Describing the continuum from ALOC to G-LOC

Introduction: G-induced loss of consciousness (G-LOC) has been extensively investigated and pathophysiology of the same has been well elucidated in the literature. The syndrome of almost loss of consciousness or ALOC has also been described which is a loose collection of signs and symptoms of a physiological, emotional, and cognitive nature. This is believed to occur under +Gz stress which is insufficient to cause G-LOC. Institute of Aerospace Medicine IAF regularly conducts high-G training for its fighter pilots in the High Performance Human Centrifuge. Episodes of G-LOC and ALOC are unintended outcomes of such training. A study was conducted to understand the nature of these episodes in the Department of Acceleration Physiology and Spatial Orientation. Material and Methods: A G-LOC/ALOC proforma was designed in the Department of Acceleration Physiology and Spatial Orientation to understand the nature and causes of the G-LOC/ALOC and was filled up by the aircrew on a voluntary basis. The data were analyzed using Microsoft Excel and SPSS 20 with significance set at 95% confidence interval and alpha at 0.05. Results: Forty-seven aircrew experiencing G-LOC/ALOC agreed to be part of the study and filled up the proforma after the episodes. However, only 42 proforma (31 G-LOC and 11 ALOC) was found suitable for the analysis. There was no statistical difference in heart rate (HR) measured during the rate of onset and G-level at which G-LOC and ALOC resulted. There was no difference in psycho-somatic manifestations of G-LOC and ALOC episodes. Conclusion: ALOC and G-LOC have similar manifestations and operational implications. There is ample evidence to suggest that ALOC is a manifestation of G-LOC syndrome rather than a separate entity.