Nitrox...with AIR computer

[BRW]

Paul,

Micronuclei persistence/generation times are user inputs
to all RGBM packages. Presently, I use something on the order
90 minutes, and that is what vendors get. Assumption is
some are always generated on dives, and especially for repets.

RGBM does not assume anything like days. And growth over
SIs is done for repets. Use material dynamics for persistence
time scales (skin collapse), and dial to data.

Bottom line in RGBM -- any persistence/generation time scale
can be easily implemented/applied. Special attention to physical
activities can thus be "inputted" to RGBM. No big deal to calcs.

Bruce Wienke
Program Manager Computational Physics
C & C Dive Team Leader

 

[Dr Deco]

Dear SCUBA SOURCE Readers:

Nuclei Generation:

What Dr Wienke says about the “adjustment of nuclei properties” to the dive tables is certainly possible. It does not, in my opinion, still adjust for the correct parameter. We could go on for days, back and forth, on this Board about this question of nuclei generation, numbers, distributions, lifetimes, permeability of interfacial shells, and viscoelastic properties of cytosol and third space fluids.

All tables can be adjusted. Varying the “m-value” and lengthening the half times adjusted Haldane tables. The tables worked, but not necessarily for the reasons given. One can make adjustments in the case of excessive workloads, but what would be the correct modifications?

One can also correct for nuclei generation (or persistence) in the next dive, but I would suggest that the diver not do this in the first place, since it could lead to DCS during that surface interval. Lengthening the surface duration could lead to a delay and the diver would not repressurize for a “treatment.” [Some animal data suggests this, but it beyond this FORUM at the current time.]

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[BRW]

All,

When I say seeds are "user inputs to RGBM", I do not
mean deco meter users (Suunto, Mares, Dacor, Hydrospace,
Zeagle, Plexus, etc) can "change"anything. That is not
an option now. Rather, the "hooks" are there.

Phase models have the right "hooks" for micronuclei
generation/persistence. Haldane models do not. And
mocking up existing Tables to do such is not the best way.
Just like deep stop "rules" are not a best approach in general
when self-consistent techniques work better.

RGBM awaits the the "latest" data on micronuclei generation,
and will implement as such. For now, as Mike points out,
such is up for grabs.

And is a very, very interesting and important part of modern
deco mechanistics for all diving.

All this was underlined at the Deep Stops & Modern Deco
Strategiers Wkshp at Tampa last February, incorporating
data, experiments, theory, and field test results. And thanks
to Dr Deco for his presentation.


Cheers,

Bruce Wienke
Program Manager Computational Physics
C & C Dive Team Leader
ut:

 

[Diver0001]

(This isn't directed at anyone in particular but I'd like to throw it into the discussion):

I've been mulling over this all day but, I just can't get over thinking that this whole Haldane/RGBM discussion is pretty pointless. I'm sure with all of the "tam-tam" on the internet about RGBM that it must be a "better" model but I must be the most mathematically challenged individual on the planet because I just don't get it. I hear all kinds of terms like "dual phase" this-and-that "bubble mechanics", "gradient factors" and hooks for some sort of micro-nuclei generation and persistence blah blah with page after mind-numbing page of formulas and I for one am hopelessly confused

Haldane is simple. It took me an hour to learn how it works and I can explain it to my 4 year old. I have tried repeatedly to read Dr. Wienke's articles on RGBM and form some sort of helicopter view of how it works but so far I haven't got anything to show for it except that bubbles start small and they grow and you don't want that. I can't even give you a list of which variables the various RGBM implementations use and how they interact so when a computer is telling me to do-this or do-that I have (a) no idea why it's saying that and (b) no particular resource for judging how much margin I still have or what the consequences will be if I don't do as my computer says. These are pretty major limitations if you ask me and as the model gets fleshed out and computer manufacturers try to "differentiate" their implementations from the competitors' then I'd say it's only going to get worse.....

I started diving with a computer in the mid '90's and I obviously bought one that does Haldane. I know everything about it and I know what to watch for. If it's cold I leave a margin, if I'm working hard I leave a margin, if I make several dives in a day I leave a margin. If I'm tired I leave a margin. It tells me the same NDL every time at a given depth and I know why. Maybe I'm some kind of dinosaur but it's comforting to know how my computer is working and I'm not averse to using my own brain/intuition/judgment to adjust my dive plan for conservatism.

I'm worried that we're going to get a new generation of computers that are so complex and so "bossy" (for lack of a better term) that you will be basically forced to "ride the computer" for lack of the basic understanding of the underlying model. Will it be safer? I'm not convinced for two reasons: (1) I don't think the Haldane model is *unsafe* as long as your brain is engaged so we're probably talking about avoiding a miniscule number of minor hits per year. Extra conservatism sounds good but as far as I know we don't have much real evidence that RGBM in and of itself is going to help people avoid the kinds of hits they're getting and more importantly the underlying reasons (blown deco or rocket-ascents, for example) for those hits. A lot of hits would have been avoided by following Haldane to the letter too but people aren't doing that either so why will the existence of RGBM change their behaviour? And (2) the model is so complex that you can't logic out what it's doing so you are at the mercy of the computer. We're fast approaching the era of computer-only dive training and I'm afraid that the "intuition" that comes from making many dives with predictable parameters will be lost on a lot of divers in the future who will see a different NDL for different reasons every time they hit the water. A bug in the algorithm could hurt people who are trained to disengage the brain and ride the computer. I'm sure this isn't the future Dr. Wienke would like to see but just wait until the training agencies get ahold of it. If *I* can't understand the model then most of the training agencies won't even try explaining it and students will be taught in massive numbers to ride the computer. I get bad vibes from that.

So...... that's out.

R..

 

[divermasterB]

Diver0001 once bubbled...
(This isn't directed at anyone in particular but I'd like to throw it into the discussion):

I've been mulling over this all day but, I just can't get over thinking that this whole Haldane/RGBM discussion is pretty pointless. I'm sure with all of the "tam-tam" on the internet about RGBM that it must be a "better" model but I must be the most mathematically challenged individual on the planet because I just don't get it. I hear all kinds of terms like "dual phase" this-and-that "bubble mechanics", "gradient factors" and hooks for some sort of micro-nuclei generation and persistence blah blah with page after mind-numbing page of formulas and I for one am hopelessly confused

Haldane is simple. It took me an hour to learn how it works and I can explain it to my 4 year old. I have tried repeatedly to read Dr. Wienke's articles on RGBM and form some sort of helicopter view of how it works but so far I haven't got anything to show for it except that bubbles start small and they grow and you don't want that. I can't even give you a list of which variables the various RGBM implementations use and how they interact so when a computer is telling me to do-this or do-that I have (a) no idea why it's saying that and (b) no particular resource for judging how much margin I still have or what the consequences will be if I don't do as my computer says. These are pretty major limitations if you ask me and as the model gets fleshed out and computer manufacturers try to "differentiate" their implementations from the competitors' then I'd say it's only going to get worse.....

I started diving with a computer in the mid '90's and I obviously bought one that does Haldane. I know everything about it and I know what to watch for. If it's cold I leave a margin, if I'm working hard I leave a margin, if I make several dives in a day I leave a margin. If I'm tired I leave a margin. It tells me the same NDL every time at a given depth and I know why. Maybe I'm some kind of dinosaur but it's comforting to know how my computer is working and I'm not averse to using my own brain/intuition/judgment to adjust my dive plan for conservatism.

I'm worried that we're going to get a new generation of computers that are so complex and so "bossy" (for lack of a better term) that you will be basically forced to "ride the computer" for lack of the basic understanding of the underlying model. Will it be safer? I'm not convinced for two reasons: (1) I don't think the Haldane model is *unsafe* as long as your brain is engaged so we're probably talking about avoiding a miniscule number of minor hits per year. Extra conservatism sounds good but as far as I know we don't have much real evidence that RGBM in and of itself is going to help people avoid the kinds of hits they're getting and more importantly the underlying reasons (blown deco or rocket-ascents, for example) for those hits. A lot of hits would have been avoided by following Haldane to the letter too but people aren't doing that either so why will the existence of RGBM change their behaviour? And (2) the model is so complex that you can't logic out what it's doing so you are at the mercy of the computer. We're fast approaching the era of computer-only dive training and I'm afraid that the "intuition" that comes from making many dives with predictable parameters will be lost on a lot of divers in the future who will see a different NDL for different reasons every time they hit the water. A bug in the algorithm could hurt people who are trained to disengage the brain and ride the computer. I'm sure this isn't the future Dr. Wienke would like to see but just wait until the training agencies get ahold of it. If *I* can't understand the model then most of the training agencies won't even try explaining it and students will be taught in massive numbers to ride the computer. I get bad vibes from that.

So...... that's out.

R..

First, I seriously doubt that you are diving a Haldane computer. You might be diving a Workman, or Buhlman ZHL-12 or ZHL-16 computer, (and yes there are differences).

Second, the big benefit in the "bubble" models is a reduced incidence of the subclinical DCS. This means not only avoiding getting bent, but also reducing the number/ and size of bubbles post dive. The benefits are less fatigue after a dive, etc.

Just because you can't get your brain wrapped around bubble models, doesn't mean that it is a bad implementation. The reason we use a computer is to simplify complex things. Any argument that says gas mechanics in the human body is anything but complex, is just wrong.

The Haldane deco tables were based on a very simple observation several years ago. The science and understanding has improved greatly, starting with Workman and Buhlman, but really getting good with Wienke, Alcott, etc.

 

[Dr Deco]

Hi “ro”:

Recreational Diving

I have a strong suspicion that many divers by now have become bewildered. One should remember that the problem, or situation, really only arises when one is deep. The recreational depths of 130 fsw or less do not present much in the line of DCS problems. Even when divers perform several dives a day for several days, the incidence of DCS is not high. It was feared that diving problems would increase when decompression computers yield profiles that would “allow” multiple dives per day. It did not result in an increase in DCS.

For tech divers, this is a different story. The decompression schedules for these are influenced by the tissue nuclei already present. The schedules given with the Haldane models will yield schedules with stops that are very long in shallow water. The models that consider “micronuclei” will yield shorter decompressions, and some of that decompression will be in relatively deep water. For technical divers, these schedules are shorter and much more convenient.

Bubbles and the Haldane Method

The first to introduce gas bubbles that were always present in tissues was E N Harvey during the 1940s. However, he did not make any tables or decompression procedures from this hypothesis. Research during the 1950s and 1960s was largely devoted to saturation diving and oxygen treatment and the beginnings of deep bounce diving (short bottom times deeper that 500 fsw). This led during the 1970s to more work on bounce diving, always with Haldane or “limited supersaturation” guidelines.

Commercial Work

Commercial work has always concentrated on the use of bells and deck decompression chambers. These procedures are different from technical scuba divers. As this group increased in numbers, they developed procedures separate from the equipment-intense methods of the military and commercial divers.

The technical divers noted, for example, that very often the felling of fatigue was reduced with deeper stops and a sense of well being increased. While this is debatable as to its reality, the notion nonetheless developed that tissue microbubbles were in a sense being kept smaller by the deep stops.

Bubble Studies

Work conducted at the University of Hawaii Physics Department investigated the properties of nuclei and small decompression bubbles in gels. While almost assuredly not the correct model for living beings, these studies nevertheless provoked thoughts in which nuclei played an essential role in decompression.

Two Phase

This is apparently a more difficult procedure to imagine for divers even though we use the principle almost daily in our own lives.

1. When opening a bottle of carbonated beverage, we are careful to allow it to “settle down” so it does not bubble out the top when opened. What is being done is to reduce the size of nuclei formed by the motion of the liquid (hydrodynamic cavitation) and allow the microbubbles to shrink down to nuclei below the Laplace limit (the size where surface tension pressures exceed the dissolved gas pressure).

2. After allowing the bottle to sit, we then unscrew the cap carefully allowing the internal gas to vent off. We say that we are “decompressing the soda pop” but in actuality we are not. What is being done is to prevent the Boyle’s law expansion of the micronuclei (thus reducing the surface tension pressure) to prevent inward diffusion of carbon dioxide. This inward diffusion into a momentarily bigger bubble will stabilize it at the larger radius and frothing will result. For a carbonated beverage, this is a deep stop or at least a very slow ascent. You can check for yourself that you did not degas the liquid by recapping and shaking. I would not do this in the living room.

This is visually all that there is to the deep stop story. As is try with many things, to optimize the process requires a “few” more steps. Thus the computers will do what is not easy to perform in practice.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[BRW]

RO,

The Training Agencies have already started
teaching phase ideas -- they are no more
complicated in laymen terms than Haldane
based training info. Besides, new guys
need modern orientation and fact. Not misfact.

Check out NAUI and IANTD and see for yourself.
And others.

You also must know that NAUI uses full up
phase Tables (RGBM) in their training, both
rec and tec divers, that is, neophytes to
hard core diving folks.

Appreciate your concern, though.

Bruce Wienke
Program Manager Computational Physics
C & C Dive Team Leader

 

[Diver0001]

BRW once bubbled...
RO,

<snip>

Check out NAUI and IANTD and see for yourself.
And others.

You also must know that NAUI uses full up
phase Tables (RGBM) in their training, both
rec and tec divers, that is, neophytes to
hard core diving folks.

<snip>

I took your advice and asked a NAUI instructor about their RGBM teaching. What the person said is this:

As for RGBM... most NAUI instructors that I know of are NOT teaching these tables nor are they making plans to do so. There are just too many tables and they are very simplistic in nature and are way over cautious on their bottom times. I have not seen an electronic version yet.

However, we are teaching a deep stop to OW students now... If your dive is deeper than 40' then you do a one minute stop at half of your deepest depth and then continue with a normal safety stop.

I suppose if RGBM just boils down in to the training to a new set of tables and a simple rule governing deep stops then even I can learn it It still bugs me though that I can't find a simple description of the workings of the model at high level. Can you suggest a source? Thanks in advance.

R..

 

[BRW]

Sorry, RO.


NAUI Europe sometimes is maverick in changing.
They can teach the old NAUI Tables, or new RGBM
ones. So can NAUI everywhere. NAUI Hdqts in the
the USA can't keep up with the demand worldwide
for the plastic RGBM rec Tables. The RGBM tec
NAUI tables are in their 3rd printing.

Both are not overly conservative if you knew
how, why, and wherefore I constructed them --
data, field testing, etc. But use an RGBM
computer instead -- and pass that on to your
NAUI cohorts in Holland. Things are really
changing in the diving world, and even for
recreational diving. Hope you can climb
aboard when you feel comfortable.

As far as the "halving rule for one minute"
for NAUI, it works fine for any set of
rec Tables (ZHL, Navy, RGBM, DCIEM, PADI, SSI,
IANTD, TDI/SDI, etc). And it came out of the
Deep Stops And Modern Deco Strategies Wkshp
in Tampa last Feb (NAUI sponsored). It is also
endorsed by experiments done, DAN analysis,
data folding, field tests. But only for rec
diving as such.

BTW, also add GUE, of course, to list of
Training Agencies teaching, explaining, and using
phase models and associated tables and software.
I believe you are familiar with GUE,

As far as finding something to read on phase
models, RGBM, I would normally suggest about
5 - 6 books from Best (BRW auhtor), the material
on the RGBMdiving.com website, or deco lists
in general. But from your comments, I have a
feeling that they might be farther above your head
than you want to reach. I suggest you contact
Tim O'Leary at Nauitec@aol.com
for NAUI's training material on phase Tables,
models, RGBM, etc. I think he can find something for you.

Copy your chagrined posts to him.

To all, thanks for the pleasant opportunity
to spent some time reading thru very interesting
posts, questions, and answers, and posting back.

Special thanks to Mike and his Regulators
for this site (probably the best overall diving
forum around). And DeepTechScuba, thanks for
the very kind words in one of your postings.

I will be gone for a bit of time, but look
forward to jumping back in when I return.

One last thing for clarification. When I
mentioned Haldane deco, Haldane software, Haldane
models, I was generically referring to all
algorithms, tables, models based on dissolved
gas methodology. That means original Haldane,
Workman USN, Buhlmann ZHL, DCIEM, Royal
Navy ,Spencer modified, hybrids, lowbrids, etc.,
using M (critical tensions), R (critical ratios),
or G (critical gradients), plus any and all ad
hoc schemes (gradient factors, P/1.6, deep
halving) concocted to emulate bubble-dissolved
gas dynamics.


Bruce Wienke
Program Manager Computational Physics
C & C Dive Team Leader