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

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-dec...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

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 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, 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.

 

[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.