Wavelet phase synchronization analysis of cerebral blood flow autoregulation
Journal
IEEE Transactions on Biomedical Engineering
Journal Volume
57
Journal Issue
4
Pages
960-968
Date Issued
2010
Author(s)
Abstract
The dynamic relationship between beat-to-beat mean arterial blood pressure (ABP) fluctuations and cerebral blood flow velocity (CBFV) variations have been intensively studied. The experimentally observed low coherence in the low-frequency band has previously indicated that the assumptions of linearity and/or stationarity, the preconditions of the linear transfer function analysis, are not valid in that frequency region. Latka et al. [M. Latka, M. Turalska, M. Glaubic-Latka, W. Kolodziej, D. Latka, and B. J. J. West, "Phase dynamics in cerebral autoregulation", Amer. J. Physiol. Heart Circ. Physiol., vol. 289 pp. H2272H2279, Jul. 2005] used a wavelet phase synchronization method to identify the instantaneous phase difference between ABP and CBFV, and low values of synchronization index were found in the low-frequency range, seeming to provide further evidence that the cerebral autoregulation system is nonstationary. Here, we focus on another possible factor corresponding for this low synchronization index-unmeasured variability. We demonstrate analytically and with a physiologically based cerebral hemodynamic model that, in the case of multiple inputs, the phase difference between one input, ABP, and the output, CBFV, will be distorted by an additional input, end-tidal CO2 ( PETCO2), and no longer accurately represent the true ABPCBFV system phase shift. We also prove that this phase distortion can be corrected if the transfer functions for ABP-CBFV and PETCO2-CBFV are known or can be estimated. A significantly increased value of synchronization index in the low-frequency band is found by using the CO2 correction term with experimental data on 13 subjects. This essentially indicates that the lack of synchronization between ABP and CBFV previously identified by Latka et al. [M. Latka, M. Turalska, M. Glaubic-Latka, W. Kolodziej, D. Latka, and B. J. J. West, "Phase dynamics in cerebral autoregulation", Amer. J. Physiol. Heart Circ. Physiol., vol.289, pp. H2272H2279, Jul. 2005] can be partly attributed to unmeasured variability. ? 2010 IEEE.
Subjects
Blood
Blood pressure
Frequency bands
Hemodynamics
Physiological models
Synchronization
Tissue
Autoregulations
Cerebral autoregulation
Cerebral blood flow
Cerebral blood flow velocities
Cerebral hemodynamics
Experimental data
Frequency regions
Linear transfer function
Low frequency band
Low frequency range
Low-coherence
Mean arterial blood pressures
Multiple inputs
Nonstationary
Phase difference
Phase distortions
Phase dynamics
Phase synchronization
Stationarity
Synchronization index
Transfer functions
arterial pressure
article
autoregulation
blood flow velocity
brain blood flow
frequency modulation
algorithm
blood pressure
brain circulation
brain cortex
computer simulation
electroencephalography
homeostasis
human
multivariate analysis
physiology
procedures
signal processing
vascularization
carbon dioxide
Algorithms
Blood Flow Velocity
Blood Pressure
Carbon Dioxide
Cerebral Cortex
Cerebrovascular Circulation
Computer Simulation
Electroencephalography
Homeostasis
Humans
Multivariate Analysis
Signal Processing, Computer-Assisted
Type
journal article