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Hypoxia: Exposure Time Until Significant Performance Effects

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Technical Report,01 Jan 2015,31 Aug 2015

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Naval Medical Research Unit Dayton Wright-Patterson Air Force Base United States

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Previous research has shown that hypoxia affects the ability of an operator to take corrective action or enact emergency procedures, and this may occur prior to the times outlined in the Time of Useful Consciousness TUC table. The quality of and decline in performance preceding total incapacitation has so far not been examined. Thus, the aim of the current work was to complement the existing TUC table by examining the rate of cognitive decline. Three altitudes 20, 22, 25k ft were simulated by a Reduced Oxygen Breathing Device ROBD. Performance was tested with simple and choice reaction time tasks and analyzed as single minute time periods compared to performance at a sea-level baseline. An analysis of the third quartile of reaction time values revealed significantly slower responses during the hypoxia exposure trials when compared to their baseline counterparts, generally ahead of the times specified in the TUC table. Results from the current study suggest that hypoxia exposure can lead to a rapid destabilization of performance earlier than those times put forward by the TUC table. By focusing on the point of incapacitation, the TUC table does not capture the performance degradation experienced before loss of consciousness.

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