS based on the radius of the curvature is a reliable tool for assessing the subglottic tracheal diameters.