Physical activity in COPD and its relationship to exercise performance and sleep

Patients with COPD may be severely limited in daily life but exercise tests may not adequately reflect this limitation. Aim: To assess whether daily activity correlates with exercise capacity and nocturnal oxygen saturation in COPD. Methods: COPD patients underwent activity monitoring (Sensewear TM ), maximal bicycle exercise test (CPET), 6 minute walk distance (6MWD) and ambulatory respiratory sleep study. Senswear TM derived activity was quantified by steps/day, daily estimated energy expenditure (EE) and average of metabolic equivalents (METs) per day. Pearson correlations of activity with exercise parameters or sleep were calculated. Results: 20 COPD patients (11 female, age 65±6y, FEV1 64±19%pred) were recruited. Patients were moderately active (7120±3492 steps/day), estimated EE was 9166±1085kJ and METs 1.4±0.2. Mean nocturnal oxygen saturation was 92±2%, oxygen desaturation index was 4.4±4.6. The steps/day correlated with FEV1%pred (r=0.51, p Conclusion: Patients with less severe airflow obstructions show higher daily activity. Daily activity measurements recorded in COPD provide important information, complementary to lung function, CPET and 6MWD since activity recordings estimate EE over several days in the setting of the patients9 everyday life. Daytime and nocturnal ventilation and oxygenation differently affect activity derived estimates of EE.