Posted by Kendall Raine on October 04, 2002 at 14:08:38:
In Reply to: Re: In water recompression posted by Steve on October 04, 2002 at 11:30:22:
Pyle put together a summary of IWR results some time ago. The IWR's conducted on air had mixed results. Some people resolved completely, some were still bent and some went into the water with minor symptoms and came back having bent the living snot out of themselves.
If you think about the process of recompression and what is going on physiologically, recompressing on air means you're potentially decreasing the inert gas gradient, not increasing it as desired. The IWR may shrink the bubble through compression, thus temporarily relieving pain, but the low gradient (you're still breathing 79% N2 at elevated PP) suggests problems may reemerge, potentially worse, when you redecompress (ascend). This fits the fact set.
Using 100% O2 provides the best gradient at any PP. The higher the PP the better, provided you don't tox in the process! While surface O2 isn't a very good gradient-the "window" is only about 1/3 open-it's not going to hurt you and may help.
Think about what Table 6 does. It puts you on 100% O2 at 2.82 ata or roughly the maximum oxygen window. The air breaks are short, 5 every 20, and are designed to slow the destructive effects of high PP O2 without compromising the gradient. Table 6 has replaced Table 5 at most facilities as the initial treatment of choice for even mild hits.