Variation of the State of Lower Limb Veins in Cosmonauts during Long-term Missions

Abstract

This paper reports changes in the main parameters of lower limb veins in 35 cosmonauts in the course of six-month space missions. Major reduction in the leg volume was shown in all cosmonauts, as well as a significant increase in venous capacitance and compliance. The rate of lower leg vein filling exhibited different trends; it was decreased in the majority of cosmonauts (n = 26, 74%) and increased in the rest (n = 9, 26%). Increases in venous capacitance, compliance, and filling rates may impact orthostatic stability (OS). These changes are among the pathophysiological mechanisms of the OS loss in spaceflight.