BLOOD VOLUME & VENOUS RETURN IN THERMAL STRAIN

该项目的长期目标是揭示 生理机制，提供了维持一个 静脉回流充足，因此心脏充盈充足 压力，在人类的热应变条件下。 我们的具体 未来五年的目标如下： 1)设计并验证一种技术， 静脉流出道阻力变化的测定 在运动和/或热应激期间在依赖静脉中蓄积。 2)以确定提供血容量的机制 已知的伴随着身体训练的扩张。 我们假设 这些都涉及到心肺压力感受器反射的减少 敏感性和合成血浆的能力增加 proteins. 3)以确定急性血容量扩张是否会改变 外周血管收缩反应对心肺 压力感受器卸载，从而模仿物理效应 训练 4)来描述体液腔室的变化 在运动过程中，同时用不同的 钠浓度。 我们假设饮用稀释盐水 在运动过程中会提供一个更好的维护身体， 水平衡和血容量。 为了实现这些目标，我们将研究 人类志愿者在运动过程中的反应， 下体负压引起的应力，以及 进行性脱水 我们会把血液循环反应 (e.g.前臂血管对主动脉阻力的变化 生理刺激（例如，中心静脉压的变化）， 这些研究。 我们将研究这些志愿者的条件， 他们的血容量被人为操纵， 血清白蛋白输注，自然，由于有氧运动， 训练 我们希望了解物理因素， 有助于血液在外周和 生理因素，以防止静脉池。 这些 研究应该提高我们对动脉控制的理解， 血压，并应提供新的知识， 人类用来抵抗晕厥的机制， 静脉回流减少。

The long-term objectives of this project are to uncover the physiological mechanisms that provide for the maintenance of an adequate venous return, and therefore an adequate cardiac filling pressure, in conditions of thermal strain in humans. Our specific aims over the next five years are as follows: 1) to devise and validate a technique that will define the role of venous outflow resistance changes in the determination of blood pooling in dependent veins during exercise and/or heat stress. 2) to determine the mechanisms that provide for the blood volume expansion known to accompany physical training. We hypothesize that these involve a decrease in cardiopulmonary baroreflex sensitivity and an increase in the capacity to synthesize plasma proteins. 3) to determine whether acute blood volume expansion will modify the peripheral vasoconstrictor response to cardiopulmonary baroreceptor unloading and thereby mimic the effects of physical training. 4) to characterize the shifts in the body fluid compartments during exercise while rehydrating with solutions of different sodium concentrations. We hypothesize that drinking dilute saline during exercise will provide a better maintenance of the body,s water balance and of blood volume as well. In order to accomplish these aims, we will study the circulatory responses of human volunteers during exercise, during gravitational stress induced by lower body negative pressure, and during progressive dehydration. We will relate the circulatory responses (e.g. change in forearm vascular resistance to the primary physiological stimuli (e.g. change in central venous pressure) in these studies. We will study these volunteers in conditions in which their blood volumes have been manipulated artificially, by serum albumin infusion, and naturally, as a result of aerobic training. We expect to learn about the physical factors that contribute to the pooling of blood in the periphery and the physiological factors that act to oppose venous pooling. These studies should improve our understanding of the control of arterial blood pressure and should provide new knowledge about the mechanisms that humans employ to resist syncope in conditions of reduced venous return.