Comparison of cardiopulmonary responses during 2 incremental step tests in subjects with COPD

It is well established that the work rate increment size affects the duration of test and physiological responses to exercise during cycling in patients with COPD. However, this has never been tested for incremental step tests.

To compare the exercise tolerance time, cardiopulmonary stress, and perception of effort between the Chester step test (CST) and a modified incremental step test (MIST).

Thirty-two subjects with COPD (FEV(1) 50 ± 15% of predicted) were randomized to perform the CST and MIST on the same day, an hour apart, on a single step (20 cm high). During tests, pulmonary gas exchange was measured continuously by a portable metabolic system.

CST had shorter duration and also lower number of steps, in comparison with MIST. However, similar cardiopulmonary responses were observed at exercise peak: oxygen uptake (V(.)(O(2))) 1.22 ± 0.59 L/min vs 1.24 ± 0.55 L/min, minute ventilation (V(.)(E)) 30.8 ± 12.7 L/min vs 30.0 ± 11.7 L/min, heart rate 86 ± 13 beats/min vs 85 ± 13 beats/min, and S(pO(2)) 87 ± 7% vs 87 ± 6%. Dyspnea and leg fatigue scores when correcting for exercise duration were higher for CST.

The slower the work rate increment during step test, the higher the exercise tolerance. Regardless of the work rate increment, cardiopulmonary stress and exertion effort at peak exercise were equivalent between tests.