The Contribution of Arterial Blood Gases in Cerebral Blood Flow Regulation and Fuel Utilization in Man at High Altitude

The Contribution of Arterial Blood Gases in Cerebral Blood Flow Regulation and Fuel Utilization in Man at High Altitude

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 P...

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Bibliographic Details
Published in:Journal of cerebral blood flow and metabolism 2015-05, Vol.35 (5), p.873-881
Main Authors: Willie, Christopher K, MacLeod, David B, Smith, Kurt J, Lewis, Nia C, Foster, Glen E, Ikeda, Keita, Hoiland, Ryan L, Ainslie, Philip N
Format: Article
Language:eng
Subjects:
Acclimatization
Adult
Altitude
Blood Flow Velocity
Blood Pressure
Carbon Dioxide - blood
Cerebrovascular Circulation
Female
Humans
Hypocapnia - blood
Hypocapnia - physiopathology
Jugular Veins - metabolism
Jugular Veins - physiopathology
Male
Original
Oxygen - blood
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Summary: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.
ISSN:0271-678X
1559-7016