The Integrative Effect of Changes in Intrathoracic Pressure on Cardiac and Cerebrovascular Function.

在呼吸过程中，胸腔内压力的变化（胸腔内压力）可以通过对心脏的左右两侧施加不同的压力来改变心脏的充盈和排空方式。由于肺、心、脑的循环是串联的，胸内压力的变化不仅会影响心脏和肺的血流，还可能通过动脉流入、颅内压力和静脉流出的变化而改变脑血流。据我们所知，这三个内在联系系统之间的重要相互作用从未被研究过，胸内压力的变化可能对肺和心脏以外的器官产生重大影响，特别是在人体自然生理平衡（体内平衡）受到挑战时。这个研究项目的目的是同时测量胸内压、心脏充盈和排空、脑血流量以及流入和流出大脑的血流量，并检查胸内压的变化如何同时改变这些系统。此外，我们将通过各种挑战来改变体内平衡，包括血容量负荷和血液中氧气和二氧化碳水平的变化。因此，研究这三个系统在任何生理刺激下如何相互作用，就有相当大的新颖性。迄今为止，很少有研究调查了胸内压的变化如何影响心功能，特别是当身体充满液体或血气发生变化时，即低氧和高二氧化碳水平。此外，没有研究系统地调查了胸内压如何影响脑血流。因此，三种系统方法的结合将大大增加我们目前在影响人体血流调节的机械因素这一重要领域的知识。

Changes in pressures within the chest cavity (intrathoracic pressure) made during breathing can alter how the heart fills and empties by placing different challenges to the right and left sides of the heart. As the lungs, heart and brain circulation are all in series, changes in intrathoracic pressure will not only influence blood flow in the heart and lungs but may also alter brain blood flow through changes in arterial inflow, pressure within the skull and venous outflow. To our knowledge, this important interaction between three intrinsically linked systems has never been studied and changes in intrathoracic pressure could have significant implications beyond the lungs and heart, especially during challenges to the body's natural physiological balance (homeostasis). The aim of this program of research is to simultaneously measure intrathoracic pressure, heart filling and emptying, brain blood flow as well as blood flow into and out of the brain and examine how changes in intrathoracic pressure simultaneously alter these systems. Additionally, we will alter homeostasis with a variety of challenges including blood volume loading and changes in oxygen and carbon dioxide levels within the blood. As such, there is considerable novelty alone in investigating how all three of these systems interact during any physiological stimulus. To date there have been few studies that have investigated how changes in intrathoracic pressure affect cardiac function especially when the body is fluid loaded or there are changes to blood gases i.e. low oxygen and high carbon dioxide levels. Additionally, no study has systematically investigated how intrathoracic pressure effects brain blood flow. Therefore, the combination of the three systems approach will add considerably to our present knowledge in this important area of mechanical factors that affect blood flow regulation in humans.