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> >> Ok, if I can paraphrase - The deeper one is the more nitrogen is being >> absorbed because of the higher PP. What you (Buehlmann?) seem to be >> saying is that the intention of the faster ascent rate from depth is to >> get the diver into a shallower depth, where the PP of nitrogen is less, >> in the quickest but safest time then slow the ascent to allow >> off-gassing to take place. That's probably a bit simplistic but in broad >> terms is that correct? > Hi Rich, Erich, George, Rob, So the concept of "Blow and go" (what we did in the old days before tri-mix)" deep air dive (e.g., 260 foot dive 25 min...then fully inflate bc to ascend ballistically to 100 feet--stay 3-5 min, then go slowly to first safety stop at 60 , 50, 40 etc) could be seen as be begging for bigger bubbles, which could be more problematic than the decreased nitrogen absorbtion "Blow and Go" was used to eliminate... Typically Blow and go was followed by pure O2 at 20 foot and 10 foot stops, with some air breaks, and this seemed (at the time) to be effective in removing or shrinking bubbles...what are your current thoughts on this. It would seem to me that at the very least, this was probably a great way to "Farm" bubbles, and probably was responsible for some micro-vascular damage. Regards, Dan >Yes, that's what the compartment-based models sa - get the hell out of >deep water quicklyy. George is right that Eric can explain the bubble >physics better, but here's my visialization of it: > >The slow initial ascent is to keep the bubbles (which exist already >anyway for a variety of reasons) relatively small. A fast ascent in deep >water will allow the bubbles to get larger, and large bubbles take longer >to "offgas" into the surrounding blood/tissues because the pressure >inside the bubble isproportionally less. It's much more complicated than >this, but you can think of compartmentt-based models (like Buhlmann) as >managing dissolved gas molecules, and bubble-based models as managing >dissolved gas molecules in additio to gas-phase molecules (bubbles). The >upshot when you work out the math is that the bubble models suggest a >need for much deeper initial decompression stops (= slower deep ascents). > >But again, this is all theory - as Robb put it, our lab-coat >rationalization of how it works. All I know for sure is that I feel much >better after long deep decompression dives if I interject additional deep >stops. > >As for computers - I just spent more money getting two EDGE computers >overhauled than it would have cost me to get any one of the fancy new >computers. Why? Two reasons. One, the EDGE is the only computer that >displays whiat I consider to be the only useful information - the tissue >graph. And two, after thousands of dives I have come to learn how to >modify my decompression profile based on what the EDGE tells me - I'm not >sure if my modification algorithm will work on a different computer. >Tables are swell for certain dives, but they are useless to fish-nerds >(like myself) diving all over the place on vertical reef walls. > >Aloha, >Rich >-- >Send mail for the `techdiver' mailing list to `techdiver@terra.net'. >Send subscription/archive requests to `techdiver-request@terra.net'. > > Dan Volker SOUTH FLORIDA DIVE JOURNAL "The Internet magazine for Underwater Photography and mpeg Video" http://www.florida.net/scuba/dive 407-683-3592
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