Hao W Y, Zhang L F, Wu X Y
Department of Aerospace Biodynamics, The Fourth Military Medical University, Xi'an, PR China.
J Gravit Physiol. 2000 Jul;7(2):P151-2.
Orthostatic intolerance (OI) following exposure to microgravity or head-down bed rest is frequently observed and is thought to be multifactorial origin. Although hypovolemia is considered as the primary cause of OI, the role played by other factors, such as the lowered vasoconstrictor responsiveness (VCR) of resistance vessels, the enhanced vasoconstriction response of cerebral vessels, and the depressed myocardial contractility need to be elucidated. It is difficult to assess experimentally how each of these changes would affect orthostatic tolerance and how these factors interact with each other. An alternative approach is to conduct simulation studies by use of mathematical models of cardiovascular system (CVS) capable of simulating the CVS response to orthostatic stress. This presentation describes the construction of the model used, and presents the preliminary simulation results illustrating the effects of varying individually the level of hypovolemia, VCR of the resistance vessels in lower limbs and abdominal viscera, VCR of the brain vessels or myocardial contractility on responses to orthostatic stress. The ultimate goal of our work was to integrate the new experimental findings and to simulate the complexity to get a thorough understanding of the mechanism of postflight cardiovascular dysfunction and orthostatic intolerance.
暴露于微重力环境或头低位卧床休息后出现的直立不耐受（OI）很常见，且被认为有多种成因。尽管血容量不足被视为OI的主要原因，但其他因素所起的作用，如阻力血管的血管收缩反应性（VCR）降低、脑血管的血管收缩反应增强以及心肌收缩力下降，仍有待阐明。通过实验评估这些变化中的每一个如何影响直立耐受性以及这些因素如何相互作用是困难的。另一种方法是利用能够模拟心血管系统（CVS）对直立应激反应的数学模型进行模拟研究。本报告描述了所用模型的构建，并展示了初步模拟结果，这些结果说明了分别改变血容量不足水平、下肢和腹部内脏阻力血管的VCR、脑血管的VCR或心肌收缩力对直立应激反应的影响。我们工作的最终目标是整合新的实验结果并模拟这种复杂性，以全面了解飞行后心血管功能障碍和直立不耐受的机制。
