Spisni study

[Dan_P]

Well, this escalated quickly

While I'm interested in any negative effect (whether pulmonary or inflammatory) O2 may or may not have so that I can take this into consideration in my diving, I'm not going to sit here and argue the obvious:
While we don't know what the inflammation means precisely, there's no denying that it's logical (though maybe, theoretically, one day proven incorrect!) to assume less of it is probably better.

I don't have a problem with that (but remain insatiably curious about the full picture).
Nor do I have any particular affiliation with, or interest in, the deep stop emphasis used on the RD-side of the Spisni-trial.

And I certainly have zero basis for a conversation on advanced computer science.

Personally, I consider it way too easy to get lost in spreadsheets and algorithms when diving (and decompression) is right in front of you - and I actually consider situational awareness and diving within one's comfort zone to be much bigger issues in diving than these questions on decompression.

Further, I don't even truly feel that I have scientific reason to believe the differences we're speaking about here, are likely to be a determining factor across clinical or sub-clinical DCS anyway.

However, with that said:

Out of this confusion, Ratio Deco was born and promoted as a viable protocol to juggling deco obligations. It's not based on science but rather a hunch filled with holes and fallacies.

Have you ever seen formal training in the use of RD?

You're talking about RD as though you're acutely aware of it's details, intricacies, evolution and history - but based on your posts, I for one suspect a significant lack of knowledge on the matter, on your part.
Therefore, the question: Have you or have you not been formally trained in the use of RD?

There's no denying that reasonable people make reasonable posts. Unreasonable people spend a lot of time trying to destroy other's credibility rather than focusing on the facts and logic at hand. They have become POV (Point of View) warriors intent on trying to inflict damage to their opponents by citing conspiracies and other contrivances. Me? I'm sticking with the Doctors here. Like when Dr. Michell posted that no, he wouldn't dive RD and he wouldn't let his loved ones dive RD, that was enough for me. The adherents can rail all they want about how great their protocol is, but Dr. Mitchell put it in perspective for me. If he's diving Fudge Factors, er Gradient Factors, then I'm going to as well. I don't have the time to devote to understanding deco theory as intimately as he does so it boils down to humility and trust on my part and I'm going to follow the good Dr's example. As a rec/cave/tek/rebreather diver who is not trying to push the limits, this really works well for me. This month starts my 50th year of diving. I plan to enjoy it and will continue to dive with caution, restraint and will follow the real experts. I've never, ever been bent and I want to keep it that way. There's nothing down there worth dying for or even getting hurt. At least not for me. I have nothing to prove to myself or others.

"Unreasonable people spend a lot of time trying to destroy other's credibility"?
I've presumably seen only a fraction of the time and energy you've spent fighting to destroy the credibility of anyone who'd dare use RD, and I'd call it substantial already.

Speaking of a point of view, your continual launch of barrages against Ratio Deco - rather often with statements actually unsupported by evidence or science that you claim to reference, might I add - is a recurring theme and, I'll be honest, very often a motivator for at least myself to interject and correct.

Personally, I think you're overestimating the strength of evidence to suggest whichever algorithm you feel is "proven right" by it, and in either case, the level by which the difference matters; even to the point where you may - or may not - trust it blindly, and in either case certainly won't hesitate to claim proof and superiority over anyone daring a different approach than yours.

Your calls to authority stand in contrast to the much, much more careful phrasings actually presented by those to whom you refer.
Those careful phrasings are not just to be seen as signals of scientific caution, but rather an actual expression of fact and seperation thereof from unsubstantiated deductions.

Thus, I consider their rendition infinitely more valuable.

I trust that implicitly.

You guys are real heroes in my book.

 

[boulderjohn]

Have you ever seen formal training in the use of RD?

You're talking about RD as though you're acutely aware of it's details, intricacies, evolution and history - but based on your posts, I for one suspect a significant lack of knowledge on the matter, on your part.
Therefore, the question: Have you or have you not been formally trained in the use of RD?

I have.

I used UTD Ratio Deco as taught to me by Andrew Georgitsis as my only means of planning decompression for several years. So did all of my friends in our UTD training group--most of whom got bent at least once.

Because I have that training, I am able to wonder what would happen in that training that would impact The Chairman's thinking. I can't think of a thing.

Perhaps an analogy would help.

I know very, very little about cobra bites. I don't know the chemical composition of the venom. I don't know how it affects the body specifically. I don't know the average length of the fangs. I don't know how aggressive cobras can be--will they attack, or do they only bite humans defensively?

I really only know one thing--if I am bitten by a cobra, I can easily die. I have therefore decided I don't want to be bitten by a cobra.

Now, you may say I don't have the right to make such a statement until I have been more thoroughly trained on the intricacies of cobra bites, but I am confident that I know enough to make that decision. I don't think any more training will change my mind.

As a former UTD diver, I can't think of anything in that training that would change Pete's mind, either.

 

[Dan_P]

@boulderjohn Why not let the man speak for himself?
He's the one speaking about the nature of RD, seemingly without supporting knowledge.

FTR I think your comparison of the deep stop emphasis employed here, to a cobra bite, is full-on absurd.

Yes, according to your narrative, your group seems to have had a disproportionate occurrence of DCS, by any measure, including among RD-divers overall.
If I knew nothing more, Occam's Razor here would lead to the deduction that the reported increase in DCS was obviously isolated to that group.

I'm sure I can find a group of drunk-driving Volvo enthusiasts who crash all the time: does that mean Volvos are unsafe... Hardly.
Probably, though, it wouldn't be too hard to find one of them who will claim that it is.

You're welcome to share the full details of your narrative which you've previously shared with me in PM, to endeavour showing me incorrect in my analysis - I'm very comfortable with negotiating that conversation.

If you don't want to, bene, let the man speak for himself, then - if the support he has for his claims is a second-hand narrative, which doesn't exactly yield a world of credibility either, then I think it's safe to say we should see his recurring RD-bashings in that light.
Here's another example.

 

[The Chairman]

Have you ever seen formal training in the use of RD?

My only connection with RD has been with seeing people get bent using it and of course with Dr. Mitchell admitting that he would never use or let his loved ones use it. For me, it's defined by its failures and questionable genesis. We've asked YOU for some studies, but you've so far failed to provide any.

I've presumably seen only a fraction of the time and energy you've spent fighting to destroy the credibility of anyone who'd dare use RD, and I'd call it substantial already.

Oh please. Show me where I've attacked your credibility one whit. The first rule of Scuba applies and I won't be holding my breath, but this is so false as to be trollish. You should be ashamed for making such an unsupported accusation. Disagreeing with someone should never be taken as "attacking their credibility". Neither should be demonstrating the flaws in their logic or their lack of evidence to support their premise.

I think you're overestimating the strength of evidence to suggest whichever algorithm you feel is "proven right" by it,

The Spinsi study seems to back me up. Other than that, I see no evidence to support RD. I believe we have asked you for a study to support your faith in RD. Sadly, none has been given to us so far.

I started out with only the rule of 120, and somehow my conservatism allowed me to dive unscathed. My diving has evolved with my understanding and I've used several protocols with great success including both tables and PDCs. The rule of 120 is now only used in pre-planning and my go-to protocol is GF as rendered by Shearwater products.

 

[The Chairman]

re's another example.

While I've been asked by friends to cease posting "Friends don't let friends Dive RD", I believe that with all my heart. Without you giving me any substantive support to accept RD, I'll continue to see it as being simply "faith-based" as opposed to being based on science. You call that "bashing", and perhaps it is. I simply don't have the faith in RD that you have and probably never will.

 

[Patoux01]

This code started as a FORTRAN code base, in the 90's, run in a DOS command. Its configuration is made in a hand typed text file, which you did in notepad. Its has to be perfectly formatted to work. Very easy to make text errors.

Yes, programmers put in arbitrary limits either side (bounds checking), to make sure the program is actually reading valid configuration data, and not garbage data from a wrongly formatted text files. That typed text has to be converted to real numbers, so wide range check are in place to make sure it reads 65 and not 6 5 or x6 or ; or , any other invalid character (or more modern problems).

The code above.... translated it says... if not within this range, terminate program. i.e. validated the input.

But if you want to pretend their is some authenticated values here, well that is your mistake.

.

So you're saying that Baker used "1.35" because he was scared one would put in "135" microns? Seriously? You think he thought "Hey, I'll put the limit at 1.00 for the algorithm, but I'll let the user input 1.34 if he wants to, because why not, that'll teach them to read my code!". Really?

 

[Dan_P]

My only connection with RD has been with seeing people get bent using it and of course with Dr. Mitchell admitting that he would never use or let his loved ones use it. For me, it's defined by its failures and questionable genesis. We've asked YOU for some studies, but you've so far failed to provide any.

I will say that I'm not surprised that this antipathy seems to be based on narrative and/or incontextual deductions about what RD is, rather than actual knowledge. If the friends you've seen bent happened to be in the same group that we addressed above with the Volvo-analogy, I wouldn't really be surprised. If so, the invitation I extended John, stands open to you as well.

As for what Simon's said, I'll play it safe here and quote the statement you're referring to, from here:

"I believe it would be challenging to justify characterizing ratio deco as "dangerous" because we have not accurately measured the absolute risk associated with its use and compared that risk with accurately measured alternatives. To deem one approach to deco dangerous in comparison to another you would have to do that and show a difference considered significant. I suppose you can interpret that as agreeing with Dan P's very technical point.

However, at the same time, the answer to essentially all The Chairman's questions is "no": I would not choose to use it myself, recommend it to my family, teach it to other divers, or encourage others to use it. This is because there is a reasonable body of evidence that there are other approaches that almost certainly carry less risk."

Remember, I have never claimed RD "out of the box" to be the optimal solution to a given decompression obligation.
That's one discussion - but calling it dangerous is a whole different ballgame.

As for studies, which statement would you like me to show man-trial support for; That it incorporates multiple avenues of decompression theory while "highlighting" relations/ratios that take into consideration practical parametres like gas logistics? That it is an educational means to develop situational awareness? That it has practical utility?
These are quintessential of RD, yet pursuing measurable metrics towards them is obviously ridiculous - if I'd claimed that RD "out of the box" was the optimal solution to a given decompression obligation, I could understand your calls for substantiation. But for the above, hardly.

It should be seen as a strategy, not an algorithm.

Oh please. Show me where I've attacked your credibility one whit. The first rule of Scuba applies and I won't be holding my breath, but this is so false as to be trollish. You should be ashamed for making such an unsupported accusation. Disagreeing with someone should never be taken as "attacking their credibility". Neither should be demonstrating the flaws in their logic or their lack of evidence to support their premise.

Here, here, and then you have sporadic nuggets like this one to another user (speaking of accusations and lack of support):

"Here's what I do understand about Ratio Deco:

• It's defective
• It's dangerous
• It was born in arrogance
• There's absolutely no science behind it
• People get hurt using it
• It merits no further study when there are far, far superior protocols that work well.
  • No, I'm not going to drink your Koolaid with you!"

he Spinsi study seems to back me up. Other than that, I see no evidence to support RD. I believe we have asked you for a study to support your faith in RD. Sadly, none has been given to us so far.

Again, you seem to be putting into my mouth a statement that RD "out of the box" (1:1, 1:2, 1:3) is superior to any other solution, as an algorithm.
I have repeatedly, ad nauseam, reiterated that's no statement of mine.
I find it practical, and I don't appraise it as dangerous. That's pretty much the full extent of what I'm saying.
Would you appraise, say, 30/85 as "dangerous"?

If you take it, don't adjust it, go to 6.000m altitude and dive it as though you're on the surface, I think you'd have a pretty bad day - the same would hold true if you used ZH-L-16 without GFs and set to altitude=0m in a similar setting.
Thus, by the logic propelling your assaults on RD, ZH-L-16 is dangerous

While I've been asked by friends to cease posting "Friends don't let friends Dive RD", I believe that with all my heart. Without you giving me any substantive support to accept RD, I'll continue to see it as being simply "faith-based" as opposed to being based on science. You call that "bashing", and perhaps it is. I simply don't have the faith in RD that you have and probably never will.

Yes, I think you're definitively qualifying as "bashing".
I also happen to think you bring up a lot of good points on many things, and have a lot of valuable knowledge and experience to share, many of which I could learn from, too.

Just not on RD, that's all.

 

[huwporter]

There is no such thing as +7... its all made up fake nonsense data. Some arbitrary limiting number does not give you free license to make stuff up.

Hi Ross,

VPMB+7 profiles are pretty much identical to VPMB+5 profiles for a 20% rounded up bottom time, as you can see in this table:

Please can you explain why a profile that is fine for one bottom time suddenly becomes fake nonsense when applied to a slightly shorter bottom time? I've asked you this several times before but you have never got around to providing an answer.

It seems to be a bit of a concern if the common practice of rounding up bottom time for conservatism suddenly produces 'fake nonsense' profiles if using VPM don't you think?

Don't you think you have a duty to warn VPM table users that they must not use the table for a longer bottom time than they actually perform due to that profile suddenly becoming 'fake nonsense'? I mean, you could easily see someone cutting bottom time a little short but still sticking to the original ascent plan, not realising that their ascent plan has now become fake nonsense? Seems like this could be a serious safety issue, no?

 

[The Chairman]

Dan, I know only one of the divers I referred to as being associated with John's group.

You call it "RD out of the box" and I see it as RD in actual use. After all, people, real people, not people in a box, were hurt. Almost all involved mental errors on the part of the diver, and they were to a person quick to point that out. The person using Ratio Deco is probably always the weakest link, and that's the real problem with it. As I've admitted, I have dove some pretty sketchy protocols (you can call it a strategy if you want). including the rule of 120 and I've yet to be bent. Considering the number of people I know that have been bent and the number that were bent by using RD, I have come to the conclusion that it's indeed unsafe. Especially compared to the stupid dives I've done and haven't gotten bent. Anecdotal? Sure. Perhaps if you could provide that study I keep asking for, I could have a more enlightened opinion. You haven't, so I have to rely on the evidence I can see.

You see, the drunk driver scenario really fits. It's my opinion that putting on Scuba gear eliminates 15/20 IQ points. Splashing another 15/20, and you can keep deducting points for every atmosphere you descend. The problem is people don't "feel" stupid: they just are. Their Bovine Index equals 1, and they don't even know it. Ergo, relying on a diver's memory is an invitation for error and getting bent. I wish I could count how many times I forgot to set the bezel on my dive watch on first descent, or the witness mark on my depth gauge. How the hell do you expect me to average depths consistently and competently, especially when I've got the IQ of a cow at a hundred feet? It's not in me and I find any protocol/strategy that requires me to do so problematic from the get-go. In fact, those were the kinds of errors that the people who got bent on RD kept referring to. Me? I want something that compensates for my depth induced ADD and that's a PDC. Can I dive without one? Sure, but I'm not going to do a deep deco dive. I know and honor my limits. RD is one of those protocols/strategies that I can live without. Besides, I don't dive to compute my deco obligation: I dive to look at the pretty fishies and appreciate the friend on my wrist that handles that hideously tedious crap for me. Sure, I check her work, and so far it's been great.

BTW, I assume that you've never been bent nor have any of your dive mates, right?

 

[Dr Simon Mitchell]

Same for the pDCS stuff - two or four sample points, not 16.

and....

Wrong. The Simon Mitchell / UWSojourner (Kevin Watts) version of ISS uses all 16 cells for a purpose they where not designed for. The 16 cell parallel model's that we use today, cannot be converted into serial model data points like you are attempting to do. All you get is one one giant number, but deco and stress is more complicated that this. Your method has no concept of stress or risk levels, cannot separate the difference from life threatening to harmless profile. Your ISS method is junk science.

This confident assertion of incorrect material perfectly illustrates why people should be extremely wary of placing any faith in what Ross says, and why he is so potentially damaging to the knowledge base of the community.

As stated previously the risk functions used in the US Navy probabilistic models utilise integral supersaturation summed across all tissues. I have spent the day in Washington with Dr Doolette who confirmed this. The US Navy does not use the Buhlmann tissue categorisations, and lumps tissues into categories that roughly correspond to fast, medium and slow. But all supersaturation is summed across all tissues in all 3 of these compartments, which equates to the same thing that UWSojourner has done. David has no problem with UWSojourner's approach. Ross simply does not understand the subject he proclaims himself expert in.

Simon, can you please show me in that yellow bar, where does the deep stop occur and how big is it? Where is the S curve placed, and how does it affect supersaturation? How much influence does the shallow stop have, and where can I see this in that yellow rectangle shape?

This line of questioning reveals how poor Ross's understanding of these matters is. The integral supersaturation is an index of decompression stress and therefore the risk of a dive. If two dives have identical gas loading, and their respective decompressions (whatever form that takes) leads one to have a higher integral supersaturation than the other, then the former has higher decompression stress and, all other factors being equal, a higher risk of DCS. The portrayal of integral supersaturation in the graph is simply not designed to show the things Ross asks about.

Simon M