### Abstract

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 CO_{2} concentration (P_{ETCO2}) 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 P_{ETCO2} 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 P_{ETCO2} 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 P_{ETCO2}-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.

Original language | English (US) |
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Title of host publication | Proceedings of the 7th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering |

Publisher | World Scientific Publishing Co. Pte Ltd |

Pages | 362-369 |

Number of pages | 8 |

ISBN (Print) | 9812568603, 9789812568601 |

State | Published - 2006 |

Event | 2005 7th International Workshop on Mathematical Methods on Scattering Theory and Biomedical Engineering - Nymphaio, Greece Duration: Sep 8 2005 → Sep 11 2005 |

### Other

Other | 2005 7th International Workshop on Mathematical Methods on Scattering Theory and Biomedical Engineering |
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Country | Greece |

City | Nymphaio |

Period | 9/8/05 → 9/11/05 |

### Fingerprint

### ASJC Scopus subject areas

- Biomedical Engineering
- Applied Mathematics

### Cite this

*Proceedings of the 7th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering*(pp. 362-369). World Scientific Publishing Co. Pte Ltd.

**Nonlinear physiological systems identification : Application to cerebral hemodynamics under orthostatic stress.** / Mitsis, Georgios D.; Zhang, Rong; Levine, Benjamin D.; Marmarelis, Vasilis Z.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*Proceedings of the 7th International Workshop on Mathematical Methods in Scattering Theory and Biomedical Engineering.*World Scientific Publishing Co. Pte Ltd, pp. 362-369, 2005 7th International Workshop on Mathematical Methods on Scattering Theory and Biomedical Engineering, Nymphaio, Greece, 9/8/05.

}

TY - GEN

T1 - Nonlinear physiological systems identification

T2 - Application to cerebral hemodynamics under orthostatic stress

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.

UR - http://www.scopus.com/inward/record.url?scp=84903702686&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84903702686&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:84903702686

SN - 9812568603

SN - 9789812568601

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

ER -