title: Detection of impaired cerebral autoregulation improves by increasing arterial blood pressure variability.
abstract: Although the assessment of dynamic cerebral autoregulation (CA) based on measurements of spontaneous fluctuations in arterial blood pressure (ABP) and cerebral blood flow (CBF) is a convenient and much used method, there remains uncertainty about its reliability. We tested the effects of increasing ABP variability, provoked by a modification of the thigh cuff method, on the ability of the autoregulation index to discriminate between normal and impaired CA, using hypercapnia as a surrogate for dynamic CA impairment. In 30 healthy volunteers, ABP (Finapres) and CBF velocity (CBFV, transcranial Doppler) were recorded at rest and during 5% CO(2) breathing, with and without pseudo-random sequence inflation and deflation of bilateral thigh cuffs. The application of thigh cuffs increased ABP and CBFV variabilities and was not associated with a distortion of the CBFV step response estimates for both normocapnic and hypercapnic conditions (P=0.59 and P=0.96, respectively). Sensitivity and specificity of CA impairment detection were improved with the thigh cuff method, with the area under the receiver-operator curve increasing from 0.746 to 0.859 (P=0.031). We conclude that the new method is a safe, efficient, and appealing alternative to currently existing assessment methods for the investigation of the status of CA.
authors.affiliation: Department of Cardiovascular Sciences, University of Leicester, Leicester, UK.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Katsogridakis
authors.forename: Glen
authors.initials: G
authors.lastname: Bush
authors.forename: Lingke
authors.initials: L
authors.lastname: Fan
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Birch
authors.forename: David M
authors.initials: DM
authors.lastname: Simpson
authors.forename: Robert
authors.initials: R
authors.lastname: Allen
authors.forename: John F
authors.initials: JF
authors.lastname: Potter
authors.forename: Ronney B
authors.initials: RB
authors.lastname: Panerai
mesh_terms: D000328:Adult; D062186:Arterial Pressure; D001783:Blood Flow Velocity; D002533:Cerebral Angiography; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D017585:Ultrasonography, Doppler, Transcranial