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At 01:50 PM 5/7/99 -0400, Robbert wrote: Hello Robbert, >What if: one took 1 breath of 100% O2 at lets say 70", notice that you >have the wrong one (because the valve is closed) and switch to the >wright one. Can 1 breath do any harm? O2 tox is both dose and time dependant. The higher the PO2, the less time you're likely to have before you tox. Predicting when a given diver will tox, however, is all but impossible. In experiments, divers have been exposed to 100% O2 at 70 FSW (over 3 AtA) until they demonstrated neurological symptoms of O2 tox. The tests were done over a period of 90 days. Any one diver showed symptoms anywhere from 10 minutes to 150 minutes after the beginning of exposure on different days. Attempts to correlate the numbers with fitness, smoking, alcohol, age, etc. were unsuccessful. What does this all mean? Taking a single breath from your O2 bottle at 70' *probably* wont tox you, but it might; there's no telling. If the alternative is to drown, you could probably breath O2 on your way to the surface, but it should be an *absolute last possible resort decision* since you'll probably tox anyway and even if you don't you'll surely get badly bent. If you discover yourself breathing the wrong gas, spit out the regulator immediately and go to your backup regulator which should be hanging around your neck. This should be an almost instinctive behavior whenever there is a gas-related problem. Once you're on back-gas again, the immediate threat is gone, and you have time to figure out what happened and how to fix the problem. I've met tech divers who are under the impression that a toxing diver is conscious and might, "if they try really hard", switch to the correct regulator while toxing. This is not so. O2 tox is very similar to an epileptic seizure. Its onset is not always preceded by any symptoms. You may get a muscle twitch or visual disturbances, or you may not. When the seizure begins, you *immediately* lose consciousness, and typically extend your neck, arms, and legs, and you open your mouth thus losing your regulator. About 30 seconds later, you begin violent periodic contractions of pretty much all your muscles including your diaphragm. With your mouth open, your regulator out, and your diaphragm contracting rhythmically, you breathe large amounts of water and drown. Even if your buddy somehow manages to put the right regulator in your mouth (very unlikely), you will not recover consciousness for several minutes. O2 tox is the primary mode of death among tech divers today. The best way to deal with O2 tox is to avoid it by proper identification *before* you put the regulator in your mouth. Having all deco bottle valves closed except the one you have identified and intend to breathe is, of course, a good safeguard. -Mike Rodriguez <mikey@ma*.co*> -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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