Efficacy of the 6-Minute Walk Test in Evaluating Ambulatory Oxygen Therapy

Abstract

To compare oxyhemoglobin saturation (SpO2) observed during the 6-minute walk test with that of pulse oximetry carried out during activities of daily living (ADLs). The efficacy of the 6-minute walk test for determining adequate oxygen flow to prevent arterial desaturation during ADLs was also analyzed. We studied 37 patients diagnosed with chronic obstructive pulmonary disease (COPD)--mean (SD) forced expiratory volume in 1 second, 26% (9%) of predicted--and compared SpO2 values obtained in the 6-minute walk test with those obtained with ambulatory pulse oximetry during ADLs. Eleven of the 20 patients with exercise-induced desaturation agreed to use portable liquid oxygen and were randomized to ambulatory pulse oximetry on 2 consecutive days, both with and without the administration of oxygen. Oxygen flow was adjusted on successive 6-minute walk tests until a mean SpO2 greater than 85% was reached. The mean SpO2 for all patients was 84% (7%) during the 6-minute walk test and 89% (4%) during ADLs (P<.001). Cumulative percentages of time with SpO2 less than 90%, 88%, and 85% were higher during the 6-minute walk test than during ADLs (P<.001). During the walk test, desaturation was detected in 27% of patients, but was not confirmed by ambulatory pulse oximetry during ADLs. In the subgroup of 11 patients using portable liquid oxygen no significant differences were found between SpO2 values recorded during the walk test and during ADLs with the appropriate oxygen flow. The 6-minute walk test is an effective method for detecting desaturation during ADLs and for establishing the oxygen flow needed to correct exercise-induced desaturation.