Oxygen Transport and Peripheral Microcirculation in Long-Term Diabetes

Abstract

The purpose of this investigation was to evaluate the impact of long-term diabetes on muscle blood flow (MBF) and oxygen transport (^vO₂) during exercise. Twelve male patients (58 ± 8 years, mean ± SD), with at least a 10-year history of diabetes controlled by insulin, and seven age-matched controls (56 ± 5 years, mean ± SD) participated in this study. No patient had been clinically diagnosed as having peripheral vascular disease, and on the average resting ankle/arm systolic blood pressure ratios were normal. Following a baseline period, 5 min of cycle ergometer exercises at 75 W were performed in the upright position and, after 1-hr recovery, in the supine position. Continuous ^vO₂ was determined via breath-by-breath analysis. MBF was measured in the vastus lateralis (VL) and tibialis anterior (TA) by ¹³³Xe clearance. In the erect position, the diabetic group (compared with the control group, respectively) exhibited significantly (P < 0.05) lower exercise MBF [ml·(100 g·min)^-1] in both VL (19 ± 2.5 vs 30.9 ± 2) and TA (13.7 ± 2 vs 22.0 ± 4), a lower steady-state ^vO₂ (1.3 ± 0.3 vs 1.7 ± 0.2 liters·min^-1) during exercise including the values in the last 15 sec of exercise, and greater accumulation of blood lactate (35 ± 2 vs 22.0 ± 2 mg/100 ml). The same trends in the data were observed during supine exercise; however, the blood pressure of the diabetics was significantly elevated during exercise when compared with that of controls. The reduced exercise MBF in the TA and VL demonstrated that impaired microvascular flow, without clinically overt peripheral vascular disease, in long-term diabetics leads to reduced oxygen delivery and exercise tolerance.