血容量减少对立位应激反应影响的仿真研究

A Simulated Study of Effects of Simulated Hypovolemia on Cardiovascular Response to Orthostatic Stress.

目的研究不同程度的血容量减少对心血管系统立位应激反应的影响 ,探讨血容量降低在航天失重后心血管失调和立位耐力降低机理中的意义。方法在仿真下体负压 (LBNP)暴露时心血管系统反应模型的血液重新分配子模型中引入血容量减少因素 ,仿真血容量减少 0～ 2 5%后LBNP时心率 (HR)和血压 (BP)变化。结果血容量减少低于总血量的 5%条件下 ,心血管系统可以通过压力反射调节作用维持LBNP时正常的HR和BP ;血容量减少超过约 1 5% ,在安静仰卧位时 ,HR和BP正常 ,但LBNP时BP迅速降低 ,系统可能失去稳定性。结论血容量减少将导致心血管系统对立位应激反应的改变。

Objective To study the effects of hypovolemia on cardiovascular response to orthostatic stress,and to investigate the role of hypovolemia in the mechanism of cardiovascular deconditioning and orthostatic intolerance induced by space weightlessness. Method The effects of loss of blood volume had been incorporated in the sub model of blood redistribution in the model developed for simulating the cardiovascular response to lower body negative pressure (LBNP).With the help of the model,we simulated the changes of heart rate (HR) and blood pressure (BP) during LBNP after 0～25% loss of blood volume. Result When the amount of decrease of blood volume was less than 5% of the total blood volume,HR and BP could be maintained in normal range during LBNP through baroreflex regulation.When the amount of the decrease of blood volume was more than 15% of the total blood volume,HR and BP could be kept in normal rang when the subject was supine and at rest.But BP fell sharply and the cardiovascular system almost collapsed during orthostatic exposure. Conclusion Decrease of blood volume causes significant degradations of cardiovascular response to orthostatic stress.