Multivariate system identification for cerebral autoregulation
Journal
Annals of Biomedical Engineering
Journal Volume
36
Journal Issue
2
Pages
308-320
Date Issued
2008
Author(s)
Abstract
The effect of spontaneous beat-to-beat mean arterial blood pressure (ABP) fluctuations and breath-to-breath end-tidal carbon dioxide and end-tidal oxygen fluctuations on beat-to-beat cerebral blood flow velocity (CBFV) variations is studied using a multiple coherence function. Multiple coherence is a measure of the extent to which the output, CBFV, can be represented as a linear time invariant system of multiple input signals. Analysis of experimental measurements from 13 different healthy subjects reveal that, with additional inputs, and the multiple coherence for frequencies < 0.05 Hz is significantly higher than the corresponding values obtained for univariate coherence with a single input of ABP. The result illustrates that the low value of univariate coherence at small frequencies may be due to the effects of and fluctuations on CBFV variability. Moreover, it is also found that the transfer function between ABP and CBFV time series identified from previous univariate techniques at low frequencies can be modified by CO 2 and O 2 reactivity and no longer represents pressure autoregulation only. Multivariate system identification provides a technique of incorporating additional variability and recovering from this artifact. Finally, a physiologically based model and its linear transfer function are used as a simulation tool to investigate possible causes of low univariate coherence. ? 2007 Biomedical Engineering Society.
Subjects
Blood pressure
Carbon dioxide
Computer simulation
Cerebral autoregulation
Cerebral blood flow
Multiple coherence
Transfer function
Brain
adult
article
biological model
blood flow velocity
blood pressure
brain
brain circulation
computer simulation
feedback system
female
human
male
multivariate analysis
physiology
vascularization
Adult
Blood Flow Velocity
Blood Pressure
Cerebrovascular Circulation
Computer Simulation
Feedback
Female
Humans
Male
Models, Cardiovascular
Models, Neurological
Multivariate Analysis
Type
journal article