susceptibility to oxygen toxicity

[matt]

Had one of my 14 year old Sport diver students ask me a question last night while I was doing ST6 that I couldn't answer. It covers an intro to nitrox and the question was:

"Does your fitness level have any effect on your susceptibility to oxygen toxicity?"

Any ideas anyone????

Cheers
Matt

[David Walker]

I've never heard anything about it, though that doesn't mean it isn't an issue. I've read a lot of "academic-type" papers relating to DCI and oxtox and stuff and it hasn't appeared in any of those...

However at a guess i'd say it would have a small affect, similar to suceptibility to DCS - very hard to quantify. I'd suggest that there's enough leeway in the recommendations to offset any fitness issues, but its always worth keeping away from the limits.

Not a nice theoretcial answer, but the best i can do :(

[Steve in Sharm]

I've never heard anything about it, though that doesn't mean it isn't an issue. I've read a lot of "academic-type" papers relating to DCI and oxtox and stuff and it hasn't appeared in any of those...

However at a guess i'd say it would have a small affect, similar to suceptibility to DCS - very hard to quantify. I'd suggest that there's enough leeway in the recommendations to offset any fitness issues, but its always worth keeping away from the limits.

Not a nice theoretcial answer, but the best i can do :(

I'd have to agree with David :) (wow, dizzy spell, sits down....) dont forget that 1.4 to 1.6 bar are (for want of a better word) "safe" PPO2's for us to work with - they are deemed safe because they are well away from the actual level that would ensure O2 toxicity, in order that differing age groups/body types/genders dont stray into this area.... So in answer to your question - seeing that you are not near max PPO2 then fitness levels should not be an issue.


Of course someone will tell us otherwise :rolleyes:

[David Walker]

I'd have to agree with David :)

:rolleyes:

[Matt-75]

Just tell him to dive with a PPO2 of 1.2 or 1.3, thats all i do, because 1.4 isnt that far from 1.5 or 1.6 which are deemed contingency levels only (or deco levels for when your on the heavy stuff). Its moot, people think im crazy for using a partial pressure of only 1.3, but hell its more of a safety margin, and i can dive for longer before my body gets too saturated.

Also staying on EAN32 for all dives wont harm you, unless your going to 40m, in which case EANx27 or 26 is a better mix. For the shallow stuff though (dives to 10-15m) i still use EANx40.

Besides all of that, im not super fit, have dived on 40 a few times and havent toxed yet, and i know tons of people who are really unfit (5 pints a night and 18st) who dive similar mixes and havent toxed, so i think the chances are good it probably wont happen.

[johnkendall]

Had one of my 14 year old Sport diver students ask me a question last night while I was doing ST6 that I couldn't answer. It covers an intro to nitrox and the question was:

"Does your fitness level have any effect on your susceptibility to oxygen toxicity?"

Any ideas anyone????

Cheers
Matt

There are a lot of therories and not a lot of research into OxTox, which is one of the reasons to avoid it as much as possible. One thing that is thought to effect OxTox is CO2 levels. An unfit person will retain more CO2 than a Fit person, and so will probably be putting themselves at an increased risk.
An unfit person will also be under increased physiological stress while diving, which may also increase the risk.

I am using words like "may" and "probably" because what research there is suggests very little predicability in OxTox other than the risk goes up as the PPO2 goes up.

HTH
J

[Mike Rowley]

I'd have to agree with David :) (wow, dizzy spell, sits down....) dont forget that 1.4 to 1.6 bar are (for want of a better word) "safe" PPO2's for us to work with - they are deemed safe because they are well away from the actual level that would ensure O2 toxicity, in order that differing age groups/body types/genders dont stray into this area.... So in answer to your question - seeing that you are not near max PPO2 then fitness levels should not be an issue.


Of course someone will tell us otherwise :rolleyes:

Lowest recorded O2 hit was on PO2 of 1.28 bar. Incidence of O2 hits rises between 1.4 and 1.6 and rises sharply from 1.6 bar upwards.:eek:

So, not too far away at 1.4 bar PO2.

Mike