Cerebral artery dilatation maintains cerebral oxygenation at extreme altitude and in acute hypoxia-an ultrasound and MRI study

• Published in: Journal of cerebral blood flow and metabolism Vol. 31; no. 10; pp. 2019 - 2029
• Main Authors: Wilson, Mark H, Edsell, Mark EG, Davagnanam, Indran, Hirani, Shashivadan P, Martin, Dan S, Levett, Denny ZH, Thornton, John S, Golay, Xavier, Strycharczuk, Lisa, Newman, Stanton P, Montgomery, Hugh E, Grocott, Mike PW, Imray, Christopher HE
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01-10-2011; Nature Publishing Group; Sage Publications Ltd
• Subjects: Acute Disease; Adult; Altitude Sickness - diagnostic imaging; Altitude Sickness - physiopathology; Biological and medical sciences; Blood Flow Velocity; Cerebral circulation. Blood-brain barrier. Choroid plexus. Cerebrospinal fluid. Circumventricular organ. Meninges; Fundamental and applied biological sciences. Psychology; Humans; Hypoxia - diagnostic imaging; Hypoxia - physiopathology; Magnetic Resonance Angiography; Magnetic Resonance Imaging; Male; Medical sciences; Middle Aged; Middle Cerebral Artery - diagnostic imaging; Middle Cerebral Artery - physiopathology; Neurology; Original; Oxygen Consumption; Partial Pressure; Radiography; Ultrasonography; Vascular diseases and vascular malformations of the nervous system; Vasodilation; Vertebrates: nervous system and sense organs; Young Adult; brain imaging; cerebral blood flow; high altitude; transcranial Doppler; MRI; Doppler ultrasound study; High altitude; Oxygen; Nervous system diseases; Cerebral artery; Nuclear magnetic resonance imaging; Cerebral disorder; Blood flow; Encephalon; Dilatation; Central nervous system disease; Hypoxia; Oxygenation; Ultrasound; Cerebrovascular disease
• ISSN: 0271-678X; 1559-7016
• DOI: 10.1038/jcbfm.2011.81

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.