Glaister D H
Crew Technology Division, USAF School of Aerospace Medicine, Brooks Air Force Base, Texas.
Aviat Space Environ Med. 1988 Jan;59(1):23-8.
G-induced loss of consciousness (G-LOC) has emerged as an important operational problem of high-performance aircraft. Since it appears that G-LOC will continue to be a problem, a requirement exists to detect its occurrence in pilots so that the aircraft may be placed on autopilot. One excellent method of detecting G-LOC physiologically, one would assume, would be based on the oxidative status of the brain. This determination can be made noninvasively with an Oxidative Metabolism Near-Infrared monitor using 4 wave lengths (OMNI-4). The OMNI-4 is capable of measuring the relative quantities in the brain of hemoglobin (Hb), oxygenated hemoglobin (HbO2), blood volume (BV), and oxidative status of cytochrome c oxidase. This instrument was tested on subjects in the USAFSAM human-use centrifuge at +3, 4, and 5 Gz with onset rates of 1 G.s-1. Results showed changes within the brain, as expected, during increased G with reductions in Hb, BV, and HbO2. Cytochrome c oxidase measurements were inconclusive. Immediately following G exposure, Hb, BV, and HbO2 "overshoots" occurred suggesting vasodilation of the cerebral microcirculation. The use of OMNI-4 in the laboratory and its possible role as a detector of G-LOC in pilots are discussed including suggestions for future developments.
重力诱导意识丧失（G-LOC）已成为高性能飞机的一个重要操作问题。由于G-LOC似乎仍将是一个问题，因此需要检测飞行员是否发生G-LOC，以便将飞机置于自动驾驶状态。可以推测，一种从生理上检测G-LOC的优秀方法将基于大脑的氧化状态。使用4个波长的近红外氧化代谢监测仪（OMNI-4）可以无创地进行这种测定。OMNI-4能够测量大脑中血红蛋白（Hb）、氧合血红蛋白（HbO2）、血容量（BV）以及细胞色素c氧化酶的氧化状态的相对量。该仪器在美国空军航天医学学校（USAFSAM）人体离心机上对受试者进行了测试，过载值为+3、4和5 Gz，起始速率为1 G.s-1。结果显示，正如预期的那样，在过载增加期间大脑内部发生了变化，Hb、BV和HbO2减少。细胞色素c氧化酶的测量结果尚无定论。在过载暴露后立即出现了Hb、BV和HbO2的“过冲”现象，表明脑微循环血管扩张。本文讨论了OMNI-4在实验室中的应用及其作为飞行员G-LOC探测器的可能作用，包括对未来发展的建议。
