Effects of Markedly Increased Intravascular Pressure on the Volume-Flow Characteristics in Venous Vessels of Human Limbs

摘要

Pilots flying high-performance aircraft are exposed to high gravitational forces in the head-to-foot direction. To maintain adequate blood perfusion in the brain during such circumstances arterial pressure a heart level must be markedly increased. Therefore, and because of the large hydrostatic pressure components that act along the vessels, pressure in vascular beds below the heart is commonly raised to levels that are high enough to result in pathological events in the peripheral vasculature. For example, petechial and venolar bleedings as well as pain, presumably due to local vascular overdistension, are common at high G-loads. However, knowledge is still limited as to what extent such extreme elevations of intravascular pressures may induce other, less apparent, pathological events in peripheral vascular beds. During previous studies concerning effects of increased pressure in arm vessels of health humans we have on a few occasions observed antegrade pulsatile flow in the brachial vein in conjunction with markedly increased intravascular pressure. This is a surprising finding since arterial-like pulsatile flow in the veins is usually associated with pathological conditions such as arteriovenous fistulas. The purpose of the present study was to investigate the effect of markedly increased local intravascular pressure on the occurrence of antegrade pulsatile flow in peripheral veins.