失重后血量减少致立位应激时心血管反应改变的仿真研究

The Changes of Cardiovascular Response to Orthostatic Stress Caused by Hypovolemia Inuced by Weightlessness:A Simulation Study

我们将计算机仿真的实验方法引入重力生理学研究领域。以 Melchior(1994)工作为基础 ,建立一个仿真立位应激 (下体负压 )时心血管反应的数学模型 ,模型包括血液重新分配、左室充盈、左室工作、外周循环、心率调节调节、外周阻力调节、静脉紧张程度调节等七个子模型。然后仿真了人体在下体负压时血压和心率变化 ,结果与同步进行的人体下体负压实验结果吻合。基于此模型 ,仿真研究了血量减少对立位应激时血压、心率和休克指数的影响。结果表明 ,超过总血量 15 %的血量减少将导致立位应激时心血管反应的明显改变 ;但是当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 L BNP时正常的 HR和 BP。本结果证明血量减少是失重后人体立位耐力不良的主要因素之一。

We introduced the method of computer simulation in the studies of gravitational physiology. Based on work of Melchior (1994), we developed a mathematical model that can be used to simulate cardiovascular responses to orthostatic stress (lower body negative pressure, LBNP). The model includes 7 sub models: the redistribution of blood, the filling of left ventricle, left ventricle working, peripheral circulation, control of heart rate (HR), control of peripheral resistance and control of venous tone. Then we simulated the changes of blood pressure (BP) and heart rate during lower body negative pressure, and the results agreed well with the results of our human experiment. By using the developed model, we also simulated the effects of hypovolemia on the BP, HR and shock index during orthostatic stress. The simulation results indicate that the cardiovascular responses to orthostatic stress change significantly when the decrease of blood volume is more than 15% of the total blood volume. However, if the amount of the decrease of blood volume is less than 5% of the total blood volume, HR and BP could be maintained in normal range by the regulation of baroreflex during LBNP. Our simulation results suggest that hypovolemia may be the main cause of orthostatic intolerance induced by weightlessness.