Comparison between an indoor and an outdoor 6-minute walk test among individuals with chronic obstructive pulmonary disease1 1No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated.

OBJECTIVES: To investigate the feasibility of an outdoor 6-minute walk test (6MWT) as a measure of functional status among individuals with chronic obstructive pulmonary disease (COPD), and to examine the relationship between performance on an indoor and an outdoor 6MWT. DESIGN: An experimental, repeated-measures crossover design. Subjects were studied on 2 separate days in the same week. Two 6MWTs-one indoors and the other outdoors-were performed on each study day, with a rest in between. The test order was randomly selected on the first day and reversed on the second day. Outdoor tests were performed on days of moderate weather conditions (mean temperature +/- standard deviation, 21 degrees +/-3 degrees C; mean wind speed, 15+/-7km/h; no precipitation) and on a flat surface (sidewalk). SETTING: Outpatient rehabilitation program in Ontario. PARTICIPANTS: Eighteen subjects with COPD (10 men, 8 women; age, 70+/-8y), 5 using supplemental oxygen at rest (forced expiratory volume in 1s, 1.0+/-0.3L; 42%+/-8% of predicted). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Distance walked in 6 minutes (in meters), duration of rest (in seconds), and change in rate of perceived dyspnea. RESULTS: There was no significant effect of setting (indoors vs outdoors) on distance walked (394+/-86m vs 398+/-84m, P=0.4), duration of rest (13+/-28s vs 9+/-20s, P=0.4), or change in rate of perceived dyspnea (2.3+/-1.7 vs 2.3+/-2.0, P=0.8). Testing day had no significant effect on walk test performance (all P>0.1). CONCLUSIONS: The results indicate that the 6MWT performed outdoors within reasonable climatic parameters may be reflective of 6MWT performance indoors.