12 September, 2010

extreme diving for work

Some quotes from a paper on the Reduced Gradient Bubble Model for scuba diving decompression calculation which I've been looking at recently. Most of what I've looked at so far has been recreational no-decompression diving, so the dives described below seem quite extreme. (for comparison, the deepest recreational dives are to about 40 metres = 130 feet, and for a maximum of 8 minutes)

Pearling fleets, operating in the deep tidal waters off northern Australia, employed Okinawan divers who regularly journeyed to depths of 300 f sw for as long as one hour, two times a day, six days per week, and ten months out of the year.
With higher incidence of surface decompression sickness, as might be expected, the Australians devised a simple, but very effective, in-water recompression procedure. The stricken diver is taken back down to 30 fsw on oxygen for roughly 30 minutes in mild cases, or 60 minutes in severe cases. Increased pressures help to constrict bubbles, while breathing pure oxygen maximizes inert gas washout (elimination).

Similar schedules and procedures have evolved in Hawaii, among diving fishermen [...] Harvesting the oceans for food and profit, Hawaiian divers make beween 8 and 12 dives a day to depths beyond 350fsw.
Consistent with bubble and nucleation theory, these divers make their
deep dive first, followed by shallower excursions.
In a broad sense, the final shallow dives have been tagged as prolonged safety stops.

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