Cardiopulmonary responses to treadmill and cycle ergometry exercise in patients with peripheral vascular disease

BACKGROUND - Peripheral arterial disease (PAD) presenting as intermittent claudication (IC) is routinely assessed as the distance or time walked to the onset of pain, which often occurs before significant cardiopulmonary stress and is subject to confounding factors such as increased body mass and altered gait. Thus, where exercise-induced cardiovascular stress is desirable, such as in cardiac stress testing or clinical trials, an alternative modality of exercise is required. Cycling will circumvent several of the associated problems of treadmill walking and may provide an alternative preferable method of exercise, although there is limited information on the physiologic response of patients with PAD to cycling. This study compared the peak cardiorespiratory responses and the repeatability of cycling and treadmill exercise in patients with PAD. METHODS - Ten men (mean age, 54 +/- 10 years) with stable IC completed two incremental exercise tests to the limit of tolerance on a treadmill and a cycle ergometer after familiarization with the outcome measures of exercise duration, work performed, respiratory gas exchange variables using continuous breath-by-breath measurement, heart rate, and ratings of perceived pain. RESULTS - Both methods of exercise assessment revealed high reproducibility in terms of absolute claudication time (treadmill, r = 0.95; cycle, r = 0.91), time to volitional fatigue (treadmill, r = 0.96; cycle, r = 0.91), and cardiopulmonary exercise responses such as the lactate threshold (treadmill, r = 0.95; cycle, r = 0.94), peak heart rate (treadmill, r = 0.94; cycle, r = 0.96), and peak oxygen uptake (treadmill, r = 0.98; cycle, r = 0.87). Cycling induced significantly higher cardiopulmonary responses (peak heart rate, peak carbon dioxide output, peak minute ventilation, and respiratory exchange ratio) than treadmill exercise. There was no difference in time to volitional fatigue or in absolute claudication time between exercise modalities. CONCLUSION - These results demonstrate that exercise testing using cycling offers an alternative method of cardiopulmonary testing for patients with IC that is equally reliable and reproducible to treadmill walking. Cycling may be preferable to treadmill exercise because it induces greater cardiopulmonary and metabolic responses and is better tolerated by patients.