title: Computational modeling of cardiovascular response to orthostatic stress.
abstract: The objective of this study is to develop a model of the cardiovascular system capable of simulating the short-term (< or = 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.
authors.affiliation: Harvard University-Massachusetts Institute of Technology Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Heldt
authors.forename: Eun B
authors.initials: EB
authors.lastname: Shim
authors.forename: Roger D
authors.initials: RD
authors.lastname: Kamm
authors.forename: Roger G
authors.initials: RG
authors.lastname: Mark
mesh_terms: D017704:Baroreflex / Q000502:physiology; D002319:Cardiovascular System / Q000503:physiopathology*; D003198:Computer Simulation; D004244:Dizziness / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008150:Lower Body Negative Pressure; D008955:Models, Cardiovascular; D011187:Posture / Q000502:physiology; D013026:Space Flight; D013312:Stress, Physiological / Q000503:physiopathology*; D018667:Tilt-Table Test