Cardiopulmonary Systems Modeling in Altered Gravity
Mechanistic simulation of cardiovascular, pulmonary, and autonomic responses to altered gravity, tilt, and lower body negative pressure.
Altered gravity produces rapid changes in fluid distribution, vascular loading, gas exchange, and autonomic control. These effects shape cardiovascular performance, influence countermeasure response, and interact with other spaceflight risks such as EVA workload and decompression stress.
Our research develops a closed-loop cardiopulmonary model that simulates these responses across terrestrial analogs and spaceflight-relevant conditions. The model is designed to capture the coupled behavior of the heart, vasculature, lungs, gas exchange, and reflex control systems as a single dynamical system.
The model combines lumped-parameter physiology with explicit control architectures to represent cardiovascular and respiratory adaptation under changing gravitational load.
- Cardiovascular structure: four-chamber heart, dynamic valves, arterial and venous compartments, and hydrostatic branch dependence
- Pulmonary structure: multi-compartment lung model with dynamic pleural pressure and zonal blood flow
- Gas exchange and control: oxygen, carbon dioxide, and inert gas exchange coupled to baroreflex, chemoreflex, stretch reflex, and autoregulation
The model is implemented in Julia using ModelingToolkit.jl and supports tilt-angle protocols, altered-gravity environments, and lower body negative pressure studies. It is built to support both forward simulation and physiological interpretation.
Design-of-experiments view of a 90-degree stand test used to probe cardiovascular adaptation under gravitational loading.
The model resolves the main physiological subsystems relevant to altered-gravity adaptation:
- Cardiovascular flow and pressure dynamics across major vascular branches
- Pulmonary mechanics and breathing-dependent pleural pressure variation
- Zonal gas exchange between lungs, blood, and tissues
- Autonomic control through arterial baroreflex, cardiopulmonary reflex, and chemoreception
This structure allows the model to represent beat-to-beat hemodynamics, fluid redistribution, and compensatory control responses in a way that is interpretable and extensible.
The model is benchmarked against known responses in tilt and LBNP protocols, including changes in compartment volumes, venous return, arterial pressure waveforms, and reflex-mediated control responses.
Validation is supported by comparison to prior physiological modeling work and by internal consistency across scenarios spanning supine, standing, tilt, and altered-gravity cases.
Reflex-response visualization showing the major effector pathways governing vascular tone, heart rate, and contractility.
- A closed-loop model of cardiovascular and pulmonary adaptation to altered gravity
- Explicit coupling between gas exchange, circulation, and autonomic control
- A simulation framework for tilt, LBNP, and partial-gravity scenarios
- A basis for individualized physiology and countermeasure analysis
This work provides a mechanistic platform for studying human adaptation in spaceflight-relevant environments. It supports countermeasure design, physiology-based mission planning, and downstream coupling to decompression, wearable sensing, and operational decision-support models.