Hemodynamic Studies of the Legs Under Weightlessness

Significant among the medical findings following prolonged space flight are reduced orthostatic tolerance and ergometric work capacity. Changes in hemodynamics of the legs with increased blood pooling and reduction in cardiac output must be considered one of the most probable causes of these effects. Concern for the above plus the observed marked tissue changes occurring in the legs during flight prompted the addition of several procedures to evaluate hemodynamic changes in the leg; resting arterial blood flow, venous compliance and muscle pumping were investigated. In so far as possible, the initial reaction to pressure in the smallest possible vein segment was examined.