Antegrade pulsatile arterial-like flow in human limb veins at increased intravascular pressure

The purpose was to study the effects of moderately to markedly increased local intravascular pressures on the flow characteristics in human limb veins. The subject was either seated inside a pressure chamber with one arm slipped through a hole in the chamber door (n = 7) or positioned supine with a lower leg extended to the outside (n = 15). By increasing chamber pressure, transmural pressure in the vessels of the test limb was increased up to +150 mmHg for the arm and +240 mmHg for the leg. Venous flow profiles and arterial flow and vessel diameters were measured with ultrasonographic/Doppler techniques. The arm vessels were studied before and during blocking of the blood flow (BBF) through the hand. Antegrade, pulsatile, arterial-like flow were observed at high distending pressures in the brachial and radial veins in all subjects and in similar to 50% of the subjects also in the cephalic vein and posterior tibial veins. In five of seven subjects, blood flow in the brachial vein remained pulsatile even during BBF. That pulsatile flow was observed in all veins may suggest that moderately to markedly elevated intravascular pressures induce propagation of pulse waves from the arteries via the capillaries to the veins, and/or induce considerable arteriovenous shunting, by forcing open arteriovenous anastomoses.