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I'll join John and Richard with a couple of comments about in water recompression therapy (IWR) of the top of my head. I want to stress that I have never tried and am not recommending IWR. It is often referred to as the Australian technique, this is not because we use it alot but it was proposed, by Carl Edmonds I think, as useful in some instances because we have very few RCCs servicing Australia and the South Pacific and retrieval of a patient to a RCC is a problem. For instance we (our Department organizes most retrievals) had a rash of 5 or 7 retrievals of DCI from the islands in a week about a month ago and they take a long time and cost about $25,000 each. If you have blown your stops and have no symptoms, there are clear procedures to follow described in many decompression tables, however, if you are trying to treat symptoms of DCI, John and Richard's comments illustrated that many factors are involved and there probably can be no clear cut guidelines. I can not agree with Richard's suggestion of recompressing to 30 fsw below relief of symtoms. I know that Hawaii is noted for its use of deep recompression profiles in RCCs, and from a pragmatic point of view, if this works do it. However there is no sound physiological basis for deep recompression. Recompression for DCI has two aims, to shrink bubbles and to provide HBO. To address the former, the volume of a bubble is related to the cube of its radius and the area to the square of its radius (I can never remember the formulas so check this V=(4Pi/3)r^3 and A=(4Pi)r^2). So the effect of compression on bubble radius and area diminishes with increasing pressure (cf. Boyle's law), after the first couple bar of compression you aren't getting much value in bubble shrinking. Next you want to breath HBO so that that you are not putting any more inert gas back into your tissues or your bubbles. HBO should also speed up the offgassing of inert gas from your tissues and bubbles. If you try recompression therapy breathing an inert gas you will be on-gassing in some tissues which will provide a inert gas resevoir for further bubble growth during subsequent decompression. Trying to recompress to below symptom relief will likely require breathing other than pure O2. Let's not fool ourselves, IWR is a quick and dirty solution to your problem, ideally you should be in a RCC, so I would not try anythig too flash, I would stay shallow and use pure O2, this will help and likely not exacerbate the DCI, trying to recompress breathing an inert gas may make things worse. If you have no submersible O2 supply stay on the surface. David Doolette ddoolett@me*.ad*.ed*.au*
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