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>Robb, > > I have also been told (not by anyone with a medical background) that >extremely rapid rates of descent will cause the blood to become acidotic. >That >is the buffers in the blood cannot compensate for the pH change, due to the >increase in ambient pressure, quickly enough. This is turn is said to >actually >cause the blood to froth, thereby contributing to nitrogen bubble formation. >Can you, or anyone else, shed any light on this? > >Brian Brian, The blood has a fairly well worked out buffering system (ain't Mother Nature grand?!) specifically evolved just to compensate for such *rapid* changes in pH. It's the severe *prolonged* changes that escape the system' s ability to compensate. It's unlikely that the relatively short duration of a descent would be reflected in a change in pH, and by what mechanism? Merely increasing pressure doesn't in itself shift the body's pH (those compensatory buffer systems are all working afterall). If increased pressure pushes more CO2 into solution... and produces more carbonic acid... the body's buffering system shifts its equalibrium and compensates... with no significant change in pH. Even if it did, specific studies have shown that mere CO2 retention doesn't create the symptoms of narcosis. Hypercapnia (the retention of CO2) gives a whole *different* set of neurologic symptoms. "Frothing" sounds pretty violoent! I sort of envision an explosive decompression at near vacuum to get that active a rate of gas coming out of solution! Acidosis, in and of itself, will not cause gases to come out of solution. It that were the case, then every diabetic going out of control of their insulin (developing ketoacidosis) would develop the symptoms of the bends... and that just ain't so. On the other hand, raising the temperature of a solution will reduce the solubility of gas in the liquid phase as will agitation (what happens when you shake a can of beer or soda?) That's the reason the training agencies all teach not to take hot showers and to avoid strenuous exercise after diving. Hope that helps a little. Robb W ======================================== CDR R.B. Wolov, MC, (FS), USNR Department of Orthopedic Pathology Armed Forces Institute of Pathology 14th & Alaska Aves. NW Washington, DC 20306-6000 wolov@hi*.co* (preferred) wolov@em*.af*.os*.mi* -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription requests to `techdiver-request@aquanaut.com'.
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