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背景:下体负压是模拟重力-惯性力场对人体循环功能影响的有效研究方法之一,在一定程度上可模拟正加速度对人体的影响。目的:探讨坐位下身负压暴露时人体心血管系统的代偿功能的变化,为高G值致空中意识丧失(G-LOC)的预防和监控提供生理学参数。设计:随机自身对照实验研究。地点和对象:实验地点在本系脑功能实验室,实验对象为15名健康自愿者青年男性,均系本校大学二年级学员。干预:采用坐位下身负压舱,每名被试者均要受到-4.00kPa、-6.67kPa下身负压的作用。主要观察指标:分别测试负压前、下身负压暴露于-4.00kPa,-6.67kPa的0.5,1,2,3,4,5min和卸压后1,3,5min的血压、心率及主观症状和客观体征等。在-4.00kPa下身负压作用时,收缩压与舒张压与负压前对照差别无显著性意义;心率在下身负压作用3,4,5min时,显著增快(P<0.05)。结果:在-6.67kPa下身负压作用时,心率在负压作用各时间点与负压作用前比较均显著增快(P<0.01);收缩压与负压前对照无明显改变,舒张压显著升高(P<0.05)。结论:坐位下身负压造成血液在下肢积聚,大脑供血量减少,心血管系统通过加强代偿功能,使大部分被试未发生晕厥前症状。随着下身负压值的进一步增大和作用时间的延长,机体出现失代偿现象,导致出现晕厥前症状。为高G值致空中意识丧失(G-LOC
Background: The lower body negative pressure is one of the effective methods to simulate the effect of gravity-inertial force on human circulatory function. To a certain extent, it can simulate the effect of positive acceleration on the human body. Objective: To explore the changes of compensatory function of human cardiovascular system during sitting negative pressure exposure, and to provide physiological parameters for prevention and monitoring of G-LOC loss in high G value airway. Design: Randomized self-controlled experimental study. Venue and Subject: The experimental site is located in our Department of Brain Function Laboratory. The subjects were 15 healthy volunteers young men, all of whom were sophomores of our university. INTERVENTIONS: The negative pressure cabin at the lower seat was used. Each subject was subjected to the negative pressure of -4.00 kPa and -6.67 kPa. MAIN OUTCOME MEASURES: Blood pressure, heart rate and subjective symptoms at 0.5, 1, 2, 3, 4 and 5 minutes after exposure to -4.00 kPa and -6.67 kPa and 1,3,5 minutes after release And objective signs and so on. There was no significant difference between systolic pressure and diastolic pressure and negative pressure control before negative pressure was applied at -4.00 kPa. Heart rate was significantly increased at 3, 4 and 5 min of lower negative pressure (P <0.05). Results: At -6.67 kPa lower body negative pressure, heart rate significantly increased at different time points of negative pressure (P <0.01), and systolic blood pressure had no significant changes Increased (P <0.05). CONCLUSIONS: Sitting negative pressure causes blood to accumulate in the lower extremities. Blood supply to the brain is reduced. The cardiovascular system compensates most patients for pre-syncope symptoms. With the further increase of the lower body negative pressure value and the prolongation of the action time, the phenomenon of decompensation occurs in the body, leading to pre-syncope symptoms. Loss of Consciousness Caused by High G Value (G-LOC