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Couple comments: > Give me a break - this is total crap. 200 cubic feet? I used 100 cubic > feet to decompress from 6 hours at 300 feet. Oxygen at 300 feet with no > mask following an exposure with an injyre diver ? Idiot, you need to > shut the f up. You have no experience with this, you have no idea what > you are talking about, and Pyle is full of shit - he knows how to get > bent, and that is about it. The Navy manual is dead wrong as well. > > We do this al of the time and do it correctly and the result is > generally no chamber at all. Get a clue. We do so much experimenting > with deco that we have a lot of these situations. Chief, As per usual, you are way out of your league here. First, I recommended 200cf because anyone with less O2 on hand is simply unprepared. We all know that I breathe less than you do, so obviously that's not the volume needed for the "IW" part - it is also the volume needed to breathe intermitently on the surface for the 8-12 hours following IWR while you work your way to the chamber (not all of us have the luxury of having one near by, as you do). Second, who is breathing O2 at 300 feet? Third, if you meant O2 at 30 feet, it's assumed that the diver is wearing a FFM. This is standard Aus protocol, as per Carl Edmonds. I recommend 25 feet as the max depth with O2, FFM or not. Fourth, if you "do this all the time", then how is it that I "know how to get bent" more than you do? Next, to "gazela": Very good summary of IWR, in my opinion. I would add a few comments: > > simple answer. IWR is practiced in Australia and Hawaii and they have > > already worked out simple protocols. It's actually performed all over the Pacific, and has been for many, many years. Also, perhaps in Australia they actually follow the protocols, but the VAST majority of IWR efforts elsewhere (including Hawaii), follow seat-of-the-pants protocols, which vary greatly from diver to diver. Perhaps the most persistent (and consistent) trends are: 1) Most use air only 2) Most leave the water with substantially less severe symptoms than when they began treatment. 3) Most do not seek follow-up treatment. In my opinion, numbers 1 and 3 need to be corrected to O2 and mandatory follow-up. Number 2, however, is a testament to the fact that this is by no means any sort of exact science, nor is there such a thing as a "correct" or "best" way to do it. > > Also the Navy Dive Manual has a > > protocol for IWR in its chapter on decompression injury treatment. I have to actually (reluctantly) side with "Sheila" (aka Katherine, aka Trey, aka G, aka pottymouth) on this one (though not in so many words). The main difference between the USN & Aus methods is that the USN does discrete stops at 20 & 10, whereas the Aus (& "Hawaiian") methods advocate a gradual continuous ascent. I think the abrupt negative delta-P's assopciated with the published USN are not apt to be beneficial, and may even work against the effectiveness of the treatement. This seems to be true both of IWR, and of deco in general. > > Two basic bits of background that you probably remember from your basic > > OW course (if you managed to stay awake). Bubbles grow exponentially- > > the larger the bubble, the more rapidly it grows. Commercial and > > Military diving allows 5 minutes between surfacing and recompression in > > a surface chamber. Second, at 33 fsw, gas volume is half that of the > > surface. Not necessarily on that last bit. Depending on the absolute size of bubble we're talking about, it may actually be less than half its starting surface volume when compressed to 33 feet (due to the nature of bubble surface tension & its relation to bubble size). But, I think you'll find that for symptomatic bubbles, this effect probably don't amount to much. > > The different protocols allow for different types of ascent. The > > simplest is to come up at 4 minutes per foot (12 minutes per meter). > > The alternative is to come up at 1 foot per minute and make 45 minute > > stops every 10 feet. Basically, you're talking the Auz/Hawaiian method in the former, and the USN method in the latter - already discussed above. > > These protocols come pretty close to reproducing in water what the Navy > > Tables do in a chamber when you look at the physics and the > > neurophysiology. An important thing to consider is that the circulation (& perfusion) in an immersed diver can be quite different from a dry diver. I believe these circulatory effects can have potentially profound effects on DCS symptom manifestation. > > There is only a minimal amount of advanced preparation required for this > > type of IWR, but it should be thought out ahead of time to avoid panic, > > confusion, and danger. Amen! > > If you're using air, the recommendation is to go 10 feet below the depth > > where symptoms are relieved, or 165 feet max then start a staged > > ascent. The last 9 meters should be on oxygen if you can get any. It's not so much a case of "if you are using air", as it is a case of "should you do a spike?". Obviously, you don't want to be breathing O2 on the spike, and since nitrox wasn't around (at least not available to diving fishermen in Hawaii) when the Hawaiian method was published, air was suggested. Also, it was depth of relief plus 30, not depth of relief plus 10. If you follow the strict method as published (depth of relief plus 30), as opposed to the often mis-quoted practice of "spike to 165", then I think the methodology is sound. The reason I think this is that, in the overwhelming majority of cases I have direct knowledge of, symptoms disappeared almost upon hitting the water, making the true "depth of relief plus 30" to be only 30 feet. In one case I know of, the symptoms onset when the diver was still at the 10-foot stop (Case # 4 of the article I published with Dave Youngblood: http://www.bishopmuseum.org/bishop/treks/palautz97/iwr.html). This diver dropped to 80-feet and the symptoms only then abated. Had he only gone to 30, he might not have resolved the symptoms at all. Incidentally, he was using only air, and left the water with no symptoms, and no recurrence. The method that I now tend to advocate was described in detail in an article I wrote for: Kay, E. and Spencer, M.P. (eds.) 1999. In-Water Recompression: The Forty Eighth Workshop of the undersea and Hyperbaric Medical Society. Undersea and Hyperbaric Medical Society and Diver's Alert Network. 108 pp. The address given is: Undersea and Hyperbaric Medical Society 10531 Metropolitan Avenue Kensington, MD 20895-2627 USA I *highly* recommend that anyone with an even remote interest in IWR obtain this document. The session is also available on audiotape, but I'm not sure where to order those. At any rate, I advocate going first to 25 feet on O2, then waiting there for a few minutes to see if symptoms resolve. Only if they do not, and only if you are equipped & prepared for a spike, do you then consider a spike. I drew-up a flow-chart to follow for the complete methodology. > > Even if you're within reach of a chamber, if you have the support > > available, I would agree with the concept of going back in to 30 feet on > > oxygen until the air ambulance is there to get you. I agree. The *immediacy* is the thing to keep in mind here. IWR offers two immediate benefits: 1) Potentially restores circulation. 2) Potentially shrinks bubbles before the biochemistry has a chance to kick in. Bear in mind that bends symptoms are likely as much a result of the biochemistry that occurs in response to bubble growth, as they are a result of the bubbles themselves. One final comment: > > > > The first assumption is that the worst thing the "omitter" has > > > > effectively done is move up the last 20 feet and out of the water too > > > > fast. By this I mean that if any of us do this at any point in any deco > > > > proper or improper, we are foaming out that last pressure gradient that > > > > NO amount of deco will remove. Only a slow ascent to the surface will > > > > allow that last bit of gas to come out in solution. Jumping up 20 feet > > > > will bring it out in bubble form, no matter what. I didn't follow the thread, so I don't know who wrote the above, but whoever it was is clearly suffering from the dangers of "a little knowledge is a dangerous thing". This person obviously has *way* too much faith in the connection between theory and reality on this issue. Aloha, Rich -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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