Descend to Decompress???

[DevonDiver]

Can I state again... as my earlier post seems to have been overlooked... In-Water Re-compression is not the same as De-compression.

Let's not drive the thread off-topic because some basic terminology isn't understood. The OP asked a pertinent question about the validity of re-descending to depth, so as to increase safety following a significantly rapid ascent.

It'd be nice to have some commentary upon that actual question.

Not all the agencies. I think in the TDI manuals it says that if you break your ceiling, but you are able to re-descend within about 3 minutes (I think, would have to look it up) you should do that rather than immediately seeking emergency treatment.

Missed Deco procedures are pretty standard across the agencies. Of course... you have to be training at a level that involves doing deco, before you learn how to act when missing deco. Thus, recreational divers won't hear of it on no-deco courses.

The process of re-descending does require a schedule of existing stops. For the recreational diver, who has no stops, there remains the valid question of where exactly they should re-descend to... if they miss their 'deco' via rapid ascent.

I will do it if the condition is serious. What is the alternative?
A full face mask would be an added bonus but it is not a standard equipment on liveaboard or dive operator.

Of course you would champion

 

[boulderjohn]

Because everyone seems to be ignoring it, I am gonig to emphasize Andy's point:

We are not talking about In-water recompression in this case!

He accurately described the difference above. People reading this thread in the hope of getting information are getting some very inaccurate advice in some of the posts.

 

[Wookie]

Can I state again... as my earlier post seems to have been overlooked... In-Water Re-compression is not the same as De-compression.

Let's not drive the thread off-topic because some basic terminology isn't understood. The OP asked a pertinent question about the validity of re-descending to depth, so as to increase safety following a significantly rapid ascent.

It'd be nice to have some commentary upon that actual question.



Missed Deco procedures are pretty standard across the agencies. Of course... you have to be training at a level that involves doing deco, before you learn how to act when missing deco. Thus, recreational divers won't hear of it on no-deco courses.

The process of re-descending does require a schedule of existing stops. For the recreational diver, who has no stops, there remains the valid question of where exactly they should re-descend to... if they miss their 'deco' via rapid ascent.



Of course you would champion

Because everyone seems to be ignoring it, I am gonig to emphasize Andy's point:

We are not talking about In-water recompression in this case!

He accurately described the difference above. People reading this thread in the hope of getting information are getting some very inaccurate advice in some of the posts.

Hello... You guys are moderators.... If you don't like the way the convo is going, you have the power of the electron. The original question was answered by many folks, all seemingly agreeing before the topic turned to IWR. Seems like it would be kind of easy to split the thread....

 

[tridacna]

This is an oldie but excellent response.

http://www.scubaboard.com/forums/ask-dr-decompression/1732-water-recompression-w-dci.html#post14833

 

[boulderjohn]

Hello... You guys are moderators.... If you don't like the way the convo is going, you have the power of the electron. The original question was answered by many folks, all seemingly agreeing before the topic turned to IWR. Seems like it would be kind of easy to split the thread....

The conversation turned to IWR on post #3 when the person posting incorrectly called it IWR. After that, a lot of people also incorrectly called it IWR and started talking about why you should or should not do IWR. Clearly some of the people posting are confused about the difference. That suggests that a lot of readers will also be confused about the difference. One procedure is considered routine by a number of agencies and is even advised in at least some instructions on popular computers, as we learned in another thread this weekend; the other is considered an extreme procedure by just about everyone. People should know the difference.

 

[Wookie]

I am sure this has been covered on here before but I couldn't seem to find it, I was sitting back thinking about if for some crazy reason you shot up from the bottom and you were fairly deep and had been down close to your time limit at certain depth. I was wondering what the consequences would be of going back down and starting your offgassing or decompressing at a depth a little above your average depth for the majority of the bottom time? Now, while I was thinking about all of this I came up with a couple different "answers" in my head, both of which could be completely inaccurate which is why I wanted to come to the forum. My first thought was that if you were diving air you would more than likely end up loading more nitrogen and possibly make a rough situation worse....... maybe you wouldn't have enough bottle to even touch the required obligation, I don't know... hopefully someone can chime in here on this! My second thought brought me to the idea that if you had been diving air for your dive but had a nitrox bottle onboard with you and switched out and went back down, you could go down to a safe depth for your mix and start the decompression there and work your way up from there making a few stops every 5 - 10ft with the extra oxygen. Would this help your situation or still make it worse? Obviously, the overall best option is to get to a chamber as quick as you can, but in this thought I was having, the situation had you a long way from a chamber....

Anyway guys, Im sure with this question you can tell that I don't know a whole lot about decompression theory or if that even applies to my question. Any added input would help give me one less thing for my mind to wander and think about before I go to sleep hahah

So thank you guys and Hope to get some decent answers!

OK, Blaine, so, disregarding all of the IWR answers we've given you, the short answer is, if I were in the situation you described (recreational dive, close to an NDL but not in deco, and an excessive ascent rate), I'd not get back into the water as I don't think it's necessary. I'd wait on the surface and self-assess and be assessed by a knowledgeable person for signs and symptoms of DCI. If you had plenty of O2, you might use it just because it never hurts to have a little O2 in ya, but I wouldn't use it if the supply were limited and you still had divers in the water or dives left to complete. If you waited a significant surface interval and no signs or symptoms occurred, I'd get in for another dive. I'd certainly take it easy on the second dive, and stay well away from my NDL's. If I were in a liveaboard situation and my tissues were very saturated, I'd think about sitting out for a extended surface interval, as long as 12 hours. As far as getting into the water and safety stopping on air after you've shot to the surface, it's allowed by the procedure of some training agencies, but my feeling is that the value is minimal. In recreational diving, depth adds nitrogen. You aren't helping yourself by getting back in to "compress the bubbles" because it just isn't necessary.

You might learn to "Flare" on ascent. A flared diver who properly practices the technique will rarely ascent faster than 60 FPM unless they have really bad luck (dropped weight belt with a stuck open drysuit inflater and a full tech wing), but that would be 3 mistakes piled on top of each other. So rare as to defy computation.

 

[BlaineAtk]

Well, this topic, as I felt this may happen, has FAR surpassed my knowledge base BUT it has at least satisfied my curiosity. Basically, what I am gathering is that unless you were in a last ditch effort, the benefits would not really out weigh the risks.... I thank all of you guys for digging you brains for this though! I never anticipate that most anyone, including myself would ever need to do do any of this nor be in my hypothetical situation but I just kept wondering and I took my knowledge and went through a logical step process of what I thought would happen and I came up with my original post. Thanks for the answers!!!

 

[Sat Diver]

It's not a matter of "max depth was 100', so go back to 100'." Once the phase change occurs it does not work the same way in reverse. I'm currently taking Adv. Nitrox/Deco and somewhere in the course materials it discussed IWR, and I want to say the depth you would have to attain is something like in excess of 165'. I'm going from memory, so I could be off.

Please go through your course materials again ... there is no way this could be correct.

---------- Post added April 30th, 2012 at 04:27 PM ----------

Although this thread is not about in water recompression, a lot of the answers refer to it.
Just a quick note -
To attempt IWR on a symptomatic diver, you need logistical backup that will far exceed the capability of most recreational dives.
It is usually easier and safer to transport the diver to a chamber even from fairly isolated spots.
I have been recompressed underwater and have been a supervisor recompressing other divers.
These are 3 to 6 hour operations, with gas switches and underwater medical monitoring.
Divers are in helmets with full comm to surface as well as tender and attendant.
PPO2's in excess of 2.5 with air breaks.
I would not recommend this to be done any other way.

... now back to the thread.

 

[DevonDiver]

Hello... You guys are moderators.... If you don't like the way the convo is going, you have the power of the electron. The original question was answered by many folks, all seemingly agreeing before the topic turned to IWR. Seems like it would be kind of easy to split the thread....

We (mods) try not to moderate excessively, even when a thread is hijacked dramatically off-course. In this instance, the hijack was accidental, because a number of posters misunderstood some relatively basic terminology. I'm content, as this has been highlighted in the thread - so any casual viewers will understand the difference between IWR and Missed Deco/Fast Ascent procedures.

It's a shame that the original questions posed in the thread weren't explored more thoroughly - as I think they are far more relevant to the average diver, compared to the notion of a recreational diver conducting any form of ad-hoc IWR - it's especially a shame because starting a theoretical debate on IWR in its own thread only takes the click of a mouse button...it's even more especially a shame, because the board is awash with old IWR debates, but I've yet to see the notion of fast-ascent rectification (missed deco for 'rec') explored coherently.

I guess that many people weren't confident to discuss missed-deco/fast ascent theory, wheras Google gives them the power to speculate about IWR - a concept which 99% of divers will never need, nor witness in a diving lifetime..

 

[Wookie]

I guess that many people weren't confident to discuss missed-deco/fast ascent theory, wheras Google gives them the power to speculate about IWR - a concept which 99% of divers will never need, nor witness in a diving lifetime..

Nor would 99.9999% of divers (that number is a SWAG, BTW) ever need to take action in the Missed deco(safety stop)/fast ascent theory. I've seen the results a million times (or maybe a couple of thousand) and never been able to attribute any of the 200 or so cases of the bends I've seen during recreational diving to missed deco(safety stop)/fast ascent. Nor could I point my finger at a missed deco(safety stop)/fast ascent to a case of the bends. The point really is moot. There is never a reason (IMHO) to re-descent following a recreational dive unless the diver is symptomatic, and then there is not a reason to re-descend, treat the diver accordingly. Modern computers will not clear following a rapid ascent or surfacing in deco by descending. The only thing that clears the computer violation is time and/or battery removal. I do not recommend (I have my liability hat on here) battery removal.

So, in answering the OP's question, we find that there is never a reason to descend following a recreational dive. Unless you're ready to dive again.