title: Differential cerebrovascular CO₂ reactivity in anterior and posterior cerebral circulations.
abstract: The potential differences in cerebrovascular responses between the anterior and posterior circulations to changes in CO₂ are unclear in humans. Using transcranial Doppler ultrasound, we compared the CO₂ reactivity of the (1) BA and PCA and (2) MCA and PCA during hyperoxic rebreathing in supine position. The reactivity in the BA and PCA was similar in both absolute (1.27 ± 0.5 and 1.27 ± 0.6 cm/s/Torr; P=0.992) and relative (3.98 ± 1.3 and 3.66 ± 1.5%/Torr CO2; P=0.581) measures, suggesting that the PCA is an adequate surrogate measure of reactivity for the BA. The MCA reactivity was greater than the PCA in absolute (2.09 ± 0.7 and 1.22 ± 0.5 cm/s/Torr CO₂; P<0.001), but not relative measures (3.25 ± 1.0 and 3.56 ± 1.6%/Torr CO₂; P=0.629). Our findings (a) confirm regional differences in the absolute reactivity in the human brain and (b) suggest that in cerebrovascular studies investigating functions mediated by posterior brain structures (e.g., control of breathing), the posterior vasculature should also be insonated.
authors.affiliation: Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada; Department of Biology, Faculty of Science and Technology, Mount Royal University, Calgary, Alberta, Canada.
authors.forename: Rachel J
authors.initials: RJ
authors.lastname: Skow
authors.forename: Christina M
authors.initials: CM
authors.lastname: MacKay
authors.forename: Michael M
authors.initials: MM
authors.lastname: Tymko
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Willie
authors.forename: Kurt J
authors.initials: KJ
authors.lastname: Smith
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Day
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000098:blood supply*; D002245:Carbon Dioxide / Q000097:blood*; D002536:Cerebral Arteries / Q000378:metabolism*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide
keywords: Cerebral blood flow; Cerebrovascular reactivity; Transcranial Doppler ultrasound