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This is a multi-part message in MIME format. ------=_NextPart_000_01F5_01BE6103.A5E81880 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable >>Guys, Can anyone tell me how you can get O2 into a controlling = tissue during deco when the total gas tension of that tissue is greater = than ambient - above blood total gas tension? Chuck Boone<< Chuck, Allow me to take a stab at this one, as a humble student of Diving = Medicine and Physiology. I think you're asking how higher fractions of = oxygen will speed off-gassing of N2 during deco. (If I misunderstood, = IGNORE the rest <g>). Even if you are saturated at depth, and breathing the same gas mix you = were previously, and your tissues have reached 'equilibrium', that does = not mean there is no gas movement. It simply means the _net_ movement is = zero, ie, for every three nitrogen molecules that goes into solution in = your tissues, three migrate out by diffusion. One of the 'gas laws' that applies to this concept is Henry's Law - = that is, the solubility of a gas is directly proportional to its partial = pressure (PP). So, if we can increase the percentage of oxygen in the gas we are = breathing (and therefore, its partial pressure), oxygen will tend to = diffuse into the tissues, and the nitrogen will diffuse out _faster_ = (because those 'three' molecules in the above example will still diffuse = out, but there are only, say two, or zero, molecules of nitrogen to = replace them). We use terms like oxygen "chasing the nitrogen out of = solution", but this is only a visual analogy, and not strictly true. If = I gave you pure argon to breathe, instead of pure oxygen, you would = off-gas the nitrogen just as quickly, because you have reduced the PP of = the inspired N2 to zero. (Natch, breathing pure argon would lead to other. . . problems <g>) And the nice thing about the oxygen, is that even though _it_ will go = into solution in your tissues, you tissues consume it, anyway, and even = if the pressure gradiant was so sudden that the oxygen would want to = bubble up, I'm not sure it would cause any real damage - it would be = metabolized before all the bad things that happen with bubbles could = occur. (That last statement is pure conjecture on my part, I've never heard of = research in that area.) This is one of the reasons why oxygen (as high a % as possible) is the = gold standard of treatment for DCS - even on the surface, if you stop = intaking N2, the gas in the bubbles will be replaced by O2, which will = in turn be absorbed or metabolized by the tissues. Hope that helps, Rich L ------=_NextPart_000_01F5_01BE6103.A5E81880 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> <HTML><HEAD> <META content=3Dtext/html;charset=3Diso-8859-1 = http-equiv=3DContent-Type> <STYLE></STYLE> <META content=3D'"MSHTML 5.00.0910.1309"' name=3DGENERATOR></HEAD> <BODY bgColor=3D#ffffff> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2>>>Guys, Can anyone tell me how you can get = O2 into a=20 controlling tissue during deco when the total gas tension of that tissue = is=20 greater than ambient - above blood total gas tension? Chuck=20 Boone<<</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2>Chuck,</FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2>Allow me to take a stab at this one, as a humble = student of=20 Diving Medicine and Physiology. I think you're asking how higher = fractions of=20 oxygen will speed off-gassing of N2 during deco. (If I misunderstood, = IGNORE the=20 rest <g>).</FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2>Even if you are saturated at depth, and breathing = the same gas=20 mix you were previously, and your tissues have reached 'equilibrium', = that does=20 not mean there is no gas movement. It simply means the _net_ movement is = zero,=20 ie, for every three nitrogen molecules that goes into solution in your = tissues,=20 three migrate out by diffusion.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2><FONT size=3D2> One of the 'gas laws' that applies = to this=20 concept is Henry's Law - that is, the solubility of a gas is directly=20 proportional to its partial pressure (PP).</FONT></FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2>So, if we can increase the percentage of oxygen in = the gas we=20 are breathing (and therefore, its partial pressure), oxygen will tend to = diffuse=20 into the tissues, and the nitrogen will diffuse out _faster_ (because = those=20 'three' molecules in the above example will still diffuse out, but there = are=20 only, say two, or zero, molecules of nitrogen to replace them). We use = terms=20 like oxygen "chasing the nitrogen out of solution", but this = is only a=20 visual analogy, and not strictly true. If I gave you pure argon to = breathe,=20 instead of pure oxygen, you would off-gas the nitrogen just as quickly, = because=20 you have reduced the PP of the inspired N2 to zero.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2>(Natch, breathing pure argon would lead to other. . = .. problems=20 <g>)</FONT></DIV> <DIV><FONT size=3D2></FONT> </DIV> <DIV><FONT size=3D2>And the nice thing about the oxygen, is that even = though _it_=20 will go into solution in your tissues, you tissues consume it, anyway, = and even=20 if the pressure gradiant was so sudden that the oxygen would want to = bubble up,=20 I'm not sure it would cause any real damage - it would be metabolized = before all=20 the bad things that happen with bubbles could occur.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2>(That last statement is pure conjecture on my part, = I've never=20 heard of research in that area.)</FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2>This is one of the reasons why oxygen (as high a % = as=20 possible) is the gold standard of treatment for DCS - even on the = surface, if=20 you stop intaking N2, the gas in the bubbles will be replaced by O2, = which will=20 in turn be absorbed or metabolized by the tissues.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2>Hope that helps,</FONT></DIV> <DIV> </DIV> <DIV><FONT size=3D2>Rich L</FONT></DIV></BODY></HTML> ------=_NextPart_000_01F5_01BE6103.A5E81880-- -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. 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