Effects of graded restriction of perfusion on circulation and metabolism in the working leg; quantification of a human ischaemia-model

Abstract

An experimental model used with the intention of mimicking the ischaemic condition in patients with arterial obliterative disease was evaluated. The influence of reduced effective perfusion pressure by increased external pressure on leg blood flow and metabolism was determined during exercise in 10 healthy subjects. Catheters were inserted into the right femoral artery and vein and into the left femoral vein. Supine one-legged (n = 5) or two-legged (n = 5) cycle exercise was performed with the subject's legs in a pressure chamber. Zero and three different levels of local supra-atmospheric pressure were applied over the legs: 30, 50 and 60 mmHg. Three submaximal work loads were used: 24, 48 and 72 W/leg. Leg blood flow was measured by the constant-infusion dye-dilution technique. Samples were also drawn from the femoral artery and vein for oxygen saturation and lactate determinations and arterial pressure was recorded. Exercise blood flow decreased progressively with increasing chamber pressure (P less than 0.001). Exposure to 50 mmHg over the working leg led to a mean reduction of blood flow by 16% and venous oxygen saturation by 12 percentage units (P less than 0.05). Lactate release increased with increasing pressure (P less than 0.05). In summary, local application of moderate positive external pressure over the working leg reduces blood flow in a 'dose-dependent' manner, and as a consequence, femoral venous oxygen saturation decreases and lactate release increases. Thus, this method makes it possible to induce graded ischaemia in human skeletal muscle during exercise in a controlled fashion.