Computational modeling of cardiovascular response to orthostatic stress

Model Status

This CellML model runs in both COR and PCEnv. The units have been checked and they balance. This is a lumped parameter model for cardiac activation based on the work of Heldt et al. 2002. This CellMl model represents a structurally complete model of a lumped parameter, physiologically-based circulatory system. It uses the Heldt et al activation function and extends the lumped parameter circulation model such that the circulation through organs is represented. The circulation includes pressures, flows, and transport of a simple substance 'x' which is neither metabolised or excreted. The parameter values for resistors, capacitors, or inductors are not quite right as the flows are not distributed according to other studies and the time-course of substance around the circuit is not correct either - hence it is just structurally correct.

Model Structure

ABSTRACT: The objective of this study is to develop a model of the cardiovascular system capable of simulating the short-term (less than or equal to 5 min) transient and steady-state hemodynamic responses to head-up tilt and lower body negative pressure. The model consists of a closed-loop lumped-parameter representation of the circulation connected to set-point models of the arterial and cardiopulmonary baroreflexes. Model parameters are largely based on literature values. Model verification was performed by comparing the simulation output under baseline conditions and at different levels of orthostatic stress to sets of population-averaged hemodynamic data reported in the literature. On the basis of experimental evidence, we adjusted some model parameters to simulate experimental data. Orthostatic stress simulations are not statistically different from experimental data (two-sided test of significance with Bonferroni adjustment for multiple comparisons). Transient response characteristics of heart rate to tilt also compare well with reported data. A case study is presented on how the model is intended to be used in the future to investigate the effects of post-spaceflight orthostatic intolerance.

Schematic diagram of full body circulation model.

The original paper reference is cited below:

Computational modeling of cardiovascular response to orthostatic stress, T. Heldt, E.B. Shim, R.D. Kamm, and R.G. Mark, 2002, Journal of Applied Physiology, 92, 1239-1254. PubMed ID: 11842064