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>Has anyone seen any updates on the theory that Osteonecrosis is caused >by elevated PO2s? Are you sure that's elevated PO2? I've not heard that theory, but as a bone pathologist new to diving, needless to say I've a personal interest in the topic. I'm at the Armed Forces Institute of Pathology and we've done some work in this area. Our theory goes that the osteonecrosis (bone death) that occures in dysbaric conditions (doc-speak for the bends) is the result of more then just N2 bubbles embolizing in the small blood vessels. Animal studies seem to show that there is a 5-fold greater solubility of nitrogen in fat cells with a swelling of the fatty tissue at the cellular level. (more reason to stay in shape and not get overweight!) In soft tissue that's not such a problem, but the marrow fat in all our bones (especially in such areas as the hips, knees and shoulders...where coincidently you get most cases of osteonecrosis) is encased in a shell of unyielding bone. As the fat cells swell, the pressure in the marrow compartment goes up and decreases the already low blood flow to these areas. We figure that the nitrogen transport out of the fatty tissue in these areas is only about half of that in other tissues. Throw in low oxygen partial pressures on top of sluggish blood flow and you essentially strangle the bone. So it may be that there is a two-fold hit on "rapid" decoms. There is the formation of bubbles (the classic theory) that is supported by the observation of microscopic damage to the lining of small blood vessels as well as doppler sound-wave detection of bubbles as well as the swelling of fat cells in bone marrow, raising the internal pressures and reducing the blood flow and supply to bone. What I need to do is start to "bone up" (sorry) on the various "tissue profiles" that are used in the commercial dive computers so I get a better feel for what I'm dealing with on just personal grounds. I'm just now getting my basic and advanced certs and am starting to surf the dive catalogs. CDR Robert B. Wolov, MC, (FS), USNR Department of Orthopedic Pathology Armed Forces Institute of Pathology Washington, DC 20306-6000 wolov@hi*.co* (preferred) wolov@em*.af*.os*.mi*
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