a standard dive table

[scuba-punk]

don't forget that the navy usually (always?) has a chamber onsite during diving operations. diver leaves the water and is bent? --> chamber. rough seas? --> yank them to the surface after their 40 foot stop and get them in the chamber in the next four minutes (kinda cool to watch). it's a matter of how much risk you are able to take. as it was said above, navy divers are in top physical condition and most working dives, navy or otherwise, are going to be deco dives.

 

[steve49589]

During the PADI AI and Instructor programs, they go into detail concerning the development of the PADI/DSAT tables.
Good information can be found in the Instructor Candidate Workbook.

 

[blueabysss]

Dr Deco thanks for the info, love an objective discussion. However, don't forget the combat diver, and that the majority of educational institutions use NOAAs dive protocols and most of them do not do decompression diving.
For the uninformed, there are a whole series of Navy diving activities that do not require a dive chamber.
The technical diver better be fit and should be compared more to the Navy diver than to the average recreational diver.
I'm familiar with all the Dive tables mentioned and I've worked on them all. I'm not going to get into a contest of which ones are more conservative or better and please lets not get into that at all.
Yes, originaly all the dive agencies used the US Navy tables (1971). That has changed over the years and each one has developed their own. By the way the US Navy also revised their dive tables several years ago. The difference between all these tables is not much, and I see no reason on why each agency has to have their own. I've seen on many a dive boat, confused divers trying to decide which of their tables they will follow. Some divers want the more liberal ones, others the more restrictive, and of course the divers that say that my agency is better than yours want only their agency's table.
The question goes back as to "Why can't the different dive agencies agree on a standarized table?" I think that the agencies would take a major step forward by doing this. Imagine them actually putting aside their differences for the goal of the recreational diver. Myself, I like to use a conservative approach when using the dive tables.
One last thing, WOW how refreshing to get positive feedback on my question from everyone here!!

 

[Dr Deco]

Dear Blueabyss:

Different Tables

Some tables are genuine, valid changes to a previous table system. The RDP was a change in the repetitive dive gas washout from the US Navy’s 120-minute compartment to the 60-minute compartment. This concept was more suitable to recreational diving. Remember that these tables are only “road maps” of the pressure in the compartments. They do not “allow” of “forbid” anything – Nature does that. They are solely for bookkeeping purposes to allow the diver to keep track of the inert gas according to some plan. Whether this “plan” is physically and physiologically correct is often debated .

U S Navy Tables

A few years ago, some U S Navy scientists developed a set of dive tables based on the probability of getting DCS. As I understand it, some cases might need a faster ascent (wartime) and there could be a willingness to sacrifice some safety with respect to “the bends” to avoid being shot on the beach. To this end, they developed tables based on probability, that is, the longer the bottom time (or shorter the decompression) the greater the risk of DCS. Some situations might warrant a trade off. Users of the tables (the fleet) did not care for the final product (as I understand the story) and it was not adopted.

{Weathersby PK, et al. Predicting the time of occurrence of decompression sickness. J Appl Physiol 1992 Apr;72(4):1541-8

Thalmann ED, et al. Improved probabilistic decompression model risk predictions using linear-exponential kinetics. Undersea Hyperb Med. 1997 Winter;24(4):255-74.}

“Bends/No bends” Limits

Observant readers of this FORUM will note that the US Navy “statistical” method does not indicate that bends is an “all or nothing” event. Rather, as the dose of nitrogen increases in your body, the probability of getting DCS increases. In addition, the seriousness of the DCS incident will [probably] increase.

“Me Too”

Some tables are what are known in the commercial world as “me too” products. Tables, or whatever, come out so that everyone can say that they have one, too.

Tables are somewhat like physical training methods. It depends quite a bit on the desired goal as to what you wish to do. Thus, strength train differences fro cardiovascular, from endurance, from weight loss, etc. Many of the NDLs were chosen with the final goal in mind (commercial or military) and such things as work load, diver fitness, availability of a chamber for repress, etc.

Repetitive Dives

There are other systems for repetitive dives than the “Repetitive Group letter.” If you wish to use another method, another table is needed. They are only road maps and do not actually model all the gas in you tissues – just an approximation. However, you cannot mix the systems together. That would be like attaching two road maps with different scales together and just moving your finger over the joint to the next road. They almost assuredly would not match!:bonk:

Decompression Tables

These are a different breed of cat. Decompression is a completely separate entity from variations on NDLs.

Dr Deco :doctor:

 

[Epinephelus]

blueabysss once bubbled...
The question goes back as to "Why can't the different dive agencies agree on a standarized table?"

You ask the question...
and then you answer it yourself

Myself, I like to use a conservative approach when using the dive tables.

The fact that you have a preference, and I have a preference, and George Irvine has a preference means that most likely, using the best research available, each of us would come up with a slightly different table based on the things we each feel are the most important.
It all boils down to "you want fries with that?"
Some do, some don't.
Who decides?
As for me, I want and enjoy the freedom of reading up on all the different theories and making up my own mind. That is to say, a single set of standardized tables would be just fine with me so long as I'm the one deciding what they are.
E. itajara

 

[BRW]

Whew, jumping in this long list of table
posts, just want to update you on NAUI RGBM
Tables, tested and released months ago.

First, they are based and derived from dual
phase mechanics. The recreational versions
are no-group, no-calc, no-fuss syntheses for
air, EAN32, and EAN36, sea-level to 10,000 ft
elevation. A tec set will be released shortly,
about 500 pages, for air, ranged trimix, heliox,
and nitrox for tec diving/training at sea level.
And for both OC and RB (constant ppO2) diving,
and with and without pure O2 switches at 20 fsw.

Both rec and tec tables have been in testing for
the past 4 years in the water. We may have tec
Tables at the NAUI Tec Deep Stops and Deco Wkshp
in Tampa on Feb 20.

Plus a comment that you have heard from many
others these days (and even 25 yrs ago but
muffled in the fog) can be summarized succintly.

On Tables up to RGBM (and some VPM never
released nor tested), all go back to Haldane
some 94 yrs ago, don't extrapolate outside fitted
data points, require excessive(unnecessary)deco,
include only 1/2 of the (gross) phase
physics, and treat bubbles in the shallow zone
instead of minimizing growth. These shortcomings
are best ameliorated by correct coarse grain
Table deco models, but can be addressed with ad
hoc field procedures. And have been.

Getting off the pulpit, best regards to all,

ut:

 

[blueabysss]

Doc,
I don't mean to put you on the spot, but i am,lol. Which 2 dive tables do you like the most for recreational diving? :boom:

 

[Dr Deco]

Dear blueabyss:

Obfuscation – Who, me? :mean:

Don’t get me wrong and believe that scientists will always engage in sesquipedalian tergiversations, obfuscations, circumlocutions, and tautologies, but…..

Tables for Recreational Diving

I personally do not have a favorite table. Having been the head of the test program for the Recreational Dive Planner from PADI, I am aware that these tables are safe under the conditions tested. This would also be true of similar tables. These tables are all far from the limits where decompression gas phase formation would occur under usual dive conditions. We had about 1200 manned-dives in that program and most divers displayed no Doppler-detectable decompression bubbles at all. This would be true of similar tables.

Additionally, these tables were tested to their limits with respect to time at bottom. Most divers do not follow such a dive plan. The tables are always “pegged” a bit because of this. Because dive computers monitor the exact profile, the calculated gas loads are always to the “model limits.”

”Under the Conditions Tested”

This is an important aspect. Prior to my studies at NASA regarding the influence of workloads during decompression, there was little but anecdotal information on this subject. We are very careful to test all decompression procedures with the workloads that would be actually encountered during decompression by EVA (“space walking”) astronauts.

If someone were to ask me how to convert a safe table into an unsafe one, I would answer that you simply increase the strenuous exercise on the surface. We know from experiments conducted over the past ten years that this would definitely increase the number of Doppler bubbles and the fraction of individuals getting DCS. This is not theoretical, it is observable in a test program.

You can control the amount of strenuous exercise that you perform on the surface, you can control whether you perform Valsalva-like maneuvers on the surface. One does not need a modified table or an expensive meter to watch this aspect.

Dr Deco :doctor:

 

[Sparky1]

As you know, the Navy delveloped these tables (or at least revised them) to take diving to the edge of the envelope. During the experimental stages, divers would be dropped to a depth and then be brought up to evaluate the nitrogen levels in there blood. It is far more detailed than that, but it gives you an idea as to how the navy tables were set.

The various agencys adapted the navy tables and for the purpose of not taking recreational divers to the limits, they set forth in their own version a more conservative time frame to prevent divers from being bent. Regardless of agency, they all decided and set 130' as a maximum recreational depth limit. The tables will vary in pressure groups and maximum allowable times for a given depth and all will claim to be safer. Every agengcy tells you to take a "SAFETY" stop rather than a deco stop. Should one decide to investigate and persue a more technical form of diving, then the tables will change and a more regimental assent will be required.

Keep blowing bubbles!!
Steve:boxing: