Epidemic decompression sickness: case report, literature review, and clinical commentary.
BACKGROUND
Decompression sickness (DCS) is a syndrome of symptoms caused by bubbles of inert gas. These bubbles are produced by a significant ambient pressure drop. Although cases are usually solitary there have been several episodes of DCS clusters. This paper reports an episode of epidemic decompression sickness and reviews the literature.


METHODS
The case reported describes six aircrewmen with DCS following an unpressurized AC-130 flight (maximum altitude 17,000 ft). Two obvious concerns-the low altitude at which DCS was encountered and the potential for epidemic hysteria-are discussed and discounted. In addition, factors contributing to this case are recounted in depth. Moreover, the literature was examined for similar cases of epidemic decompression sickness. Four other instances were discovered. Detailed qualitative analysis of these five reports was performed.


RESULTS
With this information epidemic decompression sickness is defined and classified. Two types are described-individual-based (Epi-I) and population-based (Epi-P). Epi-I is a cluster of DCS following a solitary exposure; whereas, Epi-P is a cluster of DCS following multiple exposures over time. Investigation of Epi-P follows the classical rules of outbreak investigation (time, place, person, and environment); whereas, Epi-I does not. In fact, the focus in Epi-I is almost entirely the environment. Following this outline should produce an etiology that control measures can be directed against. However, it is prudent to look beyond the etiology. Enter the Haddon Matrix, a classic public health tool that considers counter-measures before, during, and after the event.


CONCLUSIONS
These many concepts are illustrated with the presented case. Following this template, both the expert and the novice flight surgeon have a systematic and reproducible approach to these difficult puzzles.
Butler
William P
WP
USAF School of Aerospace Medicine, Brooks AFB, TX, USA. gila12@gte.net
D000328:Adult; D000337:Aerospace Medicine; D000531:Altitude; D016000:Cluster Analysis; D003665:Decompression Sickness / Q000145:classification / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D004242:Diving / Q000009:adverse effects; D006801:Humans; D007046:Hysteria / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D015994:Incidence; D008297:Male; D008887:Military Medicine; D013997:Time Factors; D014481:United States / Q000453:epidemiology