Inwater Recompression

ROB DAVIE

Some guys have all the luck with their diving situation (Mike ). For the rest of us, there is preparation.

Phi, I am glad to see your note about prepping a kit for IWR! It's one of those things, like insurance, that you hope you never need, but you're glad as hell to have it when it's needed.

As everyone has pointed out, the time lapse from onset of event to treatment is critical. Bone necrosis is one problem with delayed treatment, but that is only if you survive the other problems, most of which will be far more severe.

To put it simply, with delayed recompression, the body begins to treat the bubbles as physical objects invading the body and a whole series of events occurs, appropriately enough called a cascade, which, assuming the systems are still operational, inevitably takes the event beyond the point at which recompression is maximally functional.

The key to the success of IWR is preparation, and a bit of luck!

A full-face mask is essential. Due to the nature of the insult to the body, the environmental conditions, and the required use of extremely high PO2, it is far more likely that the patient will convulse at some point. A full-face mask is the only thing that will save him if that occurs.

A large supply of O2 is required. If one is performing the drill on surface supply, you will need many cubic feet of O2 as a dedicated supply. Here, obviously, is one of the advantages of a rebreather that is not often mentioned.

You will need a line to secure the patient to, and some weight to keep him at depth. Again, there may be a point at which your patient is unconscious. You don't want him drifting away.

You will have to arrange a series of dives by other divers to be sure that there is someone there to attend the patient. This may be a problem if all of your divers have just surfaced from deco themselves.

Finally, and this is where the luck comes in, will the sea state and environmental conditions give you the time to perform this maneuver?

I point all of these things out, not to discourage anyone from doing IWR. Quite the contrary. If you are doing the kind of diving that folks in our ranks tend to do, you will be out in EBFE somewhere, a LOOONG way from hyperbaric treatment (unless you are Mike ). In that case, IWR may be your only hope, Obi Wan.

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[SIZE=2]"CC Rebreathers will become a viable part of tech diving [U]WHEN PIGS FLY[/U]!!"--GI3[/SIZE]

silent running

Hello all. Lots of great information in the article and thanks for posting it Mr. Ducky, another great thread. My CCR buddy Captain Craig deWit of Golden Dawn related a very scary incident to me last year. He surfaced for a moment from a moderate deco OC dive to prevent one of his crew, who started the boat prematurely, from tangling a mooring line in the propeller and returned to finish his stop at 6 meters. He finished the deco felt fine, did another moderate OC deco dive and began to experience symptoms after the second dive had been completed. He imediately began to experience loss of motor control and was barely able to walk when he got in the water with a full face mask and O2 at 8 meters. The symptoms began to lessen almost imediately and were gone entirely by the time he exited the water 1hr later. He's sure IWR saved his life.
The next step would seem to be getting enough data and some models together to facilitate an IWR schedule for one's dive computer, based on the dive history before the hit. It would definitely be better than just outright guessing. It's probably asking too much of liability concious computer manufacturers, but it sure would give a little piece of mind for those of us who travel to remote dive locations.-Andy

Richard Harris

In the meantime stick to one of the recommended schedules, like the Australian IWR Schedule. No guess work required.

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"Harry"

www.divedoc.net

caveseeker7

Andy, having talked to two different chamber operators I was suprised to hear that divers' deco computer have no effect chamber treatment. That is solely based on medical assesment (symptoms) and set schedules for treatment.

Dive computer info is at best used as one mean to asses the cause for the DCS afterwards.

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Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority,
and rabidly promoted by an unscrupulous mainstream media,
which holds forth the proposition that it is entirely possible
to pick up a turd by the clean end.'!"

silent running

Thanks for the info guys. Who knew the dive profiles were not of use in DCS treatment? I guess it's treated first by it's symptoms. Well at least using the Ausralian schedule makes it very simple.-Andy

MikeH

A couple years ago, myself and 3 buddies were out diving about 6 hours(by boat) from the nearest shoreline. After surfacing from a somewhat aggressive trimix dive(but the same dive we had done numerous times without incident), and climbing onto the boat, one of the guys(we'll call him Jim) complained of numbness in his left arm. We discussed the situation for a couple minutes to try to determine if it was diving related or another medical problem, all the while preparing O2 and getting him on it. He felt better a couple minutes after getting on O2, but then slowly(over the next 20 minutes) felt worse again and lost feeling in his left leg as well as left arm. He also complained of very occasional sharp, shooting pains in his mid back. During this time, we made him drink almost 2 gallons of water.

We decided it was a case of DCS, and it would be at least 4 hours before he could get into a chamber(if evacuated by air). We discussed the options, and Jim decided he wanted to try IWR immediately since he still had full motor control. We decided that if he got worse in the water(by his determination or ours), we would pull him out and await the arrival of the Dauphin. Our plan(which was nothing more than a WAG) called for getting him down to 100' and putting him on 50/50(50% O2, 50% Helium) immediately(he had done his deco on EAN28 and O2) with a FFM. At 40', we would switch him to O2(still on a FFM).

Upon reaching 100', all his symptoms had subsided....and he had full feeling in all extremities. The only complaint at that point was a moderate headache. We kept him at 100' for 10 minutes, then started a slow ascent to 40'. The ascent took us almost an hour. At 40', we switched him to O2, at which point he complained of dizziness, but no other symptoms. After 5 minutes, we moved up to 30', where the dizziness subsided. After about 40 minutes between 30' and the surface, and almost 2 hours of IWR, we surfaced with Jim feeling very well. He had some soreness in his left shoulder, but that was it. We headed for home immediately, and took him to the nearest chamber....where they determined he probably didn't NEED a chamber ride, but did a 3 hour ride anyways just to be sure.

According to one of the docs, Jim probably had a pretty serious Type II hit....and would likely have been permanently injured/disabled if he had not received some sort of recompression treatment so promptly.

The only thing we could determine as a cause/contributing factor of this hit was that Jim had drank 5 or 6 beers the night before, and not drank any water for over 12 hours prior to the dive(only coffee on the morning of the dive). Chances are he was severely dehydrated.

In my opinion, IWR saved Jim's life. He feels it did as well. That was the last dive Jim ever made. He decided that his wife and children were too important for him to continue diving and risk any potential problems in the future. He still wants to know every detail of every dive I make....but he will never dive again himself.

Mike

abowie

This is an interesting article that highlights a number of the reasons why IWR is contravertial.

One thing that people sometimes fail to appreciate is that IWR, performed as "recommended" (eg the "Australian Tables") is done to a maximum of 9m on 100%.

This produces a maximum ambient pressure of slightly less than 2ATM and a PO2 of 1.9ATM. For a "serious" case the Australian Tables keep you down between 2.5 and 3 hours. For "mild" cases duration can be as little as 2 hours.

By comparison the pretty routine USN Table 6 takes you to 18m (2.8ATM) on 100% (with air breaks) for 5 hours or so. There are others that go to 30 to 50m and last a lot longer.

Increased ambient pressure compresses bubbles. This both increases the gas pressures within them which promotes gas diffusion out of the bubble, and also makes the bubble physically smaller, maybe allowing it to exit whatever capillary it's blocking.

High PO2 "opens the oxygen window", promoting inert gas offloading.

IWR does not generate as much pressure, nor does it offer as wide an oxygen window effect, and as such is not and can never be a comparable substitute for in-chamber hyperbaric treatment.

I thought a lot about IWR coming up to my recent Bikini trip. I was the only doctor on the trip. I was aware that the isolation of the location meant that evacuation to the "nearest" chamber might take many days.

To be honest with you I am not certain what I personally would have done if I had surfaced with significant neurological symptoms. I am very glad that I did not have to put this to the test.

If I had my choice I would always travel to locations with speedy access to a chamber, and equally if not more important, qualified staff who knew how to operate it.

Obviously this isn't always possible. Seeing as my next "big" trip is to dive under ice in Antarctica I guess I'm going to have to think about all of this again....

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Andrew Bowie

Rebreather-friendly Buddy

Yankee Rebel

Does anyone have a copy of the Australian IWR Tables? ive been putting Google to work, but my googler isnt working too well at the moment.

this has been an exceptional thread for me, having been told that IWR was a no-no and all that, but feeling that it may well be a viable option. i remember reading the article by Richard Pyle about his bend, how it came to be, and the treatment, and noted that he successfully used IWR to treat the initial hit. a very interesting subject and a great thread. thankyou for posting it on the forum.

has anyone done any updated research on the propsed IWR tables/plans? is there any new research on IWR that might add more light to it all?

Yankee Rebel

LukeN

If my memory serves right you can find them in the US navy diving manual(50 meg download)

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Luke Nelson

www.imagedive.com.au