dive computers vs dive tables vs WKPP practices

[Dr Deco]

Dear DennyB:

Decompression Methods

When comparing decompression methods, it is important to note if multiple, high-oxygen gas mixtures were used. Many times these will very favorably reduce the decompression time because the oxygen partial pressure is frequently adjusted to an optimal level.

I have my views on the rapid decompression procedures and have mentioned some of them in this FORUM from time to time over the past three years. I will again give a summary, but you should remember that these are only my views, and a large fraction of diving scientists would not at all agree with my explanation.

First, it must be remembered that as a dive becomes more complicated (that is, deeper with the decompression procedure drawn out) there are many possible decompression routes to the surface. It is highly likely that there is one optimal way for any given diver, but that path is generally not known. Thus many alternative pathways are possible, all of which could be successful but only one would be the shortest with respect to time. The way to accelerate decompression is

• reduce the number of tissue micronuclei,
• reduce the size of tissue micronuclei, and
• eliminate dissolved inert gas quickly.

Nuclei Number and Size

When divers enter the water, they reduce the musculoskeletal stress from gravity (walking) and generate few micronuclei. [This is my hypothesis based on my research at NASA.] This is true whether they are commercial or tech divers. In commercial or military diving with extended deco, the decompression procedure is conducted in a decompression chamber and the divers are encouraged to move around. This small amount of walking will generate some tissue micronuclei. [While this has not been directly tested, it is known that saturation divers decompressed in chambers get the bends primarily in their legs.] Commercial and military divers have not decompressed in the water during long decompressions for decades. It is considered dangerous to have a diver suspended in the water, chilled, and away from potential medical care.

In tech divers, the decompression is conducted in the water, and the divers remain suspended. As with astronauts, the DCS incidence is less in the absence of this musculoskeletal stress [from gravity]. My hypothesis is that this reduction in the nuclei size, both from compression and the lack of regeneration while in the water during decompression is very helpful for deco.

Pressure will also compress the micronuclei to a very great degree. In some models (e.g., the RGBM and VPM), this effect is taken into accounted.

Decompression in chambers can be rapid if the gases are switched and the divers stay seated. This was the procedure with divers in the testing program at the Institute of Underwater Medicine in Bonn, Germany. They produced few to no Doppler bubbles until they exited the chamber and walked around.

Another way of looking at this is to note that the DCS incidence determined in the laboratory is basically the incidence for a mobile diver. The DCS incidence for a seated diver is the true basic DCS incidence.

Dissolved Inert Gas Elimination

I do not believe that the halftimes expressed in the algorithms today represent different tissue compartments or types. It is true that there are different tissues in the body and that thee will have different halftimes, but the tendons and ligaments are a single tissue. I believe that the “compartments” represent the allowed halftimes of the tissues, and only one is functioning at a given time [although all are tracked.] These halftimes can be modified with physical activity that changes the perfusion (blood flow). We have done this at NASA to reduce the oxygen prebreathe times for astronauts.

I suspect that tech divers performing in-water decompression will have better perfusion than divers seated in a chamber. This will greatly accelerate decompression.

These finding were first noted for the in-water situation by the WKPP personnel and are most interesting. To me, they represent an application to diving of what we have learned about the mechanics of decompression following my arrival here at NASA in 1989.

My Hypothesis :doctor:

Again, these are basically my interpretations of the WKPP diving. It is really quite wonderful that they found this. I believe that it accords with what I have found from my research at NASA for altitude decompression.

Dr Deco :doctor:

 

[cdennyb]

I would first like to thank those of you who submitted a valid thread reply.

I assure you all that this is not a "troll", in fact I really don't have time to be bothered by such crap.

Dr. Deco's reply was fasinating and the others who replied and referenced other articles and individuals that I might further investigate are duly noted and appreciated immensely.

I verbally slap those of you who disregarded my post asking that no slams be posted. If you want to verbally abuse those in the industry that may or may not share your style, view, or opinion, please go somewhere else to do it, and to those of you who submitted the kind of feedback I really wanted, "thank you again". I will be watching for replys and posts from you since you have the mentality to read everything a persons writes and understand what they want in return. You valued opinions are looked upon with open mindedness from my side.

I will gladly accept and comments or other information regarding this situation with dive computers, v-planner tables, and other such related comparisons. and again please leave your narrow minded views of others at the door when you come in.

thank you all sincerely for posting replies.

dennis-safe diver for over 26 years now.

 

[BigJetDriver]

cdennyb once bubbled...
...I verbally slap those of you...etc.

Since I am the one who posted the troll warning, I will apologize to you, sir, for saying it. It initially had the earmarks of some of the other efforts on this board that have created some massive flame wars. Since I see that you are sincere in your desire for information, I do apologize.

As for your remark above, well.....=-)

 

[BRW]

Amen, and well said all.

Hats off to you, BJ69, for your last post.
You are a gentleman and scholar.

And most of us who know the the etiology
of those "NET flames" you mention, also
understand your feelings, though not agreeing
necessarily.

Best regards always, to all

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

 

[100days-a-year]

Just one question to the PHDs,was this a case of the empirical evidence pre-dating the applicable theories?And was there communication between WKPP divers and any deco modellers/theorists?Either way the huevos factor alone is respectable and the valuable information gained has helped to somewhat revolutionize deco diving.

 

[BRW]

Good question, 100DAY,

Today modeling and field testing are more symbiotic than
ever before, as with RGBM, and other field testing ops, like PDE,
Modelers are divers, and field testers often. And all the
shortcomings of older deco technology (Haldane M-values)
fly up in the face of modern diving, and everybody talks about it,
and has concrete data to back up their claims (like WKPP, C & C,
NAUI Tec, and 1000s of divers using new tables, meters,
and software with models tracking both dissolved gases and
bubbles). Models today are realistic, work in the field,
and are encoded in a new generation of tables, meters,
and software. Today, modeling and validation and testing are
symbiotic in the "living laboratory" -- the real world of diving
across the full spectrum of altitude, deco, mixed gases,
repets, no-deco, and sat on OC and RBs

This is, and continues to be, a major contribution by the
worldwide tec diving community over the past 10 - 15 yrs or so,
and the driving force behind an evolution to revolution in diving.

In the 70s and 80s, modelers really started to question the
old stuff, and backed it up with data in the field (like pearl
divers and fisherman), but didn't get past all the old icons
in the deco technology business. Hills is the prime example
and mover. I have some personal letters from him that I will
share with this forum that are historical gems.

In this time frame, empirical data abounded, but was either
ignored because it didn't fit the old stuff, or was dismissed as
"anecdotal" (a nice way to ignore facts in the field).

Prior to the 70s, data fitters just routinely applied the old
stuff (M-values) to the data and turned the crank. Tables
and such were severely limited by data fit range, and because
the fit equations were not a good model of reality, the results
didn't extrapolate and were limited. And 1/2 correct. Dissolved
gases are only 1/2 of the deco problem. Deep stops with
shorter deco in the shallow zone, and shorter overall deco
DO not come out of dissolved gas only models, and that is what
Haldane originally used to "fit" data. It persisted for 75 yrs
without question til the 70s.

Such is sad in a way, because Haldane tested deep stops
and found them necessary for safe and efficient staging even
back in 1908. Dual phase dynamics (dissolved gas and bubbles)
were certainly well known even in those day, and would have
allowed him to bring his data and fit equations to closure. His
competitor for an Admiralty contract to study divers and caisson
workers, Hill, had most of the right dynamics in his fit equations,
but lost the contract to Haldane. Too bad for all of us.

It's taken a century for things to retrack. Haldane was a truly
great physiologist, but not a good modeler. Haldane also
didn't know anything about micronuclei formation, and actually
assumed that seeds "never occured" in the body under gas
loadings until M-values were exceeded. He was dead wrong
then and should have talked with chemists and physicists of
his own day who could have set him straight even in 1908.

Regards,

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

 

[Dr Deco]

Dear 100 days a year:

You have a very good question of how things work in the world of science. Dr Wienke gave example of his experience, and I can also give some of mine.

[1.] There are many aspects of science that are taught in school that are in reality not correct. One is that scientists are “open to facts and will test theories.” This does not occur in many cases. For various reasons (e.g., grant money, grant money, fame, and grant money), a scientist is interested in you testing his ideas – he is not interested in testing your ideas and making you famous. Many professional will find this harsh but many others would certainly agree. Certainly those who study scientists, rather than science, such as Karl Popper, would agree.

[2.] Scientists work on the basis of theory and mechanisms. If the mechanism cannot be explained, then the phenomenon is very often written off as spurious and bogus. (Electromagnetic interaction with living tissues is an example of a possible something without a mechanism.)

Because deep stops could not be explained, they were written off by professionals as anecdotal. Even I, generally quite open, thought that much of it could be explained by selection of resistant divers in a general population (and much if this might still be true).

[3.] Micronuclei were discussed in great detail by scientists such as Edmund N. Harvey in the first half of the 19th century (1928 – 1952). When he left the field of barophysiology (he was there briefly during WW II), the concept was unattended and withered. Most scientists in barophysiology were physicians and life scientists, and these folks were not interested in cavitation theory (from German scientists of the 1920s and ‘30s), or stress-assisted nucleation. Life scientists love biochemical theories. Note the popularity of the Blood-bubble interaction concepts that lasted 30 years. None are even mentioned in the last edition of Bennett and Elliott.

[4.] Deep stops were added by the German and French scientists in Bonn during the 1970s at the DFVRL. They were an essential part of the decompression process for their commercial tables and they did not work without it. This work is largely un-referenced and is mostly forgotten. [There were problems with the high oxygen for commercial divers making repet dives.]

[5.] Brian Hills, PhD, was a great proponent of “stay deeper for longer.” He did not make great headway because of a lack of a plausible mechanism, or a good one at any rate. His “thermodynamic decompression” method keeps all helium and nitrogen in the dissolved state by never allowing supersaturation to occur (he used the “inherent unsaturation of tissue” from oxygen metabolism). Most tissue during decompression is supersaturated and most nitrogen remains dissolved. I believed that and so did Hills. He later changed his statement to “phase equilibrium” in the “critical tissue.”

Regrettably, gas phase separation occurs all the time; the bubble micronuclei are always present. In addition, the addition of diffusion-controlled exchange required the use of extremely low diffusion constants and the gas phase could only grow by collisional coalescence. Even those of us who agreed with him did not agree with him. The model simply was not correct, although there is no question that Brian’s heart is in the right place. He was trained as a chemical engineer and I count my hours and discussions with him as some of the best in my years as a professional scientist.

[6.] In most endeavors of science, it is often difficult to ascribe a discovery to one individual, and most often one can trace many individuals who made some impart. Even Einstein and relativity had some origins with Lorenz and Mach.

This FORUM has assisted in the transfer of information from the professional scientist to interested amateurs and vice versa. It continues an old tradition where science was taught directly to the people by the scientists. In such activities as the lectures at the Royal Society, this continues to this day. One of my most memorable science experiences was as a young boy reading the Christmas Lectures of Michael Faraday on The Chemical History of A Candle. [They can be found today on the internet.]

[7.] I believe that we are now entering a different era in barophysiology, one in which non-professionals are making a serious input. This is very interesting and important since many aspects of testing are out of reach of professional scientists because of legal restrictions.

Amateurs today make very valuable contributions to science. They participate in bird counts, find comets and monitor the luminosity and periodicity of variable stars. They develop better engines in hot rods and participate in archeological digs. At one time, science was performed in a large part by amateurs. They corresponded, wrote books, and gathered in groups such as the Lunar Society.

There is no reason that they cannot also contribute to diving science today.

Dr Deco :doctor:

 

[100days-a-year]

THanx,I really liked the analogy of symbiosis to describe the relationship b/w you'all and divers in the field.I am aware of how jealosy and $$$ along with fame can cause science fact to become science fiction.There are several fields of human behavioral science where all empirical evidence flies in the face of much of the published work and accepted practice.THanx again for being here to keep that from being so prevalent in diving.

 

[BRW]

Thanks, and you are welcome, 100DAY.

The biggest problem in past diving is that people didn't talk to
each other. And the label "anecdotal" was/still is often applied
to real divers doing real things in the water. The folks in white
coats turn their heads the other way because what's happening
doesn't fit into their limited (wrong is probably better) diving
algorithms, and it takes years to ondue the messy buildup.
The bigger the icon, the harder it falls. And the longer
it takes. Haldane stuff falls in that category. And it's falling.
Suddenly things like deep stops are "prudent" according to
some in white coats (even though it was reported in 1976
that deep stops reduce Doppler scores by a white coat diver).

And thank God finally. And thanks WKPP, C & C
(where I work), NAUI Tec, and 1000s of you out there
proving modern deco theory works and is safe. And is
exploding throughout the living laboratory. No surprise to
many of us.

And thus a "living laboratory of real diving" enters today.
It's the place where theory, models, data, field testing,
validation, and real divers and scientists meet for drinks and
dinner. It started in the worldwide tec diving community,
and continues.

Such is where RGBM has its roots.

Cheers,

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

 

[Scuba]

I have a question I've been wanting to ask for sometime but never got around to, until now.

In regards to the general body of knowledge about decompression diving, all the referenced work that I've seen is credited to "Western researchers".

Is this type of scientific knowledge disseminated and readily available to most interested scientists worldwide?

I have no doubt Western scientists are at the cutting edge in many fields. However, due to political, cultural, or other reasons there may exist obstacles or blocks to some of this knowledge. Specifically, I'm thinking it is possible the old Soviet state, or perhaps other politically "unfriendly" nations, may have conducted extensive studies in this field which would not be disseminated.

Is it likely there may be some already researched jewels out there to be discovered by Western scientists?