Michael E. DeBakey Institute, Texas A&M University, College Station, Texas.
Am J Physiol Regul Integr Comp Physiol. 2021 Jun 1;320(6):R851-R870. doi: 10.1152/ajpregu.00260.2019. Epub 2021 Feb 17.
Although Guyton's graphical analysis of cardiac output-venous return has become a ubiquitous tool for explaining how circulatory equilibrium emerges from heart-vascular interactions, this classical model relies on a formula for venous return that contains unphysiological assumptions. Furthermore, Guyton's graphical analysis does not predict pulmonary venous pressure, which is a critical variable for evaluating heart failure patients' risk of pulmonary edema. Therefore, the purpose of the present work was to use a minimal closed-loop mathematical model to develop an alternative to Guyton's analysis. Limitations inherent in Guyton's model were addressed by ) partitioning the cardiovascular system differently to isolate left ventricular function and lump all blood volumes together, ) linearizing end-diastolic pressure-volume relationships to obtain algebraic solutions, and ) treating arterial pressures as constants. This approach yielded three advances. First, variables related to morbidities associated with left ventricular failure were predicted. Second, an algebraic formula predicting left ventricular function was derived in terms of ventricular properties. Third, an algebraic formula predicting flow through the portion of the system isolated from the left ventricle was derived in terms of mechanical properties without neglecting redistribution of blood between systemic and pulmonary circulations. Although complexities were neglected, approximations necessary to obtain algebraic formulas resulted in minimal error, and predicted variables were consistent with reported values.
尽管盖顿（Guyton）对心输出量-静脉回流的图形分析已成为解释心血相互作用如何产生循环平衡的无处不在的工具，但该经典模型依赖于包含非生理假设的静脉回流公式。此外，盖顿（Guyton）的图形分析无法预测肺静脉压，而肺静脉压是评估心力衰竭患者肺水肿风险的关键变量。因此，本工作的目的是使用最小闭环数学模型来替代盖顿（Guyton）的分析。通过（i）以不同的方式划分心血管系统，将左心室功能分离出来并将所有血液容积归为一类，（ii）对舒张末期压力-容积关系进行线性化以获得代数解，以及（iii）将动脉压力视为常数，解决了盖顿（Guyton）模型固有的局限性。该方法取得了三个进展。首先，预测了与左心室衰竭相关的病态相关的变量。其次，根据心室特性推导出了一个预测左心室功能的代数公式。第三，推导出了一个在不忽略体循环和肺循环之间血液再分配的情况下，根据机械特性用代数公式预测从左心室分离的系统部分的流量的公式。虽然忽略了复杂性，但获得代数公式所需的近似值导致的误差最小，并且预测的变量与报告的值一致。
