interesting...

[ffelix]

Thanks to all for the great info!

Before I get flamed for not paying attention in class, let me state that I am merely contemplating my first Nitrox training and trying to get some input! ut:

This thread does raise some questions in my mind. For instance, are all the decompression standards (NOAA, PADI, etc.) based on the same supporting evidence? Is this evidence clinical? Where is most of the research coming from?

How do the various authorities feel about the WKKP lads, who seem to have a lot of ideas that disagree with the status quo?

Unlike the old PADI vs. NAUI debate, there seem to be significant differences in agency philosophy and guidelines: is there a consensus about the best source for gas training?



Thanks!

 

[Saturation]

Any agency will give you the basics, its based mostly on NOAA's experience. There is no further research in no-stop nitrox, its a done deal except in decompression.

You'll get an appropriate booklet for any course that covers the basics of pp02 and EAD. For the more extensive details, the NOAA Diving Manual has it all.

If you can, you can get it direct from the source of the protocols, Dick Rutkowski, who teaches a detailed course including chamber management, from his company Hyperbarics Inc. in Key Largo, Fl. In between, you can do fun dives on the Spiegel Grove et.al with Ocean Divers, which ports right infront of his shop.

After recreational nitrox, the controversy begins in Advance Nitrox, but you need to know the conservative basics before breaking the rules


Advanced nitrox is breathing 50-100%.

 

[ffelix]

Thanks for the help--this clears things up a bit!

FF

 

[MikeFerrara]

The most recent PADI Journal had an article that discussed the difference between the bouble bodels and Haldanian models. The recognize the work of people like BRW and the WKPP but they're position apparantly that these methods require more validation. There are lots of us diving them though.

Ross Hemmingway (author of V-planner) has a data base on his website. The software is setup to log your dives streight to the data base.

I think the methode of validation is changing. With divers doing things on a daily basis that aren't in the book yet I think were seeing divers trying things and deciding how they feel rather than waiting for a bunch of scientists to get around to it.

Outside of commercial and military decompression applications nobody seems to care enough to dump much money into research. Some work is being done by DAN and Duke but it seems mostly applicable to recreational divers. Flying after diving is a big subject because so many tourists fly home from the Caribbean after diving. I'm more concerned with getting up from the dive and usually just have a long drive from Florida or Missouri.

At this point the leading edge of decompression methods is totally outside of anything the mainstream agencies are doing. They're slowly catching up to what divers have been doing for a long time. They won't jump in all the way until they're sure it's safe though.

 

[Dr Deco]

Dear SCUBA BOARD Readers:

Basis of the Tables?

The “pedigree” of a table can be found by tracing it back to the “basis set” of no-decompression limits (NDLs). These are generally the US Navy tables. Surprisingly, the US Navy did not determine a complete set of NDLs. The Navy tested decompression tables and some NDLs were determined. Others arose by interpolation from the study. In actuality, the US Navy did not develop and test any tables suitable for recreational divers.

The results of a table’s protection from DCS are essentially clinical once they are released from the test program (which except for PADI and DCIEM does not exist). Insofar as it is possible to collect diving data, it is possible to construct tables without a prospective test program; much of the RGBM tables were developed in this fashion.

Tested Tables

PADI and DCIEM tested their tables sold for recreational divers. In the case of PADI, this was specifically in a Doppler-tested, multidive, multiday format. Giving credit where credit is due, they are to be commended for this effort.

In addition to the US Navy tables, there are the tables developed by the Royal Navy (Great Britain) and the tables tested by Professor Buhlmann in Switzerland. While many other commercial tables exist, these are proprietary and not released.

What Nature Gives to One

It is said, “What Nature gives to one, she gives to all.” The reason that tables have a similar appearance is that they are based on physical constraints provided by nature. [Apple pies will be similar because that is how piecrust and apples go together.] There is no question that individual table designers will promote certain features of their tables, often without proof, in an attempt to gain market advantage. I do not comment on most of this since, I do not think it my place to promote or disparage products in the FORUM. Careful readers will note, however, that I am usually less than enthusiastic about the “wondrous differences” in all of the decompression meters. When you are in a safe range, basically all decompression schedules will be effective. The physiology of nuclei formation becomes more important in many cases (in my opinion).

WKPP

The decompression experience of the WKPP divers is very interesting. I know about it only second hand from what I read. I believe that it works, as it does, by virtue of the fact that nuclei formation is reduced by the “abaroferric effect,” that is, the lack of weight loading causes no new tissue nuclei to be formed. This is my own view and is not a generally accepted view of the majority of diving scientists today (last I heard). I continue to hear it said, “Diving scientists do not know how they do this.”

“Getting Round To It”

Scientists are not overloaded with tasks to perform because the money to do research is not overwhelmingly available. You might think that the equipment manufacturers would put money into research, but they do not. I am told it is because the profits from the diving industry as a whole are small. (Transportation and hotels are a different matter.)

Scientists will study what someone funds them to study. Whether the study is well designed and any good is a different matter (and a longer and more expensive lecture).

Nuclei

A major hot topic among recreational and technical divers is tissue micronuclei. The control of nuclei is not a big topic among professional barophysiologists. Most do not really understand it as I developed it. The kinetogenic origin of nuclei is either omitted or given a perfunctory nod of the head – unless things have changed since I last heard. Hydrodynamic cavitation is a word not even used (actually, two words).

Because of the interesting things being done by technical divers, this aspect is of interest. At lest it is to some of us.

Dr Deco :doctor:

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

 

[Dr Deco]

Dear Scuba Board Readers:

PADI Undersea Journal

I have recently received my copy of the Undersea Journal and was able to read the article on bubble models. It is interesting as far as it goes, but I would like to add a few more words for those interested in this matter.

Nuclei and Diving

Bubble nuclei concepts are not a new matter and were first discussed in the early 1940s by EN Harvey. The application of a concept to decompression,in a meaningful manner, is much more current however, and is attributable to Dr Weinke and the RGBM. As is true with most things, there is seldom one author and usually a progression of ideas.

Nuclei are not a favorite item among the research groups. The major research groups (Royal Navy and US Navy) devoted most of their efforts in the past several decades to deep bounce diving and then saturation diving. Additional effort was spent on DCS treatment. There was also a period of several decades where effort was expended (and is still expended) on biochemical causes of DCS, an effort where I do not see the evidence and have yet to see much come out of this.

Deep stops

These were advocated by Brian Hills, PhD, but for reasons of the “oxygen window” and the prevention of bubble formation. He did not postulate the existence of preformed microbubbles existing in tissues.

A deep stop was added to the dive procedures of the German Research organization, the DFVLR, in the 1970s and was found to be necessary for their procedures to work.

Considerable effort was invested by the physicists at the University of Hawaii in investigations of bubble growth, but the bubbles in their gels all were artificially introduced during the preparation process. While decompression procedures were developed, it is not certain how well the system represented actual living materials.

Current Nuclei Work

Nuclei” carryover” was carefully monitored during the PADI test series during the development of the Recreational Dive Planner. A lot was not said about this since, in the 1980s, this would not been a topic well understood by recreational divers (or even barophysiologists, for that matter). The topic of nuclei is not confined to the RGBM.

The RGBM introduces a distribution of bubble nuclei, but it is different that that found in naturally occurring water. This might or might not be disturbing to the final table outcome. The decompression tables produced for shallow, recreational diving are longer than those for simple Haldane models (limited supersaturation).

Additionally, the RGBM does not follow the same bubble generation mechanism (stress-assisted nucleation) advocated by me. Readers of this FORM are well acquainted with my ideas of hydrodynamic cavitation and its role in decompression. This is not mainstream barophysiology, but it has been of value to NASA.

Dr Deco :doctor:

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

 

[ffelix]

Thanks Dr. Deco & everybody else for your time and expertise.

This is very useful & interesting information that is difficult to find elsewhere. It's nice to know the foundations of belief!

FF

 

[Saturation]

Dr Deco once bubbled...
Dear Scuba Board Readers:

PADI Undersea Journal Additionally, the RGBM does not follow the same bubble generation mechanism (stress-assisted nucleation) advocated by me. Readers of this FORM are well acquainted with my ideas of hydrodynamic cavitation and its role in decompression. This is not mainstream barophysiology, but it has been of value to NASA.

Dr Deco :doctor:

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

Hi Dr. Deco:

My experience suggests cavitation is probably a significant component to DCI.

Bubble models provide mechanisms to explain what Haldane modelers puts probabilistically [the Workman M-values, Buhlmann a,b values etc.,].

Unexplained are variations in decompression requirements and anecdotes of effects of exertion and that of rest.

Do you have any leads? Any experiments done in compressing anesthetized subjects to avoid all movements and determine what decompression obligations occur thus? Are there biochemical markers for acute exertion to correlate such as lactic acid, cortisol, andrenaline etc.,?

I would love to discuss this, should we spin this topic out as a new topic?

 

[Dr Deco]

Hello Saturation:

Activity and Nucleation

There are considerable data linking musculoskeletal activity and DCS. What is not demonstrable is that nucleation is the root cause. That is my extension of ideas of early researchers such as Harvey and Dean. The difference is that these individuals proposed nuclei stabilization in, e.g., cell wall junctions. These were not really thought to be stable. It is my opinion that we are dealing with a constantly renewing distribution of nuclei, generated by musculoskeletal activity. This makes sense based on work in physical systems but the direct sampling of micronuclei from intracellular fluids is not possible. Thus we simply demonstrate the presence of nuclei by depressurization, but this is conjectural (but logical).

I believe that we are dealing with what hydrodynamic engineers refer to as free stream nuclei as contrasted with wall nuclei (Harvey’s idea).

Resting Animals

Many researchers have noted that anesthetized animals are very resistant to gas bubble formation during decompression. This is probably the result of a reduction in hydrodynamic cavitation.

At NASA we have used a reduction of activity in the lower body to simulate the weightlessness of space. Decompression in space appears to be associated with a reduced level of DCS. This lower body adynamia has been described in papers and reports, not all of which are easy to obtain. Other papers are in preparation.

Other Correlations

Some of this relationship of activity and DCS was observed during WW II and appears in Fulton’s book “Decompression Sickness.” Activities are quantified in terms of distance moved or in oxygen uptake.

Dr Deco :doctor:

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

References

Powell, MR, KV Kumar, J Waligora. Joint pain and Doppler-detectable bubbles in altitude (hypobaric) decompression. Undersea Biomed. Res., 19 (Suppl.), 55, (1992).
Powell, MR, J Waligora, W Norfleet. Decompression in simulated microgravity; bed rest and its influence on stress-assisted nucleation. Undersea Biomed. Res., 19 (Suppl.), 54, (1992).
Powell, MR, J Waligora, W Norfleet, KV Kumar. Project ARGO - Gas Phase Formation In Simulated Microgravity. NASA Tech Memorandum 104762, pp. 87, (1993).
Waligora, J, Powell, MR, and W Norfleet. The abaroferic hypothesis: a mechanism for the reduction of decompression sickness in microgravity, Aviat. Space Environ. Med., 64, 421, (1993).
Powell, MR, W. Norfleet, J Waligora, KV Kumar, R. Robinson, and B. D. Butler. Modifications of physiological processes concerning extravehicular activity in microgravity. Inter. Cong. Environ. Systems, SAE Technical Paper Series, (1994).
Powell, MR, J Waligora, KV Kumar. Hypobaric decompression in simulated null gravity; a model using chair-rest adynamia. Undersea Biomed. Res., 22 (Suppl), 67, (1995).
Powell, MR, J Waligora, and KV Kumar. Decompression gas phase formation in simulated null gravity. 25th International Conference on Environmental Systems. SAE Technical Paper Series 951590, (1995).
Loftin K.C., J. Conkin, MR Powell. Modeling the effects of exercise during 100% oxygen prebreathe on the risk of hypobaric decompression sickness. Aviat. Space and Environ. Med. 68, 199 - 204, (1997).
Srinivasan, S, and MR Powell. The effects of surface tension on bubble volume changes using a mathematical model. Undersea Hyperbaric Med., 24 (Suppl.): 25, (1997).
Powell, M.R. An algorithm for the calculation of the effect of adynamia on altitude decompression risk. Undersea Hyperbaric Med., 26 (Suppl), 56, (1999).
Conkin J, Powell MR. Lower body adynamia as a factor to reduce the risk of hypobaric decompression sickness. Aviat. Space Environ. Med. 72, 202 – 214, (2001)
Dervay JP, Powell MR, Butler B, Fife CE. The effect of exercise and rest duration on the generation of venous gas bubbles at altitude. Aviat Space Environ Med. 2002;73(1):22-7.

 

[Scuba]

Hi Dr Deco

With regards to WKPP divers you wrote:

The decompression experience of the WKPP divers is very interesting. I know about it only second hand from what I read. I believe that it works, as it does, by virtue of the fact that nuclei formation is reduced by the “abaroferric effect,” that is, the lack of weight loading causes no new tissue nuclei to be formed.

Specifically, what step-s are they employing which you believe cause no new tissue nuclei formations?

With regards to animals, you wrote:

Many researchers have noted that anesthetized animals are very resistant to gas bubble formation during decompression. This is probably the result of a reduction in hydrodynamic cavitation.

Have any of these studies noted the incidence of DCS, perhaps using various decompression rates comparing anesthetized and non anesthetized animals? Have animal studies been conducted comparing various rates of physical acitvity with respect to incidence of DCS? If this is possible and has been done, what where the findings?