In Water Recompression

[kdupreez]

So I thought I'd bring this discussion to the board.. I know its either a very frowned upon topic or a "keep it in my back pocket to save my butt someday" topic.

I have done extensive research on the topic and recently DAN published an article on this as well and this spurred a renewed interested and I was wondering what everyone on this forum's opinion was on IWR?

In short, my opinion is that when presented with a life or death situation, given that you are at some remote location, like 6-24 hours away from any chamber, then if you accept the risks involved, IWR in my opinion is a GREAT tool that could potentially save your life. (Of course with the "when applied correctly with all necessary precautions and support" disclaimer)

And then there is of course the biggest differing techniques, them being the "Hawaiian", "Australian" and "Pyle" schedules and I'm not entirely convinced one way or the other.. I guess if I had a full face mask and oodles of O2, the "Pyle" method would be preferred.

I Also think its something that should be brought up in discussions with higer levels of technical diving education as a means to educate and provide the full information, rather than let inexperienced people attempt half-assed IWR because they read the wikipedia article or DAN Magazine article and then jump into 60ft on O2 with no support.

What are your guys' opinions?

And lets try and keep this discussion civil - I know the "this topic will get inexperienced divers killed" debate and prefer not to go there.. I would just like to solicit your opinion and discussion around IWR in general and whether its something you would ever attempt, if given the right tools and situation..

Here is some starter background information on the topic if you know nothing about IWR.

Alert Diver Magazine (DAN) Article:
http://www.alertdiver.com/?articleno=486

Wikipedia IWR topic:
http://en.wikipedia.org/wiki/In-water_recompression

Richard Pyle and David Youngblood's take on IWR:
http://www.bishopmuseum.org/research/tr ... 7/iwr.html

Hawaiian University Paper / Sea Grant Library paper (referenced in Pyle's and Wikipedia article):
(Diving and decompression sickness treatment practices among Hawaii's diving fishermen)
http://nsgl.gso.uri.edu/hawau/hawaut86001.pdf

.

[Joshua Smith]

I've always figured that if the chamber was more than a couple hours away, and if I wasn't already seriously debilitated, I'd probably try IWR. But- not if it was going to delay getting to a real chamber.

[CaptnJack]

I am more than willing to get back in the water. May not 100% fix things but to reduce symptoms/damage at least. But I'm going to be strategic - not do something dumb and contribute additional gas loads.

I know for a fact that even at Cove2 you are a couple of hours away from a chamber. It takes VM forever to actually get you in there and recompressed on a weekend evening. So IMHO pretty much anywhere outside of the metropolis I would probably get back in the water for awhile. I have a few times and yes my somewhat vague "subclinical" symptoms improved.

I am not convinced there's a perfect shape or time for decompression, so I am unconvinced additional time in the water re-compressing is that hard of a science either. For long/distant trips I bring gas for contingencies. But getting back in the water and using up 20cf of leftover O2 at 20ft to mitigate the progression of symptoms would be my standard course of action if someone gets out from a tech dive feeling bad. If the suitable gas were available and the buddy situation was good, I would do the same after a recreational dive.

I would not exceed ppO2 of 1.6 or go nuts on the CNS limits as prescribed by many "official" methods. I think they are unnecessarily aggressive for the purpose of reducing gas loads, symptoms and tissue damage.

[ArcticDiver]

What is the approved protocol for a missed Safety Stop?

What is the approved protocol for a missed Decompression Stop?

Seems some discussion and agreement on these would be helpful in the discussion.

[CaptnJack]

"Re-compression" = you are already symptomatic.

Missing safety stops or even deco stops does not equal recompression (yet). Who are you looking to "approve" these anyway?

[ArcticDiver]

Each of the training agencies I've taken courses under have approved protocols for what to do if either of these events occur.

[Sounder]

Missed safety stop? Remember, a safety stop is optional... it's *extra margin* that isn't required. When it's required, it becomes a decompression stop and should be planned. There have been cases of people going OOG on recreational dives because they felt required to do a 3 or 5 minute safety stop and they were plowing through their gas supply.

Yes, a safety stop is well advised... but not required. As such, I'd argue there isn't really a way to "miss" one. In practice, outside of OW classes, I never do an official safety stop - I much prefer a slow, controlled ascent to forcing 15 feet for 3 minutes or whatever. That said, if I'm diving with someone and they want an official safety stop, I'm surely not going to surface without them.

Each of the training agencies I've taken courses under have approved protocols for what to do if either of these events occur.

What does your training agency say about how to handle missed safety stops? Does it differ on a 30fsw dive versus a 120fsw dive?

[kdupreez]

Yeah, a missed safety stop or an intentionally missed deco stop is not exactly the aim of IWR..

IWR is aimed at surfacing with DCS symptoms shortly after a dive or during the ascent portion of a dive even if you completed all your deco obligation.. Or in the case of an emergency and you blew a large portion of deco and you are having DCS symptoms and help is far out..

Its a controversial topic that doesnt always align with any specific agency's sanctioned teachings..

Hence the reason for starting this discussion here.. if it was a matter of looking at what a specific agency says regarding missed or ommitted decompression, then I'd just flip open my Trimix Instructor manual..

The idea here is to spur some discussion within the technical community on this board and get some opinion on what people think of IWR as an emergency re-compression when you dont typically have a 30min window to a chamber available.

RJ - you make great points of not pushing the PO2's and at least re-compress yourself until medical help is prepped and available.

This brings up a great point that also is touched on in the IWR papers.. people who do deep dives with sometimes none or even very aggressive deco and then do a shallower dive with overly conservative deco and then another dive within recreational limits with slightly more conservatism.. I would argue that this pattern is nothing more that 2 IWR sessions post the deep deco dive and might explain why these fishermen and pearl divers can do these multi dives and remain asymptomatic of DCS..

Does that mean a very conservative nice leisurely repetitive dive on high Nitrox mixes after an aggressive deco tec dive is actually good for you and will aid in controlling the off-gassing whats still left from the previous repetitive dive and therefore limit your exposure to DCS?

.

[ljjames]

which ever tables you use, or deciding factor for using IWR, it would not hurt to have ffm and a 'tender' for your IWR... just in case the symptoms are the beginning of something worse or you do end up having O2 issues.

I'm not sure a repetitive recreation nitrox dive is quite what they had in mind... unless you are breathing 99% nitrox and swimming around at 20'. in shallow IWR they are trying to push O2 into plasma and have big gradient.

what you are describing was once known as a 'clean up' dive and practiced by aggressive tech divers in the 90's. it has fallen out of favor as a number of highly regarded divers had suspected oxygen events on an easy cheesy dive and some of them died.

[airsix]

In practice, outside of OW classes, I never do an official safety stop - I much prefer a slow, controlled ascent to forcing 15 feet for 3 minutes or whatever. That said, if I'm diving with someone and they want an official safety stop, I'm surely not going to surface without them.

Point of clarification for any readers who do not dive with Doug or have an awareness of his subscribed protocols:
The above statement could be VERY misleading. Doug isn't skipping safety stops; in fact ALL of his ascents have multiple planned stops at specific depths and intervals that go well beyond the one-stop@15ft standard. This is the case whether he is doing a recreational dive or technical dive with staged decompression. He does "safety stops", just not the basic single stop method taught in OW.

@Doug, I know you were talking about sliding stops, but yeah...

[kdupreez]

which ever tables you use, or deciding factor for using IWR, it would not hurt to have ffm and a 'tender' for your IWR... just in case the symptoms are the beginning of something worse or you do end up having O2 issues.

I'm not sure a repetitive recreation nitrox dive is quite what they had in mind... unless you are breathing 99% nitrox and swimming around at 20'. in shallow IWR they are trying to push O2 into plasma and have big gradient.

what you are describing was once known as a 'clean up' dive and practiced by aggressive tech divers in the 90's. it has fallen out of favor as a number of highly regarded divers had suspected oxygen events on an easy cheesy dive and some of them died.

No, I am I'm referring to the paper coming out of the University of Hawaii as written by Frank P. Farm, Edwin M Hayashi and Edward L. Beckman covering the Hawaiian fishermen that do these 300ft+ dives and do successive dives during a day keeping them shallower on every dive.. and for the most part coming up asymptomatic. (And mostly on air)

Then there is the Richard Pyle (the dude that brought us deep stops) that used a lot of this information including a ton of other imperial data to come up with his own IWR schedule..

IWR according to all these papers and articles is not solely done on oxygen or at a 20ft depth, in fact most if not all of the IWR theories are deeper than 20ft and some even on air.. The idea is to re-compress the bubbles that causes DCS and then re-introduce a controlled pressure gradient in order to control the bubble growth and probably limit/control additional gas diffusion leading to even more nuclei forming bubbles.

The whole idea behind IWR in my opinion is exactly the opposite of introducing a high gradient.. the problem that got you bent in the first place was the excessively high gradient that caused excessive bubble formation and growth.. What IWR lets you do (as any chamber ride), it helps you re-compress those bubbles back down to a manageable size and then you control the gradient slowly as any normal deco theory suggests.

O2 is to prevent additional on-gassing in my opinion.. and sure, it helps to accelerate the controlled off-gassing if you remove all N2 or H2 partial pressures from the equation, but thats why you need to take the O2 much deeper so you can control the gradient..

looking at the Navy table treatments, those guys take you to insane "virtual" depths on O2 so they take the N2/H2 gradients all the way down and then control them and O2 at that point is just to prevent additional on-gassing and therefore provides much more effective off-gassing.

So this "repetitive dive" theory I have is basically just a few repetitive mini IWR schedules you are doing after a aggressive Tec dive, which when you look at the theory, it explains why these people inexplicably came up asymptomatic from a crazy set of dives ?

I am no decompression professor, but this theory of a shallower recreational dive on Nitrox after a tec dive should make you gradually offgass all that residual "surface deco time" you would have had and sounds like something of an accurate theory?

But yeah, a tender for in water support, a full face mask, etc. etc. is for sure a good idea for real-deal IWR when sh1t has gone pear shaped..

.

[CaptnJack]

"Redoing" the gradient can and has worked for me and others. But you gotta be smart about it. The worst thing you can do is on-gas more and then do an equally aggressive gradient (because you're cold etc).

I would just get the whole "aggressive deco" concept out of your head. Seriously, why would you do this? Whether you had 2nd dives planned or not we dive for recreation, just do the (ascent) time.

[kdupreez]

"Redoing" the gradient can and has worked for me and others. But you gotta be smart about it. The worst thing you can do is on-gas more and then do an equally aggressive gradient (because you're cold etc).

I would just get the whole "aggressive deco" concept out of your head. Seriously, why would you do this? Whether you had 2nd dives planned or not we dive for recreation, just do the (ascent) time.

Hell No, no.. I'm not saying I'll ever do it, I was just wondering on the theory behind the guys who do it.. And based on that theory, when doing a normal conservative deco dive, a repetitive nigh nitrox dive on like an air schedule would be even better for you..

I prefer keeping my deco dives on the very safe side for sure ! I even do my plans in V-planner with a +3 conservatism setting

why push the limits when you know better, right..

.

[CaptnJack]

Hell No, no.. I'm not saying I'll ever do it, I was just wondering on the theory behind the guys who do it.. And based on that theory, when doing a normal conservative deco dive, a repetitive nigh nitrox dive on like an air schedule would be even better for you.

I would guess there's not alot of theory and pre-planning that went into these (eg pearl divers). SIs just got shorter and shorter as long as things were "working". Alot got bent and their physiology and habits got weeded out of the pool. "Did you hear what Carlos did and how bad it hurt?" That isn't going to be repeated unless the profits were great or their kids are starving.

Brian Hill researched some of these anecdotal methods, but his write-ups leave out way too many details to really understand what the natives were doing and how they arrived at those profiles.

[ArcticDiver]

My post about protocols was a half a$$ed attempt to point out that if there isn't agreement on these protocols how can there be agreement on some contoversial thing like in water recompression. Didn't do a very good job at that.

I intended to follow up by asking, assuming proper kit and adequate gas was available, what protocol a person would use for in water recompression? What about the attendent? Lots of consequential details that make me think in water recompression is much akin to a Hail Mary Pass in football.

[Joshua Smith]

My post about protocols was a half a$$ed attempt to point out that if there isn't agreement on these protocols how can there be agreement on some contoversial thing like in water recompression. Didn't do a very good job at that.

I intended to follow up by asking, assuming proper kit and adequate gas was available, what protocol a person would use for in water recompression? What about the attendent? Lots of consequential details that make me think in water recompression is much akin to a Hail Mary Pass in football.

That's because it IS a Hail Mary pass.

[CaptnJack]

That's because it IS a Hail Mary pass.

Maybe. Depends on how bad the symptoms are, if they are real bad and you are in nowheres-ville with an already flooded dry suit and a teaspoon of gas. Basically you're down 42-3, then yeah its a Hail Mary.

If symptoms are minor i.e. the score is 7-6 with 8mins left on the 40yard line with an achy arm and blotchy skin... 20mins of extra O2 time at 20ft might very well fix them completely and you can continue your vacation and even dive tomorrow. That doesn't really seem like a desperate clutch for life to me.

Grey is my favorite color :luv:

[Joshua Smith]

That's because it IS a Hail Mary pass.

Maybe. Depends on how bad the symptoms are, if they are real bad and you are in nowheres-ville with an already flooded dry suit and a teaspoon of gas. Basically you're down 42-3, then yeah its a Hail Mary.

If symptoms are minor i.e. the score is 7-6 with 8mins left on the 40yard line with an achy arm and blotchy skin... 20mins of extra O2 time at 20ft might very well fix them completely and you can continue your vacation and even dive tomorrow. That doesn't really seem like a desperate clutch for life to me.

Grey is my favorite color :luv:

Fair 'nuff. I hadn't really thought of it that way, but you're right. I've never suffered and DCS symptoms other than the sub-clinical variety- ie, really, really tired and almost feverish feeling for a few hours or days after a deco dive. Never had blotchy skin or sore joints, even. What I'm doing these days usually leaves me feeling pretty good after deco, as long as I'm well hydrated- that does seem to make a difference. I might consider IWR for some of the more remote stuff I do up in BC from time to time....but once I'm back on the boat, I usually prefer to stay on the boat. Sometimes, after deeper dives, I'll just sit on the bench and keep breathing 02 from my Meg for a while, before I get out of my kit- but I usually can't wait to get out of it.

[limeyx]

That's because it IS a Hail Mary pass.

If symptoms are minor i.e. the score is 7-6 with 8mins left on the 40yard line with an achy arm and blotchy skin... 20mins of extra O2 time at 20ft might very well fix them completely and you can continue your vacation and even dive tomorrow. That doesn't really seem like a desperate clutch for life to me.

Grey is my favorite color :luv:

I have fixed a "sharp pain in shoulder" very effectively (no, not yours (or mine) after a 240 dive. 2 more cycles of O2 and everything was perfectly fine.

However, twice now i have had sharp pains in my right forearm that I couldn't really descend to fix, spent 60 mins on the boat in once case and 30 in the other on O2 with no benefit. Both cases cleared up in 15 mins with 4 ibuprofen.

For someone severely symptomatic to where they might choke, drown, tox, spasm or whatever, obviously a whol different ball of fish.