Physiological Changes Differ between Responders and Nonresponders to Pulmonary Rehabilitation in COPD

Abstract

PurposeNot all patients with chronic obstructive pulmonary disease (COPD) experience similar benefits after pulmonary rehabilitation (PR). This pre-post PR study used a large sample of patients with COPD to determine whether PR-induced changes of oxygen uptake (VO2) kinetics and exercise responses of VO2, carbon dioxide output (VCO2), minute ventilation (V-E), V-E/VCO2, breathing frequency, and tidal volume differed between responders and nonresponders to PR. MethodsResponders to PR were defined as patients with a minimal clinically important increase in endurance time of 105 s. Isotime (=180 s) values of VO2, VCO2, V-E, V-E/VCO2, breathing frequency, and tidal volume; gains of VO2, VCO2, and V-E; and VO2 mean response time of 183 patients with COPD (forced expiratory volume in 1 s: 56% +/- 19% predicted) were compared between pre- and post-PR constant work rate tests. ResultsAfter PR, only the group of responders significantly decreased VO2 mean response time (P < 0.05), VCO2 gain, V-E gain, and isotime values of VCO2, V-E, and V-E/VCO2 (all, P < 0.001), while also improving their breathing pattern (e.g., decreased breathing frequency isotime value; P < 0.0001). These changes were not observed in the group of nonresponders. Changes in physiological exercise responses were correlated with changes in physical performance (e.g., correlation between changes in VO2 mean response time and endurance time: P = 0.0002, r = -0.32). ConclusionsPR-induced changes in physiological exercise responses differed between responders and nonresponders. Physiological changes are relevant to explain the variable improvements of physical performance after PR in patients with COPD.