VR3 BUH or VPM

Gene_Hobbs

Just to add to these a little bit (if you don't mind Andrew).

Blatteau J-É, Hugon M, Gardette B, Sainty J-M, Galland F-M. Bubble incidence after staged decompression from 50 or 60 msw: effect of adding deep stops. Aviat Space Environ Med 2005; 76:490–492.
NOTE: as of Sat night, it was still listed as the free content from AsEM.

RRR ID: 5069 but the profiles are listed in the TDS thread

If you only want the paper above and not the whole workshop, it is here.

The abstract describing their work is:
Gutvik CR, Møllerløkken A, and Brubakk AO. DIFFERENCE IN BUBBLE FORMATION USING DEEP STOPS IS DEPENDENT ON LENGTH OF BOTTOM TIME; EXPERIMENTAL FINDINGS AND THEORETICAL SUPPORT. 2007 UHMS Abstract. RRR ID 5067
Comments by Christain on their study and the profiles are listed in the TDS thread.

Other papers worth reading to be more complete in a review would include:
Marroni et. al. A deep stop during decompression from 82 fsw (25 m) significantly reduces bubbles and fast tissue gas tensions. Undersea Hyperb Med. 2004 Summer;31(2):233-43. RRR ID: 3804
with comments by Risberg and Brubakk. Undersea Hyperb Med. 2005 Mar-Apr;32(2):85-8; and author reply 89-92. RRR ID: 3805

and

Buttolph and Broome. Deep Stops During Decompression in a Swine Model of Decompression Sickness. Naval Medical Research Center Technical Report 97-40. RRR ID: 3595

and

Hills, BA. A fundamental approach to the prevention of decompression sickness. SPUMS 1978 Volume 8 Number 2. RRR ID: 6176

--Kevin, thanks for getting me to pull these.
---Hope to see you all in Salt Lake City.

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UWSojourner

Thanks for the work! After this thread I've decided to wear a helmet to the meeting.

Inspired Trainer

DiverKlondike,

where is the bashing? surely a bit of net banter is better than osteonecrosis? Our friend Ross has gotten this stuff wrong on way too many occasions in the past to be given the benefit of the doubt.

Im not sorry for treading on toes, lives and the quality of are being destroyed by all this nonsense and all you insist on doing is sending me red blobs for my 'netiquette' - i believe you are part of the problem - surely this site is about diver safety? or is it just somewhere where the unscrupulous flog their wares aided by short sighted moderators?


hope no one has any problems regarding the dangerous info that isnt correctly moderated on here...

There was some lucid elaboration on the deco part of this mail...for some reason its gone...no matter

silent running

Hi Mark, whether I've repeated Weinke's spiel or not, I'm well aware that Suunto comps don't have real RGBM in them. The manned dives I was refering to were done by USN divers using tables, not to mention all those maned dives done by the pearl divers which gave the first indication that deep stops have merit.

And if you are referring to the HE computer bending many people, this is news to me.

And again, I'm not saying that I trust any alg completely, there's just too little validation for deep he dives with any of them to be trusted completely, which is why I do the deep stops given by my RGBM computer and then pad with long shallow stops.

My best guess is that along with a very slow ascent rate, where the deep stops are first started and their length is crucial. But who knows, maybe it's just too fine a point btw where the fast tissues off-gas and the slow tissues are still on-gassing to be determined for humans as a group, given all our individual physical differences... -Andy

aainslie

I did - it's not on there.

I'll give you $1000 cash for that X1 the second you PM me - just let me know.

At the end of the day, I'm shocked that anyone thinks that stepped deep stops wtih large ascents in between make any sense at all. Once one begins to decompress, from then onwards one wants to smooth the curve to the surface as much as possible. The Blatteau paper is just dumb in this respect. As are the deep stops on a VR3. What a waste of research time, particularly given that he was putting people's health at risk.

The difficult issue - and what a lot of these discussions come down to - is how much to give back in the shallow portion if one starts decompressing earlier and deeper. And indeed when one looks at the VPM B profiles with no conservativeness, they can be pretty scary.

My personal view on this is that no one - not Ross, not Yount, no one - forces us to get out of the water. We decide. I've been a little nervous of using V-Planner and X1 for a different reason than others - that I believe that V Planner HAS been validated through thousands of dives with low incidence of DCS, but that in general we all tend to pad those by using a deeper deptha than the actual, or by planning (say) a 35 min BT and using tables for a 40 min BT. With V-Planner Live, this padding goes away. My own reaction has been to pad by using the mechanism Ross gives us, i.e. putting up the conservativeness which changes some of the bubble parameters. I use it on level 4.

Interestingly this gives deco remarkably similar to the GF model in the Inspo Vision, set to 15/85. I was really surprised at how close they were. Admittedly I haven't done deco past 30 mins on this so far but I've been intrigued.

This stuff is such a balancing game between shrinking bubbles and taking on inert gas. The science of the bubble models is definitely closer to the thermodynamics of the compression and decompression process than Buhlmann based models. I agree with Mike that bubble models are poorly verified in any scientific fashion - but isn't this a criticism of the academic community? Why are they spending so much time on stupid tests of models with poor theoretic bases - or even profiles no one dives - when there are better ones to test empirically? Whoever paid for the Blatteau experiment (the French tax payer I suppose) should definitely ask for their money back. Even an idiot like me can point out that more time spent deep during deco is not unequivocally good.

Finally on the X1/V Planner implementation - again, if you want, as a user you can just be sensible and conservative in your usage. Stay a few feet short of the suggested ceiling, and then pad the last stops if you want.

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Andrew Ainslie

Drmike

i think thats very sensible.

deep stops under some circumstances may be beneficial.
we dont know enough (clearly if you look at how vpm has been 'tweaked') and IMHO still dont know enough on how that/if that should influence shallow stops. Early implimentation of VPM suggested that it does and that the promised short shallow stop times was a pipe dream - people got bent. A sensible approach (and the one that I take) is to combine the two. Deep stops but with a longer tail. You can get that by using VPMBE max cons and bit of padding or by using VR3VPM or by using VR3buh and doing your own deep stops (possibly bending comp due to shorter pyle stop time)

I know theres individual variability but Ive followed VR3BUH and VR3VPM raw, on almost all my deep dives without case of bends so certainly for me Im confident to follow them.

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Drmike

too right. Often friends, buddies and loved ones of deep divers are the only ones who know of the subtle manifestations - but public never hear about it. I certainly know a few people with permanent strange small side effects. From short moments of 'blanking out' to occasionaly seeing stars to moments of weakness, to unexplained fever like symptoms. Interestingly most of these people are same people who constantly chase shorter deco rather than sticking to a very conservative approach

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

UWSojourner

Hi Andrew,

An issue I see with your statement above is this. If VPM has been validated through thousands of dives, but the diver padding of the profiles has essentially reduced it into the range of Buhlmann and/or Buhlmann/GF profiles, then the trials are not a valid test of VPM (probably more of a validation for GFs). VPM would never have been considered if Yount/Baker/Maiken had released their algorithm with the announcement, "Look, we just developed an extremely complex way of generating Buhlmann profiles."

In other words, the promise of VPM/RGBM was a "smarter" profile that prevented excess bubble development while at the same time cutting overall decompression time. Your choice of a conservatism level that essentially reduces VPM to GF-type profiles may be wise, but that strategy also begs the question, "Why not just use GFs?"

The test for VPM will be actual trials of profiles where VPM diverges from Buhlmann, not profiles that through parameter choice have been reduced to Buhlmann.

aainslie

Well, a few things:

1) This approach isn't unique to VPM. Pretty much everyone pads whatever comes out of their deco software. So ANY software tthat moves from tables to "live" - including GF - needs to be initially treated with caution IMHO.

2) However, some of us are more conservative than others. Fortunately for me, a lot of people actually do exactly what the computer tells them, on very low settings. They're my guinea pigs!

The X1 has a nice data collection part to it, and Ross is collecting a database of peoples' suages and actual profiles. I'm hoping that enough people a) use zero conservative settings and b) submit their dives, so that over time I can become less conservative and move up to, say, a setting of 2 or 3.

In the interim I think I have a reasonable mix of a sensible ascent path (particularly since the X1 does continuous deco, rather than stepped, a little like the VR3's "man on the line" but better), and a sensibly conservative last stop.

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Andrew Ainslie

aainslie

Mike,

One minute you're claiming that the data we have based on thousands of successful dives on V-Planner don't constitute hard data because they weren't collected in a controlled fashion, then you're using what an economist friend of mine calls a "manwho" statistic, i.e. "I know a man who...". This anecdotal evidence you're quoting here is inadmissible by your own rules, and completely unprovable.

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Andrew Ainslie