title: Cerebrovascular Responsiveness to Hypercapnia Is Stable over Six Months in Older Adults.
abstract: The primary purpose of this Brain in Motion (BIM) sub-study was to determine the 6-month stability of resting blood flow velocity and cerebrovascular responsiveness to a euoxic hypercapnic challenge in a group of physically inactive community dwelling men and men aged ≥55 yrs (range 55-92 yrs). At baseline and 6 months later 88 women (65±6 yr) and 78 men (67±7 yr) completed a hypercapnic challenge (step changes from resting end-tidal PCO2 ((PETCO2) to +1, +5 and +8 mmHg above rest) while cerebral blood flow velocity was assessed using transcranial Doppler ultrasound. Peak velocity of the middle cerebral artery (MCAv) was increased (p<0.05) at the second visit during rest (51±2 vs. 52±4); however, these differences were abolished (p>0.05) when MCAv was normalized to PETCO2. During hypercapnia, MCAv tended to be increased at follow-up, but this finding was absent when MCAv/PETCO2 was compared across time. Cerebrovascular reactivity (i.e., ΔMCAv/ΔPETCO2) was similar (p>0.05) between testing occasions regardless of the approach taken (i.e., considering only the lower step [from +1 to +5 mmHg]; the upper step [+5 to +8 mmHg]; or the complete test taken together). In conclusion, this study has shown that cerebral blood flow and cerebrovascular responsiveness to acute euoxic hypercapnia are stable in older, healthy adults over a 6-month period. Modest changes in MCAv over time must be viewed in the context of underlying differences in PETCO2, an important finding with implications for future studies considering cerebral blood flow velocity.
authors.affiliation: Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Spencer
authors.affiliation: Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Amanda V
authors.initials: AV
authors.lastname: Tyndall
authors.affiliation: Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Margie H
authors.initials: MH
authors.lastname: Davenport
authors.affiliation: Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Laurie
authors.initials: L
authors.lastname: Argourd
authors.affiliation: Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Cardiac Science, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Anderson
authors.affiliation: Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Psychiatry, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia, B3H 2E2 Canada.
authors.forename: Gail A
authors.initials: GA
authors.lastname: Eskes
authors.affiliation: Department of Cancer Epidemiology and Prevention Research, Alberta Health Services, Cancer Control Alberta, Calgary, Alberta, T2S 3C3 Canada.|Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Oncology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Friedenreich
authors.affiliation: Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: David B
authors.initials: DB
authors.lastname: Hogan
authors.affiliation: Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Snyder Institute for Chronic Diseases, Cumming School of Medicine, University of Calgary, Calgary Alberta, T2N 4N1 Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Leigh
authors.affiliation: Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Bernard
authors.initials: B
authors.lastname: Meshi
authors.affiliation: Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Eric E
authors.initials: EE
authors.lastname: Smith
authors.affiliation: Department of Medicine, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Ben J
authors.initials: BJ
authors.lastname: Wilson
authors.affiliation: Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Wilton
authors.affiliation: Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Libin Cardiovascular Institute of Alberta, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1 Canada.|Faculty of Kinesiology, University of Calgary, Calgary, Alberta, T2N 1N4 Canada.
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Poulin
mesh_terms: D000367:Age Factors; D000368:Aged; D001783:Blood Flow Velocity; D001794:Blood Pressure; D001921:Brain / Q000098:blood supply* / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000378:metabolism; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D008297:Male; D020768:Middle Cerebral Artery / Q000503:physiopathology; D010100:Oxygen / Q000378:metabolism; D010313:Partial Pressure; D012146:Rest
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen