Paradoxical Vocal Fold Motion in Difficult Asthma Is Associated with Dysfunctional Breathing and Preserved Lung Function

Abstract

Many patients with difficult asthma also have coexisting vocal cord dysfunction (VCD), evident by paradoxical vocal fold motion (PVFM) on laryngoscopy. Among patients with difficult asthma, we sought to identify clinical features associated with laryngoscopy-diagnosed PVFM. Consecutive patients with "difficult asthma" referred by respiratory specialists underwent systematic assessment in this observational study. Those with a high clinical suspicion for VCD were referred for laryngoscopy, either at rest or after mannitol provocation. Statistical analyses were performed to identify clinical factors associated with PVFM, and a multivariate logistic regression model was fitted to control for confounders. Of 169 patients with difficult asthma, 63 (37.3%) had a high clinical probability of VCD. Of 42 who underwent laryngoscopy, 32 had PVFM confirmed. Patients with PVFM more likely had preserved lung function (prebronchodilator forced expiratory ratio 74% ± 11 vs 62% ± 16, P < .001); physiotherapist-confirmed dysfunctional breathing (odds ratio [OR]= 5.52, 95% confidence interval [CI]: 2.4-12.7, P < .001), gastro-oesophageal reflux (OR= 2.6, 95% CI: 1.16-5.8, P=.02), and a lower peripheral eosinophil count (0.09 vs 0.23, P= .004). On multivariate logistic regression, independent predictors for PVFM were dysfunctional breathing (OR= 4.93, 95% CI: 2-12, P < .001) and preserved lung function (OR=1.07, 95% CI: 1.028-1.106, P < .001). Among specialist-referred patients with difficult asthma, VCD pathogenesis may overlap with dysfunctional breathing but is not associated with severe airflow obstruction. Dysfunctional breathing and preserved lung function may serve as clinical clues for the presence of VCD.