Steady-State Analysis of Gravitational Effects on Hemodynamics

Human tolerance to hypergravity is of increasing importance given the rising number of spaceflight participants. In this paper, we present a mathematical model of the human circulatory system that can predict an individual’s tolerance to hypergravity. We adopt a steady-state approach, where simplicity enables us to predict an individual’s tolerance to high gravitational acceleration (G-tolerance) with lower computational cost. Moreover, while our parameter set can be personalized to individual parameters, the model only requires cardiac output, three anthropometric measurements, vital signs, and sex to make a satisfactory prediction. Key features of the model include compartmentalization of the upper and lower circulation to allow for gravitational acceleration in the vertical direction to be varied, a model of venous collapse of the systemic veins, and feedback control to simulate regulation of heart rate and reserve volume. We also provide a case study of parameter calibration to predict G-tolerance for a single subject based on physiologic measurements before and during centrifuge-induced hypergravity. Simulation results were consistent with physiological expectations and subject report of G-related symptoms. These findings suggest that our model of the circulatory system has the potential to predict G-tolerance and serve as a clinical decision support tool to risk stratify subjects prior to spaceflight.