DECOMPRESSION-SICKNESS FROM SATURATION DIVING - A CASE-CONTROL STUDY OF SOME DIVING EXPOSURE CHARACTERISTICS

A comprehensive computerized database of diving activity for a Norwegi an offshore diving contractor [Stolt Nielsen Seaway (SNS)] covering th e years 1983-1990 has been established. The database contains detailed dive information about 12,087 surface-oriented and 2,622 saturation d ives. During this period a majority of the divers were permanently emp loyed. Preliminary analysis had suggested that decompression sickness (PCS) might be the result of exposure to factors causing pathophysiolo gic effects which accumulate over the course of a single dive or a ser ies of dives. This concept evolved into the HADES (Highest Accumulated Decompression Score) theory which assumes that DCS is predictable onc e the underlying exposure factors are understood. The incidence of DCS among the SNS divers from saturation diving in the North Sea was stud ied by use of a ''nested'' case-control design. Twenty-one case dives (i.e., dives where DCS occurred) were compared with 41 randomly select ed control dives. For these dives, several saturation dive characteris tics were established. The relative pressure change between maximum an d minimum storage depths was significantly greater among the cases. Fo r each 1% increase in the relative pressure change there was a 5% incr ease in the probability of a saturation dive resulting in DCS. Signifi cantly more cases than controls performed a saturation dive with more than one storage depth, and the data suggested that there were more an d greater ascending and descending changes in storage depth conditions among the affected divers.