GUE and Sidemount position ?

[tbone1004]

Gradient factors adjusting Buhlmann have nothing to do with bubble models to the same effect that having VPM +X has nothing to do with it becoming more like Buhlmann. The net effect is that they happen to end up looking somewhat similar, but that doesn't change the HOW for what they are doing. GF's take a theoretical limit, and artificially lower it. In VPM, the +X increases the allowed size of the theoretical bubbles in order to allow you to come up faster. Net result is they end up looking somewhat similar, in some profiles, but very different in others. The deeper you go, the more exaggerated it gets.

The report gives statistically significant differences and conclusions can be drawn that if you have to choose between Ratio Deco and GF30/80, you should choose 30/80. As said before, and as said by the people that wrote the report, they wanted to make sure that no one was saying that they believe GF30/80 is the ideal decompression algorithm, because it isn't. It was chosen as something to somewhat closely mimic Ratio Deco in terms of total decompression time and evaluate the validity of deep stops. Those deep stops have been disproven in multiple studies, including this one.
The scariest thing for me about UTD's implementation of Ratio Deco is that he says the surface atmosphere doesn't matter, which it does because it changes your depth readings. Computers read in pressure, not depth. UTD's ratio deco is based on depth, not pressure. Change the ratio between depth and pressure *i.e. altitude*, and you are diving in essence a completely different decompression strategy.
The next scariest thing on the list is the fact that he says you can do infinite repetitive dives, without any surface interval, without changing your deco strategy. The first dive of the day may well be OK because you have negligible residual nitrogen. You do that same dive 3x per day, and that last one puts you at much higher risk of getting bent.

Part three, in terms of the computer and the algorithm. I'm sorry, but AG and now your argument against using a computer is complete bullsh!t. I'll give you the benefit of the doubt and explain how computers vs. tables. vs ratio deco work under the assumption that is has never been explained to you properly.
Brief history.

First, you plan your dive on a computer, and print out tables. You print out typically 3 sets of tables with your planned dive, and a couple contingencies in case the dive goes sideways. This does not take into account anything in the water because the dive plan is preset at the surface. These is no room to make adjustments.

Ratio deco takes these tables and allows you to make adjustments if you are diving something that is nowhere near any of the tables that you printed out. It does this based on rough cut assumptions in order to make sure you get out of the water, hopefully without being turned into a pretzel.

What a computer does *and I will be referring to Shearwater computers specifically though others certainly fit in like OSTC, Freedom, etc. but not computers like Suunto or any "recreational" computer* is actually track everything, in real time, and makes adjustments accordingly. In real time, it is tracking your tissues based on whatever algorithm you have told it to work with in terms of time, pressure, and whatever gas you're breathing. Note, in real time i.e. it tracks EVERYTHING you do in the water column as it relates to pressure, time, and gas. What it can't do is track things like temperature and workload, and it can't do that because we have no idea how to implement that into a deco algorithm. We know that temperature changes how our body ongases and offgases, but we don't know to what extent, and without a rectal thermometer tied to your computer, you don't actually know what your core temp is. That said, with gradient factors, we can adjust our decompression strategy to alter our ascent profile.
Real world.
I dive 50/80 on a Shearwater Petrel as a default. I am likely going to increase that to 60/80 in the near future but need to do some bigger cave dives to see how I feel. If I am diving in known cold water and I know I'm going to be chilly, or something happens that causes me to be colder than I anticipated, I can go into my Petrel and lower that GF-Hi to 70 which keeps me in the water longer, but gives me more time to a known theoretical level of tissue saturation, in this case 70% instead of 80%.
New example. I'm doing a deep dive and for whatever reason I had to blow a deep stop. Petrel doesn't care, it just keeps tracking those tissue levels. I get to my 10ft oxygen stop and all of a sudden I feel something weird in my knee *real world example*. I don't like it so I start descending. Switch back over to backgas once I hit 25ft, and then keep doing down to about 40ft when it starts to feel better. I stay there for 5 minutes, then make a very slow progression to the surface. My computer again doesn't care that I did this, it just keeps plugging along and tracking my tissue loading.
Point of that is that a computer can implement a decompression strategy based on a known algorithm, far better than the human brain can because we can't process that kind of information that quickly. There may be savants that can, but I don't know one.

Those that say the brain can compute decompression better than a computer have some sort of ulterior motive, whether that is egotistically driven or financially driven, but there is a reason that we let computers do things for us. A good analogy is running an engine. Can you drive an engine by manually controlling the air fuel ratios, absolutely private pilots do it all the time. Can a computer do it more accurately with faster response time that results in more power and better fuel economy? Absolutely. It can't predict things like changes in fuel quality or sudden unexpected loads without human input so you sometimes have to make manual adjustments to the strategy of the fuel injection, but it will always be able to do it better than you could on your own.
Another good example is on a rebreather. Can a solenoid on a computer produce a more stable pO2 line than a human whether they are running an orifice or manual injection alone? Absolutely, you can't beat the solenoid. It has a much faster response time than you do and it is able to fire much more accurately. It can't predict that you are about to go over a hill in a cave so as you ascent it will start to fire like mad and then you have to dil flush when you get to the bottom so you may want to shut it off before you go over the hill. Either way it can track under stable conditions far better than you ever can, but you still need to make adjustments to the injection strategy based on what is going on.

The strategy is the same with decompression where you give it a set of parameters and it will track them in real time, far more accurately than the brain ever could, and without distraction. You then get to make changes to what it does based on the conditions of the specific dive.
*Unexpected workload on the bottom which would cause increased ongassing, may want to lower the GF-Hi a bit since you likely took on inert gas a bit faster than the computer was expecting
*Suddenly got cold from a drysuit flood. May want to adjust the Gf-Hi either up or down depending on how cold you are and how urgently you need to get out of the water. In ice diving I'd be more tempted to increase the GF-Hi to 85-90 and then get on O2 at the surface than stay in the cold and risk hypothermia
*Sudden surges in the surface conditions drive you deeper on your decompression stops. Computer doesn't care, it just keeps tracking. Every minute you spend deeper will take some portion of time off of the shallower stops. You'll have to stay deeper longer than you would if you were shallower since it isn't a 1:1 ratio, but you don't have to calculate in real time and I don't think UTD's RD allows for adjustments in the stop depths like that.
Trying to think about those adjustments and have to have every contingency memorized or written down and rely on your ability to think critically in emergency scenarios is not something people are inherently reliable with no matter what your level of training is. The computer is able to take an algorithm, sometimes you can choose *Shearwater, Ratio etc*. adjust that algorithm based on your specific needs and choices *GF's on Buhlmann, +X on VPM*, and if you choose to further amend that decompression strategy with things like deep or longer stops, it will track that in real time. Most importantly, it will do that without any distraction.

For the videos.
in the order that youtube spat them back. There is no "lovers tiff" with AG. This is not personal at all. This based solely on what he is saying and trying to teach. It all circles back to him saying something to the effect of "I know how to plan decompression profiles, in my head, and based on no science, but better than any scientist, doctor, or institute has done with proper experimentation, because I said so". He is asking you to blindly follow what he believes for decompression in the face of all of the science and experimentation for the last damn near 100 years. He is not able to ever say WHY the UTD RD strategy is actually better than what the dedicated algorithms can do. He can never do that because those algorithms can all be adjusted, on the fly, with whatever random additions you want to make because the computers track in real time, without distraction. It sounds VERY much like Miscavige talking about Scientology or any of the other cult leaders talking about whatever it is they want you to believe.

 

[Dan_P]

In fairness and honesty, I'm not finding/hearing the quotes posted in the past post, in any of these videos.
Could there be a preconceived notion on the subject tainting the perception of the videos in play here?
I'm not asking to be condescending - I genuinely think that's a pretty common facet in discussions about UTD, RD, Z, MX or AG.

On another note, you do make fine arguments, and again, I don't have any problem with the way you dive. My response is towards a position that there is a problem with the way that I do.

Gradient factors adjusting Buhlmann have nothing to do with bubble models to the same effect that having VPM +X has nothing to do with it becoming more like Buhlmann. The net effect is that they happen to end up looking somewhat similar, but that doesn't change the HOW for what they are doing. GF's take a theoretical limit, and artificially lower it. In VPM, the +X increases the allowed size of the theoretical bubbles in order to allow you to come up faster. Net result is they end up looking somewhat similar, in some profiles, but very different in others. The deeper you go, the more exaggerated it gets.

How is that different from taking from several input, and using them together. The computer is doing it for you, that's the stamp of approval here?
And this point touches on precisely an argument that is actually made for RD - it's about the WHY of things.
There are many links in the chain, including as I have mentioned, systems interoperability, gas logistics, correlation to gas choice, diver capacity and training progression, that's before we even start talking about Cascade, which is where the simplicity really starts to reverberate. Especially in the breather domain when using O/C bailout.
Tell me, please, how much O2-time will you get on an "optimal" gas if you lose your breather after a 25 minute dive at 90m and you need to flip to O/C?
Because probably, you've brought gas and a table that doesn't work the same way on O/C as your breather does because the ppO2 is different.
I don't see how we can have a discussion on RD, standard gasses, mCCR/eCCR, the principle of scalability or educational theory and form an opinion, without bringing up that kind of scenario.

The report gives statistically significant differences and conclusions can be drawn that if you have to choose between Ratio Deco and GF30/80, you should choose 30/80. As said before, and as said by the people that wrote the report, they wanted to make sure that no one was saying that they believe GF30/80 is the ideal decompression algorithm, because it isn't. It was chosen as something to somewhat closely mimic Ratio Deco in terms of total decompression time and evaluate the validity of deep stops. Those deep stops have been disproven in multiple studies, including this one.

I'm looking at the rapport now, literally. It doesn't say that.
It says there were no cases of DCS in either case.
It says there's no statistically significant difference in bubble presence.
It says there's a difference in inflammation levels, but the relevance is unknown.
Heck, if one wants less inflammation, cutting out bacon would probably be a better place to start.
I acknowledge that the general concensus among experts is that deep stops have previously been overemphasised.
UTD also seem to acknowledge this as well, with the implementation of RD2.0. being proof of as much.
That's a far cry from saying RD is dangerous.
And again, there are a number of other benefits to that blueprint than these studies account for.

The scariest thing for me about UTD's implementation of Ratio Deco is that he says the surface atmosphere doesn't matter, which it does because it changes your depth readings. Computers read in pressure, not depth. UTD's ratio deco is based on depth, not pressure. Change the ratio between depth and pressure *i.e. altitude*, and you are diving in essence a completely different decompression strategy.

Ok, that's an interesting notion. What would you do on the way up, hypothetically, if you were at altitude diving RD? Or, for that matter, if you were diving at sea level and overshot your NDL-time by, say, 10 minutes?

The next scariest thing on the list is the fact that he says you can do infinite repetitive dives, without any surface interval, without changing your deco strategy. The first dive of the day may well be OK because you have negligible residual nitrogen. You do that same dive 3x per day, and that last one puts you at much higher risk of getting bent.

At which point do we mention what RD actually says about repetitive dives?

It can't predict that you are about to go over a hill in a cave so as you ascent it will start to fire like mad and then you have to dil flush when you get to the bottom so you may want to shut it off before you go over the hill.

That's an interesting thing to bring up, the breather. First because of course, the solenoid can't know what you're about to do. Nor can a computer.
Second, because the UTD approach to rebreathers also was made out to be a death trap on forums. Just the kind of death trap that never actually kills anyone.
Third, because of the relevance of rebreathers to RD (what's your avg. ppO2 on ascend, need I say more).
Fourth because you can smack the MX on top of the Z, making it scalable from entry-level to, well, anywhere.

Again, I'm not saying I have a problem with the way anybody dives. I'm saying it's silly to point at the Italy project as proof that RD is dangerous, or propagate a view that RD came out of nowhere, with no apparent reasoning behind it.

 

[tbone1004]

@Dan_P what is the reasoning behind RD and why is it that AG seems to think the a distractable human brain that doesn't actually know exactly what is going on with the ppN2 and ppHe in whatever gas is being inspired is superior to a computer that tracks it in real time, or a computer tied to a CCR that knows exactly what is in the loop at all times, and can track it in real time. I have actually yet to hear the "why" he thinks it is better than what a computer can do, and you have yet to enlighten us.

Also, completely irrelevant to discussion and I know english is second language to you, but report and rapport don't mean anywhere close to the same thing. Not sure if you knew, but it sends us for a loop when we read it because rapport means buddy camaraderie vs a report which is what you are referencing.

Regarding what happens when. If diving a rebreather, you have the computer tied to the unit, or the computer that is set to CC mode with whatever setpoint you are running and then switch those computers to OC mode when you bailout. They track the partial pressures of inspired gases in real time to provide you the most accurate theoretical tissue loading possible.
Now, to your question. You plan the tables as if you were diving open circuit on equivalent gases to whatever is in the rebreather and accept that your dive plan is slightly more conservative than if you were running real time monitoring on the unit because you are saying that the inspired inert gases are higher than they will be when you are between gas plans. No need to plan separate deco schedules for staying on the unit vs. bailing out and you run whatever deco schedule is the next longest bottom time compared to what you have.
Alternatively, you use your primary computer for ascent, and if it fails, your backup computer, if both fail then printed tables, then if both failed and you have a plan that is nothing like the tables, you make a hack at RD and/or follow your buddies deco schedule since the odds of 4 computers failing is so close to 0 it isn't worth talking about.

I.e. you plan the dive at 10/70 or whatever equivalent gas mix you choose at 100m, then set first deco gas as 30/30, ean32, whatever for your 30m ish gas, 50% or 50/50 at 21m, and 100% at 6m. When on a CCR any time spent between those depths is to your advantage, so if you bailout you don't miss anything.

On repetitive dives AG clearly states a few times that you come out clean after each dive so there is no worry about repetitive dives. If he has changed that opinion, or his opinion on altitude, please enlighten me

 

[decompression]

Tom, if I may, what I get from the blogs, the study results et al, is the reason AG believes RD is better than a single computer Algorithm is this;
1. RD looked at many Deco theories (each having varying levels of scientific substantiation) and used those to form the decompression "strategy". He mentions this in the blog.
2. The user of RD becomes invested in applying the best profile for himself through experience. This differs from simply following a PDC which has limited modification ability and utilizes a single (mostly) algorithm. Less so now than years past, however.

I'm still working through my take on RD and altitude......

I've cut hundreds of profiles and compared them to RD and RD 2.0. There were considerable differences with RD but with RD 2.0 the variation with Buhlmann is slight, certainly not enough to establish a significant increased risk of DCS.

I still like to think of myself as "neutral" and unbiased when it comes to RD, I do like the discussions and continue to learn from them.

 

[Dan_P]

@tbone1004 "what Jay said" seems like a cheap statement on my part

Adding to it on my own accord, RD throughout the progression towards Cascade, includes gas logistics, correlation throughout the educational process, diver capacity and systems interoperability. Now, one might not want that from a deco strategy, and that's fair enough. But for my part, I find it makes my diving a lot easier. And there is nothing out there saying it's dangerous, including NEDU and the Italy project.

On "report" versus "rapport", you're right and I apologize for the confusion. I occasionally use my mobile device for posting, and it has a pest of a feature called Auto"correct" - now, it may be a handy for many, but for yours truly, operating mainly in Danish, often in Norwegian and German, but writing here in English - believe me, it's a headache.
Again, my apologies. "Rapport" is the Danish word for "Report", hence the mishap.

On repetitive dives AG clearly states a few times that you come out clean after each dive so there is no worry about repetitive dives. If he has changed that opinion, or his opinion on altitude, please enlighten me

What I've seen in his videos is that he says it is accounted for in the Ratio Deco-blueprint. Looking through the actual Ratio Deco material, you will see exactly what to do if doing a repetitive dive with a surface interval less than 60 minutes. I'm not going to hand out course curriculum here, but I'll say that it's on page 232 in "UTD Student and Diver Procedures" as well as the course materials and curriculum for relevant classes. Well accounted for in the blueprint and easy to negotiate.

As for overshooting NDL - and altitude diving - an "excess" if you will, is accounted for within the NDL framework.
I.e. you're doing an ascend on an NDL dive to get out relatively clean, meaning you can do the same ascend if you overshoot NDL slightly, or diving at altitude, without incurring an unacceptable risk of DCS. Or, you can think about it and adjust the ascend where and if you feel that you need to, for whichever reason you believe warrants it - dehydration, fatigue, etc.
Knowledge of various aspects of decompression impacting your diving, is a big part of the education in using RD.

Saying it's accounted for in RD is not the same as saying altitude has no impact on decompression on a general level. I think it's important to highlight the difference.
It would be a different statement, which I haven't heard AG actually say, yet is quoted for plenty in fora.

Again, understanding the why of Ratio Deco encompasses a host of factors, links in a chain, that add up to a contextual system. If one does not understand that, Ratio Deco and, for that matter, why UTD dives CC manually, might well come off odd. But, having a system that allows easy planning, diving and adjustment while easily mixing teams and swapping from C/C to O/C (whether on separate dives or bailout), builds recognition and consistency throughout a staged training progression and accounts for gas logistics and diver capacity, is, in my view, a quite handy tool, saying the least.

All this without being "dangerous". Honestly, I think bashing is unwarranted, all things considered. Including NEDU and Italy.
And again, I'm not saying diving any other way is some kind of strokery or anything to that effect. I used to.
I find RD works smoother for me, that's all.

 

[tbone1004]

once again.

How does UTD's RD determine how to pad dives? What is it evidence is it based on?

What is preventing you from doing that same padding with a computer that is tracking in real time either by staying at various depths for whatever extra amount of time you want, and/or just adjusting the algorithm to be more conservative?

You continuously bring up the subject of things being comparable for mixed teams and scaling. I dive with my GF's set the same whether I'm diving a 20ft warm water reef, a 100+ft cave, or diving under the ice. I do it with mixed teams on ccr with no issues either. WHY is RD better than using a computer to essentially eliminate the risk of human error?

 

[PfcAJ]

I've cut hundreds of profiles and compared them to RD and RD 2.0. There were considerable differences with RD but with RD 2.0 the variation with Buhlmann is slight, certainly not enough to establish a significant increased risk of DCS.

You you no idea of even knowing the DCS risk of a certain buhlmann profile, and there's no way you can know what the difference in risk is by deviating from it.

That's made up. And really the entire problem with what UTD is peddling. It's made up.

 

[HantsDiver]

You continuously bring up the subject of things being comparable for mixed teams and scaling. I dive with my GF's set the same whether I'm diving a 20ft warm water reef, a 100+ft cave, or diving under the ice. I do it with mixed teams on ccr with no issues either. WHY is RD better than using a computer to essentially eliminate the risk of human error?

It's not. Which is why you will see most tech1/2 divers with a perdix or petrol 2 after the novelty of being different wears off. And they are not just using it as an expensive bottom timer.

I can't think of a single reason why I'd want to stop using a computer. It's easier, it eliminates human error. It allows people to help me if I do make a mistake. And it looks cool.

Part of my thinks its a historical thing that's been passed down. When gue got going there were not too many decent computers around. Certainly not for mixed gas. So it became the thing. I don't think anyone can defend the none use of computers for advanced dives now.

 

[victorzamora]

How is that different from taking from several input, and using them together. The computer is doing it for you, that's the stamp of approval here?

I think this is a gross misunderstanding. The dive computer, GUE's Ratio Deco, laptop-based computer algorithms, etc work based off of algorithms based on mathematical models representing physiology. Whether that's VPM or Buhlmann or others, there's a mathematical model based off of some physiological principles. GUE's Ratio Deco directly emulates a well-understood, published, and repeatable algorithm based off of physiological principles.

UTD's Ratio Deco is an ascent strategy that started by completely ignoring all of the models based on mathematical models representing physiological phenomena.

It being on a computer has nothing to do with it.

 

[decompression]

I think this is a gross misunderstanding. The dive computer, GUE's Ratio Deco, laptop-based computer algorithms, etc work based off of algorithms based on mathematical models representing physiology. Whether that's VPM or Buhlmann or others, there's a mathematical model based off of some physiological principles. GUE's Ratio Deco directly emulates a well-understood, published, and repeatable algorithm based off of physiological principles.

UTD's Ratio Deco is an ascent strategy that started by completely ignoring all of the models based on mathematical models representing physiological phenomena.

It being on a computer has nothing to do with it.

I think this answers Toms inquiry as to what it's based on......