Common modalities of clinical exercise testing for outcome measurement in pulmonary rehabilitation (PR) include walking tests, progressive cycle ergometry (PCE) and cycle endurance testing (CET). We hypothesized that the responses after PR as measured by these tests are differentially correlated and designed this study to investigate the capacity of these 3 tests in detecting changes after PR in a group of patients with COPD.
We prospectively analysed the results of 37 male patients with stable COPD who completed a comprehensive 6-week PR program that included supervised exercise training emphasising steady-state lower limb aerobic exercise. Before and after the PR program, patients underwent 6-minute walk tests, PCE and CET at 80% of the peak work-rate achieved during PCE. Exercise performance indices of interest were the peak oxygen uptake (O2max) and work-rate (Wmax) during PCE, the endurance time during CET, and the six-minute walking distance (6MWD).
There were statistically significant improvements in the mean indices of exercise performance before and after PR: 6MWD (p < 0.001), O2max (p = 0.004), Wmax (p = 0.001), and endurance time (p < 0.001). Compared to baseline, the improvement in 6MWD, O2max, Wmax and endurance time was 16%, 53%, 30% and 144% respectively. The changes in O2max and Wmax were significantly correlated with one another (r = 0.362, p = 0.027) and the changes in endurance time and Wmax were also significantly correlated to each other (r = 0.406, p = 0.013). There was no significant correlation between changes in any other exercise index.
Among the frequently used exercise tests in PR, the most responsive index is the endurance time. The correlation between the changes in the different exercise indices in response to PR is poor.
The results of this study support the practice of using endurance procedures more often in measuring outcomes of PR.
K.C. Ong, None.