Computational model of cardiovascular function during orthostatic stress.

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Mathematical Modeling

Background:

• Orthostatic intolerance is a critical problem for astronauts after spaceflight.
• Understanding the cardiovascular system's response to microgravity and re-adaptation is vital for space exploration.
• Current life-science space programs face challenges in mitigating post-flight orthostatic intolerance.

Purpose of the Study:

• To investigate the mechanisms of post-spaceflight orthostatic intolerance using mathematical modeling.
• To simulate the cardiovascular system's transient response to orthostatic stress in microgravity-adapted individuals.
• To evaluate the effectiveness of a potential countermeasure for orthostatic intolerance.

Main Methods:

• A twelve-compartment lumped parameter model of the human hemodynamic system was employed.
• The model incorporated set-point regulation of the arterial baroreflex and cardiopulmonary reflex.
• Simulations were conducted across a range of physiological values and compared with astronaut stand-test data.

Main Results:

• The mathematical model successfully simulated transient heart rate responses to orthostatic stress.
• Simulations provided insights into hypothesized mechanisms of post-spaceflight orthostatic intolerance.
• The study explored the impact of a potential countermeasure on orthostatic stress responses.

Conclusions:

• Mathematical modeling offers a valuable approach to studying orthostatic intolerance in astronauts.
• The findings contribute to understanding cardiovascular adaptation and de-adaptation to spaceflight.
• The research supports the development of countermeasures to improve astronaut health and safety.