Dynamic cardio-respiratory-cerebrovascular interactions

我们适应日常生活挑战的能力取决于对工作的骨骼肌和大脑的血液供应。我们计划探索两个主题，突出氧气向工作肌肉输送的重要作用，并开发明确测量脑血流量的方法。我们的第一个实验将探索缺血预适应对增强肌肉功能的影响。缺血预适应是通过在血液流动受到更大挑战之前限制血液流动一段时间来完成的。最近，我们发现，停止肌肉的血液流动，然后在运动前允许短暂的恢复，会延迟肌肉代谢的适应。我们预计，缺血预适应将使肌肉为更长时间的血流停止的挑战做好准备，从而使肌肉能够很好地应对运动。我们将在现有技术的基础上增加磁共振波谱，以监测肌肉内代谢事件。通过改变吸入气体浓度和动脉血压来控制肌肉的氧气供应，将使我们能够测试假说，表明氧气在体力活动开始时调节肌肉新陈代谢的重要性。我们的第二个系列实验将检查几种情况下流向大脑的血液。我们将比较通过大脑中动脉的脑血流速度和颈部颈内动脉的绝对血流量。在初步研究中，我们确定大脑中动脉血流速度的估计在许多情况下是不正确的。我们将调查影响血压的不同药物的效果、血液二氧化碳水平的变化以及姿势的变化，以表明速度并不能准确反映脑血流量。我们的最终目标是考虑脑血流的变化如何影响呼吸的调节，并影响对直立姿势的耐受能力。通过这项研究，学生将获得有关心血管和脑血流综合机制的关键知识，这些机制有助于人类对日常生活中的身体活动和直立姿势的生理反应。

Our ability to adapt to the challenges of daily life depends on blood flow supply to the working skeletal muscles and to the brain. We plan to explore two topics that highlight the important role of oxygen delivery to working muscles and develop methods that explicitly measure brain blood flow. Our first experiments will explore the impact of ischemic preconditioning to enhance muscle function. Ischemic preconditioning is accomplished by restricting blood flow for short periods of time before a larger challenge to blood flow. Recently we showed that stopping blood flow to a muscle then allowing a brief recovery prior to exercise delayed adaptation of muscle metabolism. We anticipate that ischemic preconditioning will prepare the muscle for the challenge of longer arrest of blood flow allowing the muscle to cope well with exercise. We will add magnetic resonance spectroscopy to our existing techniques to monitor intramuscular metabolic events. Manipulation of oxygen supply to the muscle by changing inspired gas concentrations and arterial blood pressure will allow us to test hypotheses showing the importance of oxygen in regulation of muscle metabolism at the onset of physical activity. Our second series of experiments will examine blood flow to the brain under several conditions. We will compare estimates from brain blood flow velocity through the middle cerebral artery to absolute blood flow in the internal carotid artery in the neck. In preliminary research, we determined that the estimates from the middle cerebral artery velocity are incorrect in many circumstances. We will investigate the effects of different drugs that affect blood pressure, changes in blood levels of carbon dioxide and changes in posture to show that velocity does not accurately reflect brain blood flow. Our final objective is to consider how changes in brain blood flow affect the regulation of breathing and impact the ability to tolerate an upright posture. Through this research, students will gain critical knowledge about the integrative cardiovascular and brain blood flow mechanisms that contribute to human physiological responses to physical activity and upright posture in our everyday lives.