Altitude decompression sickness symptom resolution during descent to ground level.

INTRODUCTION: Altitude decompression sickness (DCS) is a health risk associated with the conduct of high altitude airdrop operations, high altitude reconnaissance, future fighter operations, hypobaric chamber training, unpressurized flight, and extravehicular activity (EVA) in space. The treatment for DCS includes the provision of 100% oxygen (O2) at ground level (GLO) and/or hyperbaric oxygen therapy (HBO). In this paper we examine the effect of repressurization to ground level from hypobaric conditions on DCS symptoms. Timely recompression (descent at first recognition of any DCS symptom) may be a safe, effective treatment for the large majority of DCS symptoms. METHODS: Data from altitude chamber exposures recorded in the Air Force Research Laboratory (AFRL) Altitude DCS Database were reviewed to determine the level of recompression required for complete resolution of 1,699 observed symptoms. RESULTS: Of the 1,699 DCS symptoms reviewed, 66 (3.9%) resolved at altitude, 117 (6.9%) resolved at ground level, and 1,433 (84.3%) resolved during descent. Increasing the pressure by 138 mmHg from the altitude of exposure where symptoms occurred resolved roughly 50% of symptoms. Little resolution of symptoms was noted with recompressions of < 50 mmHg. The greatest rate of symptom resolution occurred with recompressions of 50-250 mmHg. CONCLUSION: These findings support the concept that descent and postflight, ground-level oxygen may be sufficient to relieve the majority of altitude DCS symptoms. HBO may be reserved for serious, recurring, delayed, or refractory symptoms. The findings also suggest a need for further study of DCS symptom resolution.