The cardiovascular (CV) system is one of the major physiological systems affected during spaceflight. Altered-gravity environments cause a change in the hydrostatic pressure distribution on the body, leading to a cephalad fluid shift where blood volume in the lower extremities reduces by up to 1L and increases in the trunk and head (also known as “puffy face/chicken leg” syndrome). This leads to hypovolemia, changes in hematocrit concentration, and aerobic deconditioning. It may also be a cause of spaceflight associated neuro-ocular syndrome (SANS).

We use a computational model of the CV system to reach beyond the limitations of existing data and study the effects of changing gravity levels. This model has been validated over a number of experimental studies and is continuously being extended to include the ability to model new conditions and physiological phenomena; including exercise, pulmonary function, long duration hemodynamic changes, and metabolic cost.

The CV model is being expanded to include cerebral autoregulation, which ensures a constant blood flow to the brain despite fluctuations in systemic blood pressure. Based on cerebral artery blood velocity findings from LBNP studies, we developed a cerebral autoregulation feedback mechanism that functions within the current CV model to analyze the dynamic blood flow behavior within the brain. This research effort creates a unique opportunity to explore cerebral perfusion in conditions where human experimentation is not feasible due to subject safety.

We are also integrating the ability to mimic trauma conditions and their associated CV effects for both astronauts and pilots. We are characterizing individual differences in a wide range of subject types – varying in body type, anthropometrics, sex, baseline CV characteristics, athletic ability, and hydration – to predict physiological responses to simulated acute blood loss in different gravity scenarios. A respiratory system model is also being developed to analyze the responses of hypoxic effects based on these individual differences.