Static hyperinflation is associated with ventilatory limitation and exercise tolerance in adult cystic fibrosis

Lung hyperinflation is a potential mechanism limiting exercise tolerance. However, available data on the impact of static hyperinflation on exercise performance in adult cystic fibrosis are lacking. Furthermore, the relative contribution of both static and dynamic hyperinflation to exercise performance is unknown. Objectives The aim of this study was to determine the impact of static hyperinflation on exercise tolerance and lung dynamics in adult cystic fibrosis. Methods Clinical data of 107 adult patients with cystic fibrosis, including pulmonary function, lung volumes and cardiopulmonary exercise from the Toronto Cystic Fibrosis database, were collected and analyzed. Patients were classified as having static hyperinflation with a residual volume to total lung capacity (RV/TLC) ratio of 30% or greater. Results Patients with static hyperinflation demonstrated a significant reduction in exercise performance [peak oxygen uptake (% predicted) 70 ± 17 vs 80 ± 17; P  = .006] and were more likely to experience ventilatory limitation when exercising (Fisher's exact test P  < .001). Correlation analysis showed significant relationships between measures of static hyperinflation [RV/TLC ratio (%)] and exercise performance [peak oxygen uptake (% predicted); r  = −.38, P  < .001] and dynamic hyperinflation ( r  = −.35, P  < .001). Multiple linear regression showed that the contribution of static hyperinflation to exercise performance [peak oxygen uptake (% predicted)] was greater than that of airway obstruction (forced expiratory volume in 1 second). Conclusion Clinicians working with this patient group in a pulmonary rehabilitation or health care setting may wish to consider using measures of static hyperinflation as end points to determine program or treatment efficacy.