Body Mass Index Moderates the Effects of Portable Oxygen Transport Modality on 6-Minute Walk Distance in Patients With COPD

PURPOSE: While portable, supplemental oxygen is often necessary for patients with chronic obstructive pulmonary disease (COPD) to retain independence, it may provide functional limitations because of the increased workload imposed. This issue may result in nonuse, creating a need to identify carrying modalities that optimize transport. This study assessed the effects of 3 methods of portable oxygen transport on 6-minute walk distance (6MWD), rate of perceived exertion (RPE), heart rate (HR), and oxyhemoglobin saturation (SpO(2)). As weight status is known to impact functional ability in COPD, effects of body mass index (BMI) were also assessed. METHODS: Data were analyzed using the mixed-model procedure to test for effects of transport modality (reference, rolling cart, backpack, shoulderstrap), time (minutes 1-6), BMI, non-overweight, overweight, and interactions of these variables on outcome parameters. RESULTS: A main effect of condition was found for 6MWD, and an interaction of condition x BMI was found for HR and RPE, and of time x BMI for 6MWD and SpO(2). Participants walked the least distance in rolling cart condition, which was also characterized by the greatest RPE. For the overweight group, HR was least in the reference compared with other conditions; but for the non-overweight group, the opposite pattern was observed. At latter time points, 6MWD was greater in the non-overweight group, while SpO(2) was reduced. CONCLUSION: Results demonstrate that transport modality of portable oxygen exerts differential effects on functional performance in COPD patients and that BMI may moderate underlying physiologic factors that contribute to performance outcomes.