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Karl, >I have been reading in this group how 80/20 is not the gas to use for deco. >I have also been reading that Decoplanner is great and EAN50 @ 70 ft. and 100 >% oxygen at 20 ft. is the DIR way to go. The merits of DIR have been, and are being discussed, by many people and these lists and therefore will not be part of this discussion. I will only say that these principles work in the most extreme diving conditions you can imagine, they make dives possible that only a short time ago were thought impossible. If these principles, and all that go with them,far beyond what you read about on the net, work here, imagine what they can do for simpler dives. > In truth I haven't got the >slightest idea what the "oxygen window" means unless it simply refers to >using the closest PO2 that is below 1.6 that you can get to. The oxygen window refers to a variation between the partial pressures of oxygen on the arterial and venous sides. It comes into play when we have saturated the hemoglobin with O2 and are forcing O2 to dissolve into plasma, which is also used. Assuming a resting workload and continued cardiac output, O2 demands should stay the same which will allow the dissolved levels to climb, to a point that is dependent on pressure, as long as O2 is being breathed. The O2 window should become set at pressures higher than we should see during safe decompression PO2's. The goal is to come as close to this "window", as well as the "curve", as possible to maximize the physiological benefits of decompression. >Now the question I have to ask is that if 80/20 is only used by strokes, why >is it that on a dive to 200 ft. on 18/35 for 30 minutes, doing a deco using >EAN 36 @ 110 ft. and EAN 80 @ 30 ft. actually results in a shorter deco than >EAN50 @ 70 ft. and 100% oxygen @ 20 ft.? I have run the same dive mentioned above and do not get the same results that you have obtained. I also ran several other dives along the same line and with different, but still appropriate gases, and saw an average of four minutes saved by using 50 and 100. Remember that deco programs are nothing more than an easy way to do the mathematical computations that should provide us with a safe time needed to avoid DCS. The reality behind the physiology, which varies from day to day, is often different than what we obtain from such calculations. Four minutes are neither here nor there and are truly inconsequential. The most appropriate approach is to understand the mechanics and the physiology of what is happening to us on a cellular level, and to use that knowledge to achieve the best outcome down to the cellular level. >Any explanations why the stroke mix seems to get you out of the water sooner? As was mentioned before, albeit in slightly different terms, the goal is not necessarily to get out of the water sooner (when we are only talking minutes) but to do the correct amount of deco as well as to simultaneously reap all of the physiological benefits while subsequently reducing the physiological damage. One must consider the damage that this activity can reap on cells and think in a long term fashion in order to reduce damage and hopefully be problem free when we are all chasing each other in wheelchairs and screaming over the hum of our hearing aids. Sincerely, Scott Hunsucker BTW the N2 comment in your last post did not take into consideration that once we stop breathing from a reg we are no longer under pressure and therefore N2 is no longer a concern. There is a small amount of N2 that is dissolved in our tissues all of the time, but breathing N2 at the surface will not get you bent. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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