University College, London. Centre for Altitude, Space and Extreme environment medicine. Caudwell Xtreme Everest Research Group (Including: Wilson, Mark H., Edsell, Mark E. G., Davagnanam, Indran, Hirani, Shashivadan P., Martin, Dan S., Levett, Denny Z. H., Thornton, John S., Golay, Xavier, Strycharczuk, Lisa, Newman, S. P. (Stanton P.), Montgomery, Hugh E., Grocott, Michael P. W. and Imray, C. (Chris)). (2011) Cerebral artery dilatation maintains cerebral oxygenation at extreme altitude and in acute hypoxia : an ultrasound and MRI study. Journal of Cerebral Blood Flow & Metabolism, Vol.31 (No.10). pp. 2019-2029. doi:10.1038/jcbfm.2011.81

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Abstract

Transcranial Doppler is a widely used noninvasive technique for assessing cerebral artery blood flow. All previous high altitude studies assessing cerebral blood flow (CBF) in the field that have used Doppler to measure arterial blood velocity have assumed vessel diameter to not alter. Here, we report two studies that demonstrate this is not the case. First, we report the highest recorded study of CBF (7,950 m on Everest) and demonstrate that above 5,300 m, middle cerebral artery (MCA) diameter increases (n=24 at 5,300 m, 14 at 6,400 m, and 5 at 7,950 m). Mean MCA diameter at sea level was 5.30 mm, at 5,300 m was 5.23 mm, at 6,400 m was 6.66 mm, and at 7,950 m was 9.34 mm (P<0.001 for change between 5,300 and 7,950 m). The dilatation at 7,950 m reversed with oxygen. Second, we confirm this dilatation by demonstrating the same effect (and correlating it with ultrasound) during hypoxia (FiO2=12% for 3 hours) in a 3-T magnetic resonance imaging study at sea level (n=7). From these results, we conclude that it cannot be assumed that cerebral artery diameter is constant, especially during alterations of inspired oxygen partial pressure, and that transcranial 2D ultrasound is a technique that can be used at the bedside or in the remote setting to assess MCA caliber.

Item Type:	Journal Article
Subjects:	Q Science > QP Physiology
Divisions:	Faculty of Medicine > Warwick Medical School
Library of Congress Subject Headings (LCSH):	Cerebral arteries -- Dilatation, Cerebral circulation -- Measurement, Transcranial Doppler ultrasonography
Journal or Publication Title:	Journal of Cerebral Blood Flow & Metabolism
Publisher:	Nature Publishing Group
ISSN:	0271-678X
Official Date:	2011
Dates:	Date Event 2011 Published
Volume:	Vol.31
Number:	No.10
Page Range:	pp. 2019-2029
DOI:	10.1038/jcbfm.2011.81
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Open Access

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