[Shifts in human venous hemodynamics in long-term space flight].

Veins and venous hemodynamics before, during and after long-term space flights (SF) were evaluated with the ultrasonic (B-scan, Doppler) techniques and occlusion plethysmography. Fifteen cosmonauts were investigated in eight SFs of about 6 months in duration. In three SFs, 30 investigations of the main veins in different parts of the body were fulfilled with participation of 7 cosmonauts. In five SFs, 48 investigations of venous distensibility in legs were fulfilled with occlusion plethysmography with participation of 8 cosmonauts. Femoral veins tended to increase distension throughout SF. Exaggerated leg veins distensibility and compliance was persistently observed during application of occlusion from the early period of SF (wks 1-2) which, in our opinion, extenuates the reduction in LBNP tolerance and post-flight degradation of orthostatic stability. These shifts were growing markedly till months 2-3 of exposure to microgravity and tended to stabilize at the worst (as compared with prelaunch values) level at the end of six-month SFs.