Physical Inactivity, Functional Status and Exercise Capacity in COPD Patients Receiving Home-Based Oxygen Therapy

Chronic obstructive pulmonary disease (COPD) has systemic consequences that lead to reduced physical activity in daily life (PADL). Little is known about PADL and its associations in individuals with COPD on home-based long-term oxygen therapy (LTOT). The objective of the study was to determine whether there is an association between severe physical inactivity and pulmonary function, fatigue, dyspnea, functional status and exercise capacity in individuals with COPD on home-based LTOT using electric oxygen concentrators and to investigate which of these variables could influence inactivity in these individuals. The population sample included 39 individuals with COPD who were on LTOT (69 ± 8 years, FEV₁: 32 ± 14% predicted). They were assessed in terms of PADL (number of steps/day), fatigue (Fatigue Severity Scale - FSS), dyspnea (Medical Research Council - MRC scale), functional status (London Chest ADL scale [LCADL] and Timed Up and Go [TUG] test) and functional exercise capacity (Six-Minute Step test [6MST] and Sit-to-Stand test [STST]). PADL was markedly low (1444 ± 1203 steps/day) and associated with daily duration of LTOT (r = -0.50), fatigue (r = -0.36), LCADL (r = -0.41), 6MST (r = 0.48), and STST (r = 0.53) (p < .05 for all). Multiple linear regression revealed that daily duration of LTOT and STST explained 39% of the variability of PADL. Longer daily duration of LTOT, fatigue, worse functional status and exercise capacity were all associated with physical inactivity in individuals with COPD on LTOT, whereas daily duration of LTOT and the STST were determinants of reduced physical activity.