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Predictors of barotrauma events in a Navy altitude chamber.

BACKGROUND
Barotrauma in the flight environment is a significant cause of incidents and mishaps. Upper respiratory infections and allergic rhinitis are considered to increase the risk of barotrauma in the changing pressure environment. In an attempt to identify antecedent conditions as predictors of barotrauma, all adverse outcomes which occurred in a Navy altitude chamber during 1993-94 were investigated.


METHODS
A retrospective study of chamber logs, pre-chamber screening questionnaires, and a medical waiver database was conducted on altitude chamber trainees at the Naval Aerospace and Operational Medical Institute. Barotrauma cases were confirmed by reviewing ENT consultation records. Chamber screening questionnaires and medical waiver status were compared between barotrauma cases and a control group from the same chamber runs.


RESULTS
Of 5851 trainees, 193 (3.3%) experienced adverse events during this period, with an additional 9 events occurring to inside observers. Barotrauma, with 160 cases, accounted for the greatest number of these events. Upper respiratory symptoms were present in 12 (7.7%) of the barotrauma cases and 15 (4.8%) of the controls. Waivers for upper respiratory conditions such as allergic rhinitis were present in 9 (6.1%) of the barotrauma cases and 17 (5.7%) of the controls. Under-reporting of upper respiratory conditions on pre-chamber screening was found however, with only 7 of 28 cases with recent cold symptoms reporting this prior to chamber training.


CONCLUSIONS
No significant differences were found in predictors for barotrauma between cases and controls in this study group.