TY - GEN
T1 - Nonlinear physiological systems identification
T2 - 2005 7th International Workshop on Mathematical Methods on Scattering Theory and Biomedical Engineering
AU - Mitsis, Georgios D.
AU - Zhang, Rong
AU - Levine, Benjamin D.
AU - Marmarelis, Vasilis Z.
PY - 2006
Y1 - 2006
N2 - The effects of orthostatic stress, induced by lower body negative pressure (LBNP), on cerebral hemodynamics were examined in a nonlinear context. Spontaneous fluctuations of beat-to-beat mean arterial blood pressure (MABP) in the finger, mean cerebral blood flow velocity (MCBFV) in the middle cerebral artery, as well as breath-by-breath endtidal CO2 concentration (PETCO2) were measured continuously in ten healthy subjects under resting conditions and during graded LBNP to presyncope. A two-input nonlinear Laguerre-Volterra network model was employed to study the dynamic effects of MABP and PETCO2 changes, as well as their nonlinear interactions, on MCBFV variations in the very low (VLF; below 0.04 Hz), low (LF; 0.04-0.15 Hz) and high frequency (HF; 0.15-0.30 Hz) ranges. Dynamic cerebral autoregulation was described by the model terms corresponding to MABP, while cerebral vasomotor reactivity was described by the model PETCO2 terms. The magnitude of the linear and nonlinear MABP-MCBFV Volterra kernels increased substantially above -30 mm Hg LBNP in the VLF range, implying impaired dynamic autoregulation. In contrast, the magnitude of the PETCO2-MCBFV kernels reduced during LBNP at all frequencies, suggesting attenuated cerebral vasomotor reactivity. These changes may reflect a progressively more unstable circulation that could ultimately lead to cerebral hypoperfusion and syncope.
AB - The effects of orthostatic stress, induced by lower body negative pressure (LBNP), on cerebral hemodynamics were examined in a nonlinear context. Spontaneous fluctuations of beat-to-beat mean arterial blood pressure (MABP) in the finger, mean cerebral blood flow velocity (MCBFV) in the middle cerebral artery, as well as breath-by-breath endtidal CO2 concentration (PETCO2) were measured continuously in ten healthy subjects under resting conditions and during graded LBNP to presyncope. A two-input nonlinear Laguerre-Volterra network model was employed to study the dynamic effects of MABP and PETCO2 changes, as well as their nonlinear interactions, on MCBFV variations in the very low (VLF; below 0.04 Hz), low (LF; 0.04-0.15 Hz) and high frequency (HF; 0.15-0.30 Hz) ranges. Dynamic cerebral autoregulation was described by the model terms corresponding to MABP, while cerebral vasomotor reactivity was described by the model PETCO2 terms. The magnitude of the linear and nonlinear MABP-MCBFV Volterra kernels increased substantially above -30 mm Hg LBNP in the VLF range, implying impaired dynamic autoregulation. In contrast, the magnitude of the PETCO2-MCBFV kernels reduced during LBNP at all frequencies, suggesting attenuated cerebral vasomotor reactivity. These changes may reflect a progressively more unstable circulation that could ultimately lead to cerebral hypoperfusion and syncope.
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U2 - 10.1142/9789812773197_0035
DO - 10.1142/9789812773197_0035
M3 - Conference contribution
AN - SCOPUS:84903702686
SN - 9812568603
SN - 9789812568601
T3 - Proceedings of the 7th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering
SP - 362
EP - 369
BT - Proceedings of the 7th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering
PB - World Scientific Publishing Co. Pte Ltd
Y2 - 8 September 2005 through 11 September 2005
ER -