Cardiac output is determined by the interaction of cardiac pump function and the mechanical properties of the peripheral circulation that govern venous return. Increasing pleural pressure impedes peripheral venous return but aids cardiac ejection; on the other hand, decreasing pleural pressure can augment venous return but impedes the emptying of the left ventricle, creating an increase in aortic pressure. Whether a fall in pleural pressure leads to an increase or decrease in cardiac output depends upon the functional state of the heart and its sensitivity to changes in afterload. Understanding the effect of pleural pressure on cardiac output may lead to the development of therapeutic or diagnostic techniques using altered pleural pressure.
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