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+-On9/1/00 10:43 PM, Guy Morin wrote: GM>It is natural GM >for oxygen to be a more efficient at effecting decompression, GM >that is the entire basis for using hyperoxic gasses, there GM >is nothing new in your post. Then we agree that 100% O2 is "more efficient at effecting decompression" than 80/20. Since you understand that to be the case as well, what is your rationale for promoting 80/20? If you're still going to take the position that 80/20 is better even in the face of the obvious, please list the citations, journal articles, man hours of testing, theory and mathematical models that support your position since it goes against what you clearly know to be the case. But I know that you can't come up with any rationale because there are no such reliable proofs. Why do you dive 80/20, Guy? Because someone told you to and now you'd rather go to all lengths to justify it than admit you're wrong. Like I said in my first post, you're exactly what's wrong with technical diving because you're not only wrong, you're blind to what's right. Here's a favorite quote from the techdiver archives: "Technical diving can kill you , listening to dumb assholes is the first step to getting killed." That's you, Guy. You are so dangerously wrong, no one should listen to you. > GM >Concentration gradients are precisely what using hyperoxic GM >gasses have been about from the start, there is no added magic GM >in your analysis. There's no added magic in any of these discussions. My intent was to restate the basics of established deco theory for the benefit of people who were unclear on a few particulars or who wanted to understand the pros and cons of 100% O2 vs. 80/20 deco. It was you who claimed without a basis that established concepts like oxygen windows -- a concentration gradient -- were mythical. You do remember that post, Guy, now that you're backpedaling? > GM >Again Bill, it's hard to not see this holy grail of yours as GM >just marketing, the oxygen window, as you state it below GM >offers nothing new, and the analysis again neglects taking GM >oxygen breaks in the comparison with the 36/80 deco. I see -- the oxygen window goes from being a "unicorn" to "holy grail" to being "nothing new." That's the fastest about face I've seen on this list in a long time. As far as oxygen breaks are concerned, I haven't addressed them yet, so your criticisms are just straw men. Let's discuss air breaks -- or more appropriately, back gas breaks -- since no diver who needs them should be diving air. First, the only thing you are correct about, Guy, is that no present model or algorithm accounts for their effects. However, any of the current deco software packages could be easily modified to do so, by adding 5 minutes on back gas for every 25 on 02 or 80/20 after a certain CNS clock percentage is reached. Simple programming. I have also noticed that in each of your posts you inflate the percentage of deco taken up by back gas breaks so you can pretend that it's so significant that it undermines the other advantages of 100% O2 over 80/20. But that really isn't the case, is it Guy? The standard break is 5 minutes on back gas for every 20-25 minutes on O2 (or 80/20), so they're going to account for at most 16.7% of every *hour* on O2 -- usually far less since there are very few people regularly doing dives that require a full hour on pure oxygen. For purposes of this discussion, we can break technical diving into 3 types of dives: 1. The vast majority of bounce dives (like 200' for 30 minutes) that don't require back gas breaks on either 100% O2 or 80/20. For those dives, Guy, you've already agreed above that 100% O2 is the better deco gas, so enough said. 2. Those relatively few long exploration dives that will require back gas breaks whether the deco mix is 80/20 or 100% O2. Since either deco gas choice will require back gas breaks, and you've already agreed that 100% O2 is the better deco gas choice, you should be using 100% O2. Why aren't you Guy? Oh, I forget, you don't do these dives do you? If you did, we would have heard about them already, wouldn't we? 3. The small number of dives that require back gas breaks on 100% O2 but not on 80/20. There are so few profiles that fall into this middle ground that I haven't been able to come up with a single one of them, but I know they exist theoretically. And since your frighteningly stupid posts might have people consider 80/20 for these few dives, I have to address it. Dives that fall into this category will have at most one back gas break, because a longer dive would require a back gas break on 80/20 as well. That's 5 minutes on back gas. So the real question for these does is: Is 80/20 deco more efficient at removing inert gas than 100% O2 deco with a 5 minute back gas break? To answer that question, you wrote this idiocy in another 80/20 deco post: GM >On a final note on the 80/20 deco saga, given that the WKPP GM >spends a third of the time on back gas, and two-thirds on pure GM >O2, let's work out the weighted O2 concentration, over time: > GM >Let's assume that back gas is 14% O2. > GM >...66 x 1.0 + .33 x .14 = 0.7062 Guy - Tell me you're really not this clueless about decompression? Arithmetically weighted averages?! I want to make it clear to anyone who might read this in your post: It is wrong. It is dangerous. Don't use it, follow it, or even consider it right for a moment. Guy -- for your own sake, find a good technical diving instructor and go back to class. Guy - the only way you can *examine* the effect of a 5 minute back gas break after 20 minutes of 02 is by looking at the inert gas tensions in each of the 16 tissue compartments minute by minute for each of the 20 minutes on O2, and then look at the 16 tissue compartments minute by minute after 5 minutes on back gas -- and then compare those inert gas tensions to each of the 16 compartments during 25 minutes on 80/20 at the same depth on the same profile and bottom mix. If you just want a number instead of an explanation, you can compare those same 16 compartments at the end of the 25 minutes on each deco gas selection. The fact that you don't understand this fundamental concept should demonstrate to everyone, whether they agree with my deco gas choices or not, that what you're writing is worthless and you don't know what you're talking about. GM >And I thought this was going to be interesting. And I knew from your first post that it wasn't going to be. I just didn't appreciate that you'd be so clueless that you're dangerous. By the way, there was one remark from an earlier post of yours that I ignored that's worth responding to. You said no one is going to win the Nobel prize for deco theory and -- this I found really amusing -- "for most of the decompression models out there, I don't think one can get a math degree for a single one of them." Here's Bruce Wienke's email address: brw@la*.go*. He's a physicist at the Los Alamos Nuclear Laboratory working on bubble mechanics -- as I understand it, one of the most complex and difficult areas of applied physics. He's also the author of the RGBM deco model, which incorporates his bubble mechanics research. It's the model underlying Abyss, all the Naui-Tek tables, and the new line of Suunto computers. In my opinion -- and this is only my opinion -- it may be the most important work in deco modeling since Buhlmann. I think you should write Dr. Wienke and break the news that his work isn't that difficult, really doesn't require a math degree, and is not going to earn him a Nobel prize, because you obviously know more about decompression than he does. And while you're at it, tell us what training agency you write tables for. Have a nice life, Guy. > > >Bill Wolk wrote: > >> On 8/29/00 1:29 AM, ScottBonis@ao*.co* wrote: >> >> >Let me try to ask my question in a slightly different way. If I weren't >> >worried about oxygen toxicity (this is just a fictious example here), then I >> >get the impression that the theory is that deco'ing on 100% O2 at 30 feet or >> >forty feet would be more efficient at offgassing nitrogen than deco'ing on >> >100% O2 at 20 feet. Is this correct, or am I all screwed up again? >> >> Scott - >> >> The short answer is yes, you're absolutely correct. The textbook >> definition of an "oxygen window" is "the difference between total gas >> pressures in arterial and venous blood; exists because oxygen is partly >> metabolized by the tissues, so venous oxygen pressure is lower than >> arterial oxygen pressure." >> >> But we use the term a little differently when we talk about >> decompression. We essentially use "oxygen window" to represent the >> difference between the concentration of inert gas dissolved in tissue vs. >> the concentration of oxygen and inert gas in arterial blood. >> >> If you'll excuse a bit of an oversimplication, I think I can make the >> concept (and deco) a whole lot clearer: Remember the concept of osmosis >> from biology? If you have a high concentration of a substance on one side >> of a cell membrane and a low concentration on the other, the substance >> will cross the membrane until the concentration on both sides is equal. >> The more of the substance on one side and the less on the other, the >> higher the osmotic pressure >> -- literally the force that the substance on >> the high concentration side exerts as it tries to push through the >> membrane. And usually, the higher the osmotic pressure, the faster the >> substance moves towards equalization. Like lots of people pushing >> through a turnstyle. This is the key. >> >> In deco, you have tissues that are oversaturated (highly concentrated) >> with inert gas -- on one side of the cell membranes. If you breathe 100% >> oxygen, your arterial blood carries large amounts of O2 in both >> hemoglobin and plasma. When it reaches the saturated tissues at the >> capillary level (where arterial blood gives off its oxygen and thereby >> becomes venous blood), the high osmotic pressure (lots of inert gas in >> the tissue and none in the blood) forces the N2 and He from your tissue >> in the bloodstream --> decompression. At the same time the high osmotic >> pressure on the other side (lots of 02 in the blood, less in the tissue) >> forces O2 into the surrounding tissue, which has the effect of >> oxygenating tissue and reducing swelling and clotting -- essentially, >> healing the cellular damage caused by deco diving. >> >> The more oxygen in your blood, the larger the osmotic pressure >> differential or "window" forcing inert gas out of the surrounding tissue >> and therefore the more efficient (and faster) the deco. Now, at this >> point it sounds like F02 and not P02 is what matters since hemoglobin >> only binds a set number of 02 molecules, but here's another key: higher >> pressures force more oxygen to dissolve in plasma where it's carried >> without hemoglobin. So the higher the P02, the more oxygen is carried > >> over all in the blood and therefore the greater the oxygen window where >> gas is exchanged at the tissue level. > >> Now you can easily see why 80/20 is a poor choice of deco gas compared >> with 100% 02 -- 80/20 reduces the oxygen window because the blood is not >> only carrying dissolved oxygen, it's also carrying nitrogren -- so >> there's lower osmotic pressure and therefore less inert gas moving from >> tissue to blood (and therefore slower, less efficient deco) and there's >> also less oxygen moving from blood to tissue (resulting in more residual >> cellular damage). It's less efficient all around. >> >> In putting this post together, I ran across a couple of websites that are >> worth bookmarking [Cobber -- add these to your links page]: >> http://www.oxytank.com/quanda.htm >> is a terrific resource on hyperbaric oxygen therapy and physiology that >> clears up a lot of concepts and misconceptions about O2 and deco. The >> other link is a hyperbaric medicine glossary -- >> http://www.gulftel.com/~scubadoc/glssry.html -- which is where I found >> the definition of oxygen window. >> >> Best - >> >> Bill Wolk >> >> On8/29/00 1:29 AM, ScottBonis@ao*.co* wrote: >> >> >And finally my basic question, the one I tried clumsily to ask previously, >> >remains exactly what is the relationship between this level of dissolved >> >oxygen in blood plasma (if that's what the "window" is), or the PP(O2) in >> >the >> >deco gas that gives rise to it (if that's what the "window" is), and the >> >rate >> >of off gassing of nitrogen. I'm just having a lot of difficulty following >> >the concept. >> > >> >> Best regards -- >> >> Bill >> >> -- >> Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. >> Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > >-- >Guy > > > > > Best regards -- Bill -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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