Trajectories of functional exercise capacity in patients undergoing pulmonary rehabilitation

Background: Pulmonary rehabilitation (PR) is now considered fundamental when managing patients with chronic respiratory disease. The individual variation in functional exercise capacity (FEC) response to PR within the cohort is unknown. The purpose of this study was to identify FEC patterns in response to PR in patients with chronic respiratory disease using the trajectory modeling method. Methods: The data of 67 patients with the chronic respiratory disease were retrospectively reviewed and analyzed in this study. All patients received once-weekly supervised training for 8 weeks. Six-minute walk distance (6MWD) was used to measure FEC. Muscle strength and 6MWD were assessed at baseline, Week 4, Week 8 and monthly for two months after PR completion. Group-based trajectory modeling (GBTM) was used to identify patterns in 6MWD in response to PR. The generalized estimating equation method was then used to detect the differences within and between the trajectories of identified groups across time. Results: Patients were grouped into low- (n=13), moderate- (n=34) and high- (n=20) FEC group based on GBTM analysis. All groups demonstrated significant improvements in 6MWD and leg muscle strength after 8-week PR. Compared to the high-FEC group, a greater proportion of the patients in the low-FEC group required oxygen supplementation during training and had worse baseline leg muscle strength. Conclusions: Patients showed distinct patterns of 6MWD changes in response to 8-week PR. Distinct characteristics for the low-FEC group included poor lower extremity strength and a greater proportion of required oxygen use at home and during training.