Peak cardiorespiratory and metabolic responses during the six-minute stepper test in people with COPD: A pre-planned...

The six-minute stepper test (6MST) is increasingly used to assess functional exercise capacity in people with chronic obstructive pulmonary disease (COPD). However, the physiological responses elicited during the 6MST and their relationship to those obtained during cardiopulmonary exercise testing (CPET) remain incompletely characterised.

How do peak cardiorespiratory and metabolic responses obtained during the 6MST compare with those measured during CPET, and does the 6MST elicit maximal physiological responses?

This pre-planned ancillary cross-sectional study included individuals with COPD who performed incremental CPET and two 6MSTs with breath-by-breath gas exchange analysis. Peak responses as well as symptoms were compared between tests.

Sixty-five participants were included (mean age 61 (SD 9) years; median FEV₁ 1.3 (IQR 0.9 to 1.7) L). Most peak physiological responses were comparable and moderately to strongly correlated between the 6MST and CPET, with marked intraindividual variability in responses. Heart rate and symptom burden were similar to slightly higher during the 6MST, while systolic arterial blood pressure was clinically higher. Peak oxygen uptake corresponded to approximately 60% of predicted values during both tests, and about 10% of participants achieved conventional criteria for maximal cardiac and metabolic exercise during the 6MST. Ventilatory limitation was the predominant limiting factor during both tests.

The 6MST elicits substantial but generally submaximal cardiac and metabolic stress, and provides complementary, rather than interchangeable, information to CPET. These findings support the clinical utility of the 6MST while highlighting the need for cautious cardiovascular monitoring.

NCT04008615.