title: The contribution of arterial blood gases in cerebral blood flow regulation and fuel utilization in man at high altitude.
abstract: The effects of partial acclimatization to high altitude (HA; 5,050 m) on cerebral metabolism and cerebrovascular function have not been characterized. We hypothesized (1) increased cerebrovascular reactivity (CVR) at HA; and (2) that CO2 would affect cerebral metabolism more than hypoxia. PaO2 and PaCO2 were manipulated at sea level (SL) to simulate HA exposure, and at HA, SL blood gases were simulated; CVR was assessed at both altitudes. Arterial-jugular venous differences were measured to calculate cerebral metabolic rates and cerebral blood flow (CBF). We observed that (1) partial acclimatization yields a steeper CO2-H(+) relation in both arterial and jugular venous blood; yet (2) CVR did not change, despite (3) mean arterial pressure (MAP)-CO2 reactivity being doubled at HA, thus indicating effective cerebral autoregulation. (4) At SL hypoxia increased CBF, and restoration of oxygen at HA reduced CBF, but neither had any effect on cerebral metabolism. Acclimatization resets the cerebrovasculature to chronic hypocapnia.
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Willie
authors.affiliation: Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: MacLeod
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Kurt J
authors.initials: KJ
authors.lastname: Smith
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Nia C
authors.initials: NC
authors.lastname: Lewis
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Glen E
authors.initials: GE
authors.lastname: Foster
authors.affiliation: Department of Anesthesiology, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
authors.forename: Keita
authors.initials: K
authors.lastname: Ikeda
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Ryan L
authors.initials: RL
authors.lastname: Hoiland
authors.affiliation: Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
mesh_terms: D000064:Acclimatization; D000328:Adult; D000531:Altitude; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002245:Carbon Dioxide / Q000097:blood*; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D016857:Hypocapnia / Q000097:blood / Q000503:physiopathology; D007601:Jugular Veins / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D010100:Oxygen / Q000097:blood*
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen