PADI Divemaster vs TDI Extended Range

[Rhone Man]

For my earthly sins I decided to refresh my PADI Divemaster qualification the other day, for which I had to resit all the exams.

In the physiology section, the exam has two separate questions broadly along the lines of: what do you do if you accidentally overstay the NDL and then surface? I was just about smart enough to realise that, this being PADI, the answer is always going to be "For God's sake don't get back in the water!" But it did immediately strike me that this is very much the opposite of what they teach you on the TDI Extended Range course; where so long as you can get back down in less than 3 minutes, you can multiply out your stops and complete your decomopression.

I am not sure if this is a question or a comment, but it grates on me slightly have two such opposite viewpoints in circulation. Does anyone know what PADI teaches on missed decompression at the tec level? Do they change their stance, or stick with the "stay dry" approach?

[ucfdiver]

If I ever "accidentally" overstayed NDL, and "accidentally" surfaced before I was clear, I would give up diving period, as that would be a good sign I'm too stupid to dive. I can however, see where factors beyond your control force you to surface before completing deco, and what to do after that I think would be an interesting conversation to hear everyone's views.

No idea what PADI teaches, but I was taught that in water re compression is a near last resort. If I skipped a few minutes of deco I'd probly avoid repetitive dives and just stay on dry land, then go to the chamber if needed.

My logic is that Dan says DCS can have the following symptoms-
- Paralysis, muscle weakness
- Confusion, personality changes, bizarre behavior
- Amnesia, tremors
- Staggering
- Coughing up bloody, frothy sputum
- Collapse or unconsciousness

I'd much rather find out I had these on dry land than attempting to restart deco. I'm curious to hear what others think.

[Blackwood]

^^ lol

Maybe the word "accidentally" isn't the best choice.

How's about "the situation causes you to surface without completing a decompression obligation."

That way the question covers things like injury, medical issues, flooded suits in extremely cold water, dangerous conditions, etc..

[ucfdiver]

^^ lol

Maybe the word "accidentally" isn't the best choice.

How's about "the situation causes you to surface without completing a decompression obligation."

That way the question covers things like injury, medical issues, flooded suits in extremely cold water, dangerous conditions, etc..
I guess I was editing my post to include that as you were making yours :)

I think it's got to be a judgment call based off of how severe it is, and how close a chamber is. I've heard of people vomiting multiple times in the chamber, and falling flatt on their a$$ within minutes of surfacing due to DCS. I think it would have to be an extreme situation for me to get back in the water. If you look in the thread I'll post below, you'll see however, that some have successfully treated minor cases that I would have taken a chamber ride over, so it's certainly a judgment call. I have a feeling if I lived in a remote area that doesn't have a chamber nearby, I'd be more likely to use this method.

My cavern instructor actually discussed how it's done, and made it seem as if that's the "thing to do" if you overstay NDL or deco time.....scary thing is that he never once mentioned the risks of doing so :confused:

Here's an interesting thread on it that does what I'd consider a good job of showing the risk and benefits-
http://www.direxplorers.com/dir-decompression-forum/5915-oh-dear-youre-bent-long-way-home-iwr-anyone.html

As always, the rubicon is a good source. There was a link on tds posted a while back about this with lots of resources.

Edit-- Found it!
http://rubicon-foundation.org/IWR.html

[Blackwood]

That'll teach me to use the ^^ instead of [quote] :P


However: agreed, it should be situational.

If you know you missed a little deco but are asymptomatic and have the ability to go back and either pay time-and-a-half or whatever your omitted deco methodology (http://www.ndc.noaa.gov/pdfs/USNDeco3.pdf) calls for, go for it.

If you're suffering a major type 2 hit in a distant location hours away from a chamber, and if the team/dive-op/support crew/whatever is equipped (know-how, manpower and gear) to support In Water Recompression (http://en.wikipedia.org/wiki/In-water_recompression#In-Water_Recompression_Tables), go for it.

But if you bend yourself while diving off e.g. Catalina, get on Oxygen and - if needed - to the chamber (it's right there).



Of course, we're not really answering Rhone Man's question. I'm not sure how many DSAT trained divers are on these boards.

[muddiver]

It seems to me that PADI (and a number of other basic SCUBA cert agencies) use the "stay dry" approach for the reasons mentioned above that could cause a drownding incident. If my memory serves me correctely, even the U.S.N. Diving Manual reccomends that in water deco after surfacing to be a last resort treatment for DCS. In my opinion, returning to the water to complete your stop/deco is just a continuation of the dive, unless you exceed the :10 surface interval rule for repet dives. Staying out because you missed your stop seems a bit too much on the conservitive side.

[Blackwood]

Staying out because you missed your stop seems a bit too much on the conservitive side.

You also have to listen to your body.

This is an extreme hypothetical, but if, say, I know I'm bent on the way up at say 100 feet, I'm not going back down to do some stops that will likely be ineffective. Rather, I'm sucking down Oxygen and getting to a 165' chamber ASAP. But if I have a little twinge in my elbow upon surfacing, sure I'll get back in the water.


For more good reading, here's the USN Dive Manual chapter on Hyperbaric Therapy (http://www.coralspringsscuba.com/usn/Chap21.pdf).

[DA Aquamaster]

It was pretty routine in both military and commercial diving to decompress to the 40' stop, then pull the diver to the surface and blow them back down to 40' within 5 minutes to complete the stops.

The difference of course is treating "missed" stops in water versus in a chamber.

What PADI used to teach way back in the day (mid 1980's) was that if you got back under water in less than 5 minutes and were symptom free that in water deco for omiited deco was acceptable. The idea was then to spend 1/4 of the 10' stop at 40', 1/3 of the 10' stop at 30 ft, 1/2 the 10' stop at 20' and then 1 1/2 times the 10 ft stop at 10'. This was based on the US Navy ommitted deco procedures of the time. The US Navy still has a similar propotcol although it has been updated to use 100% O2.

Practically speaking, if you missed deco on a square profile on US Navy tables tables you have probably missed a lot more offgassing than if you miss a 10' or 20' stop on most of today's current tables as quite frankly many of those "deco" schedules would be considered "no deco" dives on the much less conservative US Navy tables.

That difference in conservatism between the US Navy tables and various newer tables has I think skewed the perception of the value of going back down for an ommitted deco procedure versus just staying on the boat, sucking O2 and hydrating. Obviously if the profile would still leave you within the US Navy limits, the odds of a hit are still fairly low - less than 1% on a single dive and less than about 4-5% on a repetitive deco dive - and lower still with administration of O2.

In most places I dive, a chamber is still several hours away and if I miss significant deco (well outside the US Navy table limits) and have the option of in water recompression versus being bent for several hours while I am evacuated to a chamber I'd opt for in water recompression if the alternative is a near certain DCI hit with several hours passing before treatment can start.

[rjack321]

For a type 1 hit I am almost certainly getting back in the water - if I have enough of a suitable gas. I have done it once, wasn't a huge deal and definitely fixed the issue. My SI was about 90mins so I would put this into the IWR category more than the omitted category - we hadn't missed any stops, my buddy did the same profile and was fine. The nearest chamber was 3-7 hours away.

For a type 2 hit I am almost assuredly not getting back into the water.

Somewhere in between will depend on how far I am from EMS to stabilize me and a chamber to treat me. For a really serious hit you may very well die on O2 before you can get treated, so keep that in mind as you develop your personal decision tree. Getting back down before your symptoms progress maybe your only chance of survival.


Rich Pyle has a few good papers out there discussing how even using air for IWR people rarely got worse. IWR being a bit of a drawn out version of omitted deco. The concept that you will on-gas sooooo much more and make the DCS worse is a bit of a fallacy. They are on Rubicon.

[hobodiver]

The Navy and Commercial divers also have the benefit of FFM/Helmets and endless supplies of gas.

Personally, I wouldn't rule out in water recompression, but it would depend on how much of a deco obligation I had, and how close to the nearest chamber.

[Thalassamania]

IWR is NOT a "drawn out version of omitted deco."

Omitted deco is a non-symptomatic diver returning to the water and using an enhanced deco schedule to get back to the surface.

IWR is a symptomatic diver returning to the water and using an treatment table to get back to the surface.

[rjack321]

IWR is NOT a "drawn out version of omitted deco."

Omitted deco is a non-symptomatic diver returning to the water and using an enhanced deco schedule to get back to the surface.

IWR is a symptomatic diver returning to the water and using an treatment table to get back to the surface.

Maybe in your mind. To me, they are merely symantic distinctions between how long you have been out of the water and how symptomatic you are. Both use more deco than might have originally been called for. Omitted is typically 1.5x the original while IWR may or may not use an official "treatment table". In many cases the latter is not occuring with medical direction and the gases and equipment needed to follow one of the few official IWR table are not available. Yet it is attempted anyway, go figure.

[dab]

I am not sure if this is a question or a comment, but it grates on me slightly have two such opposite viewpoints in circulation.

I think one has to keep in mind the target audience. PADI is teaching the recreational diver who may likely have a limited amount of gas remaining, in a single tank, and little or no understanding of decompression theory. TDI is teaching a Technical Diver and the diver likely is diving a set of doubles, with some remaining gas reserve and a basic understanding of decompression theory.

[Thalassamania]

Maybe in your mind. To me, they are merely symantic distinctions between how long you have been out of the water and how symptomatic you are. Both use more deco than might have originally been called for. Omitted is typically 1.5x the original while IWR may or may not use an official "treatment table". In many cases the latter is not occuring with medical direction and the gases and equipment needed to follow one of the few official IWR table are not available. Yet it is attempted anyway, go figure.Not in my mind, that's the specification of the those who developed the tables. Symptomatic vs asymptomatic are not semantic distinctions, they are specific observations of a patient's condition. If anyone has trouble telling the difference I recommend that they take a field neurological exam course. Recompression, in-water or in a chamber, without a specific treatment table and plan is, at least to my way of thinking, pretty sketchy.

[rjack321]

Not in my mind, that's the specification of the those who developed the tables. Symptomatic vs asymptomatic are not semantic distinctions, they are specific observations of a patient's condition. If anyone has trouble telling the difference I recommend that they take a field neurological exam course. Recompression, in-water or in a chamber, without a specific treatment table and plan is, at least to my way of thinking, pretty sketchy.

I know the field neuro exam. But that only addresses certain types of symptoms. In the case of omitted deco people can progress to symptomatic in short order or even after redescent (although its less unlikely). Symptoms can also be confused with other conditions (e.g. hypothermia) and even under the best controlled conditions its often difficult for a hyperbaric physician to decide whether a symptom is due to DCS or something else.

IWR itself has been developed by trial and error and there are very few IWR treatment tables. Some being too complicated or risky for the equipment or conditions at hand. The fact is that many documented patients of IWR did it successfully with minimal understanding of deco and without even using oxygen nevermind following a published protocol. (which may have helped them avoid O2 toxicity)


It is also interesting (and somewhat disturbing) to note that
none of the divers included in this survey were aware of
published methods of IWR (i.e. all were ÅØinging it?
inventing the procedure for themselves as they went along)
and all had used only air as a breathing gas.
pg 157 from: Rubicon Research Repository: Item 123456789/6083 (http://archive.rubicon-foundation.org/6083)

So for all practical purposes someone omitting deco and presenting with mild symptoms is likely to be better off redoing a bunch of deco either per an established "omitted" protocol or per an IWR treatment table isn't particularly important. Very few patients get worse by trying.

Obviously you need to be smart about it and not use 100% O2 at a PPO2 of 2 for an hour without a FFM, etc.

[muddiver]

You know, if you had bothered to read the original question posted you would not be making an a** of yourself going off on a tangent about treatment protocals and IWR.

--Diver off bottom.

[Thalassamania]

I know the field neuro exam. But that only addresses certain types of symptoms. In the case of omitted deco people can progress to symptomatic in short order or even after redescent (although its less unlikely). Symptoms can also be confused with other conditions (e.g. hypothermia) and even under the best controlled conditions its often difficult for a hyperbaric physician to decide whether a symptom is due to DCS or something else.

Then you know what symptoms are, that's the first decision point and you proceed from there. If someone is on the omitted deco path and becomes symptomatic then they must be shifted to a treatment path.


IWR itself has been developed by trial and error and there are very few IWR treatment tables. Some being too complicated or risky for the equipment or conditions at hand. The fact is that many documented patients of IWR did it successfully with minimal understanding of deco and without even using oxygen nevermind following a published protocol. (which may have helped them avoid O2 toxicity)

pg 157 from: Rubicon Research Repository: Item 123456789/6083 (http://archive.rubicon-foundation.org/6083)

So for all practical purposes someone omitting deco and presenting with mild symptoms is likely to be better off redoing a bunch of deco either per an established "omitted" protocol or per an IWR treatment table isn't particularly important. Very few patients get worse by trying.

Obviously you need to be smart about it and not use 100% O2 at a PPO2 of 2 for an hour without a FFM, etc.IWR was not "Developed" developed by trial and error, it was "MacGyvered" repeatedly by people who got themselves into bad spots and had no other hope of a way out.

Treatment tables are treatment tables regardless ot the compression source. As far as the choice between redoing a bunch of deco and adopting an IWR protocol ... those are radically different approaches and call for dramatically different levels of equipment support.

I am not opposed to IWR, not by any stretch. I reviewed Rich's article for aquaCorps before it was published and I have provisioned National Science Foundation Research Vessels for IWR.

My real point is the Omitted Deco is a routine problem that is handled with a routine solution but that can progress to DCS, while IWR is an emergency solution to a potentially life threatening medical issue, DCS, that is best handled by proper planning and practice.

Sorry for the tangent, I just thought clarification was critical. Here's my bashful :mooner:ss. :D

[rjack321]

You know, if you had bothered to read the original question posted you would not be making an a** of yourself going off on a tangent about treatment protocals and IWR.

--Diver off bottom.

Well I imagine that omitted deco is discussed by many instructors for different agencies. Whereas IWR is not, or rarely is. DSAT being an arm of PADI probably has a fairly scripted "book" answer (to both) that I would be curious to know. However nobody here has coughed it up, maybe its one of the few discretionary areas of their program.

[muddiver]

I would be interested to know as well if any programs, including PADI/DSAT, provide any IWR guidelines. I usually dive using the U.S.N. tables because they offer the flexability to switch to the Std. Air Tables when I get close to or blow the No "D" tables. Therfore I would have the option of a IWR, if I had the gas, the surface support, warm water, etc.

[Thalassamania]

I would be interested to know as well if any programs, including PADI/DSAT, provide any IWR guidelines. I usually dive using the U.S.N. tables because they offer the flexability to switch to the Std. Air Tables when I get close to or blow the No "D" tables. Therfore I would have the option of a IWR, if I had the gas, the surface support, warm water, etc.Me too, or I use my ancient EDGE or SKINNYDIPPER computers that are Navy based so I can calculate a usefull repetitive dive group.

[Rhone Man]

Decent article on IWR on Wikipedia: In-water recompression - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/In-water_recompression)

The original question was posed on the basis of being asymptomatic and being able to get right back down again (good example in Gary Gentile's book on the Andrea Doria when he and Tom Packer had to do exactly that on a blown dive profile).

[rjack321]

The original question was posed on the basis of being asymptomatic and being able to get right back down again (good example in Gary Gentile's book on the Andrea Doria when he and Tom Packer had to do exactly that on a blown dive profile).

Are you looking for the DSAT omitted deco recommendation?
Any agency?
Or common sense? :D

[boulderjohn]

Thre is a sure fire procedure to finding the actual answer to this question.

1. Pick up your RDP.
2. Turn it over.
3. Read the third paragraph in the first column, the one titled Emergency Decompression.

[boulderjohn]

Explanation:

TDI Extended Range, Deompression Procedures, etc. are classes in which decompression stops are part of the normal procedures. They teach you how to adjust those stops should you overstay your welcome. All its planning assumes you are doing decompression stops from the start.

The PADI RDP is strictly no decompression in its design. Since it includes no decompression stops to begin with, it can't tell you how to adjust them. It can't put you "back on the grid" unless it truly clears you out.

When Spencer, et al did their research to determine the controlling compartment for no decompression diving, they determined that for just about all the dive profiles possible within the range of those tables, the 40 minute compartment controlled the dive. In order to add a conservative measure, they based the tables on the 60 minute compartment.

If you exceed the RDP NDL's, then slower compartments will be controlling your dive, and the RDP is not equipped to handle that.

Thus, if you overstay the NDL's by a brief amount, they require a pretty conservative deco stop followed by a 6 hour surface interval, with 6 hour chosen because it washes out the 60 minute compartment.

If you stay longer, then you get an even more conservative deco stop, followed by a 24 hour SI, which washes out even a 240 minute compartment. By golly, unless you have really gone off the table, your tissues should be in good shape by then.

That is a very conservative approach to decompression. The message I get from it is that if I want to do decompression diving, I should be using a decompression algorithm, and not one that is designed purely for recreational diving.

[Rhone Man]

Thanks, Boulderjohn, and whilst I appreciate all that, it still comes back to this for me: if you miss mandatory decompression, PADI are telling you that it is safer to stay on the boat, and TDI are saying that if you can do it quickly, it is safer to go back down. They cannot both be right if they both express it to be a general rule.

I don't think the fact that the RDP calculates surface intervals on a 60 minute compartment affects anything other than length of surface interval. If I find myself at the surface with my computer blaring that I missed a mandatory deco stop (planned or unplanned), the decision as to what to do next will not be based upon which tables I used to plan the dive.

[boulderjohn]

PADI's emergency decompression methods require extended stops as well as longer surface intervals.

Controlling compartments also determine stops. The purpose of a an ascent profile, whether it is based on an ascent rate alone or an ascent rate plus deco stops, is to prevent the controlling compartment(s) from exceeding its (their) M-value(s). The ascent profile in the RDP assumes that the controlling compartment (60 minute) will safely off gas on ascent. It further assumes that the slower compartments will not raech their M-values during ascent because they did not get close enough to saturation on the dive itself. If the NDL is exceeded, then there is an assumption that a slower compartment will reach its M-value limit on ascent and thus require a different ascent profile. Thuis will allow the slower compartment to off gas before leaving the water.

BTW, I am not extolling the PADI emergency decompression system. I am just explaining it. I am also TDI trained.

[Blackwood]

Does anyone know what PADI teaches on missed decompression at the tec level? Do they change their stance, or stick with the "stay dry" approach?


Thre is a sure fire procedure to finding the actual answer to this question.

1. Pick up your RDP.
2. Turn it over.
3. Read the third paragraph in the first column, the one titled Emergency Decompression.

PADI teaches its "DSAT Tec" courses using the RDP?

[Peter Guy]

If I find myself at the surface with my computer blaring that I missed a mandatory deco stop (planned or unplanned), the decision as to what to do next will not be based upon which tables I used to plan the dive. Is this perhaps a sign of the "Measure with a micrometer, mark with chalk and cut with an ax" problem with decompression "science?" Exactly how "mandatory" IS a "mandatory deco stop" for any particular dive?

And yes, I'd love to hear from a DSAT instructor on this issue -- any of them out here in ScubaBoard Land?

[boulderjohn]

PADI teaches its "DSAT Tec" courses using the RDP?

I believe I misread the purpose of the question--thanks for pointing it out. I was reading it as a question about the divemaster certification, which is fully recreational.

[rjack321]

Thanks, Boulderjohn, and whilst I appreciate all that, it still comes back to this for me: if you miss mandatory decompression, PADI are telling you that it is safer to stay on the boat, and TDI are saying that if you can do it quickly, it is safer to go back down. They cannot both be right if they both express it to be a general rule.

I don't think the fact that the RDP calculates surface intervals on a 60 minute compartment affects anything other than length of surface interval. If I find myself at the surface with my computer blaring that I missed a mandatory deco stop (planned or unplanned), the decision as to what to do next will not be based upon which tables I used to plan the dive.

Ummm yes they can both be right. You seem to be missing the audience here.

If you miss a few minutes of deco on the RDP you are probably not even going to be bent. Stay on the boat, go on O2, watch for symptoms. Its hard to miss more deco than that as a recreational diver since you should have been on a recreational plan if you were using the RDP. A recreational plan which has run over on time or depth is highly unlikely to have enough gas to complete omitted deco (often expressed as 1.5x the original deco time). Why would you carry enough gas for a tech dive on your recreational dives? Why would you use the RDP to plan deco dives? The deco shown is merely there as a contingency if gas supplies allow. You'll notice its truncated at about 15mins - cause the RDP was never intended as a deco planning tool. Even if you skipped the maximum deco the RDP is guessing at, you are still better off on surface O2 and watching for symptoms since you are assumed to have neither sufficient quantities of backgas nor a deco gas when diving a recreational RDP plan. If you brought all that stuff you are using the wrong tools to plan deco dives. Slightly bent on the boat is fixable, drowned due to OOA is not.

If you plan a deco dive with your TDI training you may miss 5 mins of deco. Or you could miss 50 minutes. If you are asymptomatic and otherwise have the gas and there are no hurricanes on the horizon of course you can go back down and do an omitted deco schedule since you brought enough gas and thermal protection to stay in the water at least this long. If you are symptomatic you still have the option of going back down (which maybe the best option). You planned for a tech dive, you get to chose what to do.

[sweatfrog]

With DSAT, if you omit decompression from deeper than 20 feet, return to the first stop depth as quickly as possible (ideally less than five minutes) and decompress according to schedule up to and including the 40 foot stop. Extend the 30 foot stop and all shallower stops by 1.5 times their scheduled times.

For more information look into getting the Tec Deep Diver Manual.