Richard Pyle on Pyle Stops

Steve

Sorry for the cross post but I felt that there was enough good stuff in this thread to warrant the faux par.

http://thedecostop.com/forums/showthread.php?t=19052

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caveseeker7

Thanks for the link, Steve.
Good stuff, isn't it, gets you thinking.

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Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"

Mdemon

What a thread. Caveseeker, is he on here? You might want to prompt him if not...

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www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

deepreef

If you mean me, then yes, I am. I've been monitoring this forum as well, and as I mentioned on the thread on the other forum, I'm still a bit overcommitted with work, etc. -- so I'm not quite ready to jump back into the online discussion thing just yet. But at some point (probably later this year), I hope to return to the same level of active engagement of online community discussion that I used to do on the various email lists.

When I do, I'll post a proper introductory note in the Introductions forum.

Aloha,
Rich [ard Pyle]

bgpartri

Welcome.

RebreatherWorld seems incomplete without you.

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Good judgment comes from experience. Experience comes from bad judgment.

Mdemon

Cool! And welcome!

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www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

koputai

Someone want to copy and paste the relevent text here? I'm not on deco stop and don't really want to join another forum just to read a post.

Cheers,
Jason.

jhaaja

Here comes two posts from Richard:

Hi Matt,

I haven't been diving much lately (too busy with work, family, etc.), so I guess technically the answer to your question is "no" (simply because I've not been diving much).

But when I do dive deep (now, in the past, and in the forseeable future), I indeed still use the same ascent method that I have been using all along.

I should point out, however, that the "method" I use isn't exactly what most people refer to as "pyle stops". The "formal" method that I wrote about in DeepTech way back when was actually cobbled together in the 45 minutes that I wrote that article. Sometimes I follow those half-depth increments reasonably closely (especially during blue-water ascents), but more often my stop depths are dictated by the terrain, or the fish I've collected, or how paranoid I happen to be that day.

The only reason I came up with the half-depth stop procedure was to provide some sort of simple method to get people to think about their deep ascents, and slow those deep ascents down a bit. Simply saying "slow down your deep ascents" doesn't really get people to think about it much. But following a specific pattern of ascent with discrete stops more effectively gets people to pay attention to the deep part of the ascent.

Don't get me wrong -- I think the method that has come to bear my name is a reasonable approximation to what might be optimal, and it happens to coincide with other deep-stop methods reasonably closely (probably well within the scope of "noise" inherent to diving physiology, spread across a varied group of divers doing dives in a varied spectrum of conditions). So I would still recommend it as much now as I ever would have recommended it.

But really the main point is to slow down the deep ascent, and avoid the temptaion to "get the hell out of deep water" and bee-line it for the first decompression stop.

The other "big" factors in decompression, in my opinion, are hydration, exertion level on the bottom, and breaking up the "quadruple whammy" that happens at the final stages of a decompression dive:

1- sudden ascent to the surface through the depth span with the most dramatic volumetric expansion;

2- sudden switch from ~1.6atm PO2 to 0.2atm PO2

3- sudden transition from weightlessness to the world of gravity

4- sudden increase in physical exertion

#3, I think, is perhaps the most under-appreciated, as it has a huge impact on blood distribution in your body, which I can't possibly believe is entirely neutral to DCS symptom manifestation (and I would guess is detrimental). #2 also has an effect on vasoconstriction -- which again seems unlikely to be neutral with respect to DCS symptoms.

But empirically, the tightest correlation of all for problems after long deep dives [in our experience] is with level of exertion on the bottom. Almost a perfect 100% bidirectional correlation, in fact.

So....decompression profile (including deep stops) is no doubt important for avoiding DCS. But the more I do this, the more I come to appreciate that other factors that have nothing to do with depth, time, and gas mixture (and therefore are not accounted for by essentially any deco model in current use), may have as much, or even more impact on the probability of DCS after a deep (by our standards) dive.

And incidentally...I haven't used US Navy tables since the "bad old days" of deep air diving. I've always added my deep stops to DCAP (the algorithm I've been using since I started rebreather diving) -- and DCAP already puts the initial "required" stops much deeper than Buhlmann or most other non-bubble models. So I guess I've been doing deep stops on top of deep stops.

Aloha,
Rich
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Re: Does Richard Pyle still use Pyle stops?
Quote:
Originally Posted by Matt Reed
The relevance of still teaching US Navy/Buhlmann/DCIEM tables even with 'pyle' stops was questioned when there is so much other information which has grown out of that initial 1/2 the depth technique.


I'm actually happy to see that the techniques have moved on....but I'm not so sure we really understand much more about deco now than we did 10 or 15 (or even 20) years ago. Sure, there are more sophisticated approaches to deco modelling, and more complex math -- and a lot of that is meaningful progress because it layers the techniques on a more solid theoretical framework. But as far as I can discern, it's still primarily theoretical.

I know there have been some empirical studies, and even some controlled experiments -- and I think those are important. But as I understand it, none of those studies have really focused on improving algorithms, or confirming the validity of new algorithms. Maybe I've been out of touch.

We do have a growing body of "robust anecdote", of course (which is all that my own practice of deco is based on). And some of that evidence might help guide us in the right direction. But just because there are more sophisticated software applications based on all sorts of complex decompression models, doesn't mean they're more effective at preventing DCS symptoms. Indeed, as I alluded to earlier, essentially none of them take into account various factors that may be as important as (if not more important than) depth/time/mix.

So I guess my point is, while the mathematical approaches to calculating decompression schedules might have become more sophisticated, I'm not sure how much evidence there is that they actually reduce the liklihood of DCS symptoms after any particular dive.

Quote:
Originally Posted by Matt Reed
So I thought it would be nice to know what you were doing yourself, as I imagined there has been some evolution of your dive planning.



Certainly our techniques have evolved. But I can't really say they've "trended" much. By that I mean that they change -- but they change based on particular circumstances, rather than some attempt to move towards a "better" way of doing things. It's not that I don't think we could be doing better (I'm absolutely sure we could -- and we've got some ideas we want to play with, like GPS-enabled radios on our SMBs). But it's more the situation that our techniques respond so much to particular circumstances, that it's not clear what the trend is, if any.

Basically, if it ain't broke; don't fix it. Or as Bill Hamilton put it in our context: "What works, works". And right now, about the only thing I can think of that seems to be "broke" with what we currently do, is exertion at depths greater than about 380 feet. How do we address that? More helium? Less helium? Slower deep ascents? Faster deep ascents? Slower or faster descents? Physical activity on the deco stops? Relaxation on the deco stops? More in-water hydration? Longer shallow stops? Waterproof iPods?

So many different things to try. If we find something that seems to solve the problem of exertion at depth, I'll certainly be happy to report it.

Aloha,
Rich
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JH