Monitoring Adult Subglottic Stenosis With Spirometry and Dyspnea Index: A Novel Approach

Objective The aim was to examine the correlations among the anatomic Cotton‐Myer classification, pulmonary function tests (PFTs), and patient‐perceived dyspnea or dysphonia in patients with subglottic stenosis and identify measurements accurately reflecting treatment effects. Study Design Prospective cohort study. Setting Tertiary referral center. Method Fifty‐two adults receiving endoscopic treatment for isolated subglottic stenosis were consecutively included. Correlations were calculated among the preoperative Cotton‐Myer scale, PFTs, the Dyspnea Index (DI), and the Voice Handicap Index. Receiver operating characteristic curves were determined for PFT, DI, and Voice Handicap Index pre‐ and postoperative measurements. Results The Cotton‐Myer classification correlated weakly with peak expiratory flow ( r = −0.35, P =. 012), expiratory disproportion index ( r = 0.32, P =. 022), peak inspiratory flow ( r = −0.32, P =. 022), and total peak flow ( r = −0.36, P =. 01). The DI showed an excellent area under the curve (0.99, P <. 001), and among PFTs, the expiratory disproportion index demonstrated the best area under the curve (0.89, P <. 001), followed by total peak flow (0.88, P <. 001), peak expiratory flow (0.87, P <. 001), and peak inspiratory flow (0.84, P <. 001). Patients treated endoscopically with balloon dilatation showed a 53% decrease in expiratory disproportion index (95% CI, 41%‐66%; P <. 001) and a 37% improvement in peak expiratory flow (95% CI, 31%‐43%; P <. 001). Conclusion Expiratory disproportion index or peak expiratory flow combined with DI was a feasible measurement for the monitoring of adult subglottic stenosis. The percentage deterioration of peak expiratory flow and increase in expiratory disproportion index correlated significantly with a proportional percentage increase in DI.