Influence of raised venous pressure on the flow properties of blood.

This study posed the question of whether the blood flow properties from the anticubital and ankle vein of healthy subjects varied under different hydrostatic conditions. The blood flow properties from the vena cubitalis and the ankle vein do not vary to any greater degree during lying, whereas during standing the blood viscosity, plasma viscosity, hematocrit, and plasma protein concentration increase significantly. Furthermore, they are significantly higher than in venous blood taken from the arm at the same time. The oxygen partial pressure in venous blood from the arm is significantly higher than in the ankle venous blood after 5 minutes of standing. These results show, among other things, that under the various hydrostatic conditions present in different body regions, the blood flow properties differ considerably. From the pathophysiologic point of view, it is important that during standing the return of blood is made even more difficult because of the increased blood viscosity resulting from fluid loss from the intravascular space to the interstitium.