Coherent averaging of pseudorandom binary stimuli: is the dynamic cerebral autoregulatory response symmetrical?

Katsogridakis, Emmanuel, Simpson, David M, Bush, Glen, Fan, Lingke, Birch, Anthony A, Allen, Robert, Potter, John F and Panerai, Ronney B (2017) Coherent averaging of pseudorandom binary stimuli: is the dynamic cerebral autoregulatory response symmetrical? Physiological Measurement, 38 (12). pp. 2164-2175. ISSN 0967-3334

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Objective: Previous studies on cerebral autoregulation have shown the existence of hemispheric symmetry, which may be altered in stroke and traumatic brain injury. There is a paucity of data however on whether the response is symmetrical between those disturbances that cause cerebral hyperperfusion, to those that cause hypoperfusion. Our aim was to investigate whether the responses of cerebral autoregulation to haemodynamic stimuli of different directions are symmetrical. 
 Approach: Using a previously described assessment method, we employed coherent averaging of the cerebral blood flow velocity (CBFV) responses to thigh cuff inflation and deflation, as driven by pseudorandom binary sequences, whilst simultaneously altering the inspired CO2. The symmetry of the autoregulatory response was assessed with regards to two parameters, its speed and gain. Using the first harmonic method, critical closing pressure (CrCP) and resistance area product (RAP) were estimated, and the gain of the autoregulatory response was calculated by performing linear regression between the coherent averages of arterial blood pressure (ABP) and CBFV, ABP and CrCP and finally ABP and RAP. A two-way repeated measures ANOVA was used to assess for the effect of the direction of change in ABP and the method of CO2 administration. 
 Main results: Our results suggest that whilst the direction of ABP change does not have a significant effect, the effect of CO2 administration method is highly significant (p<10-4). 
 Significance: This is the first report to report to demonstrate the symmetry of the autoregulatory response to stimuli of different directions as well as the short term dynamics of RAP and CrCP under intermittent and constant hypercapnia. As haemodynamic stimulus direction does not appear to have an influence, our findings validate previous work done using different assessment methods.

Item Type: Article
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
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Depositing User: Pure Connector
Date Deposited: 14 Oct 2017 05:07
Last Modified: 22 Oct 2022 03:15
DOI: 10.1088/1361-6579/aa9086

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