Development of a Decompression Algorithm for Constant 0.7 ATA Oxygen Partial Pressure in Helium Diving.
NAVY EXPERIMENTAL DIVING UNIT PANAMA CITY FL
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A total of 1582 man dives were done to test a computer algorithm used to compute decompression schedules for a closed circuit underwater breathing apparatus which maintains a constant 0.7 ATA PO2 in a helium diluent. The 47 test dives were all single depth dives up to 300 FSW deep with total dive times approaching 4 hours. The first three phases of testing resulted in a computer algorithm which appeared initially safe but which subsequently produced an unacceptably high incidence of decompression sickness DCS on a later dive series. Investigation of this high incidence of DCS on later dives lead to the identification of a workup phenomenon which showed that previous HeO2 diving will significantly reduce individual susceptibility to DCs. Further testing resulted in a computer algorithm which would compute safe decompression schedules for divers who are not worked up. The overall raw incidence of DCS for the entire dive series was 3.73 with 37 of all symptoms being Type 2. The overall incidence of DCS was 3 lower than that found during testing of a similar computer algorithm using a constant 0.7 ATA PO2 and a nitrogen diluent but the proportion of Type 2 DCS was higher using a helium diluent than when using a nitrogen diluent.
- Stress Physiology