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Scott, I'll add "A bakers dozen" to the wkpp website. Good thinking, Jeff Scott Migaldi wrote: > Bill, > > This post is well thought out and lucid. I have not read anything this > good on this list in a long time. I know you and George, JJ, and the > rest of WKPP have great ideas and I wish that you would share them often > with the rest us. Could you possibly use you web site to post these > white papers and procedures? > > Keep up the good work, > Scott > > >From wwm@sa*.ne* Wed May 13 11:43:13 1998 > >Received: from simba.safari.net (simba.safari.net [206.96.248.2]) by > zen.kr.com (8.8.4/8.6.9) with ESMTP id OAA10445 for <cavers@ca*.co*>; > Wed, 13 May 1998 14:19:20 -0400 (EDT) > >Received: from wwm.safari.net (annex3-3.safari.net [206.98.157.113]) by > simba.safari.net (8.8.8/8.6.6) with SMTP id OAA17861; Wed, 13 May 1998 > 14:20:22 -0400 (EDT) > >Message-ID: <3559E57F.6FD2@sa*.ne*> > >Date: Wed, 13 May 1998 14:25:03 -0400 > >From: Bill Mee <wwm@sa*.ne*> > >Reply-To: wwm@sa*.ne* > >X-Mailer: Mozilla 3.01C-KIT (Win95; U) > >MIME-Version: 1.0 > >To: cavers@ca*.co* > >CC: techdiver@aquanaut.com > >Subject: Baker's Dozen Revisited > >Content-Type: text/plain; charset=us-ascii > >Content-Transfer-Encoding: 7bit > > > >Fellow Divers, > > > >Once again the subject of 80/20 rears it's ugly head. We are now told > >that the use of this peculiar gas mix is somehow or the other possibly > >an unwritten defacto IANTD teaching standard. Let me remind you that > the > >WKPP does not use this gas mixture for anything and if you made the > >mistake of showing up with this stuff you would never get out of the > >parking lot. For those who may forget the past and possibly repeat it > I > >reiterate the famous "Baker's Dozen" reasons why we do not use this > gas. > > > >If you think reason #12 is a joke may I point out that the dive boat > >which carried, the now late, Tai Wilkerson on his final fatal dive had > >no oxygen on board. They did however have 80/20. > > > >One of the reasons for carrying pure oxygen as a deco gas is that it > >will be immediately available in an emergency. The administration of > >pure oxygen is SOP in the aftermath of almost all forms of diving > >related accidents. This may prove to be an issue in subsequent > wrongful > >death litigation in that having "no pure oxygen" is essentially > >indefensible and could be considered negligent. > > > >Using some homebrew dive table program to justify the use of 80/20 is > >not reasonable inasmuch as the Buhlmann algorithm (upon which almost > all > >of these programs are based) is a diffusion based compartmental model > >which does take into consideration micro-physiological issues. > > > >PLEASE REREAD the Baker's dozen and take this seriously. > > > >Regards, > > > >Bill Mee > > > > > >> > >> > ---------------------------------------------------------------------- > >> A (BAKER'S) DOZEN REASONS WHY WE DO NOT USE 80/20 (By George Irvine) > >> > >> 1) This gas was introduced in an effort to overcome the inability of > >> unqualified student "tech" divers to control their buoyancy in open > >> water, and is as such is yet one more concession to doing things in a > >> convoluted fashion to offset a self- inflicted set of problems > brought > >> on by the "doing it wrong" thinking that pervades diving today. > >> > >> 2) A heavy sea is not a problem for a deco stop if it is not posing a > >> lung-loading problem. Look at your depth guage in a heavy sea and > "see" > >> for yourself what the changes are - insignificant, and if they are > not, > >> you should either not have been diving or incurring a decompression > >> liability of this magnitude in the first place. In the event of a > change > >> in conditions during the dive, see below where the 80/20 becomes a > >> liability rather than an asset. > >> > >> 3) In the interest of using a standardized set of gases for which > you > >> can permanently mark your bottles , it is a poor concession to > inability > >> to sacrifice the benefits of pure O2 to accommodate a real or > perceived > >> lack of skill - learn to dive before taking up techdiving. > >> > >> 4) In this same interest you will find that when you graduate to > real > >> diving, as in caves, you will not want to accelerate your ppo2 at > >> lower depths while still being faced with a long decompression at > >> shallower depths, and making bizarre mixes to do this is a dangerous > >> mistake (just like the fantasy of holding an accelerated ppo2 on a > >> rebreather throughout a deco). I am anticipating the thinking that > the > >> 80/20 crowd would then go to an additional oxygen in cave without > >> accounting for total exposure, and subject themselves to the risk of > tox > >> in the final deco steps. Tox you do not get out of - bends you do. > >> > >> 5) The 80/20 mix is in fact totally useless and contraindicated as a > >> deco gas. At thirty feet it is only a 1.52 ppo2 ( the real 1.6 ppo2 > >> gas would be 84/16) and as such does not either provide the right > >> oxygen window, nor does it does it work as well as pure oxygen > without > >> an inert gas at any depth. The gas mixing in your lungs has already > >> lowered the effective ppo2 enough to prevent spiking at 20 feet > anyway > >> with the use of pure oxygen - in other words, we are dealing with a > >> simplistic misunderstanding here, or "old wives tale" that is typical > in > >> diving. > >> > >> 6) If 100% oxygen is a perceived buoyancy control risk at 20 feet, > then > >> why is the same ppo2 ( intended) not a risk at 30 feet? This shows > the > >> total lack of reasonable logic involved in the decision to use this > gas, > >> as well as a lack of understanding of the whole picture ( see the > rest > >> of this discussion). > >> > >> 7) Along those lines, all we hear is howling about "oxygen cleaning" > >> above 40% mixtures, and dive shop proprietors on here complaining > about > >> scuba tanks with oxygen in them being filled in their shops. With a > >> pure oxygen system, the tank only ever gets filled with oxygen from > >> oxygen tanks, not from every dive shop compressor it sees. Again , > this > >> shows the total inconsistency of agency thinking, and reveals that > the > >> true reason for this gas is to pretend to lower liability for > teaching > >> incompetents to dive, which is bull, and to attempt to accrue some > >> inventive accomplishments to the dive agency pundits who themselves > >> prove that they do no real diving by making this recommendation > >> in the first place. This is like the colored regs, the stages on > either > >> side, the quick-release buckle, and the poodle jacket: nonsense of > the > >> most obvious nature developed through one-dimensional thinking by > those > >> whose universe of understanding is not only severely limited, but > blinded > >> by the hubris of not being the "inventor" of the techniques that > work. > >> > >> 8) Any perceived decompression benefit of using a higher ppo2 at 30 > >> feet with 80/20 is then given back by the lowered ppo2 at 20 feet, > not > >> to mention the fact that the presence of the inert gas in the > breathing > >> mixture defeats the purpose of using oxygen in the first place ( see > >> the Physiology and Medicine of Diving) . The ppo2 of 80/20 at 20 > feet > >> is 1.28, not much of an oxygen window, and at 10 feet it is 1.04 - > >> useless for deco. To make matters worse, you can not get out from > your > >> 30 foot stop in an emergency ( not doing the other stops) on the > 80/20 > >> mix without really risking a type 2 hit. > >> > >> 9) This is a dangerous method to achieve a greater total volume of > gas > >> for the bad breathers (another obvious reason the gas is in vogue), > who > >> should not be incurring these decos, and even that benefit of having > >> more gas is lost since it is breathed at 30 feet, and then has to > last > >> for the other stops. The fact is that gas is effectively saved by > using > >> the lower deco gas up to this point, relying on the pressure > gradient > >> to both achieve the deco and provide a break from high the previous > >> gas's higher PPO2 prior to going to pure oxygen where the spike > could > >> be a problem on an extreme exposure without an adequate low ppo2 > break ( > >> again this shows that the 80% user is a neophyte diver with no real > >> experience or understanding of the true risks of these dives) . > >> > >> 10) The 20-30% longer 30 foot time on the lower ppo2 is not only > >> overcome on the pure oxygen at the next stops, the breaks do not > come > >> into play until the initial good dose of pure oxygen has been > absorbed, > >> since you are not spiking from a high pervious dose without a break > >> that is effectively achieved on the previous gas. These things need > to > >> be understood and taught by the agencies, not some superficial > >> convolution that is designed to obfuscate the problem rather than > >> openly acknowledge and deal with it in a responsible fashion. > >> > >> 11) In an emergency situation, getting onto the pure O2 for 20 > minutes > >> or so (for long dives something approximating the bottom time or a > any > >> decent interval) would give you a real good shot at getting out of > >> the water having missed the rest of your deco and living through it > >> with pain hits only. You have to think these things all the way > though, > >> not go for the transparent superficial thinking of those who merely > are > >> trying to "make their mark" with some "great" idea they can call > their > >> own. The acid test is , as always, is the caliber of the divers who > >> adopt these practices. > >> > >> 12) If there is some problem with your deco or you otherwise develop > >> symptoms and need oxygen either on the surface or back in the water, > it > >> is silly to have not had it there all along. 80/20 is a joke for that > >> purpose, unless you have asthma, in which case any accelerated oxygen > >> mix would be a nightmare. This is again part of the "thinking it all > the > >> way through" philosophy which is obviously missing from the 80/20 > >> argument. > >> > >> 13) Only a card-carrying stroke would do somethng like this, and > >> showing up with 80/20 is no different than wearing a sign on your > back > >> saying "I am a stroke, and have the papers to prove it". It announces > to > >> all the world that you have no clue, kind of like wearing clip-on > >> suspenders or having dog dirt on your shoes. > >> > >> George Irvine > >> Director, WKPP > >> "Do It Right" (or don't do it at all) > >> > ----------------------------------------------------------------------------- > >> Bill Mee's post: > >> > >> George, > >> > >> Thank you for exhaustively laying the reasons why we or anyone else > >> should not use 80/20. The only thing missing from this discussion > is > >> the Q.E.D. at the end. > >> > >> Reason #8, reiterated here for discussion purposes is perhaps the > >> soundest reason, among many very cogent ones, as to why this practice > >> should be avoided: > >> > >> " Any perceived decompression benefit of using a higher ppo2 at 30 > feet > >> with 80/20 is then given back by the lowered ppo2 at 20 feet, not > to > >> mention the fact that the presence of the inert gas in the breathing > >> mixture defeats the purpose of using oxygen in the first place ( see > >> "The Physiology and Medicine of Diving") . The ppo2 of 80/20 at 20 > >> feet is 1.28, not much of an oxygen window, and at 10 feet it is 1.04 > >> useless for deco. To make matters worse, you can not get out from > your > >> 30 foot stop in an emergency ( not doing the other stops) on the > 80/20 > >> mix without really risking a type 2 hit. " > >> > >> The rush to embrace this practice, recommended by technical diving > >> diving opinion leaders, was widespread and in retrospect, irrational > and > >> poorly thought out, like so many of the "trial balloons" in this > field > >> of endeavor. It seemed to many, at first glance, to be a simple means > of > >> increasing one's supply of deco gas while eliminating its bothersome > >> volume and mass. In fact, the perceived benefits transform into > >> liabilities when subjected to a thoughtful analysis. When you view > >> decompression as a two pronged challenge: to progressively widen the > >> oxygen window and increase the diffusion gradient to maximize passive > >> transport of dissolved inert gas, it becomes clear that the 80/20 > >> solution falls short on both requirements at a critical point in the > >> decompression profile. > >> > >> Section 11 emphasizes a very compelling argument for those who are > >> concerned with managing dive related crises. When diving in the open > >> ocean divers and boat operators should always be prepared to "scram" > the > >> deco at any time. This could be for any number of reasons, not the > >> least of which might be a sudden change in the sea conditions or > >> unscheduled events such as dive accidents or impending ship > collisions. > >> Just follow the Whitefish Point thread for an excellent example of > why a > >> deco may require being aborted (or never started in the first place). > >> > >> Most unfortunately the "80/20 problem" bears a strikingly resemblance > to > >> several other ad hoc technical contrivances mentioned in this same > >> article (section 7) i.e. dual bcs, colored regulators, bilateral > stage > >> bottle positioning, poodle jacketed second stages and harness quick > >> releases. All of these ideas, while seemingly reasonable, become > >> tainted when subjected to thoughtful review. > >> > >> Good show Director Irvine. > >> > >> Bill Mee > > > > ______________________________________________________ > Get Your Private, Free Email at http://www.hotmail.com -- Jeff Bentley jbentley@cr*.co* http://www.crl.com/~jbentley -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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