Blood Flow in the Calf During and After Exercise: Measurements with Doppler Ultrasound and Venous Occlusion Plethysmography in Healthy Subjects and in Patients with Arterial Occlusive Disease

Abstract

To investigate the pattern of the blood flow in the calf during exercise, a method with a high resolution in time, i.e., a Doppler velocimeter on the popliteal artery, was used. The instrument was calibrated by simultaneous measurements with strain gauge venous occlusion plethysmography at rest, during exercise hyperemia and during reactive hyperemia. Ten healthy subjects and 6 patients with arterial occlusive disease were studied. They exercised in the supine position on a calf ergometer, with various loads and relaxed completely during the relaxation phases of the rhythmic exercise and after the exercise. In general, the blood flow reached a steady state (healthy subjects) or limited state (patients) after some time. The plethysmographically measured peak volume flow immediately after exercise was related to the volume flow in the relaxation phases during the preceding exercise by comparing the mean Doppler frequencies in these periods. In all persons, these volume flows were virtually equal. After rhythmic isotonic exercise, the static flow reduction during isometric contractions were studied. In most persons, the flow was reduced to 50% of the initial value at a muscle torque of .apprx. 16% of the reference torque, i.e., the torque around the ankle joint when the person stands on 1 leg, with the heel just off the floor. The dynamic flow reduction during rhythmic isotonic exercise also depended on the heart phase (systole, diastole). In a number of cases, it was possible to reduce this effect by averaging over a large number of contractions during a steady state. The results were in good agreement with those of the static flow reduction, taking into account a backward arterial squeeze effect at the onset of the contraction and a forward release effect during the release of the contraction. In the healthy subjects, the post-exercise peak volume flow (qeh) could be much larger than the peak volume flow during reactive hyperemia (qrh). The post-exercise peak volume flow was linearly corrected for the increased mean blood pressure (q''eh) and compared with the peak volume flow during reactive hyperemia, q''eh = k times qrh. For the healthy subjects, k rather strongly depended on the load, with k < 1.35; for the patients, values of k up to 1.5 were found.