Patient-specific modelling of head-up tilt

Area of Science:

• Physiology
• Biomedical Engineering
• Computational Biology

Background:

• Short-term cardiovascular responses to head-up tilt (HUT) are crucial for maintaining blood pressure homeostasis.
• Complex cardiovascular regulation mechanisms are involved in adapting to postural changes.

Purpose of the Study:

• To develop a patient-specific computational model simulating cardiovascular dynamics during HUT.
• To utilize heart rate as an input to predict arterial blood pressure changes during HUT.
• To investigate cardiovascular regulation by modeling blood pooling and adjustments in cardiac contractility and vascular resistance.

Main Methods:

• A five-compartment model of the systemic circulation (arteries, veins, left ventricle) was created.
• A physiologically based submodel accounted for gravitational blood pooling in lower extremities.
• Cardiovascular regulation was modeled by adjusting cardiac contractility and vascular resistance.
• Patient-specific parameters were estimated using sensitivity analysis, parameter prediction, and non-linear optimization.
• The model was validated using aortic and carotid HUT data from five healthy subjects.

Main Results:

• The patient-specific model successfully fitted dynamic changes in arterial blood pressure at the carotid bifurcation level.
• The model provided physiologically reasonable estimates for parameters like blood pressure, blood volume, and cardiac output, even where direct measurements were unavailable.

Conclusions:

• A patient-specific modeling approach can accurately capture cardiovascular responses during HUT.
• This modeling technique offers a valuable tool for estimating unmeasured physiological variables and understanding cardiovascular regulation in response to postural stress.