title: Surviving Without Oxygen: How Low Can the Human Brain Go?
abstract: Bailey, Damian M., Christopher K. Willie, Ryan L. Hoiland, Anthony R. Bain, David B. MacLeod, Maria A. Santoro, Daniel K. DeMasi, Andrea Andrijanic, Tanja Mijacika, Otto F. Barak, Zeljko Dujic, and Philip N. Ainslie. Surviving without oxygen: how low can the human brain go? High Alt Med Biol 18:73-79, 2017.-Hypoxic cerebral vasodilation is a highly conserved physiological response coupling cerebral O2delivery (CDO2) to metabolic demand with increasingly important roles identified for the red blood cell (sensor) and nitric oxide (effector). In the current article, we reexamine previously published cerebral blood flow (CBF) and arterial blood gas data obtained in freedivers and mountaineers, extreme athletes in whom the lowest arterial partial pressures of O2(19-23 mmHg) and greatest extremes of carbon dioxide (16-61 mmHg) were recorded during (acute) maximal static dry apnea or (chronic) exposure to terrestrial high altitude. Data highlight compensatory increases in CBF (+96% in freedivers to +209% in mountaineers relative to normoxic baseline controls) that were sufficient to sustain CDO2(+24% in freedivers to +183% in mountaineers) even in the face of the most severe reductions in arterial O2content (-61% in freedivers to -9% in mountaineers) reported in the literature, consistent with the conservation of mass principle. These unique findings highlight to what extent cerebral vasodilation likely contributes toward these athletes' extraordinary abilities to survive in such harsh environments characterized by physiological extremes of hypoxemia, alkalosis, and acidosis helping define the human brain's remarkable limits of tolerance.
authors.affiliation: 1 Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales , Glamorgan, United Kingdom .|2 Faculty of Medicine, University of British Columbia-Okanagan , Kelowna, British Columbia, Canada .
authors.forename: Damian M
authors.initials: DM
authors.lastname: Bailey
authors.affiliation: 3 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: 3 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: 3 Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia-Okanagan , Kelowna, British Columbia, Canada .
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Bain
authors.affiliation: 4 Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center , Durham, North Carolina.
authors.forename: David B
authors.initials: DB
authors.lastname: MacLeod
authors.affiliation: 4 Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center , Durham, North Carolina.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Santoro
authors.affiliation: 4 Human Pharmacology and Physiology Laboratory, Department of Anesthesiology, Duke University Medical Center , Durham, North Carolina.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: DeMasi
authors.affiliation: 5 School of Management, Libertas International University , Zagreb, Croatia .
authors.forename: Andrea
authors.initials: A
authors.lastname: Andrijanic
authors.affiliation: 6 School of Medicine, University of Split , Split, Croatia .
authors.forename: Tanja
authors.initials: T
authors.lastname: Mijacika
authors.affiliation: 6 School of Medicine, University of Split , Split, Croatia .|7 Faculty of Medicine, University of Novi Sad , Novi Sad, Serbia .
authors.forename: Otto F
authors.initials: OF
authors.lastname: Barak
authors.affiliation: 6 School of Medicine, University of Split , Split, Croatia .
authors.forename: Zeljko
authors.initials: Z
authors.lastname: Dujic
authors.affiliation: 1 Neurovascular Research Laboratory, Faculty of Life Sciences and Education, University of South Wales , Glamorgan, United Kingdom .|3 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 / Q000502:physiology; D000531:Altitude; D001784:Blood Gas Analysis; D001921:Brain / Q000098:blood supply; D002560:Cerebrovascular Circulation / Q000502:physiology; D004242:Diving / Q000502:physiology*; D006801:Humans; D000860:Hypoxia / Q000097:blood* / Q000503:physiopathology; D009051:Mountaineering / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption / Q000502:physiology; D012189:Retrospective Studies; D014664:Vasodilation / Q000502:physiology
chemical_list: D010100:Oxygen
keywords: brain; carbon dioxide; freediver; mountaineer; oxygen; vasodilation