Gray matter blood flow change is unevenly distributed during moderate isocapnic hypoxia in humans

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Title Gray matter blood flow change is unevenly distributed during moderate isocapnic hypoxia in humans
Author Binks, Andrew P.; Cunningham, Vincent J.; Adams, Lewis; Banzett, Robert B.
Journal Name Journal of Applied Physiology
Editor Jerome A Dempsey
Year Published 2008
Place of publication United States
Publisher American Physiological Society
Abstract Hypoxia increases cerebral blood flow (CBF), but it is unknown whether this increase is uniform across all brain regions. We used H215O positron emission tomography imaging to measure absolute blood flow in 50 regions of interest across the human brain (n = 5) during normoxia and moderate hypoxia. PCO2 was kept constant (44 Torr) throughout the study to avoid decreases in CBF associated with the hypocapnia that normally occurs with hypoxia. Breathing was controlled by mechanical ventilation. During hypoxia (inspired PO2 = 70 Torr), mean end-tidal PO2 fell to 45 ± 6.3 Torr (means ± SD). Mean global CBF increased from normoxic levels of 0.39 ± 0.13 to 0.45 ± 0.13 ml/g during hypoxia. Increases in regional CBF were not uniform and ranged from 9.9 ± 8.6% in the occipital lobe to 28.9 ± 10.3% in the nucleus accumbens. Regions of interest that were better perfused during normoxia generally showed a greater regional CBF response. Phylogenetically older regions of the brain tended to show larger vascular responses to hypoxia than evolutionary younger regions, e.g., the putamen, brain stem, thalamus, caudate nucleus, nucleus accumbens, and pallidum received greater than average increases in blood flow, while cortical regions generally received below average increases. The heterogeneous blood flow distribution during hypoxia may serve to protect regions of the brain with essential homeostatic roles. This may be relevant to conditions such as altitude, breath-hold diving, and obstructive sleep apnea, and may have implications for functional brain imaging studies that involve hypoxia.
Peer Reviewed Yes
Published Yes
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Copyright Statement Self-archiving of the author-manuscript version is not yet supported by this journal. Please refer to the journal link for access to the definitive, published version or contact the author[s] for more information.
Volume 104
Issue Number 1
Page from 212
Page to 217
ISSN 8750-7587
Date Accessioned 2009-04-27
Language en_AU
Research Centre Menzies Health Institute Qld
Faculty Griffith Health Faculty
Subject Medical Physiology
Publication Type Journal Articles (Refereed Article)
Publication Type Code c1

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