My Journey into UTD Ratio Deco

[Kevrumbo]

I would love to hear how modern science explains these skin bends. Is George Irvine lying? Is he telling the truth but he is a biological oddity? I find it a bit odd that Richard Pyle did most of his dives in Hawaii and never met George Irvine. yet both of them were reporting getting bent on shallow stops and these bends would mysteriously vanish when deep stops were added.

Thoughts?

Still can be attributed to post-dive Slow Tissue Surfacing Supersaturation and VGE stress (with worst case latent bubbling coming through a right to left shunt), per the interpretation of the NEDU Deepstop Study.

The current implementation and trend of de-emphasizing deepstops with higher GFlo and lower GFhi (to extend the shallow O2 deco stop profile) is now considered to be the better more efficient response and strategy.

 

[CAPTAIN SINBAD]

Still can be attributed to post-dive Slow Tissue Surfacing Supersaturation and VGE stress (with worst case latent bubbling coming through a rigt to left shunt), per the interpretation of the NEDU Deepstop Study.

But why would the symptoms go away with inserting deep stops tho? If NEDU study is correct then the GUE divers should have noticed better decompression with longer shallower stops instead of the deep ones.

 

[rjack321]

I would love to hear how modern science explains these skin bends. Is George Irvine lying? Is he telling the truth but he is a biological oddity? I find it a bit odd that Richard Pyle did most of his dives in Hawaii and never met George Irvine. yet both of them were reporting getting bent on shallow stops and these bends would mysteriously vanish when deep stops were added.

Thoughts?

The definition of deep and the amount of time spent "deep" has changed (along with ascent rates). And is also dependent on dive duration and surface deco too. Its fairly well known the GI3 was sucking on O2 after various dives. And the Rich Pyle was "only" stopping at 1/2 his depth, then 1/2 the next interval etc up to his intersection with a dissolved gas curve. And none of that experimentation had any statistical validity....

So in a nutshell...
Way back when people (1980s) were diving experimental tables by Hamilton and others
They added deep stops and that helped mitigate them to some extent (1990s)
Yount/Wienke published their bubble work (1998- 2000ish)
People added way too much time deep and/or shortened the overall time because they suspected they were avoiding the "bend and mend" which was previously suspected.
VPM hits the market about this time as a commercial product - looks so scientific too...
Many people add too much time deep with GFs of 20/85 and such stuff, RD is 5/95ish reflected the misnomer that deep stops avoid bubbles forming so you don't have to get rid of them later.
VPM 2+ seems to confirm that deeper is better even if shorter overall.

Finally we start getting hard data that this is all just a thought experiment and some divers are still stuck in 2005 era deep stops...

 

[boulderjohn]

It was part of GUE repertoire too. Here is a direct conversation with George Irving:

Audience: A question I wanted to get to but it's getting a bit late now: we have Lake Tahoe here at 6000ft. How would you deal with diving at that altitude?

George: I basically ignore it. [audience laughs] You can calculate altitude in the programs and all. Your body adjusts right away anyway just so it all becomes relative again. Stay at Lake Tahoe for a couple days, your body is at 6000ft and stays there. So it's not going to be like you're going beyond decompression steps when you get out of the water. It not you could be beamed to Lake Tahoe and do a dive and come up. But I pretty much ignore that altitude silliness. They make too much of it, I think. But I went skiing at Lake Tahoe, and didn't have any problems. [audience laughs] I didn't get bent. But I really don't know. I mean, I don't know of anybody that ever had any issues with any of that. But they always have some special deco. But I've never seen any problems. I really don't know, though. It's out of my realm, other than I don't believe it. From what I know of decompression I don't believe it's a problem. That's got to be a cool place, though, to dive.

BAUE George Irvine Lecture

I believe this is the primary reason for the "altitude doesn't matter" attitude, and as I wrote in a recent thread, it is really sad. IMO, it reveals a serious problem with the whole system. GI3 somehow got the reputation for knowing all there was to know about diving, but this really shows his limitations. He speaks about one aspect, and only one aspect, of the issues related to diving at altitude, and he clearly believes that this one aspect is the only thing you have to be concerned about. In reality, it is only one minor consideration for altitude diving, and in truth he is probably right for the most part. Most divers can ignore that aspect. It is the others he didn't know about that matter.

For a more detailed description of all the details, including the ones he clearly didn't know about, go here.

So what happens is that people who looked upon hims as a God followed his every word and did not question anything. They are still doing that.

 

[PfcAJ]

Trey was right about a lot of stuff, but also dead ass wrong about a lot too.

 

[JohnnyC]

Trey was right about a lot of stuff, but also dead ass wrong about a lot too.

Fashion being the least egregious..... PS congrats on the NSS-CDS gig! Fingers crossed we never have to hear from you in anything other than a past-tense context.

 

[Dan_P]

I would love to hear how modern science explains these skin bends. Is George Irvine lying? Is he telling the truth but he is a biological oddity? I find it a bit odd that Richard Pyle did most of his dives in Hawaii and never met George Irvine. yet both of them were reporting getting bent on shallow stops and these bends would mysteriously vanish when deep stops were added.

I think it's important to remember that it's not black and white.

Purely hypothetically;
Deep stops "ought to" bring about improvement in the decompression process in lieu with the theoretical support they always had, if it weren't for slow tissue on-gassing and inflammation response - Bubble Induced Platelet Aggregation (BIPA).
Obviously, we've got studies to suggest that those two factors outweigh any theoretical benefit;

However, if we assume a scenario where slow tissue on-gassing is less of an issue than what we saw in the NEDU-study (using actual gas and not freezing), then I think relatively, a lot is left on BIPA (think Spisni).
If, then, a person is genetically predisposed to a lessor relative CCL5-response, then it could be theorized that "deeper" stopping could be beneficial to some such individuals.
Maybe GI3 and AG are some such "deep stoppers".

Right?

Or, there's an element of placebo effect.
I mean, would it be possible for the physiological decompression process to improve as a result of a subject thinking they're on an optimal decompression profile? I wouldn't be surprised.

Either would be a sound hypothesis, I think - but, obviously, there's nothing to prove either.

 

[kensuf]

It was part of GUE repertoire too. Here is a direct conversation with George Irving:

Audience: A question I wanted to get to but it's getting a bit late now: we have Lake Tahoe here at 6000ft. How would you deal with diving at that altitude?

George: I basically ignore it. [audience laughs] You can calculate altitude in the programs and all. Your body adjusts right away anyway just so it all becomes relative again. Stay at Lake Tahoe for a couple days, your body is at 6000ft and stays there. So it's not going to be like you're going beyond decompression steps when you get out of the water. It not you could be beamed to Lake Tahoe and do a dive and come up. But I pretty much ignore that altitude silliness. They make too much of it, I think. But I went skiing at Lake Tahoe, and didn't have any problems. [audience laughs] I didn't get bent. But I really don't know. I mean, I don't know of anybody that ever had any issues with any of that. But they always have some special deco. But I've never seen any problems. I really don't know, though. It's out of my realm, other than I don't believe it. From what I know of decompression I don't believe it's a problem. That's got to be a cool place, though, to dive.

BAUE George Irvine Lecture

Contrary to public opinion, George Irvine was never a GUE instructor.

 

[Storker]

if we assume a scenario where slow tissue on-gassing is less of an issue than what we saw in the NEDU-study (using actual gas and not freezing)

Being cold reduces tissue perfusion, so it should affect on- (and off-)gassing negatively, not positively as you indicate.

 

[Dan_P]

Being cold reduces tissue perfusion, so it should affect on- (and off-)gassing negatively, not positively as you indicate.

Yep, exactly.
If ice cold towards the end of a dive, on the face of it, that would favor shallow stopping disproportionately.

If the effect of cold and the aggregation of doing the whole deco dive on air, weren't present, then the hypothesis goes that BIPA assumes a greater relative portion of causation behind negative impact of deep stopping - if one subject then doesn't have the same BIPA-level but less due to genetics, that could explain how one subject's "perfect" first stop depth could be deeper than the next subject's. Hypothetically, that is.

If GI3 and AG have better experiences with deep stops than the next guy, maybe the above could serve as a potential explanation.

Well, that, or Placebo.

Or something else entirely.