Differences Between UTD and GUE

[Blackwood]

I would be very interested in learning how GUE/UTD determined it is not a factor.

The idea is you've done enough deco in the water that the increased surface gradient shouldn't be a problem.

 

[rjack321]

Sorry for the delay--I have been offline. We had in very brief initial depth for only a minute to clear a ledge we did not expect to find, and then we were at about 150 for a while, then ascended to about 120 to complete the dive. I did take the average from the BT, including the descent (which was rapid). I can't give the exact figures--I am out of the country doing this from memory.

This was our third day of diving similar profiles. On the previous days, we did some very shallow dives (like 30-50 feet afterwards), and on the last day we only did the one dive.

My friend had a third day of treatment and is doing very well now. His doctor was very adamant about the altitude factor. He got a major lecture about it.

I would be very interested in learning how GUE/UTD determined it is not a factor.

150ft is not a 25/25 with O2 deco dive for UTD (or GUE for that matter).

All in all this is a pretty aggressive dive. Its a very aggessive profile for the gases; combined with what seems to be little personal experience with the gases, the depth, or altitude. So I'm not really surprised that at least one of you ended up bent trying to apply RD to this profile.

John are you and your buddy UTD Tech1 trained?

 

[Rainer]

Have to agree with Richard. This is outside the envelope for a 25/25+O2 dive (at least as taught by UTD: issues with depth, exposure, experience, possible issues with average depth, altitude, etc).

150ft is not a 25/25 with O2 deco dive for UTD (or GUE for that matter).

All in all this is a pretty aggressive dive. Its a very aggessive profile for the gases; combined with what seems to be little personal experience with the gases, the depth, or altitude. So I'm not really surprised that at least one of you ended up bent trying to apply RD to this profile.

John are you and your buddy UTD Tech1 trained?

 

[Blackwood]

Have to agree with Richard. This is outside the envelope for a 25/25+O2 dive (at least as taught by UTD: issues with depth, exposure, experience, possible issues with average depth, altitude, etc).

Yah, and that's a LOOOONG way to go to the first bottle. Decompression aside, rock bottom would be crushing.

 

[boomx5]

Yah, and that's a LOOOONG way to go to the first bottle. Decompression aside, rock bottom would be crushing.

That's one of the reasons I've never liked using only O2 for deco.

 

[rjack321]

Rock bottom for a 43min dive at 130ft is already pretty big. Too much for me in my typical LP85s, although I'd have enough in my 95s/119s/130s.

Alot of UTD Tech1 divers have joined our ranks locally in the past 8 months. I have probably done more dives in this range than in the previous years because of that. For these new deco divers, a typical UTD Tech1 dive might be ~35mins max 120ft with a 110ft average followed by 1,1,1,2,3,3,8 (O2) & 3-5 up deco. All in all a pretty conservative beginning tech diver profile.

Anytime you aren't building slowly from your own personal experience you run a higher than normal risk of the kinds of problems experienced here.

 

[lamont]

Sorry for the delay--I have been offline. We had in very brief initial depth for only a minute to clear a ledge we did not expect to find, and then we were at about 150 for a while, then ascended to about 120 to complete the dive. I did take the average from the BT, including the descent (which was rapid). I can't give the exact figures--I am out of the country doing this from memory.

This was our third day of diving similar profiles. On the previous days, we did some very shallow dives (like 30-50 feet afterwards), and on the last day we only did the one dive.

in decoplanner you can input your profile (manually entering the stops you actually did) and gases and altitude and then it will show you the gradient factor loading for that dive.

My friend had a third day of treatment and is doing very well now. His doctor was very adamant about the altitude factor. He got a major lecture about it.

I would be very interested in learning how GUE/UTD determined it is not a factor.

i haven't ever come across a statement from GUE/UTD that it isn't a factor.

 

[boulderjohn]

OK, I did not respond to these last messages because I did not want to continue discussing uncertainties. Lamont and I had a very nice extended private conversation on this topic, and we both did some independent research. Here is what we learned.

GUE does not have an official position on altitude, but JJ believes it should be considered when planning decompression. Schedules should be more conservative than at sea level.

Andrew (and thus UTD) does not believe altitude needs to be considered when planning decompression.

 

[Waterskier1]

My experience has been solely with UTD, and the approach has so far been very different from what is described here. The instructional materials tell what is wrong with Bulmann and why a Buhlmann profile is not followed. There is a graph showing a Buhlmann ascent compared with what Andrew calls a "proper" ascent (RD), and there is a significant difference.

John, can you provide a source for the "proof" or "explaination" or whatever you are referring to that "tell what is wrong with Bulmann and why a Buhlmann profile is not followed"? Is this someones opinion, or is it backed up by scientific assumptions and testing and backed by peer consensus? I've read a bit on deco models, and what they are trying to model (and that is the key-they are only models, not exact estimators of the human body), and have seen how some take certain things other don't as more important, but never seen a proof that any one model was "wrong".

OK, I did not respond to these last messages because I did not want to continue discussing uncertainties. Lamont and I had a very nice extended private conversation on this topic, and we both did some independent research. Here is what we learned.

GUE does not have an official position on altitude, but JJ believes it should be considered when planning decompression. Schedules should be more conservative than at sea level.

Andrew (and thus UTD) does not believe altitude needs to be considered when planning decompression.

While I'm still looking into the whole "deco in the water" philosophy, I suspect that both agencies comments probably make the assumption that 1) the diver is acclimated to the altitude where the dive is being performed and 2) that the diver remains at the dive site altitude for some period of time before ascending to altitudes 4000-6000 feet greater versus an immediate departure as quick as possible. Do you (or does anyone here) know those assumptions?

I'm not trying to propagate a "he said" argument. But I would like to understand better (and not just take someone's word) about how the models attempt to depict the off gassing that our bodies go through. The scientist/engineer in me yearn for facts, especially if there is implication that such facts do indeed exist.

 

[boulderjohn]

John, can you provide a source for the "proof" or "explaination" or whatever you are referring to that "tell what is wrong with Bulmann and why a Buhlmann profile is not followed"? Is this someones opinion, or is it backed up by scientific assumptions and testing and backed by peer consensus?

It is in the course materials for technical diving classes. I will go into the rest of your question later.

While I'm still looking into the whole "deco in the water" philosophy, I suspect that both agencies comments probably make the assumption that 1) the diver is acclimated to the altitude where the dive is being performed and 2) that the diver remains at the dive site altitude for some period of time before ascending to altitudes 4000-6000 feet greater versus an immediate departure as quick as possible. Do you (or does anyone here) know those assumptions?

There is no explanation other than what I will add at the end. Acclimatizing oneself would only be a factor if you were looking at residual nitrogen before the first dive. The issues surrounding altitude are more often related to (1) discrepancies between what your depth gauge reads and your actual depth and (2) the greater N2 pressure gradient upon surfacing when surfacing at altitude.

I'm not trying to propagate a "he said" argument. But I would like to understand better (and not just take someone's word) about how the models attempt to depict the off gassing that our bodies go through. The scientist/engineer in me yearn for facts, especially if there is implication that such facts do indeed exist.

I suggest you go right over to the Ask Dr. Decompression section of the board and look at the thread on the Oxygen Window Revisited. There you will find an explanation for your questions, and I suspect that as an engineer you will not be satisfied.

The sense I have is that there is a feeling that none of the existing models and theories are proven. None of the science is certain. In these cases, people have been doing something a certain way for a while and it seems to be working. For example, the explanation I was given for altitude not being a consideration is that plenty of dives are done at altitude without taking it into consideration, with no ill effects. Therefore...