Sekiguchi C, Yumikura S, Murai T, Miyamoto A, Yajima K
Space Station Program Office, National Space Development Agency of Japan, Tokyo.
Aviat Space Environ Med. 1993 Jul;64(7):599-605.
Hemodynamic and hormonal responses to lower body negative pressure (LBNP) after 12-h head-down tilt (HDT) were examined to investigate the mechanism of orthostatic intolerance following spaceflight. Ten young healthy male volunteers participated in the experiment. After 6 degrees HDT for 12 h, the tolerance to 1 h continuous -30 mm Hg LBNP was tested. Variables were measured before and after HDT, during LBNP, and 1 and 10 min after LBNP. Significant reduction in leg volume and plasma volume were observed at the end of 12-h HDT (500 ml and 5.5%, respectively). In the tolerant group, stroke volume index (SI) was decreased by 35% after 15 min LBNP, and carotid arterial blood flow (CBF), by 27% at the end of LBNP compared to the pre-LBNP value. Of the 10 subjects, 5 developed presyncope during LBNP; they exhibited remarkable reduction in SI, CBF, and heart rate, and increased secretion of ADH and adrenaline during or just prior to presyncope. This non-tolerant group tended to be hemo-concentrated from the start of the experiment. However, it will require a prospective study to determine if this variable is a reliable predictor of the outcome of the post-HDT LBNP test from data collected at the end of HDT.
为研究太空飞行后体位性不耐受的机制，对12小时头低位倾斜（HDT）后下体负压（LBNP）的血流动力学和激素反应进行了检查。10名年轻健康男性志愿者参与了该实验。在6度HDT 12小时后，测试了对1小时持续-30 mmHg LBNP的耐受性。在HDT前后、LBNP期间以及LBNP后1分钟和10分钟测量各项变量。在12小时HDT结束时，观察到腿部容积和血浆容积显著减少（分别为500 ml和5.5%）。在耐受组中，与LBNP前的值相比，LBNP 15分钟后每搏输出量指数（SI）降低了35%，LBNP结束时颈动脉血流量（CBF）降低了27%。在这10名受试者中，有5名在LBNP期间出现前驱晕厥；他们在晕厥期间或即将晕厥前表现出SI、CBF和心率显著降低，以及抗利尿激素（ADH）和肾上腺素分泌增加。这个不耐受组从实验开始就有血液浓缩的倾向。然而，要根据HDT结束时收集的数据确定该变量是否是HDT后LBNP测试结果的可靠预测指标，还需要进行前瞻性研究。
