Expiratory central airway collapse in stable COPD and during exacerbations

Background: Tracheal obstruction resulting from expiratory tracheal deformation has been associated with respiratory symptoms and severe airway exacerbations. In chronic obstructive pulmonary disease (COPD), acute exacerbations (AECOPD) create large intrathoracic pressure swings which may increase tracheal deformation. Excessive central airway collapse (ECAC) may be diagnosed when the tracheal area on expiration is less than 50% of that on inspiration. The prevalence of ECAC in AECOPD and its temporal course have not been systematically studied. Methods: We prospectively recruited healthy volunteers (n=53), stable outpatients with COPD (n=40) and patients with hospitalised acute exacerbations of COPD (AECOPD, n=64). 17 of the AECOPD group returned for repeat evaluation when clinically well at 6-12weeks. All subjects underwent dynamic 320-slice computed tomography of the larynx and trachea during tidal breathing, enabling quantitation of tracheal area and dimensions (mean±SD). Results: No healthy individuals had ECAC. The prevalence of ECAC in stable COPD and AECOPD was 35% and 39% respectively. Mean tracheal collapse did not differ between stable COPD (57.5±19.8%), AECOPD (53.8±19.3%) and in the subset who returned when convalescent (54.9±17.2%). AECOPD patients with and without ECAC had similar clinical characteristics. Conclusions: Tracheal collapse in both stable and AECOPD is considerably more prevalent than in healthy individuals. ECAC warrants assessment as part of comprehensive COPD evaluation and management. Further studies should evaluate the aetiology of ECAC and whether it predisposes to exacerbations.