Behavior of Vascular Beds In the Human Upper Limb at Low Perfusion Pressure

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Abstract
A technique of venous occlusion pressure plethysmography was used to examine the behavior of blood flow in the hand and forearm during reduced perfusion pressure. The trend of flow following sudden reduction in perfusion pressure was recorded, and steady-state pressure-flow curves were constructed. Epinephrine iontophoresis allowed discrimination between forearm skin and muscle blood flow. Pressure-flow curves for the hand were parabolic, convex to the pressure axis, and passing close to the zero point. There was no progressive change in flow once perfusion pressure and flow were initially reduced. Autoregulation was evident in forearm muscle and was more marked in chronically sympathectomized limbs. When perfusion pressure was reduced, blood flow fell, then rose to a new, steady level. Pressure-flow curves were concave to the pressure axis and intersected it at close to zero.