Oxygen uptake during constant-intensity exercise in patients with peripheral arterial occlusive disease

The purpose of the present study was to evaluate the oxygen uptake (VO2) response to walking in patients with peripheral arterial occlusive disease (PAOD) at a constant velocity and to determine whether the oxygen uptake observed during constant-intensity exercise in this population is associated with the severity of PAOD. Forty-nine PAOD patients with intermittent claudication were recruited (values are mean +/- SD) [age = 66.4 +/- 8.0 years, weight = 83.3 +/- 16.0 kg, body mass index = 28.8 +/- 5.6, ankle/brachial systolic blood pressure index (ABI) = 0.63 +/- 0.18, VO2peak = 13.02 +/- 2.99 ml/kg/min]. Patients were evaluated during a 2.0 miles/h walk on a treadmill until maximal claudication pain or for a maximum of 20 minutes. On average, patients walked for a duration of 10.3 +/- 5.8 min. Despite the constant absolute intensity during the exercise bout, there was a significant (p < 0.01) 4.0% increase in VO2 from min 3 of exercise (10.58 +/- 2.02 ml/kg/min) to min 5 (11.01 +/- 2.18 ml/kg/min) and a further 4.0% increase from min 5 to the end of exercise (11.46 +/- 2.32 ml/kg/min). Expressed as relative exercise intensity, this represented an increase from 80.8 +/- 18.3% to 87.1 +/- 18.0% of VO2peak from min 3 to the end of exercise. The magnitude of increase in VO2 during the exercise bout was not correlated with resting ABI (r = 0.00, p = 0.68) or post-exercise ABI (r = 0.04, p = 0.73). There was a nonsignificant trend towards a correlation between the time to onset of claudication pain and the magnitude of increase in VO2 (r = 0.25, p = 0.08). Results of this study suggest that an increase in VO2 occurs during constant-velocity walking at a high relative intensity in PAOD patients. This increase in VO2 does not appear to be related to the severity of PAOD.