Escape from a disabled submarine: decompression sickness risk estimation.

Individual crewmember escape from a disabled U.S. Navy nuclear submarine has never been necessary, but remains an important contingency. Decompression sickness (DCS) is one of the foreseeable risks and a robust mathematical model of DCS incidence has been used to estimate the magnitude of this risk under a variety of escape scenarios. The model was calibrated with over 3000 well-controlled human pressure exposures, less than 2% of which simulated pressure profiles of submarine escape. For disabled submarine depths < 300 ft of sea water (fsw) and internal submarine pressures of <11 fsw (arguably the most likely conditions), the DCS risks are comparable to those routinely undertaken by U.S. Navy divers--less than 5%. For progressively deeper depths and especially for higher submarine internal pressures, the risk of DCS becomes much greater, including unknown chances of permanent injury and death. Variations from the baseline escape procedure are explored, including equipment differences, delays in exiting the submarine and changes in the oxygen content of the breathing mix.