title: Use of resistance-area product derived from Doppler MCA velocity to estimate the range of active cerebrovascular regulation.
abstract: The purpose of the present study was to explore the development of a method to estimate the range of active cerebrovascular regulation using resistance-area product (RAP) derived from transcranial Doppler ultrasound recordings of middle cerebral artery blood velocity (MCAV) obtained before and after physiologic challenge. Intracranial pressure (ICP), arterial blood pressure (ABP), and MCAV were monitored on 9 patients before and after challenges with either Noradrenlin or CO2 inhalation. One patient was monitored at 24, 48, 72, and 96 hrs. For each cardiac cycle a value of RAP was computed from the inverse of the slope of the regression line of paired values of aligned MCAV and ABP recordings. Mean values of percent change of difference of RAP (% delta RAP) versus change of cerebral perfusion pressure (CPP) were computed. Theoretical values of % delta RAP were derived from reported lab values of percent change diameter of arterioles versus ABP. Of the nine patients, 22% (2/9) demonstrated either impaired dilation and/or constriction. Furthermore, the correlation between theoretical and experimental values of % delta RAP and CPP (n = 34) was strong (r = .86, p < .005). The serially-monitored patient failed to dilate during all CO2 challenges and to fully constrict to the Noradrenlin challenge at 72 hrs. % delta RAP associated with corresponding changes of CPP may have value as a clinical method to estimate the range of active cerebrovascular regulation.
authors.affiliation: Department of Electrical and Computer Engineering, University of Memphis, Memphis, TN, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Daley
authors.forename: C W
authors.initials: CW
authors.lastname: Leffler
authors.forename: S
authors.initials: S
authors.lastname: Jackson
authors.forename: I
authors.initials: I
authors.lastname: Piper
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation; D006259:Craniocerebral Trauma / Q000000981:diagnostic imaging / Q000503:physiopathology*; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012044:Regression Analysis; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods; D014655:Vascular Resistance / Q000502:physiology*