safety stop on 80% O2.

[wedivebc]

It seems to me he is asking more about a sudden oxtox hit due to the exertion.

My guess is that's pretty hard to predict at what level of exersion from what PpO2 people are at risk.

You're probably right but I believe the risk is higher when you are closer to the top of the cns clock. I would be more concerned about the sudden high exersion at higher exposure levels. When diving CCR that is the usual setpoint therefore my loop would usually contain 80% fo2 at 20fsw. I have often exerted myself under those conditions without any effect,

 

[BigJetDriver]

1.3 PPO2 is considered a conservative setting and is usually held through-out most of any RB dives. (Inspiration model)

 

[hecker-the-wrecker]

It seems to me he is asking more about a sudden oxtox hit due to the exertion.

My guess is that's pretty hard to predict at what level of exersion from what PpO2 people are at risk.

Thank you, this was exactly my concern. I'm curious to see what the good doctor says. I think my dive buddy was safe, he's in excellent physical shape. I however could loose a few pounds.

 

[Rick Murchison]

Within the NOAA time limits, I do not believe there has ever been a documented CNS O2 hit at 1.3 (or below). Ever.
Rick

 

[Dr Deco]

Hello readers:

With oxygen toxicity, exertion and exercise all contribute to an increase in carbon dioxide in the blood. This is known to be a factor in oxygen toxicity of the CNS form. In hyperbaric treatment facilities, the patients are at rest and can tolerate much higher PO2s with impunity.

Exercise is a different question. To my knowledge, physical conditioning does not play a role in CNS toxicity.

As the others have indicated, this appears to be a low and tolerable situation.

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology September 10 - 11, 2005 :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[Dr. Doug Ebersole]

The MOD for EAN80 is 33 fsw (for 1.6 ATA). I would not worry about the exertion per se though the reccommendation from IANTD is to decrease your maximum PO2 by 0.05 for each of cold water, heavy exertion, and long decompression. With a maximum PO2 of 1.6 for deco (though I know you were actually doing a "safety stop") and decreasing by 0.05 each for cold water and exertion, you could still safely be at 1.5 ATA which would be a depth of 28 fsw. Therefore, if your buddy could safely stay shallower than 28 fse he should be fine with the EAN80. However, if the anchor line had the chance of pulling him deeper, I would worry about oxygen toxicity and recommend doing as you did and switching back to your bottom gas.