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

Introduction: 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.