Effect of treadmill exercise on blood gases and acid-base balance in patients with intermittent claudication.

Blood gases and lactate and pyruvate concentration were measured in arterial and popliteal venous blood in 6 control subjects and 34 patients with intermittent claudication before, during, and after treadmill exercise of 10 min duration. Oxygen saturation, oxygen extraction, base excess, and standard bicarbonate were calculated. The transition from resting supine position to upright position on the treadmill caused the popliteal venous oxygen saturation to fall from 49.4% to 26.3%. In patients, during exercise a further decrease (to 11%) was observed. During treadmill exercise the popliteal venous PO2 did not fall below 16.5 +/- 1.1 mm Hg in the controls. Individual values during exercise varied between 6.4 mm Hg and 17.9 mm Hg in patients. A critical oxygen pressure was reached in 10 patients. Lactate concentration was found to increase to values as high as 14 mmol/l in popliteal venous blood. The lactate-pyruvate ratio varied between 12.9 and 106.3 during exercise, and the corresponding values for venous blood pH were 7.38 and 6.92. Changes in the PCO2, lactate, and pH in arterial and popliteal venous blood showed a significant correlation. The decrease in the base excess was greater than the corresponding increase in the blood lactate concentration. It is concluded that analysis of the acid-base balance in patients with intermittent claudication is best carried out by the regional catheterization technique.