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This morning i read the following article. in days of old this was the kind of thing I looked forward to seeing on this list instead of all the garbage that so often now fills it. Take a look at what is coming down the line in the next 2-3 years... REPRINT FROM: PRESSURE, UNDERSEA AND HYPERBARIC MEDICAL SOCIETY April 1997, Volume 26, Number 2 BIOCHEMICAL DECOMPRESSION: A Fundamentally New Approach. Susan R. Kayar Our research team at the Naval medical Research institute in Bethesda, Maryland, is working on a radically different method for decompressing divers. Safe decompression currently depends on the loss by passive diffusion of breathing gases that went into solution in the diver's tissue's while at depth. Our new approach envisions an additional active removal of some of these gases by biochemical processes, utilizing bacterial metabolism as the source for the biochemical machinery. The bacteria are packaged, swallowed, and delivered to the large intestine of the diver before the start of the dive. During the dive, some of the gas that is carried in the blood diffuses into the intestine, down the partial pressure gradient created by the metabolism of that gas by the bacteria. End products of this metabolism have a safe route for elimination from the intestine. Judicious selection of the bacterial species prevents a pathological response to the bacteria, which are outcompeted by the native intestinal flora and eliminated over a period of one to a few days following the dive. We have had recent success with the early stages of demonstrating the feasibility of biochemical decompression , using hydrogen as the diluent gas in the breathing mixture and hydrogen-metabolizing bacteria introduced into the intestines of laboratory animals. In our experimental model, bacteria that metabolize hydrogen and carbon dioxide to methane and water were placed in the large intestines of rats. When the rats were pressurized in a hyperbaric chamber, the rate at which they released methane increased with increasing pressure of hydrogen in the chamber, starting within minutes from the introduction of the hydrogen. Methane release rate decreased as hydrogen was later flushed out of the chamber. This demonstrated that hydrogen breathed by the rats was reaching the bacteria on a time scale of seconds to minutes and that the environmental conditions in the intestine were suitable for these bacteria to metabolize the hydrogen . By measuring the total volume of methane released during the dive, we estimated the minimum volume of hydrogen removed from the rats. We had a sample dive profile for the rats breathing hydrogen and oxygen in which we knew that the occurrence of decompression sickness for untreated animals was approximately 50%. We predicted that the volume of hydrogen removed by the bacteria was sufficient to reduce the risk of decompression sickness on this dive profile to 20%. Our prediction was found to be accurate for animals up to 24 hours following bacterial treatment. Hydrogen diving was originally proposed by Arne Zetterstrom, an innovative young engineer with the Swedish Navy in the early 1940's. Zetterstrom recognized that hydrogen, due to its small molecular mass, would reduce the difficulties with ventilating lungs when breathing high-density gases, such as encountered by divers breathing helium-gas mixtures at great depths. Arne Zetterstrom met a tragic death during an experimental hydrogen dive in 1945m and research in hydrogen diving died with him for the next several decades. However, interest was revived in the 1970's. This past summer COMEX announced success with their twelfth human trial, using a trimix of Hydrogen, helium and oxygen to a depth of 210 meters in the open sea. Biochemical decompression with the use of hydrogen-metabolizing bacteria has thus a very real application in human diving today. When we scale up from rats to humans, our results predict that hydrogen biochemical decompression could potentially shorten decompression time from deep saturation dives by several days. Hydrogen biochemical decompression also could reduce counterdiffusion effects potentially encountered during gas shifts, when divers switch from a gas mixture containing hydrogen to one containing helium or nitrogen. Even more exciting is the possibility that nitrogen metabolizing bacteria can be used to achieve biochemical decompression for air dives. While we are still years of animal and then human research away, the possibility exists that swallowing a few capsules the night before a dive might make sport divers safer from the risk of decompression sickness. This work supported by NMRDC work unit no. 61153N MR04101.00D-1103 The opinions and assertions contained herein are those of the author and are not to be construed as official or reflecting the views of the US Navy or the naval service at large. Christopher M Parrett President Abysmal Diving Inc. Makers of Abyss, Advanced Dive Planning Software 6595 Odell Place, Suite G, Boulder, Colorado, 80301 USA http://WWW.ABYSMAL.COM Phone, 303-530-7248 Fax, 303-530-2808 -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send list subscription requests to `techdiver-request@aquanaut.com'.
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