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On Fri, 24 Jul 1998 CHKBOONE@ao*.co* wrote: > Is a trimix dive ever actually able to induce a useful oxygen window > during the course of a typical decompression schedule ? > > I am talking here about the real oxygen window that operates between a > bubble / tissue or bubble / blood interface rather than the concentration > gradient it is often mistaken to be. > Chuck, The much maligned term "Oxygen window" actually refers to a popular theme from the 70's (supersaturation theory) that has to do with optimizing the total tissue saturation. It's based on the idea that deeper tissues naturally run an O2 partial-pressure deficit, and that that deficit can be filled by inert gasses during deco. Under normal pressures, this deficit plays a significant part in drawing O2 into the tissues, due to the gradient differential. Note that the true definition of "oxygen window" has nothing to do with either inert gas partial pressure gradients or bubble formation, as popular banter would suggest. > It seems that our practice of maintaining relatively high PPO2 during deco > would serve to keep the oxygen tissue tensions higher than that of any tissue > bound bubbles and the drop in venous PPO2 such a small percentage of the total > that there would be little or no opportunity to diffuse any O2 out of bubbles > in either environment during an ascent after the first gas switch. Chuck, in all honesty, you're mixing terms and concepts here in a way that frankly makes little sense. Among other things, arterial, venous, or any other O2 tensions have little or nothing to do with the real issue, which is inert gas management (whether bubble, microbubble, or theoretically potential bubble). Diffusing O2 out of bubbles is the least of worries. Regards, -Will > For a blood bound bubble to experience an O2 window effect it must pass > from the arterial blood to the venous blood. How do they get on the > arterial side ? > > What does breathing 100% O2 on the surface do to the odds of establishing > an O2 window ? What good does it do to replace inert bubble gasses with O2 > if there is no mechanism to deflate them ? > > It appears that the oxygen window is a relatively useless phenomenon to > the mix diver though it may be invoked to some extent by air divers who do not > switch gasses on ascent. > > This assumes, of course, that there is such a thing as tissue bound > bubbles that are sufficiently isolated from the blood stream as to only off- > gas to the tissues. > > Looking for other thoughts, ideas, and criticisms here ! > > Chuck Boone > > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. > -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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