The Contribution of Arterial Blood Gases in Cerebral Blood Flow Regulation and Fuel Utilization in Man at High Altitude. Issue 5 (May 2015)

• Record Type: Journal Article
• Authors: Willie, Christopher K; MacLeod, David B; Smith, Kurt J; Lewis, Nia C; Foster, Glen E; Ikeda, Keita; Hoiland, Ryan L; Ainslie, Philip N
• Is Part Of: Journal of cerebral blood flow & metabolism. Volume 35:Issue 5(2015)
• Page Start: 873
• Page End: 881
• Publication Date: 2015-05
• Subjects: cerebral blood flow measurement; -- energy metabolism; -- environment; -- high altitude; Cerebral circulation -- Periodicals; Brain -- Metabolism -- Periodicals; Brain -- Blood-vessels -- Periodicals; Cerebrovascular disease -- Periodicals; 612.824
• DOI: 10.1038/jcbfm.2015.4
• Languages: English
• ISSNs: 0271-678X

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.