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Very informative post. One question about this, Could you also get bent like this doing non-deco training dives? For instance, say I am at the quarry practicing with a new lift bag in 50' of water. If I stay in no-deco time limits but am going from 50' to the surface multiple times in a short time period would this expose some sort of risk of CNS DCS? -K ----- Original Message ----- From: Simon L Hartley <shartley@sc*.ed*.au*> To: <techdiver@aquanaut.com> Cc: <trey@ne*.co*> Sent: Tuesday, June 05, 2001 7:38 PM Subject: FWD: bouncing - the risks (was RE: Diving after BENDS) > >Return-Path: <owner-techdiver@aquanaut.com> > >Errors-To: owner-techdiver@aquanaut.com > >From: trey@ne*.co* (Trey) > >To: "Wkpp@Ya*. Com" <wkpp@ya*.co*> > >Subject: bouncing - the risks > >Date: Tue, 22 May 2001 07:30:58 -0400 > >X-MSMail-Priority: Normal > >X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6600 > >Importance: Normal > > > > > > Guys read this for once. > > > > WHY WE DO NOT BOUNCE DIVE AFTER DIVING IN THE WKPP > > > >It is ok to offgas from the tissues into the blood stream in bubble form in > >the later steps of decompression as it is a more efficient, faster way of > >getting rid of the remaining gas ( by reduced pressure ) than by elevated > >oxygen alone ( which starts taking exponentially more time with greater > >risk) . However, this depends on having a good lung filter and no shunts. > >All of you have been PFO tested if you are diving with us. > > > >The correct way to ascend from the last stop is one foot per minute for the > >bigger dives. > > > >The greatest potential for offgassing in bubble form is when the pressure is > >totally removed back to one ATA out of the water. Now you get a real shower > >of bubbles , relative to what was happening in the water. A good , clean > >deco with the foot per minute ascent reduces this dramatically . > > > >In MOST people, the greatest bubbling occurs out of the water and continues > >for up to four hours, not even peaking for a couple of hours. In a well > >vascularized, fit person like me, it is over with in 30 minutes. Don't bet > >on that with most of you. > > > >In ALL people, the bubbles continue to grow in size after the pressure is > >off. They accumulate like gas into themselves from the surrounding blood or > >tissues ( if there are bubbles in the tissues or injury sites ) and they > >grow bigger. This is why you feel pain later rather than earlier if the > >bubbles are in joints or tissues - they get bigger before they begin to > >shrink. This is why what starts out as micro bubbles can get by the lungs > >and grow and get lodged downstream, and you get neurological symptoms later. > > > >Now here is the important part. If you understand everything I have said > >above, then you know that bouncing to 20 feet or whatever to pick up a > >bottle and immediately returning to the surface is the like giving yourself > >a home-made PFO: the bubbles in the venous side compress enough to get past > >the lungs and then will reexpand on the arterial side and lodge in the worst > >places , the spine and brain blood supplies. You do not want this. > > > >If you dive after dive, stay down and let everything reset. Get the bubbles > >all compressed, and then deco out and ascend accordingly. > > > >I do not want support divers diving support within four hours of doing a > >real dive or deep support. This works out fine, since we have support > >activities lasting up to 18 to 24 hours and need to rotate everyone. > > > >Let me assure you that we have found this out the hard way in the past. > >Parker used to get hot as hell when it would happen. In those days we had > >"volunteers", and they would all get bent diving to 20 feet to pick up > >bottles. We have also seen some severe cases of this where dives were done > >away from the project with no support, and the players went back for bottles > >later and got hammered. > > > >Don't do it. Also, obviously, do not freedive after a dive. When you want to > >freedive, do that first and then go scuba diving. > > > >Any questions from WKPP guys? > > > >-- > >Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > >Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > > > > > > Simon > > Simon L Hartley > RSM Website Coordinator\First Year Course Coordinator > Associate Lecturer > School of Environmental Science and Management > Southern Cross University > P.O. Box 157 > Lismore NSW, Australia 2480 > Ph: (02) 66203251 or (61 66) 203 251 > Fax:(02) 66212669 > E-mail: shartley@sc*.ed*.au* > > http://www.scu.edu.au/schools/esm/staff/pages/shartley/ > > http://www.scu.edu.au/schools/esm/ > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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