Hypoxia training: symptom replication in experienced military aircrew.
BACKGROUND
Military aircrew are trained to recognize the signs and symptoms of hypoxia in a safe environment using a variety of methods to simulate altitude. In order to investigate the effectiveness of hypoxia training, this study compared the recall of hypoxia symptoms in military aircrew between two consecutive hypobaric chamber hypoxia training sessions conducted, on average, 4.5 yr apart.


METHODS
Previously trained subjects completed a questionnaire immediately before and after they underwent refresher hypoxia training and recorded the occurrence, order, and severity of symptoms experienced. Responses from refresher training were compared with their recall of symptoms experienced during previous training.


RESULTS
There was no difference in the recall of most hypoxia symptoms between training sessions. Slurred speech was recalled more frequently from previous training compared to refresher training (14 vs. 4 subjects), whereas hot/cold flushes were recalled less frequently from previous training compared to refresher training (5 vs. 17 subjects). There was a statistically significant difference in overall hypoxia score (10.3 vs. 8.3), suggesting that from memory subjects may underestimate the level of hypoxia experienced in previous training.


CONCLUSIONS
A high level of similarity between the recall of previously experienced hypoxia symptoms and recent experience supports the effectiveness of hypoxia training. These results replicate the finding of a 'hypoxia signature' reported by a previous study. Small differences in the recall of some symptoms and in overall hypoxia score highlight the importance of drawing attention to the more subtle symptoms of early hypoxia, and of using training techniques which optimize aircrew recall.
Aviation Medicine Unit, Royal New Zealand Air Force (RNZAF), Auckland, New Zealand. ben.johnston@airnz.co.nz
Ben J
BJ
Johnston
Gareth S
GS
Iremonger
Sheena
S
Hunt
Elizabeth
E
Beattie
D000328:Adult; D000337:Aerospace Medicine; D000531:Altitude; D000704:Analysis of Variance; D001184:Articulation Disorders / Q000209:etiology; D001259:Ataxia / Q000209:etiology; D001273:Atmosphere Exposure Chambers; D003072:Cognition Disorders / Q000209:etiology; D004244:Dizziness / Q000209:etiology; D005260:Female; D005483:Flushing / Q000209:etiology; D006801:Humans; D006987:Hypesthesia / Q000209:etiology; D000860:Hypoxia / Q000150:complications* / Q000175:diagnosis* / Q000523:psychology; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D008889:Military Personnel / Q000193:education*; D010806:Physical Education and Training; D011795:Surveys and Questionnaires; D014202:Tremor / Q000209:etiology; D014474:Unconsciousness / Q000209:etiology; D014786:Vision Disorders / Q000209:etiology; D055815:Young Adult