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At 01:04 PM 8/17/99 EDT, Scaleworks@ao*.co* wrote: Hello Kevin, >I have seen divers on a rare occasion up here breathe their 36% from the boat >to the anchor line in a stiff current, and switch to bottom mix at 10 or so >ft when they are not exerting themselves as much. > >Comments? It's not necessary. A healthy person can easily maintain hemoglobin oxygenation while breathing a mildly hypoxic mix even during moderate exertion. People do it all the time when they go mountain climbing or skiing. At 10,000 feet, for example, the PO2 is equivalent to breathing about a 15% O2 mix at sea-level. Prolonged heavy exertion at this pressure will probably make you a little light-headed, but the few minutes it takes to pull yourself to the down-line isn't likely to do it, and by the time you're 10 feet underwater, the PO2 becomes hyperoxic anyway. You'd have to be diving very, very deep to really need a travel mix. On a side note, breathing 100% O2 on the surface to hyperoxigenate your blood just before jumping is nearly ineffectual since a healthy person already keeps hemoglobin nearly 100% saturated under normoxic conditions. You'd get more out of *mild* (emphasis on the word mild) hyperventilation before jumping to give you a *slight* CO2 deficit when you hit the water. I'm talking about one or two deep breaths of air here... the goal is a slight reduction in CO2 in anticipation of the CO2 buildup during the coming exertion... not enough to affect the breathing reflex. -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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