Accumulated 02 following a large number of repetitive Nitrox dives over 3 days.
- Thread starter Astran
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I believe the more correct term is P02. Its what I see most often in medical use. I see pp02 used most often related to dive gas mixes on dive sites. I seldom see ppO2 used in medical literature.
Think of the formula for Dalton’s Law...
Think of the formula for Dalton’s Law...
PO2 and PPO2 are used interchangeably by divers.
The mantra of every CCR diver's training is "always know your PO2." The reference is not to the tank pressure of the O2 bottle. It means what is the partial pressure of oxygen in your loop.
The mantra of every CCR diver's training is "always know your PO2." The reference is not to the tank pressure of the O2 bottle. It means what is the partial pressure of oxygen in your loop.
Sure. Just like NOAA does....
You could just say P, of course, but no reason not to add the additional info.
If someone hands me a tank and says the pressure is PO2=100 bars, I need to know if he means it is 100% O2, and half full, or full but only half of the gas is O2.
Those are written with subscripts. That was my point earlier.
On the dive site, we also worry about PPN2 and PPHe. So, being explicit and not sloppy is important.
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PO2 can be 1 or 1.6 or 2.0 or 3.1 or whatever.
In this context its synonymous with PPO2 although the latter is (more) specific for diving.
That's just because the vast majority of medical literature is normo-baric and 1 bar pressure is assumed.
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did you get your questions answered?I didn't think any lines were crossed either.
And I am one of probably many who learnt a quite a bit as well.
But a few of the recent posts have confused me. My EAN course was from PADI in Dec 2010, let me declare that up front.
1. In post # 182 Tursiops says "AT PPO2 (not PO2) of ....". My question is not related to the meat of the post, just on the PPO2 vs PO2. I thought they were the same (?).
2. In post # 176 rjack321 says
"there are 3 parts to oxygen and nitrox use
the depth mod
the CNS has a 90min half-life while the oceanic uses a 24hrclock
the daily pulmonary limits do not have a half life - and you exceeded those"
a. I am under the impression that there is no half life with respect to CNS toxicity.
b. I am under the impresion that there may well be a half life with respect to pulmonary toxicity. Maybe 90 minutes, maybe 120 minutes. Some computers take this into account explicitly, some may explicitly not, and some may be silent as to what they do.
Could someone please advise?
3. With respect to what Manatee Diver said in post # 192
"Not only that but those numbers are for pulmonary not for CNS. Recreational computers don't even bother calculating the pulmonary numbers because it is very very hard for non-occupational divers to hit it."
and what GJC confirmed in post # 197
"Absolutely correct about pulmonary, but the exposure over time may also make you more susceptible to a CNS hit if you do another nitrox dive or have to take a chamber ride."
a. I am under the understanding that the so called "oxygen clock" tracks oxygen loading with respect to pulmonary toxicity. The NOAA tables refer to pulmonary toxicity, not CNS toxicity. Divers and various computers (to my regret, even Shearwater) are using a misnomer by referring to a "CNS clock". It is not primarily CNS related.
b. Just so that I clearly understand this, let me go out on a limb and say that CNS toxicity is related only to depth for a given EAN%. You can spend unlimited time within 1.4 ATA, and consider that safe diving practice with respect to CNS toxicity. (I understand about diver to diver and day to day variation, I am specifying "safe diving practice", acknowledging that "things happen".)
Could someone please advise?
the CNS clock has a 90min half life (in theory).
the pulmonary limits run on a 24 hour clock with no half life, and they are cumulative over multiple days as well.
and you definitely can't stay at a ppO2 of 1.4 indefinitely.
GJC
Contributor
No not tank pressure, pressure delivered. Like PO2 1.4 ATM. Maybe the exact definition is wrong, but it just helps me to think of it this way.
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