+Gz Acceleration Loss of Consciousness: Time Course of Performance Deficits With Repeated Experience

Abstract

We examine the time course of performance recovery from gravity-induced loss of consciousness (GLOC) and evaluate the utility of exposing participants to repeated bouts of GLOC in promoting recovery time. A substantial number of accidents among fighter pilots have resulted from episodes of GLOC. U.S. Air Force doctrine holds that when pilots experience GLOC, impairment lasts for 24 s, in which there are 12 s of complete unconsciousness and 12 s of confusion. However, there is reason to suspect that performance efficiency associated with GLOC is degraded well before unconsciousness sets in and that more than 24 s are required for performance efficiency to return to baseline levels. Additionally, there is a belief that repeated exposure to GLOC will reduce recovery time. Centrifuge simulators were used to induce GLOC in U.S. Air Force personnel with math and tracking tasks employed to emulate flight performance. Participants were tested once per week for 4 consecutive weeks. On average, performance deficits appeared 7.44 s prior to the onset of unconsciousness and persisted for 55.6 s following the GLOC event. Repeated exposure failed to moderate these results. The temporal course of performance deficits produced by GLOC far exceeds prior estimates. The problem is more serious than previously envisioned and it is not alleviated by repeated exposure to GLOC. U.S. Air Force doctrine regarding the severity of GLOC and the utility of repeated exposure to this problem needs to be revised and these data incorporated into future aircraft auto recovery systems.