Improvement in FEV1 after acute COPD exacerbations are driven more by changes in hyperinflation than changes in proximal airway volume

Abstract

Recovering from a COPD exacerbation is typically associated with an improvement in FEV1. The common perception is that FEV1 is determined by the characteristics of the larger airways (generations 2-6). Aims: We investigated the relationship between changes in FEV1, airway volume and lung hyperinflation in patients recovering from an acute COPD exacerbation. Methods: Airway volume and hyperinflation were assessed using a novel imaging method called Functional Respiratory Imaging (FRI) in 50 COPD patients during an acute exacerbation and 6-8 weeks after recovery. Results: A significant correlation was observed between the improvement in FEV1 and the change in FRI based airway volume (R = 0.3, p = 0.045,). However, the change in FEV1 with FRI based hyperinflation was considerably stronger (R = 0.46, p = 0.002). Conclusions: Our data suggest changes in FEV1 after an acute COPD exacerbation are more likely driven by changes in hyperinflation, possibly resulting from small airways inflammation, than larger airway inflammation. We are now evaluating a multiple regression model to determine the contribution of changes in individual FRI based parameters to the overall change in FEV1