title: Effects of breathing air containing 3% carbon dioxide, 35% oxygen or a mixture of 3% carbon dioxide/35% oxygen on cerebral and peripheral oxygenation at 150 m and 3459 m.
abstract: The effects of gas mixtures comprising supplementary 3% carbon dioxide, 35% oxygen or a combination of 3% CO(2) plus 35% O(2) in ambient air have been compared on arterial blood gases, peripheral and cerebral oxygenation and middle cerebral artery velocity (MCAV) at 150 m and on acute exposure to 3459 m in 12 healthy subjects. Breathing 3% CO(2) or 35% O(2) increased arterial blood oxygen at both altitudes, and the CO(2)/O(2) combination resulted in the most marked rise. MCAV increased on ascent to 3459 m, increasing further with 3% CO(2) and decreasing with 35% O(2) at both altitudes. The CO(2)/O(2) combination resulted in an increase in MCAV at 150 m, but not at 3549 m. Cerebral regional oxygenation fell on ascent to 3459 m. Breathing 3% CO(2) or 35% O(2) increased cerebral oxygenation at both altitudes, and the CO(2)/O(2) combination resulted in the greatest rise at both altitudes. The combination also resulted in significant rises in cutaneous and muscle oxygenation at 3459 m. The key role of carbon dioxide in oxygenation at altitude is confirmed, and the importance of this gas for tissue oxygenation is demonstrated.
authors.affiliation: University Hospitals Coventry and Warwickshire NHS Trust, Department of Vascular Surgery, Clifford Bridge Road, Walsgrave, Coventry CV2 2DX, UK. chrisimray@aol.com
authors.forename: C H E
authors.initials: CH
authors.lastname: Imray
authors.forename: S
authors.initials: S
authors.lastname: Walsh
authors.forename: T
authors.initials: T
authors.lastname: Clarke
authors.forename: C
authors.initials: C
authors.lastname: Tiivas
authors.forename: H
authors.initials: H
authors.lastname: Hoar
authors.forename: T C
authors.initials: TC
authors.lastname: Harvey
authors.forename: C W M
authors.initials: CW
authors.lastname: Chan
authors.forename: P J G
authors.initials: PJ
authors.lastname: Forster
authors.forename: A R
authors.initials: AR
authors.lastname: Bradwell
authors.forename: A D
authors.initials: AD
authors.lastname: Wright
mesh_terms: D000328:Adult; D000388:Air; D000531:Altitude; D000532:Altitude Sickness / Q000097:blood / Q000503:physiopathology*; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000378:metabolism; D002245:Carbon Dioxide / Q000097:blood / Q000494:pharmacology* / Q000502:physiology; D002536:Cerebral Arteries / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism; D010092:Oximetry / Q000379:methods; D010100:Oxygen / Q000097:blood / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D010313:Partial Pressure; D019265:Spectroscopy, Near-Infrared
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen