Fomina G A, Kotovskaia A R
Aviakosm Ekolog Med. 2008 Mar-Apr;42(2):21-5.
Purpose of this work was to elicit the role of hypovolemia in the development of hemodynamic shifts and loss of orthostatic tolerance in humans during prolonged space flights (PSF). Correlation analysis of the data of in-flight ultrasonic investigations of hemodynamics in resting cosmonauts and bio-impedance measurements of body liquids in different periods during PSF pointed out that changes in the left ventricle filling and renal artery resistance (Rren) reflect the degree of hypovolemia with r = 0.95. The dependence of orthostatic tolerance on hypovolemia fell short of this ambiguity. Lower body negative pressure tests (LBNP) performed by 15 cosmonauts in different periods of PSF typically correlated with the body hydration status at r = 0.94; however, several cosmonauts showed a substantial loss of LBNP tolerance despite a moderate hypovolemia. Therefore, we may hypothesize that hypovolemia is a significant yet not the sole factor in orthostatic disorders. Deconditioning, altered control of hemodynamics, decreased vasoconstriction of arterial vessels and increased compliance of the leg veins have an important, in some cases decisive role in degradation of orthostatic tolerance.
这项工作的目的是探究低血容量在长期太空飞行（PSF）期间人体血流动力学变化和直立耐力丧失发展过程中的作用。对静息状态下宇航员飞行中的血流动力学超声检查数据与PSF不同阶段体液的生物阻抗测量数据进行相关性分析指出，左心室充盈和肾动脉阻力（Rren）的变化反映低血容量程度，相关系数r = 0.95。直立耐力对低血容量的依赖性并非如此明确。15名宇航员在PSF不同阶段进行的下体负压试验（LBNP）通常与身体水合状态相关，相关系数r = 0.94；然而，几名宇航员尽管存在中度低血容量，但LBNP耐受性却大幅下降。因此，我们可以假设低血容量是直立性障碍的一个重要但并非唯一的因素。去适应、血流动力学控制改变、动脉血管血管收缩减少以及腿部静脉顺应性增加在直立耐力下降中具有重要作用，在某些情况下起决定性作用。
