Mr fish
Active Member
I can not say id be happy with that , IE Banning of forum members,
Im sorry your so concerned
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My DCS Hit
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Im sorry your so concerned
Can we separate the deep stop debate from vpm itself? It seems it's always argued about deep stops and vpm in the same sentence.
My dive buddy and I have well over 1000 hours on vpm, and never a niggle.. Most of our dives are between 200-360 feet. We rarely, if at all see a deep stop. Ascend at a reasonable rate, we have never actually had to do a deep stop. Vpm gives us more bottom time and less deco. It works for us.
Now looking at dons dive, he ascended 400ft without a stop. Even common sense would dictate you need to stop a few times along that distance. That allows too much bubble formation.
I think deep stops are more relevant to extreme dives, not dives most of us do. The debate on deep stops seems to be more academic than practical
My dive buddy and I have well over 1000 hours on vpm, and never a niggle.. Most of our dives are between 200-360 feet. We rarely, if at all see a deep stop. Ascend at a reasonable rate, we have never actually had to do a deep stop. Vpm gives us more bottom time and less deco. It works for us.
Now looking at dons dive, he ascended 400ft without a stop. Even common sense would dictate you need to stop a few times along that distance. That allows too much bubble formation.
I think deep stops are more relevant to extreme dives, not dives most of us do. The debate on deep stops seems to be more academic than practical
AdrianSmith
New Member
I understand everyone is entitled to their opinion and I respect your right to feel differently. I happen to believe that such egregious, ongoing and long term violations of the terms of use agreement warrant banning, at least until the offending member learns that the community will not tolerate their behavior.
-Adrian
Adrian, I agree that much of Ross's statements tend to be filled with name calling and repetitious claims without content to back them up. That said, many people have indicated to me by private message that they have benefited from Simon's and UWSojourner's posts which have detailed, consistent and fact based responses based upon actual control studies, peer reviewed papers and current understanding of decompression science, as generally accepted by the majority of the world's leading decompression scientists. Throughout this discussion Ross has continually shown that he can not produce verified research to back his claims. Indeed he has not really even tried to do so, but has instead relied on name calling. I suspect that most of the readers, if not virtually all of them, have decided long ago to embrace facts and data and not be persuaded by noise. Ordinarily, we would place Ross on a time out to let things cool down, but we feel that the explanations being offered by Simon and Kevin, as well as a handful of others, have been worth the effort to fight through the noise. If the name calling and vitriol continue, we will probably step in and let the thread take a time out.
AdrianSmith
New Member
Randy, thank you for your reply. I appreciate the response and your reasons for leaving the thread alone for now.
-Adrian
Jeff what lead you to choose VPM instead of GF style models please and can you explain a bit more about how you don't have to make a deep stop, I thought a spread of deeper stops was necessary to the model to inhibit bubble growth in the faster tissues, but I am just exploring all this.
Do you have a conservancy level set up on it at all?
Nitrogenius
oppinionated ;)
I think it boils down to different definitions and understanding of "deep stops".. the "original" deep stop or pyle stop was a stop purpously added deeper than the deco model prescribed. Likely Jeff is refereeing to such stops when talking about deeps stops
then VPM decompression profiles are more a slower ascent rate starting deep rather than real stops.. that might be another reason.
of course most VPM profiles as well as GF profiles with a low GFlo are prescribing fairly deep stops that other refer to as deep stops and most of the discussion has been based on..
Brett Eldridge
New Member
Agreed.
Maybe we need new terminology. Maybe we should use "first stop" to define the first stop any given model and/or GF would require that is 1 minute or greater and "deep stop" to refer to the original Pyle method.
While true that the "first stop" would likely be cleared during ascent, it would at least give a relative sense of how deep a given model would require somebody to "stop" on their ascent.
- brett
Exactly.
From my viewpoint, seems most people arguing against vpm, are arguing academically, and may never even have actually dove using vpm I may be wrong, but that's how it seems, as I don't see deep stops, rarely even anything below 100ft, that wasn't already burned off on ascent.
Asked above why we use vpm, the answer was already in my post. Longer bottom times, less deco.. We set one computer to 50/90 and for short dives, it was pretty close to vpm. But deeper and longer, they dramatically diverged. Dives we could do in 2.5-3 hours, were not even doable, and became more like 5 with all the deco. Deeper- Longer dives it diverges badly. In our 2 weeks in truk, we probably averaged about an extra 15-20m of bottom time on the deep wrecks.
For 6 years we ran+2,but now run+3, but for no real reason than to just buffer abit. I think it added maybe 5m. I can tell no difference.
Jeff could you advise which profiles were similar between VPM and 50/90 GF and where the divergence started in terms of profiles?
Also did you start using VPM before the "deep stop" debates started and does it accurately reflect current thinking on the need for longer shallow time to compensate for longer aggregate deep time?
I think the differentiation between "Pyle Stops" I.e a stop at depth outside of a given model makes sense, but if a model is designed to include deep stops in the way that I thought VPM was and that a low GF low figure dictates, then I think the lines and definitions are blurred.
So have I understood correctly that VPM does mandate deeper stops than a dissolved tissue model (without manipulation) or am I missing something!
Given that RGBM was an attempt to cover the best of both worlds, why didn't it work or was it superseded in popularity by GF style models that appear more utilised, or at least do in the UK.
UWSojourner
Active Member
The history of the discussion would clearly say, "No". I think the reason, for the most part, is the extreme defense of VPM-B by Ross who pops up in ALL these discussions. He has probably done more to promote the shallower profile approach than anything the NEDU could ever have done. You need a proselytizing heretic to really promote a full definition of orthodoxy.
Take this thread for example. A discussion about a DCS event quickly allowed Ross to begin promoting, at all costs, VPM-B as the solution. Your experience with VPM-B aside, current research cannot lead you to the conclusion that VPM-B is the cure for this profile. So what could have been a discussion about dive planning, fast ascent rates, work at depth, risk, etc. simply devolved into answers to the same set of Ross's VPM-B promotions that have been answered on numerous forums over the years.
I believe the recommendation for those who have found a deco model that works for them is to stick with it, or make changes in small increments. Personal experience, however, is a poor yardstick by which to make generalized recommendations to a large group of divers. And the research available today is strong enough to say that your "Vpm gives us more bottom time and less deco" is in reality simply a belief. That so far it has worked for you says nothing about what, on average, divers would experience by acting on that belief.
It seems like divers are taking practical steps to adjust their decompression strategies based on results of academic studies. The US Navy took a very practical step and declined to use the bubble models they were developing. Clearly this started with academic studies, but divers are understanding the practical implications of that research.
My personal move away from deep stops was based upon several years of personal testing during Innerspace by the Dan Docs performing a multi year trans thoracic echo cardiogram bubble test on me. As I eventually moved from an 15/85 GF with Pyle Stops, to what eventually became 40/70 GF, my bubble scores decreased significantly. For me personally, this was a real eye opener and was all of the personal proof I needed. We can argue all we want about whether bubbles in the heart are a perfect indicator of DCS stress or not, but they can't be good for you! 
I am further comforted by the fact that the most current, widely recognized consensus within the decompression scientific community points towards the direction in which I have moved.
I am further comforted by the fact that the most current, widely recognized consensus within the decompression scientific community points towards the direction in which I have moved.Nitrogenius
oppinionated ;)
well I guess it all depends how one defines deeper dives and longer dives..
if you are doing overall runtimes of 2,5-3 hrs but usually do not see any stops below 100ft using VPM it seems as if you are doing long bottom times at rather shallower (or medium depth dives)
It should look different at deeper shorter BT dives (more bounce dives) which this discussion seemed to focus at
It is true that I never dove VPM but I have seen a fair set of comparisons of the profiles and generally the comparable risk VPM strategies (same overall runtime) did prescribe deeper stops than GF approaches with a "higher" GF lo (lets say bigger than 30)..
such first "prescribed" stop depth is what the discussion focusses on and not the traditional "added Pyle stop" while obviously the core statements would also apply to such Pyle stops.
Maybe in your perception the "disconnect" is due to not comparing apples to apples. The only reasonable indicator of comparing deco approaches in my opinion is overall decompression time or runtime (the later with a fixed set of depth and bottom time). When you make the observation that one approach is giving you half the overall run time over the other the inherent DCS risk of such approach may differ immensely. Now you seem to be getting away with "fairly aggressive" decompression approaches without issue, so likely you have a high overall tolerance against DCS formation. Now the "trick" would be to find the right set of GFs that matches such runtime without starting decompression deeper than with the VPM.. This likely will result in a fairly high GF hi.. very likely way above 100 from your descprition. Then to start to sensibly raise the GF lo and see what GF high you would need to keep the RT equal which will bring down the GF hi and then slowly raising the GF hi again keeping GF lo stable and thus reducing RT or increasing BT to facilitate your potential high tolerance to optimize your decompression approach if it is longer BT/shorter RT you are chasing after..
Can't speak for Jeff but knowing something about the sites he's often diving I'm guessing the differences are due to deco "credit" being applied by VPM for intermediate stops on a multileveling profile up slope. Buhlmann is not giving the same credit for that time significantly below the stop depth.
I'll keep this really simple. If there were no DCS incidents I might be inclined to agree with you. But since there are bent divers in those studies, how do they demonstrate:
'"The deeper stop approach is the most successful and has the lowest injury rates for the 16+ years its has been in use."
Deeper than what?
More successful that what?
Lower injury rates than what?
Mr fish
Active Member
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=2ahUKEwiaicSdke_cAhXMKewKHcYrB9UQFjABegQIBxAC&url=https://www.johnchatterton.com/wp-content/uploads/2013/03/NEDU_TR_2011-06.pdf&usg=AOvVaw3rf3HSiWcO0MaFjUJPZFiQ
im sure you all have see the test paper ,
dont know why ist called the deepstop v deco at the right stop depth , lol
it has not a lot to do with how i dive ,
no deep stop looks like a lot of deco and all in the right place ,
so called deepstops looks more like two dives then cut short at the last stops ,
first lot got bend working to hard o2 use was running at 2.3lpm to 1.4lpm ,( i use about half the 1.4lpm) , and cold to boot , plus the shitty po2 (im nice and warm and have a good po2 to breath )
2nd lot got bent for all the abover pluse its as good as two dives then a small back end , to small by 20mins or more ,
tables were made to give information they wanted , ross has seen his arse and it go.s on and on .
some smart peps got some info they could work with
the rest of us well not so much , ie we did,nt get a lot ,
run the profiles on your bendmenow planners , you can see how much slack the first lot got ,
and how the slack was cut back for the deeper stops ie not in the right place ,
cant call them tables as we know them so lets just say the test profiles ,
top side fizz , well if one deco is short and the other lets you fizz in the right place , you get what your looking for, A maybe and A could be ,
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My posts in this thread are about how Don's dive exceeding the tolerable limits of human abilities in the ascent, offered lots of information and scientific measures, and why his ZHL + GF simple is not capable of planning dives this deep because its way beyond its useful range.. noted that only bubble models have the required math to create ascents that can account for these limits.
You lot offered numerous alternatives but you can't properly justify them. It's you lot who got all offended with the fact that your "new, more efficient" deco method, simply does not work here. Tough luck for you.
Of course the Mitchell fan boys have to stomp over everything to prop up the fallacies with endless distractions.
I remind you again, VPM-B has been to these depths very successfully, while your "new, more efficient" deco method, has not. But you are entitled to your denial.
Simon Mitchell
Well-Known Member
And we cycle right back to the start where it was pointed out that based on ascent rate alone Don's dive did not correlate well with evolving GF approaches, and that even if it did it is utter nonsense to try to draw conclusions about the wider appropriateness of a decompression approach based on the outcome for one diver on one dive. These are indisputable facts.
Math that results in a surfacing GF of 130 from Don's dive. But true to form you see nothing wrong with simply manufacturing an argument to paper over this highly concerning metric. So now you are insisting that surfacing supersaturation doesn't matter! And you do this even though the one lesson we can take from all the published experimental comparisons of deeper vs shallower decompressions to date is that greater slower tissue supersaturation later in the ascent and at the surface is much more important than bubble models assume it to be.
Based on what we can deduce from the published studies to date (and from UWSojourner's ISS evaluation), it is highly likely that if a formal experiment with enough subjects in each group was conducted using Don's decompression (but performed with a correct ascent rate) vs a VPM-B decompression (with every diver surfacing at GF130) then the VPM decompression would produce more DCS.
See the evaluations of ISS performed by UWSojourner, combined with knowledge of the outcomes of the formal experimental comparisons of deeper vs shallower stop approaches conducted to date, which suggest that over-emphasising protection of fast tissues whilst allowing greater supersaturation in slower tissues is associated with worse outcomes.
How do you "justify" VPM??? It has no testing across any depth range. None.
And you know these things how? Are you some sort of all-seeing eye whose magical powers allow you to constantly and simultaneously monitor the activity of every individual in the global diving community. This is an outrageous inference. You have some deep VPM dives on your database, but you don't collect outcomes so you don't even know how they turned out. More importantly, you have no idea how many bad outcomes there have been on VPM dives that are not on your database. You have no idea how many very deep dives have been done on GF successfully or unsuccessfully. Your readiness to uncritically adopt patently false arguments-of-convenience like this should be a huge red flag to anyone reading these threads.
Simon M
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Simon Mitchell
Well-Known Member
Hello Jeff,
The one thing that the formal evaluations of deeper vs shallower stop approaches have taught us to date is that there is nothing magical about the bubble model approach of protecting fast tissues from supersaturation early in an ascent that could be expected to facilitate "longer bottom times, less deco". Every time these approaches have been carefully compared in human experiments the result is more DCS and / or more bubbles and / or more inflammatory activation in the deeper stop approaches. The face validity of these results is enhanced by ISS evaluations like the ones posted by UWSojourner here which show greater supersaturation levels in the deeper stop approaches.
Your obvious scepticism about all this is (quite understandably) based on your own good outcomes when using VPM. I don't dispute these outcomes for one picosecond. Nor would I recommend you change if VPM is working for you. But for perspective, it is important you understand that humans are not all equal in respect of vulnerability to DCS. Some are bubblers and some are not. In my life as a diving physician I have seen divers who have been doing outrageous things (off the scale of any deco algorithm we use) for many years with no problems. My point is that your successful use of VPM says little about it as a source of truth for the wider community. That is why we do proper studies, and I have mentioned the results of those performed to date above.
It is entirely plausible that your diving would be even safer (that is, you would be further away from the edge of risk) if you used an approach with less emphasis on deep stops. To illustrate this (entirely hypothetically), lets say you have done 3000 dives, and your risk using VPM is 1 case in 4000 dives. It would therefore not be surprising that you have not had a case of DCS yet. But another approach might have a risk of 1 case in 6000 dives. The alternative would therefore be safer. This is just hypothetical and not intended to reflect reality in any objective sense. But the best evidence we currently have is that bubble models have no particular qualities that facilitate "longer bottom times, less deco" and I wanted to discuss how the fact that you appear to have reaped such a benefit so far may be an attribution error, and that it is your physiology rather than the model that is working for you at the moment.
Simon M
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