"re-assessing deco profiles and deep stops", plus other bits..

[GLOC]

RC,

When you say 'pure' do you mean?

1. 100% fractional content of a gas e.g. 100% O2 or 100% He
2. A gas which contains 100% inerts e.g. 20% He, 80% N2
3. A gas which contains a mixture of O2, He and N2?

In the case of 3, what is pure about it?

Do you also mean that O2 is carried in one cylinder and the 'pure' gas in another being mixed inside the unit?

Regards

 

[anarchista]

RC. In light of the abilities Google Translate, can I please ask you to post your smaller posts in Polish (or type it up and then use GT to get the translation and compare it to what you are trying to say) as this might alleviate some of the language problems. This is an English language speaking forum.

The barrier is not on the side of the language, often a conceptual gap.

greet rc

 

[anarchista]

Do you also mean that O2 is carried in one cylinder and the 'pure' gas in another being mixed inside the unit?

YES
1. 100% fractional content of a gas e.g. 100% O2 or 100% He or 100% N2.
2. A gas which contains 100% inerts e.g. 20% He, 80% N2

greet rc

 

[lolwhat]

RC does not have good english, but probably much better than your polish!

Your analogy falls apart when you consider that I, a native English speaker with zero ability to communicate in Polish, am not even attempting to post on boards where communication in Polish is expected. However, I'll take your comment on asking/ignoring under advisement.

The barrier is not on the side of the language, often a conceptual gap.

Your assumption is incorrect.

 

[matt]

In light of the abilities Google Translate, can I please ask you to post your smaller posts in Polish (or type it up and then use GT to get the translation and compare it to what you are trying to say) as this might alleviate some of the language problems. This is an English language speaking forum.

Did the forum fix the multi-byte font issue to enable this, GLOC?

Let's try - this is in polish from Google Translate:

Zobaczymy, czy to ma hiddeous kwestii zestawu znaków uniemo***380;liwiaj***261;cych google translate zosta***322;y u***380;yte ...

Answering my own question - no, it's still not possible to post here in polish.

 

[Wilbo]

Guys,

Your participation is of course voluntary. You can choose to participate or not. We hope you do..

We will always be welcoming of contributors from every corner of the globe. While our primary language might be that of English, language is sometimes a barrier that we cannot avoid.

Please be tolerant.

 

[Dave Sutton]

A mod might consider moving everything from post 121 and moving it to a thread called something like re-assessing deco profiles and deep stops, it seems to have taken a nose dive from there, it's still an interesting conversation if you can look past the blatant sanctimoniousness from some ESL protagonists.

Concur.

Wilbo? Time for a magic moderators-act?



Dave

 

[Dave Sutton]

RC,

When you say 'pure' do you mean?

1. 100% fractional content of a gas e.g. 100% O2 or 100% He
2. A gas which contains 100% inerts e.g. 20% He, 80% N2
3. A gas which contains a mixture of O2, He and N2?

In the case of 3, what is pure about it?

Do you also mean that O2 is carried in one cylinder and the 'pure' gas in another being mixed inside the unit?

Regards

Reading thru, it appears to be "B", use of purely inert diluent to avoid PPO2 increase upon descent. He's made a few allusions to this if you read carefully.

Noting as a data point that when we did the deep work with CCR's for saturation bell lockout (umbilical fed) we had pure He as diluent. This was in the 150-300 meter depth range.


Dave

.

 

[Wilbo]

Placeholder

As requested, I've separated the thread below moving the off topic posts to here.

was part of 'Electronic vs manual CCR' - http://www.ccrexplorers.com/showthread.php?t=14017

Please keep the above clean and on topic.

If you continue with this thread, please be civil, or go elsewhere.

 

[anarchista]

Noting as a data point that when we did the deep work with CCR's for saturation bell lockout (umbilical fed) we had pure He as diluent. This was in the 150-300 meter depth range.

We know that there is a no disaster at great depths using this variant
mixing (in the big closed circut).
Why have to be a problem, at shallower depths.

In a few posts I talked about mixing on the fly suitable mixtures, is a solution which uses a patented mixing based on the program, is complicated.
It just means so much and so many, it is easy and possible.

Arguments: "this is a bad method, because it is a bad method" simply showed how shallow is the understanding of the CCR and SCR technology across the closed circuit diving.

rc greet

Zobaczymy, czy to ma hiddeous kwestii zestawu znaków uniemo***380;liwiaj***261;cych google translate zosta***322;y u***380;yte ...

Let's see if this is the character set hiddeous impossible were used google translate ...

 

[WFO]

Reading thru, it appears to be "B", use of purely inert diluent to avoid PPO2 increase upon descent. He's made a few allusions to this if you read carefully.

Noting as a data point that when we did the deep work with CCR's for saturation bell lockout (umbilical fed) we had pure He as diluent. This was in the 150-300 meter depth range.


Dave

.

Does that Canadian forces rebreather use pure He as well?

 

[anarchista]

Does that Canadian forces rebreather use pure He as well?

Dave talks about the great closed circuits in saturated systems.
Compression on heliox especially fast, can cause HPNS. TMX is better.

Completely different elements must be used as the use of nitrogen, air, helium, nitrogen-helium-oxygen mixture. mixing is based on the differential pressure across the laminar resistance. The author's name (J.B. Morrison) is written in one of the entries can easily get to what was used there.
http://rebreathers.pl/forum/download.php?id=81
A little more information was on the Carltech, at Cobham there is no such information.
In uspto.gov are still available, but they are worth military secrets.
This design blind diver metabolism, only modernized Dolphin or working SM Draeger.
It has been 40 years. Modernization of the prior 30 years was the ascent corrector ppO2

rc greet

 

[ebt]

There are already several models of tissue developed, many decompression took place.
They are accurate enough to know that deep stops will extend the total decompression time, it will also be safer.

rc greet

thanks for the red matey

this thread seems to be covering many topics now, which makes it harder to follow:

1. constant PPO2 decompression
2. gradient factors/deep stops
3. use of pure inerts as diluent.

from where I'm sat as "joe diver", I value scientific papers/research, but I also temper them with real world experience and the understanding that 'science' changes its mind over time as new theories evolve, or new experience needs explanation. I also think that while an algorithm might output an answer to x decimal places, it doesnt mean the algorithm is reflecting whats happening in vitro to the same accuracy. Biological systems are by their very nature variable.

So for me, trying to chase a tight constant PPO2 on ascent is a waste of time. The human body is not a tightly engineered item, they all vary between subjects and even between themselves over time. As long as you're 'close enough' and have padded your deco appropriately, you'll be fine. I dont know of any research to prove/disprove an acceptable level of variance, but its interesting if you model OC gas switching ascents vs constant ppo2 ascents (using your favourite planner). Theres not a lot in it if you have reasonable switches/mixes.

When it comes to gradient factors, Im sure no one is surprised that a <100/<100 ascent generates a better decompression end result. Thats simple logic.

For me, pure inert dil, whilst it makes sense mathematically is a riskier proposition in the real world. For a variety of reasons the diver may find themselves inadvertently breathing dil and its always good to have a life sustaining dil. For a start it removes the capability to do a dil flush while on the loop, which is a basic sanity check for our O2 sensors. Im sure that someone will now refer to the military use of inert dils, but I'd suggest those divers operate under tight operational constraints that are not applicable to the pleasure diver. I'd be interested to hear more about pure dil use, in cases of system failure.

Regards...

 

[GLOC]

Good post Zak, have a green to more than compensate

 

[anarchista]

thanks for the red matey

this thread seems to be covering many topics now, which makes it harder to follow:

1. constant PPO2 decompression
2. gradient factors/deep stops
3. use of pure inerts as diluent.

from where I'm sat as "joe diver", I value scientific papers/research, but I also temper them with real world experience and the understanding that 'science' changes its mind over time as new theories evolve, or new experience needs explanation. I also think that while an algorithm might output an answer to x decimal places, it doesnt mean the algorithm is reflecting whats happening in vitro to the same accuracy. Biological systems are by their very nature variable.

So for me, trying to chase a tight constant PPO2 on ascent is a waste of time. The human body is not a tightly engineered item, they all vary between subjects and even between themselves over time. As long as you're 'close enough' and have padded your deco appropriately, you'll be fine. I dont know of any research to prove/disprove an acceptable level of variance, but its interesting if you model OC gas switching ascents vs constant ppo2 ascents (using your favourite planner). Theres not a lot in it if you have reasonable switches/mixes.

When it comes to gradient factors, Im sure no one is surprised that a <100/<100 ascent generates a better decompression end result. Thats simple logic.

For me, pure inert dil, whilst it makes sense mathematically is a riskier proposition in the real world. For a variety of reasons the diver may find themselves inadvertently breathing dil and its always good to have a life sustaining dil. For a start it removes the capability to do a dil flush while on the loop, which is a basic sanity check for our O2 sensors. Im sure that someone will now refer to the military use of inert dils, but I'd suggest those divers operate under tight operational constraints that are not applicable to the pleasure diver. I'd be interested to hear more about pure dil use, in cases of system failure.

Exchange pleasantries.

Review Book:
"Possibility of Selection Decompression for Diving Apparatus type AMPHORA" 2012 y.
"Possibility of Selection Decompression for Diving Apparatus type CRABE" 2011 y. know better modelers from our modern perspective. (s***261; napisane po polsku)

Dave offered training in hypoxia, but did not take the testing of such risks. Which quickly lead to hypoxia. He had no relevant information, the early symptoms can be observed in this situation.

Even Canadian SCR does not allow inert gas to the breathing surface, works up to 8 m an oxygen closed circut. Also other solutions which are reported to protect sewn into action. Provide adequate mixture to depth.
Errors thick, spin cylinder of oxygen there are also IT istructor.
(As the only written clearly about the concerns, thank you.)

rc greet

 

[emmbee]

I also think that while an algorithm might output an answer to x decimal places, it doesnt mean the algorithm is reflecting whats happening in vitro to the same accuracy. Biological systems are by their very nature variable.

Absolutely (although I believe you meant in vivo; in vitro is in a petri dish).

Consider the Big 2 (Buhlmann+GFs and VPM). Buhlmann arbitrarily models 16 (12, 8) compartments, assumes that an exponential law governs ongasing and offgasing in each of these (the on/offgassing model) and further assumes a linear law specifies what minimum ambient pressure can be tolerated (the deco model). Testing was used to adjust all the constants to make the model "safe" (for a certain value of safe )(although ZHL16A used formulas to derive the a and b deco model constants from the on/offgasing model constants, if anyone knows how those formulas were arrived to, I'd be interested). GFs are just a dodgy hack to fix up the deco linear law to do deep stops (put down the flamethrower, that's what I'm diving too ). VPM uses bubble modeling for the deco model; the on/offgasing model is the same.

Yeah, blah blah blah, quite right, sorry. The point here is that none of that even pretends to describes what's happening to the body. Never mind a body in diving conditions, working, or not, getting cold, getting dehydrated and so on.

So for me, trying to chase a tight constant PPO2 on ascent is a waste of time.

IMHO, largely, yes.

There's a thing that's sometimes forgotten: the ppO2, in and by itself, is irrelevant to deco (so long as it's above 0.15 bar or so, that is ). It's important however because, oxygen being metabolised, you don't need to decompress it. So whatever pressure is taken by the oxygen is taken off the the rest, the inerts, which we do need to decompress. The higher the ppO2, the lower the ppN2 and ppHe, and therefore the less ongasing or the more offgasing.

Considering ongasing on the bottom, say 60m, 7 bar. With a ppO2 of 1.3, ppInerts will be 5.7. With 1.2, it will be 5.8. That's less than 2% extra. Not going to change the deco obligations all that much (of course "not all that much" is a relative concept).

Considering then, what you were saying, the ascent, say from 1.3 at 60m straight to 21m. If the ppO2 is kept stable at 1.3, ppInerts will be 1.8 bar. If, on the other hand, oxygen is lazily added and the diver gets there at 1 bar ppO2, ppInerts will be 2.1 bar. Okay, bit of a difference. But, compared to what it was on the bottom (5.7), you lost 3.9 bar in the first case and 3.6 in the second. Most of the gains with regards to ppInerts during the ascent are due to the ascent itself, not the ppO2. And it's not all that long, anyway, so again it won't change your deco obligations all that much.

When it's rather more important to have a high (and stable) ppO2, is when doing the stops.

IMHO, I'm not qualified to do any of this on CCR, it's all theory, and all that.

Cheers,

Matthieu

 

[tecdiverdude]

Made that nice and simple.
Green for u

 

[rossh]

I started out using Bhulman based IANTD tables and I didn't get bent.

The I moved to Deco planner 35/85 and didn't get bent.

Then on to a VR3 on zero safety and didn't get bent.

And now on Shearwater GFs on 20/90 and still not getting bent.
(This in on trimix dives mainly 40-80m range for 180min run time in the last 11 years)

Only thing I will say is on OC using IANTD tables i was doing much much shorter dives (avg 20-30min bottom time as apposed to 40-60mins on CCR)

The only relevant things here is the "get shallow quick VR3" with Pyle stops as opposed to the 20/80GF I was running for two years on Decoplanner.

So it seems regardless of which system I have used I have got away with it despite being older, unfit and a long time smoker.

<cut...>

ATB

Mark

And there you have it.... No matter what decompression concept you used, they all were successful. This is because each of those methods has sufficient safety margin built in so that each one will work on its own. None of those deco methods are bad, but some are less desirable for side affects though. So the moral of the story is to choose the deco concept you prefer and stick too it.


Not picking on you here below Mark:

There is a current trend in diving, and particularly CCR diving, to keep inflating and adding more deco time onto the plan. There is often little or no justification from a decompression risk point of view. Its done purely for safety reasons, to add more safety onto more safety, and its an endless pursuit. I agree that a safe return is the most important part of diving, but this endless increasing of time has no more benefit to reducing risk.

I joked here once about 20/50 profiles, but I expect that profile will arrive and be used one day.

Regards

 

[Iain3]

In my view we have added the deep stops with the purpose of mimicking VPM bubble model which is untested and has little or no validation outside a calculator.

I didn't think deep stops were to mimic VPM, I thought they were used because people like Pyle felt better for having done them. There may be very little data evidence regarding the effectiveness of deep stops, and thus no ability to say if they have a significant impact but there is qualitative, annecdotal data on it, which is still valid.

There must be enough technical dives being conducted now to gather some of this data. If we put together a survey that people could enter some demographics, a dive log with profile, results, etc we could start that process. Occurences of bends or dying are hard to model as such a rare event (thankfully), but you could model after-dive effects, whether people feel tired, sluggish, sprightly. We just need people willing to invest a little time after each dive to fill in a survey. Maybe set up a survey-monkey survey, approach people here, spread to rebreather world, YD and other locations, and see if we get enough to give meaningful answers.

 

[anarchista]

Obviously I'm not one of them, but the key thing here is, neither are you. In fact, due to your continued reluctance to back up anything you say (besides "somebody said"), your tendency to move the goal posts or completely change subject as soon as somebody has a valid criticism of your claims, your tendency also to resort to ad-hominems (even if ignoring insults as poor translation), and the general dishonesty of demanding of others to prove their claims while not doing any of that yourself, I'm starting to believe you're just another internet troll.

"Na tamtych Kalatówkach (2009 rok) przywo***322;ywa***322;em nast***281;puj***261;ce materia***322;y
dotycz***261;ce g***322;***281;bokich przystanków dekompresyjnych:

1) Richard L. Pyle, "The Importance of Deep Safety Stops", Deep Tech. 5:64;
1996

2) J.P. Imbert, J. Hugon. In search of models behind successful
decompressions. Stage de Plongee Scientifique, Banyuls, France, 2004

3) LeMessurier and Hills. Decompression Sickness. A thermodynamic approach
arising from a study on Torres Strait diving techniques.
Hvalradets Skrifter, 1965, Nr. 48, 54-84.

4) TB Buttolph, JR Broome. Deep stops during decompression in a swine model
of decompression sickness. NMRI 97-40, 1997

5) Gutvik CR, Mollerlokken A, Brubakk AO. Difference in bubble formation
using deep stops is dependent on length of bottom time.
(...) EUBS 2007, Sharm el-Sheikh, Egypt

6) Schellart N, Brandt Corstius JJ, Sterk W. Effect of a deep stop on VGE
bubbles after a 20 msw dive.
EUBS 2007, Sharm el-Sheikh, Egypt

7) Marroni,-A; Bennett,-PB; Balestra,-C; Cali,-Corleo,-R; Germonpre,-P;
Pieri,-M; Bonuccelli,-C1. WHAT ASCENT PROFILE FOR THE
PREVENTION OF DECOMPRESSION SICKNESS? II - A FIELD MODEL COMPARING HILL AND
HALDANE ASCENT MODALITIES,WITH AN EYE TO THE DEVELOPMENT
OF A BUBBLE-SAFE DECOMPRESSION ALGORITHM DAN Europe DSL Special Project
01-2002 "Haldane". Proceedings of the 28th Annual Meeting of
The European Underwater and Baromedical Society, Brugge, Sept. 4-8,2002

8) MARRONI,-A; CORLEO,-RC; BALESTRA,-C; LONGOBARdi-P; GERMONPRE,-P;
VOELLM,-E; PIERI,-M; PEPOLI,-R. THE USE OF A "PROPORTIONAL
M-VALUE REDUCTION CONCEPT" (PMRC) CHANGING THE ASCENT PROFILE WITH THE
INTRODUCTION OF EXTRA DEEP STOPS REDUCES THE PRODUCTION OF
CIRCULATING VENOUS GAS EMBOLI AFTER COMPRESSED AIR DIVING. DSL SPECIAL
PROJECT 01/2001. Proceedings of the European Underwater and
Baromedical Society (EUBS) Hamburg, 12 - 16 Sept. 2001

9) A. Marroni, et al. A deep stop during decompression from 82 fsw (25 m)
significantly reduces bubbles and fast gas tensions. UHM
2004; 31(2): 233-243.

10) JE Blatteau, M. Hugon, B. Gardette. Deep stops during decompression
from 50 to 100 msw didn't reduce bubble formation in man.
UHMS Workshop "decompression and the deep stop" 24-25 June 2008, USA

11) Gerth WA, Gault KA, Ruterbusch VL, Melton JL, Doolette DJ. Empirical
evaluation of the efficacy of deep stops in air
decompression diving. NEDU Protocol Number 05-23/32174, 2005"

I received an answer J.Kot.

greet rc