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.