微重力条件下人体体液调节模型的分析与改进思考

航天和模拟微重力时研究表明：微重力与现有模拟微重力模型时人体生理学变化的主要差异表现在低压区循环和体液、电解质代谢。微重力生理研究的人体模型在进一步了解微重力对人体的生理影响和机理中不可缺少,有必要将现有人体模拟微重力模型加以改进。利用人体不同角度和不同压力制度的立位倾斜（ＨＵＴ）加下体正压、头低位卧床（ＨＤＴ）加上体负压,测量心血管参数、体液调节因子、肾排泄的有关指标,与航天中的相应指标对照,筛     

血容量减少对立位应激反应影响的仿真研究

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0－25％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时政党的HR和BP;血容量减少超过约15％,在安静仰卧位时,HR和BP正常,但LBNP时BP迅速降低,系统可失去稳定性。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。     

头低位卧床7d对立位心肺循环功能的影响

目的观察短期模拟失重对立位心肺循环功能的影响,为进一步研究失重时心血管功能下降机理积累资料。方法６名健康男性被试者,头低位６°卧床７ｄ。分别观察卧床前、后立位心肺循环功能的变化。心肺循环功能检测选用ＸＸＨ－２０００型小循环心功能检测仪。结果头低位卧床７ｄ致被试者立位耐力降低,卧床后右心室射血期（ｊ－ｚ）缩短,右心室排血效率降低（Ｑ－ｊ／ｊ－ｚ升高）,提示右心功能减退。心血管调节适应性反应减弱,右心功能储备降低。结论ｃ波高度（ｈｃ）、ｃ波高度与Ｚ波高度的比值（ｈｃ／ｈｚ）可作为评价立位耐力或预测立位晕厥的指标;小循环心功能检测法评价立位心肺循环功能的变化有一定的前景。     

下体负压对抗失重／模拟失重后立位耐力降低的研究进展

下体负压对抗失重／模拟失重后立位耐力降低的研究进展姚永杰吴兴裕在航天或头低位倾斜模拟失重时，如缺乏必要的对抗措施，通常要发生立位耐力不良，表现为：休息时心率较飞行或卧床前增快、体位性低血压、同等负荷下最大和次大氧耗量减少。在立位应激时，航天员可发生心...     

失重或模拟失重时下肢顺应性变化研究的进展

失重或模拟失重引起下肢顺应性的增加,使立位时有较多的血液潴留在下肢,回流至右心房的血液减少,从而促使心输出量和动脉血压的下降,因而其变化是失重或模拟失重后立位耐力下降的主要机理之一.其研究对于深入理解立位耐力的下降机理和发展对抗方法具有一定意义.本文对失重或模拟失重时下肢顺应性的变化、测量方法、变化机理和防护方法等方面进行了论述.     

失重或模拟失重时下肢顺应性变化研究的进展

失重或模拟失重引起下肢顺应性的增加，使立位时有较多的血液潴留在下肢，回流至右心房的血液减少，从而促使心输出量和动脉血压的下降，因而其变化是失重或模拟失重后立位耐力下降的主要机理之一，其研究对于深入理解立位耐力的下降机理和发展对抗方法具有一定意义，本文对失重或模拟失重时下肢顺应性的变化，测量方法，变化机理和防护方法等方面进行了论述。     

失重或模拟失重对人体交感肾上腺活动的影响

失重或模拟失重对人体交感肾上腺活动的影响杨玉华高淳航天时航天员的体液头向转移，使机体产生一系列的生理、生化变化。心血管功能失调是航天员返回地面时超重耐力和立位耐力下降的主要原因。因此失重对心血管系统的影响、失重时心血管系统的适应性变化过程，一直是航天...     

航天飞行口服补液方案研究分析

航天飞行中体液头向分布引起的血浆容量减少是航天员飞行后立位耐力不良的重要诱因,在返回地球前进行口服补液已成为美国和俄罗斯航天飞行任务中的一项标准执行程序。通过回顾国外航天飞行后航天员体液与血浆容量变化情况,综述了美俄在轨飞行返回前口服补液方案及研究进展,比较了美俄方案的异同。美俄均采用等渗或接近等渗盐溶液,按乘员体重计算口服补液量。俄罗斯方案主要针对长期任务,航天员乘联盟飞船返回,用于对抗飞行后立位耐力不良;美国方案主要针对短期任务,航天员乘航天飞机返回,除用于对抗飞行后立位耐力不良外,同时防止再入期间+Gz加速度导致航天员意识丧失进而影响操作。针对国内外长期航天飞行任务返回阶段特点,对在轨口服补液饮品配置和执行方案进行分析,并利用地面试用实验初步验证了该方案的合理性和可行性。     

航天飞行后立位耐力不良的中医病因病机及防护措施研究进展

航天飞行后立位耐力不良严重影响航天员返回地面的适应能力。中医的整体理论适合航天医学问题研究。准确认识飞行后立位耐力不良的病因病机,能做到辨证论治,做好针对性干预。综合分析了航天飞行后立位耐力不良的中医病因病机,总结得出航天飞行后立位耐力不良的中医病因包括重力变化、节律变化、性别差异、航天器特殊生活环境的变化、心理因素、饮食因素等6个方面,中医病机为脏腑功能紊乱,调整适应能力下降,以及气血不足,清阳不升和血供动力不足。同时综述了中医对抗飞行后立位耐力不良措施的研究进展,对中医药及针灸在防治航天飞行后立位耐力不良中的应用进行了展望。     

航天中各阶段心脏动力学变化

人体正常动脉血压的维持依赖于心功能正常。国外载人航天活动各阶段心脏动力学参数是检测的重点之一。虽然航天中有关心脏动力学参数的报道不尽一致，但一般都观察到航天后立位应激时心脏动力学参数有较大变化，立位耐力降低的机理尚不清楚，心脏动力学变化对立位耐力的影响也有待探讨。本文对国外载人航天活动各阶段有关心脏动力学的变化及变化机理作一简要概述。     

模拟失重对心血管功能的影响及下体负压的对抗作用

总结了近年来本实验室有关模拟失重对心血管功能影响及下体负压对抗作用的研究，讨论了模拟失重致立位耐力不良的机理可能与心血管功能降低，脑血流降低及内分泌改变等有关，以及采用数学模型方法探讨失重致立位耐力降低机制的作用意义，重点论述了下体负压对抗方案问题。     

航天活动各阶段动脉血压的变化

人体动脉血压（BP）是4大生命体征之一,动脉血压某种程度上可反映心血管功能状态。国外载人航天活动各阶段动脉血压总是作为一种重要的心血管参数。虽然航天中有关血压的报道不尽一致,航天后立位应激时低血压普遍存在,航天后立位耐力降低的机理实质上是航天后立位低血压的机理。本文对国外载人航天活动各阶段有关动脉血压的报道和航天后立位低血压的机理研究作一简要概述。     

前庭系统适应性变化对心血管调节和立位耐力的影响

空间飞行初期人体感受到的空间适应综合征,主要由前庭传入的改变和体液头向分布引起,这种适应性的逆向变化同样发生在人体由微重力返回正常1G重力时,造成航天员返回后出现步态不稳及立位耐力下降。动物模型的证据和人体实验的部分数据表明,前庭系统通过自主神经系统影响心血管调节,其中耳石感受器的传入起着重要作用。由于心血管调节异常引起的立位耐力下降是载人航天的重要医学问题。在心血管功能和立位耐力下降过程中前庭系统功能变化有重要影响。     

航天中的心血管问题

人体的心血管系统具有向全身各组织、器官输送营养物质、排泄代谢产物、参与体液和电解质的调节、维持体内环境稳定的作用,并具有防御和保护功能。心血管系统是维持人体进行正常生理功能的重要系统,它的功能改变必然引起体内其它生理系统功能的紊乱。载人航天实践证明,轨道飞行中的微重力对心血管系统有明显的影响,可引起心血管功能失调。因而,微重力对心血管系统的影响及其防护措施的研究已成为航天医学研究中的一个重要课题。     

Head-out immersion in the non-human primate: a model of cardiovascular deconditioning during microgravity.

BACKGROUND: Orthostatic intolerance is a common complication associated with spaceflight. It has been speculated that this is due to changes in blood volume and alterations in cardiovascular reflexes. The objective of the current study was to develop a model that would allow us to study the cardiovascular system and the regulation of blood volume during short-term microgravity exposure in the primate with the intent of eventually being able to elucidate those factors responsible for the orthostatic intolerance. HYPOTHESIS: Head-out water immersion in the conscious non-human primate simulates the cardiovascular and volume regulatory responses observed in astronauts during exposure to microgravity. METHODS: Four monkeys were chronically instrumented for measuring BP and heart rate and then conditioned to the primate restraint chair. They were then subjected to 72 h of head-out water immersion (two immersions in three monkeys and one immersion in the fourth) in order to simulate the cardiovascular and renal effects of the microgravity environment. RESULTS: During the immersion, there was an increase in arterial BP (ABP) and central venous pressure (CVP) and a reflex decrease in heart rate (HR). Urine flow (UV) increased and water intake decreased, producing a negative water balance. This was not associated with an alteration in food intake. CVP and UV decreased following de-immersion. There was also resetting of the arterial baroreflex control of HR. Significant tachycardia occurred after the immersion that was associated with a decrease in ABP. CONCLUSION: These results are similar to those observed in astronauts during and after spaceflight, suggesting that head-out water immersion of the non-human primate provides a good model for studying cardiovascular and renal adaptations to spaceflight.     

模拟失重或微重力条件下中心静脉压变化的研究进展

微重力（μＧ）时体液头向转移可能是引起机体一系列变化的始动力。中心静脉压（ＣＶＰ）是衡量模拟失重（ＳＷ）或μＧ时体液头向转移的一个重要指标,也是持续监测心充盈 压唯一可能的手段。同时ＣＶＰ与本液调节关系密切。近年航天医学研究表明：μＧ早期没有出现ＣＶＰ升高,与以前ＳＷ的结果存在直接矛盾。本文概述ＳＷ时ＶＣＰ的变化、μＧ时ＶＣＰ的变化、ＳＷ或μＧ时的防护措施对ＶＣＰ的影响和μＧ时ＣＶＰ下降机理,阐明     

Orthostatic response in rats after hindlimb unloading: effect of transcranial electrical stimulation

INTRODUCTION: Orthostatic hypotension is a commonly observed phenomenon after exposure to microgravity and in various forms of autonomic failure. It has been suggested that insufficient activation of supraspinal structures responsible for descending sympathetic drive could play a significant role in this disorder. We examined the effect of transcranial electrical stimulation (TES) of autonomic nuclei within the brain on the orthostatic hypotension induced by exposure to simulated microgravity using a hindlimb unloading model. METHODS: There were 20 male Wistar rats that were suspended by their tail with the angle of elevation between the cage floor and the rat's body approximately 40 degrees. There were 11 age-matched Wistar rats used as cage controls. Orthostatic stability was examined by using an orthostatic challenge test (450 head-up test for a period of 3 min). In 10 rats from the tail-suspended group, the orthostatic challenge test was applied during TES. RESULTS: In the rats exposed to simulated microgravity (tail suspension), the orthostatic challenge test caused a significant decrease in mean arterial blood pressure by 18.4 +/- 2.2%. TES attenuated this microgravity-induced orthostatic hypotension to 9.5 +/- 1.8% (P < 0.05), which was similar to the observed response to an orthostatic challenge in the control group (6.9 +/- 1.1%). DISCUSSION: Results of this study suggest that TES significantly reduces the changes in blood pressure during an orthostatic challenge test in animals exposed to simulated microgravity. Our observations support the notion that a reduction in descending sympathoexcitatory input from supraspinal structures could contribute to orthostatic hypotension and intolerance observed in astronauts following their return from spaceflight.     

Peripheral effector mechanism hypothesis of postflight cardiovascular dysfunction

Studies on the mechanisms of cardiovascular dysfunction after space-flight are important to illustrate the cardiovascular effect of microgravity and develop appropriate multi-system countermeasures for future long-duration spaceflights. Over the past 10 yr, we have systematically studied the adaptational changes in structure and function of both the heart and vessels, using the tail-suspension rat model to simulate microgravity effects. Our results indicate that simulated microgravity induced atrophic changes and reduced contractility of the heart muscle, and upward- and downward-regulation in structure, function, and innervation state of vessels in the brain and hind body of the rat. In addition, more recent advances in relevant ground-based and space-flight studies from different laboratories have also been reviewed. Based on these studies, it has been speculated that, in addition to hypovolemia, the microgravity-induced adaptational changes in the structure and function of the two main effectors of the cardiovascular system, i.e., the arterial smooth muscle and the cardiac muscle, might be among the most important mechanisms responsible for postflight cardiovascular dysfunction and orthostatic intolerance. In this paper we will review the available evidence with comments.