OP
Yep, exactly!
UTD Decompression profile study results published
- Thread starter Dr Simon Mitchell
- Start date
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Kev, Dr. Mitchell had been very clear in other posts here in SB, by saying he don't know how shallow the deep stops shall start, that he personally uses 50/80-85 but that was his preference, not that he recommended directly.
for the moment I will try 45/75 and see how I feel after the dives.
for the moment I will try 45/75 and see how I feel after the dives.
UWSojourner
Contributor
Just to be clear. Based on the current state of the evidence, you would "recommend" de-emphasizing the types of deep stops generated by VPM-B, or RGBM, etc., right?
So based on the currently available information, you would say it is a rational guess that GF50/80, or GF45/75, or ... is likely closer to the unknown "optimal" than is a profile using the same runtime generated by VPM-B, RGBM, or RD. And let's assume that the dive is sufficiently deep/long so that we're talking about more than just 5 or 10 minutes of decompression.
Would those types of statements be ok?
CAPTAIN SINBAD
Contributor
Seems like John Chatterton was right all this time.
"On the subject of decompression, my perspective it is pretty simplistic. Diving physiology is molecular, variable, and very complex. Decompression algorithms are just numbers, approximating all that complex stuff. Regardless, there is one, and only one, single cause of decompression sickness, and that is........ not doing enough decompression!!
If you do enough decompression, you do not get bent.
Once you have left the bottom, you need to do the decompression for that particular dive you just did. I train students to figure out how much deco is enough, by understanding the dive ahead of time, understanding human physiology, and interpreting the dive on the fly.
Doing more conservative profiles, or doing additional decompression beyond that required by the profile (shallower than the Magic Depth of 30'), is cheap insurance against DCS. Track your dive using a quality dive computer that gives you all the data you need, if not more, and be willing to adjust as needed.
IMHO Deep Stops, or Pyle Stops, do not work . I believe they increase, as oppose to decrease, the inherent risks of DCS. It appears that the US Navy Experimental Diving Unit basically agrees with me in their paper on the use of deep stops, Redistribution of Decompression Stop Time From Shallow To Deep Stops Increases Incidence of Decompression Sickness in Air Decompression Dives. This is another paper which I think every diver should read."
"On the subject of decompression, my perspective it is pretty simplistic. Diving physiology is molecular, variable, and very complex. Decompression algorithms are just numbers, approximating all that complex stuff. Regardless, there is one, and only one, single cause of decompression sickness, and that is........ not doing enough decompression!!
If you do enough decompression, you do not get bent.
Once you have left the bottom, you need to do the decompression for that particular dive you just did. I train students to figure out how much deco is enough, by understanding the dive ahead of time, understanding human physiology, and interpreting the dive on the fly.
Doing more conservative profiles, or doing additional decompression beyond that required by the profile (shallower than the Magic Depth of 30'), is cheap insurance against DCS. Track your dive using a quality dive computer that gives you all the data you need, if not more, and be willing to adjust as needed.
IMHO Deep Stops, or Pyle Stops, do not work . I believe they increase, as oppose to decrease, the inherent risks of DCS. It appears that the US Navy Experimental Diving Unit basically agrees with me in their paper on the use of deep stops, Redistribution of Decompression Stop Time From Shallow To Deep Stops Increases Incidence of Decompression Sickness in Air Decompression Dives. This is another paper which I think every diver should read."
OP
Hello,
Yes, that is a fairly accurate summary. For someone like me, recommending something requires an evidence base on which to base the recommendation. As you suggest, I do believe we have sufficient evidence base to recommend backing away from deep stops as prescribed by bubble models on significant deep decompression dives. However, I do not believe I have an adequate body of evidence to claim I know what optimal gradient factors are, and in particular, exactly how far to ratchet back the GL-low to de-emphasize deep stops. I am happy to reveal that my best guess at an intelligent option at the present time is somewhere around 50/-. But I would stop short of strongly advocating or recommending it.
I think that the point was that my perspective as articulated in the above paragraph was being compared to Andrew Georgitsis's fairly strong advocacy for RD practices, and I don't believe that what I do and he does are the same.
Simon M
I'm actually glad to see this coin beginning to fall. Just to add a little historical context, when RD was first developed the technical computers on the market sucked. There was no really good alternative to cutting tables and very little in the way of on-the-fly flexibility in the run plans.
RD offered the flexibility but at the cost of cutting a precision line with an axe and at the cost of only working in a narrow bandwidth of dive types, hence standard gasses and some other related "ballast" that forms the paradigm.
Of course there were egos who were highly invested in being right about everything. Some of those people used extensive bullying and instrumental aggression to quell dissenting voices and in the process RD was characterized as a lot of things it was not, including "efficient". It was never efficient. It was never intended to be efficient (I believe). It was intended to be a pragmatic solution to offering some compact and easy to remember on-the-fly flexibility, which it did.
If it had been "sold" as a pragmatic solution we wouldn't be here discussing it now. However the players involved at the time had such a pathological need to appear to be omniscient that critical voices were bullied, ridiculed, coerced, harassed, ostracized, jeered, sneered and even threatened to the point that nobody was questioning ANYTHING related to DIR at one point. This, of course, was at the height of the DIR wars, at which time I believe AG was the training director at GUE.
With the advent of decent computers and with the further development of our understanding of deco theory, ratio deco should have been summarily abandoned. The solution it offered was no longer necessary and other solutions should have been developed and refined.
That didn't happen.
Instead we are still talking about it 10 years later, which is an indication that many divers still aren't modernizing their procedures. The biggest concern of all, in my mind, is that AG won't let it go. A charismatic individual who has positioned himself as the center of attention and has taken on the responsibility for forming other divers' thinking cannot and should not base that thinking on junk science (or worse, gut feeling). It's irresponsible at best!
R..
dreamdive
Contributor
forming other divers' thinking cannot and should not base that thinking on junk science (or worse, gut feeling). It's irresponsible at best!
Who needs science! Heck, look at all the evidence we have on the use of Nitrox and people still claim they can "feel" when they are diving air. Now people can feel when they are diving different GF's!
WITH ALL THIS NONSENSE, WHY IS NOBODY POINTING OUT THAT WHAT YOU DIAL INTO YOUR COMPUTER DOES NOT MEAN YOU ARE EXECUTING IT.
I really hope that Shearwater one day will allow the review of ones ACTUAL GF that was dived vs what is dialed in.
Who needs science! Heck, look at all the evidence we have on the use of Nitrox and people still claim they can "feel" when they are diving air. Now people can feel when they are diving different GF's!
WITH ALL THIS NONSENSE, WHY IS NOBODY POINTING OUT THAT WHAT YOU DIAL INTO YOUR COMPUTER DOES NOT MEAN YOU ARE EXECUTING IT.
I really hope that Shearwater one day will allow the review of ones ACTUAL GF that was dived vs what is dialed in.
LiteHedded
Contributor
RD the way gue teaches it is still a fine solution. it DOES work pretty well in certain situations
Unless I misunderstand what you are asking for I believe that info can be extrapolated from reviewing the dive log in the desktop software.
Yeah. What @wedivebc said. I think you can download your log into Subsurface and also see your actual GF99 for all points during the dive, if you want. At least, you can see it as a tissue bar graph. I think maybe you cannot see the numerical GF99 value. That is actually a feature that I have requested on the Subsurface mailing list.
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