Modeling individual differences in cardiovascular response to gravitational stress using a sensitivity analysis.

Area of Science:

• Cardiovascular Physiology
• Computational Biology
• Biomedical Engineering

Background:

• Human cardiovascular (CV) system responses vary significantly across individuals in different gravitational environments.
• Computational modeling offers a way to predict CV responses, but complexity and individual parameter variations pose challenges.
• Accurate individual CV response prediction is vital for spaceflight and understanding physiological adaptation.

Purpose of the Study:

• To investigate the influence of hemodynamic model parameters on cardiovascular responses during a simulated tilt test.
• To identify the subset of parameters most critical for predicting systemic physiological outcomes under varying gravity.
• To enhance the accuracy of computational models for individual cardiovascular response prediction.

Main Methods:

• A 21-compartment lumped-parameter hemodynamic model was used.
• Sensitivity analysis, employing Latin hypercube sampling and partial rank correlation coefficients, was performed.
• Model parameters were varied across a normal physiological range under simulated gravity from 0g to 1g.

Main Results:

• Parameters related to large vein properties (length, resistance, compliance) and right ventricular function most influenced CV outcomes.
• Cardiac and large vein parameters were dominant across most outcome measures, including heart rate, stroke volume, and blood pressure.
• Parameter influence remained consistent across different gravitational levels.

Conclusions:

• Accurate valuation of specific model parameters, particularly those related to the heart and large veins, is essential for precise CV response simulations.
• Fitting models to data in 1g can improve predictive accuracy for responses in reduced gravity environments.
• This sensitivity analysis provides a roadmap for optimizing computational models for individual cardiovascular predictions.