Two 6-minute walk tests are required during hospitalisation for acute exacerbation of COPD

Abstract

The 6-minute walk test (6MWT) is recommended to be performed twice to accurately assess exercise performance in stable chronic obstructive pulmonary disease (COPD) due to the presence of a learning effect. It is unknown whether a learning effect exists when the 6MWT is performed during hospitalisation for acute exacerbation of COPD (AECOPD). This study investigated whether repeat 6MWTs are necessary when conducted in inpatients with AECOPD. Pooled analysis was undertaken of data from two studies (Australia and Brazil) involving 46 participants (25 males, mean age 67.2 years, FEV1 43% predicted) admitted with AECOPD. Two 6MWTs, separated by ≥20 minutes, were performed on the day of discharge. Six-minute walk distance (6MWD; primary outcome), perceived dyspnoea (Borg scale), heart rate and oxyhaemoglobin saturation were recorded. 6MWD data from tests one (T1) and two (T2) were analysed via visual inspection of Bland-Altman plots. Factors associated with test improvement or decline were explored. Mean 6MWD difference between T1 and T2 was 6.2 m, however limits of agreement were wide (-92.2 m to 104.5 m). 32 (70%) participants improved (by any distance) from T1 to T2 by a mean (± standard deviation) of 32 m ± 28 m. Of these, 14 (30%) improved by a distance > 30 m. Fourteen (30%) participants recorded poorer 6MWD at T2 by a mean of 52 m ± 36 m. No factors were able to identify participants who improved or declined upon repeat testing. When performed in patients admitted to hospital with AECOPD, the 6MWT needs to be conducted twice in order to better estimate 6MWD.