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

PURPOSE Not all patients with chronic obstructive pulmonary disease (COPD) experience similar benefits following 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 (V[Combining Dot Above]O2) kinetics and exercise responses of V[Combining Dot Above]O2, carbon dioxide output (V[Combining Dot Above]CO2), minute ventilation (V[Combining Dot Above]E), V[Combining Dot Above]E/V[Combining Dot Above]CO2, breathing frequency and tidal volume differed between responders and non-responders to PR. METHODS Responders to PR were defined as patients with a minimal clinically important increase in endurance time of 105 s. Isotime (=180 s) values of V[Combining Dot Above]O2, V[Combining Dot Above]CO2, V[Combining Dot Above]E, V[Combining Dot Above]E/V[Combining Dot Above]CO2, breathing frequency and tidal volume; gains of V[Combining Dot Above]O2, V[Combining Dot Above]CO2 and V[Combining Dot Above]E; and V[Combining Dot Above]O2 mean response time of 183 patients with COPD (forced expiratory volume in 1 second: 56±19%predicted) were compared between pre- and post-PR constant work rate tests. RESULTS Following PR, only the group of responders significantly decreased V[Combining Dot Above]O2 mean response time (p<0.05), V[Combining Dot Above]CO2 gain, V[Combining Dot Above]E gain and isotime values of V[Combining Dot Above]CO2, V[Combining Dot Above]E and V[Combining Dot Above]E/V[Combining Dot Above]CO2 (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 non-responders. Changes in physiological exercise responses were correlated with changes in physical performance (e.g. correlation between changes in V[Combining Dot Above]O2 mean response time and endurance time: p=0.0002, r=-0.32). CONCLUSION PR-induced changes in physiological exercise responses differed between responders and non-responders. Physiological changes are relevant to explain the variable improvements of physical performance following PR in patients with COPD.