A near-infrared spectrophotometric method for studying brain O2 sufficiency in man during +Gz acceleration.
A technique for the noninvasive monitoring of cerebral oxygen status was evaluated on volunteer subjects on the USAF School of Aerospace Medicine centrifuge. By using multiwavelength near-infrared spectrophotometry, the instrumentation measured changes in the quantities of reduced and oxygenated hemoglobin (and their sum, an indicator of cerebral blood volume), and the quantity of oxidized cytochrome c oxidase within the forebrain. Tests used acceleration of up to 9 G with onset rates from 0.1 to 5.0 G.s-1, anti-G suits and straining maneuvers, and hyperoxic and hypoxic breathing mixtures. In general, +Gz acceleration produced a fall in blood volume within the cerebral microcirculation with a relative increase in the content of reduced hemoglobin and a tendency towards reduction of cytochrome c oxidase. These findings are discussed in relation to accepted changes in arterial blood pressure, cerebral blood flow, and arterial oxygen saturation caused by acceleration exposure.
Glaister
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USAF School of Aerospace Medicine, Crew Technology Division, Brooks Air Force Base, San Antonio, Texas.
Jöbsis-VanderVliet
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D000054:Acceleration; D001810:Blood Volume; D001921:Brain / Q000378:metabolism*; D002560:Cerebrovascular Circulation; D003576:Electron Transport Complex IV / Q000378:metabolism; D006112:Gravitation; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D008991:Monitoring, Physiologic; D010101:Oxygen Consumption; D013055:Spectrophotometry, Infrared / Q000379:methods*; D014636:Valsalva Maneuver
D006454:Hemoglobins; D003576:Electron Transport Complex IV