Gradient Factors and Deep Stops

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SB is fascinating place. Was like watching the crazy scene around a traffic wreck here, vs the near unanimity of position regarding the importance of perfusion in offgassing as people talked about the risks of DCS when taking a hot shower or hot tub in this thread. DCS in Cozumel

At least one person in this thread is on a completely different planet from the rest of us. How much more valuable would V-planner be if it were modified to incorporate changing medical evidence about deep stops? It is hard when you bet on the wrong pony, I know. Just don't bet on him next week, and the week after, and the week after.
 
SB is fascinating place. Was like watching the crazy scene around a traffic wreck here, vs the near unanimity of position regarding the importance of perfusion in offgassing as people talked about the risks of DCS when taking a hot shower or hot tub in this thread. DCS in Cozumel

At least one person in this thread is on a completely different planet from the rest of us. How much more valuable would V-planner be if it were modified to incorporate changing medical evidence about deep stops? It is hard when you bet on the wrong pony, I know. Just don't bet on him next week, and the week after, and the week after.

V-Planner already includes all that the nedu test revealed... there is nothing extra to add. i.e. that the existing gas kinetic formula (as used everywhere) work very effectively, and that they are aligned correctly with risk shown in the test. Note that all existing models and dive computers use these formula, including ZHL and VPM-B. Nothing to fix here. Sorry to disappoint you.

The other part the nedu test showed - thermal stress - is not easily quantifiable, and no existing model tries to realistically adjust for this. I had conversations with Neal Pollock about measuring this somehow, but he was not able to help. Thermal stress (like in the hottub problem) is currently left to the diver to decide when and what to act upon. It's one of those things that divers just have to avoid.


If you would like to have GF plans instead, then switch to MultiDeco. Both programs are included with your registration purchase.

.
 
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V-Planner already includes all that the nedu test revealed... there is nothing extra to add. i.e. that the existing gas kinetic formula (as used everywhere) work very effectively, and that they are aligned correctly with risk shown in the test. Note that all existing models and dive computers use these formula, including ZHL and VPM-B. Nothing to fix here. Sorry to disappoint you.

See the second half of this post.
 
Of course, deeper stop style planning and bubble models have been the most successful deco approach in rec and tech dives for the last 15 years.

Ross,

Having once used your program religiously many years ago for several years, and was very happy with the 'results', I am sorry to say IMO you are dead wrong with the above statement 'now'.

Ten years or so ago, deep stops maybe, but not any longer in the majority, again IMO.

EDIT. Highlighted / added what I only meant to to emphasize in particular

Kevin Denlay
 
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(Anybody try this 90msw profile in figure 1 above yet?):shocked:

Kevin, is what you refer to an 'Eric Baker' generated table?

If so, no and yes. If yes, no from 90m that is, and if that is one off Eric's then yes :giggle:, but from 120/130m dives where he cut us some custom 'pre-release' - so to speak - tables in the mid 90's (when he was working / co-operating - dare I say 'guinea pigging' - with Larry Green :acclaim: in the deep Florida caves, who was diving / using them as Eric generated various 'models' daily shall we say) with a very similar look to the what you refer too.

Problem for us was these were open water dives we were doing (as opposed to cave dives where you can stage gas along the way) and the quantity of the mix / mixes one needed to carry for the deep stops caused us to abandon their use after only several dives.:facepalm:

If it ain't one of Eric's, then no, period.:surrender:
 
Ross,

Having once used your program religiously many years ago for several years, and was very happy with the 'results', I am sorry to say IMO you are dead wrong with the above statement 'now'.

Ten years or so ago and before, maybe, but not any longer in the majority, again IMO.

Kevin Denlay

Hi Kevin,

Now... ? Today the focus is on "low stress" deco with an abundance of over inflated shallow time. Naturally all that add on safety time, has a great outcome. That is of course, the basis of all deco planning: the speed vs time compromise.

That does not diminish the success of VPM-B and deeper stops in tech diving, which was dominant for at least a decade. Still the two dominant tech training agencies today teach and use a deep stop approach.

Recreational divers the world over now, very much follow a pseudo deeper stop / slower ascent pattern, and will likely continue to do so.


The worst period in deco history statistics, was around the year 2000. Injury rates were rising steady up to that time, and then reversed have been in decline ever since. GF was introduced in the late 90's and started to take hold about then, and VPM-B became available in 2003. RGBM was around 2000 I think. It may seem strange to imagine now, but good computer deco programs were hard to find back then.


One can credit any number of things for this reduction in injury rates: better training, improved standard equipment, better planning techniques and smarter choices in mixes and gas swaps, and better deco models and planning tools, and increased use of wrist computers.


However, this latest trend of "low stress" deco, is very late to the game, and it remains to be seen if it has any actual value. Right now its a theoretical improvement only - the "go slow" approach, but were we going too fast before hand? I don't think so.


Cheers
 
Ross,

Thanks for your reply.

Not sure / don't think it would make much/any difference to your answer but have edited my post just slightly to empasize what I meant / was referring to in particular.

But personally (and let me repeatedly state 'personally' ad infinitum, especially for those that think I would be so presumptous as to give advice to them or am giving advice with what I write to anyone, especially anyone who didnt ask for it); in my personal experience and opinion, repeat opinion (which I am after allowed to have when last I looked after all) a happy medium between the two, i.e. real deep stops and drawn out long shallow stops seemed to be just that - again in my own personal experience - i.e. a happy resultant medium.
 
One can credit any number of things for this reduction in injury rates (my emphasis): better training, improved standard equipment, better planning techniques and smarter choices in mixes and gas swaps, and better deco models and planning tools, and increased use of wrist computers.

Ross,

First, I would congratulate you on a much more balanced paragraph on this issue than you have produced in the past (when you have been enthusiastic about attributing your perceived improvement in safety almost solely to the use of bubble models).

Unfortunately, you continue to perpetrate an unsubstantiated claim that the rate of decompression sickness (DCS) in technical decompression diving has declined. To calculate a "rate" you need a numerator (number of DCS cases in technical decompression dives) and a denominator (number of technical decompression divers or dives). You actually have neither. All you (sort of) have is an imprecise and tangentially relevant numerator (number of DCS cases in ALL recreational diving).

It is true that the number of DCS cases in all recreational diving has been reported as falling by a number of authorities. An example is our own data: see this post. However, this tells you very little about what is going on in technical diving. In terms of numbers, technical decompression diving is a tiny subset of the all recreational diving and it would be possible (and indeed plausible) for DCS numbers in all recreational diving to be falling whilst numbers in technical decompression diving are actually rising. Put another way, you cannot look at the numbers of DCS cases for all recreational diving and simply assume that the same trends hold in technical decompression diving. Put yet another way, you don't even have an accurate numerator, let alone a denominator.

Then there is the issue of what those numbers actually mean (and that is where the denominator becomes important). For example, the fall in DCS cases in all recreational diving may be nothing to do with safety improvements and simply about numbers of participants. Again, see this post for a real published data example of how this appears to be at least part of the explanation in our jurisdiction. I am not suggesting that numbers of technical divers are decreasing, but this is a great example of how easy it is to make errors in attributing causation for an apparent trend without having all the facts.

One of those other relevant facts, that came into play at virtually exactly the same time as VPM appeared, was an international agreement that milder cases of DCS could be managed adequately without recompression. There are no accurate data describing exactly how this impacted on recompression treatment numbers globally, but based on discussion at diving medical meetings it is likely to be substantial. This is yet another example of a way in which attribution of causation for lower DCS treatment numbers can be confounded.

Finally, as I have told you in the past, based on experience of acting in the role of medical officer for over 10 major technical diving expeditions to remote locations, I believe there is a substantial burden of unreported relatively mild DCS among technical divers that is self treated in the field. It follows that even if we had a numerator for DCS cases in technical decompression dives, there would be problems with accuracy.

The issue of trends in decompression safety is one of fundamental importance to the sphere of my professional interest. It follows that every time you misrepresent that issue on diver educational forums I will point out the flaws in your argument. That paints you in an unfavourable light and is time consuming for me. So why don't you just stop doing it??

Simon M
 
That does not diminish the success of VPM-B and deeper stops in tech diving, which was dominant for at least a decade. Still the two dominant tech training agencies today teach and use a deep stop approach....
 
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Depends on your definition of deep stops, but If you are counting GUE in those two, that is no longer true. When I took T2 in January 2017 we were taught the new protocol, which calls for ascending at 30ft a minute to the first buhlman stop, as defined by Decoplanner set at 20/85.
Is the protocol always 20/85, or does it vary with situation?
 
https://www.shearwater.com/products/swift/

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