Computational Model Estimates of Cardiovascular Deconditioning Due to Long-Term Microgravity Exposure in Space Missions

In this study we provide results from a Computational Model (NELME: Numerical Estimation of Long-term Modified-gravity effects) of the cardiovascular system deconditioning under modified gravity exposure. Orthostatic hypotension is a well-known risk that may put a human mission into jeopardy due to the effects caused by a transition from long-term hypogravity to sudden gravity exposure. This factor is mitigated when astronauts return to Earth because of external medical help is available but it may be a problem when landing on Mars or other deep space scenarios. We simulate a number of different mission scenarios at different gravity levels. Parameters of the model have been calculated and results have been validated from available experimental data from previous experiments in parabolic flights and experiments with diverse exposure to different gravity loads. Results show that vascular resistance is not mitigated by Moon or Mars gravity from two weeks to nine-months exposure. Results of the intensive numerical simulations show a at response of the vascular resistance when returning to the Earth gravity until g=0.45 g(Earth). Then the response is nearly lineal until g=0.78 g(Earth) when normal values from g(Earth) are recovered. Aerobic exercise is not enough to fully compensate this decondition, with women benefitting more than men. A total risk of putting a human mission in jeopardy is then estimated, showing that a Mars mission returning to Earth is still safe to be conducted in accordance with previous studies. Other Moon-based scenarios are estimated as well. This model has been successful in estimating the risks associated with cardiovascular deconditioning in human long-term missions in space, with unprecedented and substantial variability of gravity exposure, thermal stress and mission scenarios as compared to previous studies.