AltitudeOmics: effect of ascent and acclimatization to 5260 m on regional cerebral oxygen delivery.
Cerebral hypoxaemia associated with rapid ascent to high altitude can be life threatening; yet, with proper acclimatization, cerebral function can be maintained well enough for humans to thrive. We investigated adjustments in global and regional cerebral oxygen delivery (DO2) as 21 healthy volunteers rapidly ascended and acclimatized to 5260 m. Ultrasound indices of cerebral blood flow in internal carotid and vertebral arteries were measured at sea level, upon arrival at 5260 m (ALT1; atmospheric pressure 409 mmHg) and after 16 days of acclimatization (ALT16). Cerebral DO2 was calculated as the product of arterial oxygen content and flow in each respective artery and summed to estimate global cerebral blood flow. Vascular resistances were calculated as the quotient of mean arterial pressure and respective flows. Global cerebral blood flow increased by ∼70% upon arrival at ALT1 (P < 0.001) and returned to sea-level values at ALT16 as a result of changes in cerebral vascular resistance. A reciprocal pattern in arterial oxygen content maintained global cerebral DO2 throughout acclimatization, although DO2 to the posterior cerebral circulation was increased by ∼25% at ALT1 (P = 0.032). We conclude that cerebral DO2 is well maintained upon acute exposure and acclimatization to hypoxia, particularly in the posterior and inferior regions of the brain associated with vital homeostatic functions. This tight regulation of cerebral DO2 was achieved through integrated adjustments in local vascular resistances to alter cerebral perfusion during both acute and chronic exposure to hypoxia.
University of Colorado Denver Anschutz Medical Campus, Department of Emergency Medicine, Altitude Research Center, Aurora, CO, USA University of Colorado Colorado Springs, Department of Biology, Colorado Springs, CO, USA asubudhi@uccs.edu.
Andrew W
AW
Subudhi
University of Lausanne, Institute of Sport Sciences, Lausanne, Switzerland University of Geneva, Lemanic Doctoral School of Neuroscience, Geneva, Switzerland.
Jui-Lin
JL
Fan
University of Colorado Denver Anschutz Medical Campus, Department of Emergency Medicine, Altitude Research Center, Aurora, CO, USA.
Oghenero
O
Evero
University of Lausanne, Institute of Sport Sciences, Lausanne, Switzerland.
Nicolas
N
Bourdillon
University of Lausanne, Institute of Sport Sciences, Lausanne, Switzerland.
Bengt
B
Kayser
University of Colorado Denver Anschutz Medical Campus, Department of Emergency Medicine, Altitude Research Center, Aurora, CO, USA.
Colleen G
CG
Julian
University of Oregon, Department of Human Physiology, Eugene, OR, USA.
Andrew T
AT
Lovering
University of Colorado Denver Anschutz Medical Campus, Department of Emergency Medicine, Altitude Research Center, Aurora, CO, USA.
Robert C
RC
Roach
D000064:Acclimatization / Q000502:physiology*; D000531:Altitude; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D008297:Male; D020768:Middle Cerebral Artery / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D012039:Regional Blood Flow; D055815:Young Adult
D010100:Oxygen