Source for Rec Dive Tables?

[lekrigbaum]

What is the source for the Recreational Dive Tables? Are the PADI, NAUI, SDI, etc tables all different or is there a common source for those tables? Thanks for any info.

[DevonDiver]

Most agencies utilise Doppler-Modified US Navy tables. You can get these via an online search, as they are 'open source'. PADI designed its own tables, which offer some benefits for shorter surface intervals and longer NDLs for repetitive dives.

[NetDoc]

There is no one single source, but most have their roots in the Navy Dive Tables.


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A common misconception is that PDCs (Personal Dive Computers) have their roots in the tables, which is simply not true. All tables and PDCs are based on algorithms derived from various decompression models. Some are more conservative than others.

[cudachaser]

Try this link: NOAA No Deco Air (http://www.ndc.noaa.gov/pdfs/NoDecoAirTable.pdf)

[TSandM]

All tables use a fairly similar mathematical underpinning. They assume the body is divided into "compartments", each of which loads and unloads nitrogen at a defined rate. They also make assumptions about the maximum nitrogen tension each compartment can tolerate before bubbling. Most models assume the compartments load and unload independently of one another, but I believe there is one that assumes that they load serially.

The reason the tables come up with different numbers is the differences in the number of compartments, the half-lives of the specific compartments they use, and the differences in the assumed maximum tensions. But the mechanics of the mathematics are essentially the same.

Tables of all flavors are subjected to some degree of validation, but the amount of validation varies.

A good book to read about all this is Mark Powells Deco for Divers, or Lippmann and Mitchell's Deeper into Diving. You can also find Erik Baker's papers, "Understanding M-values", and "Clearing up the Confusion about Deep Stops" in various locations on line.

[Mr Carcharodon]

The first modern diving table was developed by the Scottish physiologist J. S. Haldane and adopted by the Royal Navy in 1908. Haldane’s tables were used through the early 1960’s. Haldane developed his tables based on studies of animal subjects that were exposed to various pressures and times and then examined for signs of decompression illness. Based on these experimental trials Haldane developed a theory that decompression sickness could be avoided if dissolved gas pressure is keep to less than twice ambient pressure.

The work for the sixty or so years after Haldane were largely refinements of Haldane’s work. Refinements included adjustments for longer and deeper dives; collection of data on human subjects, and dive tables for gases other than air.

PADI and DSAT developed a new set of tables in the 1980’s to support recreational diving. The feeling at the time was that the US Navy tables were not conservative enough for the population of recreational divers. That was because the Navy tolerated a fairly high bends rate of 1-2%. They tolerated this rate in part because they had facilities to immediately treat bent divers. Also Navy divers were generally considered to be less predisposed to DCS because they were younger and fitter the general diving population. And working Navy dives had different depth/time profiles that were typical for recreational dives. DSAT reduced the allowable tissue pressures relative to the Navy tables and used a faster tissue compartment to control the dives. DSAT did extensive validation on their tables on human subjects in hyperbaric chambers and in the water. They also used Doppler bubble scores to assure consistency across different depth/time pairs. The DSAT tables have proven to be safe for the general diving population. So much so that DCS is a pretty rare cause of death in diving compared to drowning, embolism or cardiac events. Also I would be remiss if I did not point out that Michael Powell, “Dr. Deco” here on Scubaboard, was directly involved in the DSAT work.

NAUI published a set of tables in 2002 based on RGBM (reduced gradient bubble model). RGBM sets dive limits based on an assumed maximum tolerated number or volume of bubbles. RGBM arrives at a volume by integrating pressure gradient v. time with extra squiggles and jots thrown in for good measure. It is interesting to note that there is considerable overlap between RGBM and the Haldanian models in that in both cases pressure gradient is used as a control. But the bubble models (of which VPM is another) are more general and can be applied to more unique situations than the Haldanian models. Of course a lot of the generality is lost once the model is distilled enough to make a table.

Baker's papers at decompession.org are a good place to start. As is Haldane's 1908 paper at Rubicon Research.

[DaleC]

In the 1960-1970's the Canadian military developed their own set of tables (DCIEM) which are, I believe (could be corrected) based on the most comprehensive depth tested research to date. They are conservative and have a far less acceptable rate of DCS risk associated with them than say, the old US navy tables.
When using the US tables one has to keep in mind that there was (for navy divers) a fairly high acceptable rate of DCS as they had chambers on board their vessels for rapid treatment. That may not be the same risk an isolated diver would find acceptable.

[Hepcat62]

In the 1960-1970's the Canadian military developed their own set of tables (DCIEM) which are, I believe (could be corrected) based on the most comprehensive depth tested research to date. They are conservative and have a far less acceptable rate of DCS risk associated with them than say, the old US navy tables.
When using the US tables one has to keep in mind that there was (for navy divers) a fairly high acceptable rate of DCS as they had chambers on board their vessels for rapid treatment. That may not be the same risk an isolated diver would find acceptable.

Another thing to keep in mind is that most military-originating tables were cut with the average military diver in mind (and that's who they tested). You can read that as, "divers in excellent physical shape". My 30 year old civilian software engineer's body is going to decompress a bit differently than a 22 year old diver in combat-ready condition. :)

[scjoe]

I don’t know where the idea that the Navy has a 1-2% bend rate comes from.

According to a piece published around 2001 by Larry Taylor who was then the Dive Safety Coordinator at the University of Michigan, from 1990-1995 there were 382 reported cases of DCS in 648,488 dives logged by the Navy. He cited as his source of this information a US Naval Safety Center report published in 1997. If my math is correct that is a 0.06% accident rate.

In the hands of scientific divers, the rate is even lower. James Stewart was the dive safety officer at Scripps from 1960 to 1991. Scripps used the Navy Tables during that period. In writing about the use of the Navy Dive Tables, he once stated, “The Scripps program has over 200,000 cumulative dives since the early 1950s. We have had only a single case of decompression sickness.”

[Mr Carcharodon]

I don’t know where the idea that the Navy has a 1-2% bend rate comes from.



It comes from Workman's 1965 paper: CALCULATION OF DECOMPRESSION SCHEDULES FOR NITROGEN-OXYGEN AND HELIUM-OXYGEN DIVES, NAVY EXPERIMENTAL DIVING UNIT WASHINGTON D C
Workman, RD. Captain Workman was a medical officer assigned to the Navy Experimental Diving Unit. "Tolerated" 2% is a key, which is to say that was the expected bends rate for dives to the limits of those tables. If Scripps did lots of dives to 30 fsw and got no bends that is hardly surprising.

You can download it at Rubicon.

[TSandM]

My understanding is that the biggest reason for PADI's development of new tables was that the Navy tables, while liberal on the first dive, were extremely conservative for repetitive diving. This was based on a number of assumptions, including the choice of controlling compartment, and that the worst case was diving after a mandatory decompression dive.

PADI's tables were slightly more conservative on the initial dive, but far more liberal on repetitive dives. They used a different controlling compartment, and did not assume a dive beyond NDLs for the first dive.

I again highly recommend the books I mentioned. If you read them, you begin to realize how murky decompression is, and how far from revealed truth any tables or computer algorithms really are.

[scjoe]

Obviously in the millions of dives the US Navy has done, they have not treated 20,000 cases of decompression sickness. 2% at the extreme and limited number of dives that take place for NEDU purpose or deep search and recovery is a different thing and hardly comparable to the recreational use of Navy tables. Since you feel the Scripps folks are shallow divers, the following is the full quote from Stewart:

"The program at Scripps Institution of Oceanography has historically used the U.S. Navy tables.
I had the good fortune to know Bob Workman and to work with Ed Lamphier during the 1958 atomic tests in the Pacific. The tables had just been promulgated and we put them through just about every kind of repetitive dive profile one could dream up. There were four of us from Scripps and we had an eight man Navy team working with us. Our main task was implanting and retrieving tsunami recorders near blast sites, but during that three month period we logged over 1200 dives, to depths in excess of 190 fsw.
In the years following we conducted research dives to document the sand movement in the Cabo San Lucas and Los Frailes submarine canyons. On many dives we were on the extreme exposure tables and on many others the 190-foot repetitive dive table. These projects usually involved six of us, and were conducted for a three week period each six months, over a number of years.
The Scripps program has over 200,000 cumulative dives since the early 1950s. We have had only a single case of decompression sickness. It occurred during a multi-day, multi-dive kelp research cruise. Six people made the last dives, all on the same profile. Ironically, the person who hung off at ten feet for two minutes got hit. We find that use of the U.S. Navy tables is safe and adequate. Our university guidelines for diving safety state that "Any dive table used must be at least as safe as the U.S. Navy tables."

[Mr Carcharodon]

Workman reported a 2% bends rate. Scripps may have done lots of dives but if we do not know the details of the dives it does not shed much light on anything.

[DaleC]

I will try to recall where I read about the accepted DCS risk for navy divers and post a link if I do. I do remember it having to do with the fact that they had chambers on station that allowed for immediate recompression; thus the risk, while present theoretically when using the tables, was greatly mitigated in practice.

The DCIEM tables (IIRC) were generated by monitoring thousands of both wet and chamber dives and when DCS was indicated they rolled back the limits so that the final tables represent a lower DCS risk when applied against navy tables. However, like the navy tables, they are more liberal for the initial dive and more conservative for repetive ones than PADI tables. DCIEM researchers also created the first dive computers; both a top side model and a divable version.

[James S]

"They are conservative and have a far less acceptable rate of DCS risk associated with them than say, the old US navy tables."

If one is using the "old" tables they should know that the USN tables are updated periodically and in fact have been recently updated.

[DaleC]

Well, let's say at the same time the DCIEM tables were generated.
It's not a contest.

[gcbryan]

The devil is in the details in this subject matter as well. As I recall (reading) the Navy didn't have a lot of experience with repetitive dives because that's not generally what they did. They had enough bodies to do longer dives and to send someone new down if another dive was needed.

Sometimes various tables that appear to be far apart aren't really when you compare the underlying assumptions of the table. One may have short NDL's because a direct ascent at 60 fpm can be used while the other may assume a slower ascent with various stops or provisos to correct for age, cold water, or whatever. People don't always take that into account when comparing tables.

As was mentioned, there's a lot of voodoo involved as well:)

[Mr Carcharodon]

This is just speculation but some of the details driving DCS rates may be the availability and cost of treatment. If the Navy had decompression chambers on site and there was no direct cost to using them economics would suggest higher usage rates than in a civilian population that did not have have ready access to a chamber and had to pay for it if they did. Availability seems to drive the utilization rates for many treatments. Anyway I do not know if the Navy and Scripps kept score the same way if you will.

[lekrigbaum]

Well,that's kind of overwhelming. What I was hoping to find is a set of tables that would be freely usable in a web application. I guess I'm assuming that PADI, NAUI, SDI, et al, have the set of dive tables their organization uses copyrighted. ANother question along the same line is that if the users are required to be a certified diver, wouldn't that mean that they purchased a set of tables from their certifying authority during their initial training? If so, would they be entitled to use those tables obtained from a different source, i.e. - a web app that has a copy of those tables? Thanks.

[Kern]

Buy any set of tables you like & use them.

Find a set on the web, borrow from a friend, etc. I doubt the table copyright police will come after you.

Some tables are in the public domain, fell free.

Some web apps are free, some aren't, but some of those are still available for trial periods, with nag screens, reduced functionality, etc.

[Mr Carcharodon]

Oh you want a web based electronic table? There are none that I am aware of. You can get copies of several different tables on the web. Several are from government agencies (US Navy and NOAA) and do not have copyrights. As far as requirements to use certain tables there may be requirements for a given class but beyond that you can use what you find. As already noted there are differences based on the assumptions that were made when the tables were written.

[Cap335]

Both VPM and RGBM source code is on the web in fortran and Bruce Wienke has a book out on RGBM Buhlmann has 4 books out but you would only need the latest one.

[rjack321]

Well,that's kind of overwhelming. What I was hoping to find is a set of tables that would be freely usable in a web application. I guess I'm assuming that PADI, NAUI, SDI, et al, have the set of dive tables their organization uses copyrighted. ANother question along the same line is that if the users are required to be a certified diver, wouldn't that mean that they purchased a set of tables from their certifying authority during their initial training? If so, would they be entitled to use those tables obtained from a different source, i.e. - a web app that has a copy of those tables? Thanks.

What is your web app trying to do?

[Mr Carcharodon]

Both VPM and RGBM source code is on the web in fortran and Bruce Wienke has a book out on RGBM Buhlmann has 4 books out but you would only need the latest one.


Do you have a link for RGBM source code?

[lekrigbaum]

The app is an expansion of a phone app Ihad to access dive info. This calculates pressure groups, rnt, and so on. It was made for me but some buddies have been interested in it so I thought I'd dress it up a bit. I've adapted the PADI tables for my use, but I figured PADI would object to using them on the web since they get a cut. I figure that anyone who wants to use it would be okay as long as they own a set of tables, but someone brought up the point of using other tables. Also, it's not hard to make the app use any tables, it's just the pain of typing them in. The app is looking okay, but the issue of dive tables has been a headache for me.

[bvanant]

Do you have a link for RGBM source code?

I thought that Bruce was licensing the source for like $7500 but that was several years ago. I think you can get source for VPM but I haven't looked in a long time.
Bill

[Thalassamania]

PADI did their own, most of the other agencies just cut the US Navy tables back one step with no testing or real medical rationale.