Verhoeff Kevin, Mitchell Jamie R
Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and.
Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada; and
Adv Physiol Educ. 2017 Sep 1;41(3):348-353. doi: 10.1152/advan.00190.2016.
Because the heart and lungs are confined within the thoracic cavity, understanding their interactions is integral for studying each system. Such interactions include changes in external constraint to the heart, blood volume redistribution (venous return), direct ventricular interaction (DVI), and left ventricular (LV) afterload. During mechanical ventilation, these interactions can be amplified and result in reduced cardiac output. For example, increased intrathoracic pressure associated with mechanical ventilation can increase external constraint and limit ventricular diastolic filling and, therefore, output. Similarly, high intrathoracic pressures can alter blood volume distribution and limit diastolic filling of both ventricles while concomitantly increasing pulmonary vascular resistance, leading to increased DVI, which may further limit LV filling. While LV afterload is generally considered to decrease with increased intrathoracic pressure, the question arises if the reduced LV afterload is primarily a consequence of a reduced LV preload. A thorough understanding of the interaction between the heart and lungs can be complicated but is essential for clinicians and health science students alike. In this teaching review, we have attempted to highlight the present understanding of certain salient aspects of cardiopulmonary physiology and pathophysiology, as well as provide a resource for multidisciplined health science educators and students.
由于心脏和肺位于胸腔内，了解它们之间的相互作用对于研究每个系统至关重要。这些相互作用包括心脏外部约束的变化、血容量重新分布（静脉回流）、直接心室相互作用（DVI）以及左心室后负荷。在机械通气期间，这些相互作用会被放大，导致心输出量减少。例如，与机械通气相关的胸内压升高会增加外部约束，限制心室舒张期充盈，从而限制心输出量。同样，高胸内压会改变血容量分布，限制两个心室的舒张期充盈，同时增加肺血管阻力，导致DVI增加，这可能会进一步限制左心室充盈。虽然一般认为胸内压升高会使左心室后负荷降低，但问题是左心室后负荷降低是否主要是左心室前负荷降低的结果。对心肺之间相互作用的透彻理解可能很复杂，但对临床医生和健康科学专业学生来说都是必不可少的。在这篇教学综述中，我们试图突出当前对心肺生理和病理生理某些显著方面的理解，并为多学科健康科学教育工作者和学生提供一个资源。
