Beyond all the initial pages on the math he has some interesting comments at the end of the paper.
Hi EFX,
Slightly off topic, but hopefully interesting.
Thanks, I had not seen Bruce's RGBM article in a while, and decided to remind myself of the 'interesting comments'. The 'Empirical practices' bit caught my eye because it is often raised in discussions about bubble models.
I and a number of colleagues have always been fascinated by Bruce's citation of empirical decompression practices of Torres Strait Islanders and Hawaiian diving fishermen as being supportive of deep stop / bubble model approaches. In the article you posted he characterises these practices as...
"...deeper decompression stops, but shorter decompression times than required by Haldane theory, were characteristics of their profiles".
...and says...
"While the science behind such procedures was not initially clear, the operational effectiveness was always noteworthy and could not be discounted easily. Later, the rationale, essentially recounted in the foregoing (description of RGBM)
, became clearer".
It is worth reflecting on what we actually know about the "operational effectiveness" of these decompressions because it is indeed "noteworthy".
In the case of the Torres Strait Islanders, and after reading the paper where Bruce apparently got his information [1] this is what David Doolette and I concluded in a recent textbook chapter [2].
"The earliest of these papers, an observational study of the practices of pearl divers in the Torres Strait of Australia, often cited as unqualified support for deep stops, is difficult to obtain and worth summarizing here. These pearl divers performed air dives to depths up to 80 msw followed by empirically-derived decompression schedules that had deeper stops and were somewhat shorter than accepted navy decompression schedules. Thirteen depth/time recordings were made of such dives, and these dives resulted in 6 cases of DCS (46% incidence). The remaining data was a count of dives performed from four fishing vessels over a two month period and these 468 man-dives resulted in 31 reported cases of DCS (7% incidence)."
In the case of the Hawaiian fishermen, the paper where Bruce apparently got his information [3] says:
"
All divers interviewed had experienced one of more incidents of decompression sickness (DCS) which they treated by immediate in-water recompression. Some divers reported experiencing DCS symptoms as often as one out of three diving days".
As David and I said in the textbook chapter [2]:
"It takes a certain cognitive dissonance to interpret these high incidences of DCS as supporting a deep stops approach".
Simon M
References:
1. Le Messurier DH, Hills BA. Decompression sickness: a thermodynamic approach arising from a study of Torres Strait diving techniques. Hvalradet Skrifter 1965; 48: 84.
2. Mitchell SJ, Doolette DJ. Extreme scuba diving medicine. In: Felletti F (ed).
Extreme Sports Medicine. New York: Springer Publishers; 313-333, 2017.
3. Farm FP Jr, Hayashi EM, Beckman EL. Diving and decompression sickness treatment practices among Hawaii's diving fishermen. Sea Grant Technical Paper UNIHI-SEAGRANT-TP-86-01. Honolulu: University of Hawaii Sea Grant College Program; 1986.
