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Aldo, I'll try to mix comments and information a bit.... > - If a diver gets stressed by some danger, If the stress is mental, he may get out of breath, but not accumulate, rather get rid of CO2 by hyperventilation. so induce risk of cramps. Then when he develops an "Essouflement" by breathing only on top of his tidal volume, then he will probably not breathe sufficienly to exchange his CO", leading to accumulatio. > produces a lot of CO2, this is normally done by exertion, fighting a current, lifting anchors,etc. > which hits his brain First the CO2 hits sensor which will act in a specific way. CO2 upsets the pH balance, and the natural reaction is increased ventilation, in order to lower the CO2 level. and increases significantly hos O2 need: CO2 is carried in the venous blood stream at the same place which is occupied by oxygen in the arterial stream, at blod cell level. Now if there is to much CO2, it may occupy the oxygens place for to long, leading to what you may have called O2 need. ( in fact, I think it is much more complicated as I am able to explain here) > - will the RB respond to such quicly changes and much higher > demand of O2 __without__ producing an anoxia and a blockout ? The type of stress you mentioned, mostly mental, will not increase oxygen need as much as you may think, though you may be feeling well out of breath. Most oxygen you breathe will jyust be ventilated in and out. Not a problem in a semiclosed rebreather like the Atlantis, it is pretty safe in this respect unless you swim hard near the surface, or do work in excess of a demand of 2,5l Oxygen/minute, equalling an open circuit surface equivalent of 62,5 l/min ( strange enough , this is the CE approval quantity) Not a problem in E/CCR as well, Oxygen will be sensored and added, CO2 scrubbed, if your scrubber is not down, Not a problem in a properly set ( ratiowise, for the gas breathed) DC 55/ SCDS/ Halcyon type of rebreather as well, or even less, because each single breath you get a certain portion of fresh gas. It may be a waste of gas , though, if you ventilate beyond your need. This all may have a special meaning for people with a history of Asthma, of which I am not to sure. However , in a rebreather, you will not have cold gas induced airway irritation. Just my 2cc. cheers Matthias -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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