Predictors of daily physical activity in COPD patients undergoing pulmonary rehabilitation

Abstract

Physical inactivity is very common in patients with COPD. Improvement in daily physical activity has been documented in COPD patients following the completion of a pulmonary rehabilitation (PR) program, however, the predicting factors of daily physical activity have not been thoroughly studied. Therefore, we set out to investigate the predictors of daily physical activity in COPD patients undergoing PR. We studied 76 Caucasian, ambulatory COPD patients. Patients had: age, years=66±8, FEV1, %pred=49±19, FVC, %pred=80±19, FEV1/FVC, %=47±13, and DLco, %pred=56±20. Patients had 3.2±2.4 exacerbations in the year before. All patients underwent a hospital based comprehensive PR program. The duration of the program was 8-weeks with a frequency of 3 sessions per week. Daily physical activity measurements were performed by using a patient activity monitor validated for COPD. At baseline, vector magnitude units (VMU) were 420 (318, 589) and following completion of the PR, VMU were 444 (304, 629). The difference in VMU prior and following PR was related with the following baseline measurements: age (r=-0.294, p=0.010), 6MWT (r=0.254, p=0.027), PaO2 (r=0.289, p=0.016), St George’s Respiratory Questionnaire (r=-0.263, p=0.023), and the number of exacerbations the year before (r=-0.294, p=0.010). Following multivariate analysis, the PaO2 and the number of exacerbations the year before were the strongest predictors of the difference in VMU prior and following PR (r=0.392, p=0.026). In conclusion, the magnitude of changes in daily physical activity in COPD patients following the completion of PR program is influenced by the degree of hypoxemia and the number of exacerbations the year before.