Yao Y J, Wu X Y, Sun X Q, Hao W Y, Wei Y B, Cao X S
Department of Aerospace Medicine, Fourth Military Medical University, Xi'an China.
Space Med Med Eng (Beijing). 1999 Dec;12(6):401-5.
Objective. To investigate the effects of 24 h -6 degrees head-down tilt bed-rest (HDT) on cardiovascular function and response to orthostatic stress. Method. -6 degrees head-down tilt bed rest for 24 h in 6 healthy males, aged 22-23, were observed. The changes of cardiac function were observed by electrical impedance instrument before and at 0th, 6th, 12th, 18th and 24th hour of HDT, and blood pressure were recorded and urine were collected. The changes of cardiovascular response to head up tilt (HUT 90 degrees, 10 min) before and post HDT were recorded. Result. During HDT, HR reduced significantly than that of pre-HDT (standing). HR at 6th, 12th, and 18th hour of HDT reduced significantly than that at 0th hour of HDT. Stroke output (SO) and stroke index (SI) [correction of CI] at 0th, 6th, 12th, and 24th hour of HDT were higher than pre-HDT value. Cardiac output (CO) and cardiac index (CI) at 18th hour of HDT were significantly lower than those at 0 h of HDT. Total peripheral resistance (TPR) at 18th hour of HDT were higher than that at 0th of HDT. During HUT before and post HDT, HR, MBP, TPR were significantly increased, SO, [correction of SV] SI, CO and CI were significantly reduced. DBP were significantly increased and PP were reduced significantly during HUT post-HDT. Hourly average value of urine during 0-4 h were higher than those during 4-12 h and 12-24 h. Conclusion. 24 h -6 degrees head-down tilt bed rest has significant effects on cardiovascular function and response to HUT in humans.
目的。探讨24小时-6°头低位卧床休息（HDT）对心血管功能及对直立位应激反应的影响。方法。观察6名年龄在22 - 23岁的健康男性进行24小时-6°头低位卧床休息的情况。在HDT前及HDT第0、6、12、18和24小时，使用电阻抗仪观察心功能变化，记录血压并收集尿液。记录HDT前后头高位倾斜（HUT 90°，10分钟）时心血管反应的变化。结果。在HDT期间，心率显著低于HDT前（站立位）。HDT第6、12和18小时的心率显著低于HDT第0小时。HDT第0、6、12和24小时的每搏输出量（SO）和每搏指数（SI）[CI校正]高于HDT前值。HDT第18小时的心输出量（CO）和心指数（CI）显著低于HDT第0小时。HDT第18小时的总外周阻力（TPR）高于HDT第0小时。在HDT前后的HUT期间，心率、平均动脉压（MBP）、TPR显著升高，SO、[SV校正] SI、CO和CI显著降低。HDT后HUT期间舒张压（DBP）显著升高，脉压（PP）显著降低。0 - 4小时尿液每小时平均值高于4 - 12小时和12 - 24小时。结论。24小时-6°头低位卧床休息对人体心血管功能及对HUT的反应有显著影响。
