Analysis of G-induced Loss of Consciousness (G-LOC) and Almost Loss of Consciousness (A-LOC) incidences in high-performance human centrifuge at Institute of Aerospace Medicine Indian Air Force

Institute of Aerospace Medicine (IAM) Indian Air Force (IAF) conducts operational training in Aerospace Medicine for IAF fighter aircrew since 2009. This includes high-G training with qualifying criteria of demonstrating ability of the aircrew to sustain 9G for 5 s in closed-loop run (pilot-in-control) wearing anti-G suit while performing anti-G straining maneuver (AGSM). Incidences of inadvertent almost loss of consciousness (A-LOC)/G-induced loss of consciousness (G-LOC) are an unavoidable unintended consequence of such training. The aim of the paper is to study the incidence of G-LOC and A-LOC and its nature in the high-performance human centrifuge (HPHC) and compare it with our previous experiences. Material and Methods: A G-LOC/A-LOC proforma was designed at the Department of Acceleration Physiology and Spatial Orientation at IAM IAF to understand the nature and cause of the G-LOC/A-LOC. This was to be filled up by the aircrew on a voluntary basis. The data were analyzed using Microsoft Excel with a significance level set at 95% confidence interval and alpha ≤0.05. Results: Fifty-two aircrew (19.92%) experienced inadvertent G-LOC/A-LOC in 83 such episodes (54 G-LOC and 29 A-LOC) during the period January 2018–December 2018. Forty-seven aircrew experiencing G-LOC/ALOC agreed to be part of the study and filled up the proforma after the episodes. The incidence of G-LOC in the institute has reduced significantly over the past two decades, perhaps due to change in the HPHC used for training of aircrew. The incidence of G-LOC found in this study is comparable to the global incidence. Rise in heart rate was higher during A-LOC than G-LOC and was found to be statistically significant (t statistic = 2.33; P = 0.01). Relative incapacitation period was lesser than absolute incapacitation period during G-LOC and was found to be statistically significant (t statistic = 3.29, P = 0.001). G-level at which Type II G-LOC occurred was significantly higher than the Type I G-LOC. Conclusion: The incidence of A-LOC/G-LOC has reduced over the past two decades of high G training in IAF and is comparable to global incidence.