Current and emerging technology in G-LOC detection: noninvasive monitoring of cerebral microcirculation using near infrared.
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.
Glaister
D H
DH
Crew Technology Division, USAF School of Aerospace Medicine, Brooks Air Force Base, Texas.
D000401:Aircraft; D002560:Cerebrovascular Circulation; D003072:Cognition Disorders / Q000209:etiology*; D003244:Consciousness Disorders / Q000175:diagnosis / Q000209:etiology*; D006112:Gravitation; D006801:Humans; D007259:Infrared Rays; D013677:Medical Laboratory Science; D008833:Microcirculation / Q000503:physiopathology*; D008991:Monitoring, Physiologic; D010101:Oxygen Consumption