Thermal status of saturation divers during operational dives in the North Sea

The principal aim of the present study was to monitor the core temperature (Tc) of a population of saturation divers conducting routine deep dives at different locations in the United Kingdom sector of the North Sea and to assess whether current dive procedures are adequate in preventing deleterious decreases in Tc. A total of 30 divers, with an average (SD) of 19.3 (6.6) yr of experience as saturation divers, participated in the study. The survey included 59 dives conducted at six locations (Scott Field, Norfra Pipeline, Hudson Field, Pierce Field, Forties Field, and Bruce Field) from four Diver Support Vessels (Rockwater 1, Semi 2, Bar Protector, and Discovery). The depth of the dives monitored ranged from 54 to 160 meters of seawater (msw), and the duration of the dives from 31 min to 7 h 30 min. before each dive, divers were requested to ingest a radio pill and strap a data logger to their abdomen. Upon returning to the chamber within the Diver Support Vessel following a dive, they provided subjective ratings of thermal perception (7 point scale) and thermal comfort (4 point scale) for the period just before, during, and immediately after the dive. In 55 dives, Tc of saturation divers working at depths to 160 msw for up to 6 h with water temperatures ranging from 4 degrees to 6 degrees C increased above the pre-dive core temperature of 37.4 degrees (0.620+/-0.6 degrees C). In four dives there was a decrease in Tc: 2 divers had a 0.2 degrees C fall in Tc, and 2 bellmen had a decrease of 0.4 degrees and 1.0 degrees C. The subjective responses of divers indicated that they were thermally neutral (neither warm nor cold) and comfortable before and immediately after the dives. The current practice of providing thermal protection with hot water suits to saturation divers working in the North Sea is adequate for preventing the risk of hypothermia and maintaining thermal comfort.