Influence of orthostatic pressure changes on blood flow in fingers in generalized scleroderma

Autoregulation of blood flow, i.e. tendency towards the maintenance of constant blood flow during changes in arterial perfusion pressure head, has previously been demonstrated in human cutaneous and subcutaneous tissue. The response seem to depend on local intrinsic mechanisms, and the study of autoregulation can yield information as to the reactivity of vascular smooth muscle cells to normal metabolic and myogenic stimuli. Nine patients and 6 normals were studied. Blood flow was measured in subcutaneous tissue of fingers by the local 133Xenon washout technique. A decrease in arterial perfusion pressure head was obtained by graded elevation of the arm above heart level. In 5 normals and 7 patients, blood flow was also measured in a subcutaneous vascular bed made passive by injection of a 133Xenon-papaverine mixture. In this paralysed vascular bed, blood flow diminished corresponding to the decrease in perfusion pressure during elevation of the arm, while in the normal vascular bed blood flow remained almost constant. Patients suffering from generalized scleroderma took an intermediate position. This finding is compatible with an intrinsic vascular smooth muscle cell defect in generalized scleroderma.