Are the measurement properties of incremental exercise tests similar between patients with COPD and CHF?

We investigated whether the differences in exercise limitation between patients with chronic obstructive pulmonary disease (COPD) or chronic heart failure (CHF) affect the repeatability or responsiveness of incremental exercise tests. Patients with COPD (Medical Research Council dyspnoea grade 2-5) and patients with CHF (New York Heart Association class II-IV) performed two incremental shuttle walk tests (ISWT) following familiarisation and two incremental cycle ergometer tests (ICE) within 2 weeks. Both tests were repeated on completion of a pulmonary rehabilitation (PR) programme. One hundred and twelve patients were recruited. In response to exercise, patients with COPD were more likely than patients with CHF to have a ventilatory limitation (p < 0.001) and less likely to have a cardiovascular limitation (p < 0.001). The ISWT distance and ICE peak volume of oxygen uptake (VO₂Peak) were similarly repeatable (p = 0.11 and p = 0.47 for time and disease effect) and responsive to PR (p = 0.44 and p = 0.67) between diseases. There was no difference in repeatability or responsiveness with either a ventilatory or cardiovascular limitation to exercise (p > 0.20 for all comparisons). The coefficient of repeatability across the cohort was 60 m for the ISWT and 0.270 L/minute for ICE VO₂Peak. The minimum important difference (MID) for the ISWT in both diseases for PR was 30 m. The repeatability and responsiveness of the ISWT distance and ICE VO₂Peak are similar between patients with COPD and CHF and are unaffected by differences in exercise limitation. A change of 60 m in the ISWT or 0.270 L/minute in ICE VO₂Peak is required to be 95% certain that a true change has occurred within an individual patient. For a group of patients with either COPD or CHF, the MID for the ISWT distance is estimated to be 30 m.