Lower limb vasodilatory capacity is not reduced in patients with moderate COPD

Abstract

We compared exercise capacity (peak O2 uptake) and lower limb vasodilatory capacity in 9 patients with moderate chronic obstructive pulmonary disease (COPD) (forced expiratory volume in 1 s = 55 ± 3 % predicted) and 9 age-matched healthy control subjects. Peak O2 uptake was measured via open circuit spirometry during incremental cycling. Calf blood flow (CBF) measurements were obtained at rest and after 5 minutes of ischemia using venous occlusion plethysmography. While peak O2 uptake was significantly lower in the COPD patients (15.8 ± 3.5 mL/min/kg) compared to the control group (25.2 ± 3.5 mL/kg/min), there were no significant differences between groups in peak CBF or peak calf conductance measured 7 s post-ischemia. peak O2 uptake was significantly correlated with peak CBF and peak conductance in the control group, whereas there was no significant relationship found between these variables in the COPD group. However, the rate of decay in blood flow following ischemia was significantly slower (p<0.05) for the COPD group (-0.036 ± 0.005 mL/100 mL/min/s) when compared to controls (-0.048 ± 0.015 mL/100 mL/min/s). The results suggest that the lower peak exercise capacity in patients with moderate COPD is not related to a loss in leg vasodilatory capacity.