Including gravitational stress in a blood pressure wave propagation model for cardiovascular space physiology

Human factors remain an important issue for long term space flight. In particular, a better understanding of the response of the cardiovascular system to changes in orthostatic stress is crucial for the development of better countermeasures for astronauts. The goal of this study is to better characterize blood fluid shift during orthostatic stress using 1D pulse propagation model that will includes the effects of gravity on the arterial and venous system. Effects of gravity and vein collapsible properties were implemented in a 1D pulse wave propagation model. For single artery/vein model, we have shown that the model is able to simulate hydrostatic pressure and qualitatively reproduce increased arterial blood volume flow after a muscle contraction that is an influential phenomenon in orthostatic tolerance via increased venous return. To go forwards to a qualitative estimate of in vivo data, a model of the full circulation has to be considered and peripheral vascular regulation has to be implemented. We aim at a better represention of physiological responses and provide new information about the relative importance of the different phenomena involved in fluid shift towards the lower body.