Chest. January 2005;127:110-116

Objectives

Pulmonary rehabilitation (PR) that includes exercise training can improve exercise tolerance and quality of life for patients with COPD. However, the degree of benefit from PR is variable. We hypothesized that the exercise response to PR varies depending on the initial factors that limit exercise.

Design, setting, participants, and measurements

We retrospectively analyzed the change in exercise capacity after PR in 290 nonhypoxemic patients with COPD. We classified patients into the following subgroups on the basis of primary limitation seen on initial exercise testing: (1) ventilatory-limited (VL); (2) cardiovascular-limited (CVL); (3) mixed ventilatory/cardiovascular-limited (VLCVL); and (4) noncardiopulmonary-limited (NL). We compared outcomes among subgroups.

Results

In the entire study population, PR led to increased timed walk distance (30.3%; P < .0001) and maximal oxygen consumption (Vo₂max) (84.8 mL/min; P < .0001). Stepwise multiple regression selected age, ventilatory reserve at peak exercise, and exercise arterial oxygen pressure as individual predictors of improvement in Vo₂max. Maximal oxygen consumption increased in the VL subgroup (30.4 mL/min; P = .008), the CVL subgroup (109.0 mL/min; P < .0001), the mixed VLCVL subgroup (61.3 mL/min; P < .0001), and NL subgroups (110,5 mL/min; P < .0001). The improvement in Vo₂max was greater in the CVL subgroup than in the VL subgroup (P < .0001). Timed walk distance improved to a similar degree in all subgroups (26% to 36%).

Conclusions

Patients with nonventilatory exercise limitations experience the greatest increase in Vo₂max after PR. However, even patients with severe ventilator limitation can improve exercise tolerance with PR.

Comment

Pulmonary rehabilitation is well known to improve exercise tolerance among persons with COPD. However, the magnitude of benefit is variable, even among persons with comparable baseline lung function. The factors that determine the magnitude of improvement in exercise tolerance following PR are incompletely understood. Previous studies have suggested that the degree of dyspnea, and extent of ventilatory limitation versus components of limitation related to skeletal muscle dysfunction may affect gains achieved in PR. The present study, a retrospective analysis of exercise gains following PR among 290 patients with nonhypoxemic COPD, examines this issue further. All patients in this study had significant improvements in both walking endurance and Vo₂max. However, those patients who had ventilatory limitation to exercise identified on pre-rehabilitation cardiopulmonary exercise testing achieved lesser gains in Vo₂max than did persons with cardiovascular or noncardiopulmonary causes of exercise limitation. Importantly, walking endurance improved to the same degree in all patient groups. The findings of this study are consistent with those previously reported, that ventilatory limitation to exercise may limit certain aspects of gains expected following PR. However, all patients, including those with ventilatory limitation to exercise, can achieve gains in endurance, which may be more important than maximal exercise capacity in terms of performance of routine daily activities. Therefore, the finding of ventilator limitation on cardiopulomary exercise testing should by no means exclude patients from participating in PR. It may, however, be worth considering to adjust the exercise prescription for persons with severe ventilatory limitation, aiming for lower-intensity exercise that may be better tolerated by such patients in the long term, as opposed to pushing the patient to perform exercise training at high intensity needed to achieve gains in aerobic fitness and Vo₂max. Additional studies are needed to clarify this further.