Accompanied versus unaccompanied walking for continuous oxygen saturation measurement during 6-min walk test in COPD: a randomised cross-over study

Study question Is there i a difference in the 6-Min Walk Test (6 MWT) distance when the assessor accompanies the patient to continuously measure oxygen saturation (SpO₂) compared to the patient walking unaccompanied?

Methods We conducted a prospective randomised cross-over study to evaluate the impact of the assessor walking with the patient during 6 MWT (6 MWT_with) versus patient walking alone (6 MWT_without). At the end of a pulmonary rehabilitation programme, each patient performed two 6 MWTs in random order and separated by 30 min rest.

Results 49 COPD patients (GOLD II-IV) were included. In a regression model adjusting for period and subject, accompanying the patient resulted in a lower walking distance (mean difference −9.1 m, [95%CI, −13.9 to −4.3], p=0.0004). Notably, six patients walked more than 30 m further (minimal important difference, MID) in one of the two conditions (6 MWT_with: n=1, 6 MWT_without: n=5). There were no between-sequence-group differences in heart rate, dyspnoea and leg-fatigue, and SpO₂. The median (interquartile range) number and duration of SpO₂ signal artefacts were high but not different between the experimental conditions (6 MWT_with: 17 [4, 24], 34 s [7, 113], 6 MWT_without: 11 [3, 26], 24 s [4, 62]).

Answer to the question On a study population level, we observed a statistically significant difference in 6 MWT distance between the two experimental conditions, however, the magnitude of difference is small and may not be considered clinically relevant. Nevertheless, in a clinical setting, unaccompanied walking resulted in a substantially higher walking distance pointing towards strictly standardised testing methodology, in particular in pre-post study designs.