反复体位改变是指将人体仰卧位固定于倾斜床上，在短时间内进行多次不同体位交替变化的过程。我们前期的研究发现，一定模式的反复体位改变可引起健康人出现房室传导阻滞、阵发性室上速等典型心电图节律异常，不同模式的反复体位改变对人体心血管调节功能的影响可能存在明显差异。本课题通过人体实验，比较两种不同模式反复体位改变对人体立位耐力和头低位耐力影响的差异；分析心电图节律、心率和血压变异性、压力反射敏感性、下肢血流、脑血流、血管阻力等生理指标及醛固酮、肾素等神经-体液调节因子的变化特征及其相关性；采用人工神经网络BP算法，建立心血管功能评价模型。研究结果将有助于阐明不同模式反复体位改变心血管效应的差异及机理，为其在航空航天医学研究、航天员和飞行员选拔训练、临床上血管迷走性晕厥病人的训练治疗中应用提供理论依据和实验支持。

We use the tilt bed to change supine body repeatedly among different angles during a short time. Previous studies found that some specific model of repetitive postural change could induce typical arrhythmia in the healthy, such as atrioventricular block and paroxysmal supraventricular tachycardia.This study makes the comparison between two different models of repetitive postural change experiments and researches on the difference of effects on orthostatic tolerance and head-down-tilt tolerance by the analysis of physiological indexes such as ECG, variability of heart rate and blood pressure, baroreflex sensitivity, lower limb blood flow, cerebral flow,and vascular resistance etc.The characteristic and correlation of biological indicators like aldosterone and rennin are also analyzed contemporarily. The evaluating model of cardiovascular function is made by BP algorithm of artificial neural networks. The results will be helpful to clarify the difference and mechanism of different models of repetitive postural change experiments, which could provide theoretical and experimental supports to aerospace medicine research, selection of pilots and astronauts and the training therapy for cardiovascular vagal syncope patients.