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"Poodle Jackets" are those dumb little color-coded fabric second stage covers that theoretically prevent people who can't mark their tanks correctly and follow a hose from breathing the wrong gas. Nanci At 09:38 PM 5/13/98 -0400, Deco wrote: >Thanks for posting this again. I seem to have misplaced my previous copy. >Could you explane the term poodle jacketed second stages. This term is not >used up here. > >Thanks > >Tim Ross >-----Original Message----- >From: Bill Mee <wwm@sa*.ne*> >To: cavers@ca*.co* <cavers@ca*.co*> >Cc: techdiver@aquanaut.com <techdiver@aquanaut.com> >Date: Wednesday, May 13, 1998 3:20 PM >Subject: Baker's Dozen Revisited > > >>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 >> > > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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