Effect of "vein pump" activation upon venous pressure and blood flow in human subcutaneous tissue.

The effect of "vein pump" activation upon superficial venous pressure and blood flow in human subcutaneous adipose tissue was studied in 6 normals and 2 patients with venous insufficiency. Blood flow in subcltaneous tissue was measured at the lateral malleolus by the local 133Xenon washout technique, with the subject placed in a supine position. During passive lowering of the leg blood flow decreased 50 per cent and total vascular resistance increased 136 per cent. Activation of the vein pump by continuously tipping the foot up and down caused a decrease in venous pressure of 5 mmHg in horizontal position. Venous pressure increased only by 8 mmHg when the leg was lowered during exercise. In this situation blood flow remained constant corresponding to an increase in vascular resistance of 42 per cent. However increasing venous pressure to 28 mmHg by venous stasis in the lowered leg during exercise caused an additional increase in vascular resistance of 82 per cent. In the patients with venous insufficiency exercise did not prevent the decrease in blood flow during lowering of the leg. Hence venous pressure elevation of 25 mmHg or more caused an additional increase in vascular resistance in subcutaneous tissue, "vasoconstrictor response". It is concluded that this "vasoconstrictor response" depends on a vasoconstrictor impulse transmission from veins to arterioles, veno-artertolar reflex.