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Current and foreseeable models may not be describing any sort of truth, but they do appear good at determining useful boundaries (time and depth limitations) around which a desired outcome (limited DCS risk) appears most likely. I do not mean to belittle that success in the least. We maintain a high degree of confidence we will not suffer decompression sickness on most dives, and that is no small achievement.
In essence the quantitative experience of pearl divers pleads in favor of deep stops as opposed to quantitative experience of US Navy tables, which is in favor of dissolved gas limits
Captain Sinbad,
You are perpetrating a myth. Did your read the link in Jarrod's article which is to an extract in a book chapter in which David Doolette and I cite the data that you believe "pleads in favor of deep stops"?
Here is what it says:
“The few studies available at the time of adoption of deep stops by technical divers [53,55] have been interpreted to support this notion. The earliest of these papers, an observational study of the practices of pearl divers in the Torres Strait of Australia [53], 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). It takes a certain cognitive dissonance to interpret these high incidences of DCS as supporting a deep stops approach.”
In: Feletti F, editor. Extreme sports medicine. Basel: Springer International Publishing; 2016. p. 313-33.
It is hardly a ringing endorsement for the pearl divers' deep stop approaches.
Jarrod's fundamental approach to this discussion is, I believe, flawed. He maintains a deeps stop vs shallow stop perspective, but the truth is every decompression has to have its deepest stop and in that sense we all believe in deep stops. The thing we wish to try to avoid is making our deepest stops too deep for optimally efficient decompression. The point indicated by the currently available data is that bubble models and at least one ratio deco approach impose deepest stops that are too deep for optimally efficient decompression. That's it. In espousing a position in which you are either for deep stops or against them one could encourage a (potentially risky) belief among the 'against group' that endlessly shallower stops may be better, but that has never been the message.
Simon M
Ya, I thought that the article would speak for itself. Here are some points worthy of looking at:
"It is not my intent to re-litigate the previous three sections of this article, but an interesting, and I believe, underappreciated aspect of Brian Hills’ pearl diver study provides a nice segue. What I find most interesting are the roughly 3,000 deaths and injuries of an unknown quantity that helped shape those unique ascent profiles. In other words, how was this conclusion affected by the elimination of those who are more susceptible to injury, and how much was due to a lack of rigor in the study ?"
In essence the quantitative experience of pearl divers pleads in favor of deep stops as opposed to quantitative experience of US Navy tables, which is in favor of dissolved gas limits.
I was expressing Jarrods thoughts in my words. That is not my view at all.
Except that's not what is says.
If you kill or maim thousands of your diver population (which is finite in the case of the pearl divers), then sure those who are left - they can pretty much "decompress" any old way. The only divers left are the hyper offgassers. They are the worst population to try and extrapolate to a broader body of <all divers>
"... can we now definitively conclude that Hills, the pearl divers, and the tech divers were wrong? " JJ
Asked another way, we might inquire how the conclusions reached by Hills and those technical divers are different from the way modern-day decompression tables have come into being." JJ