Accumulated 02 following a large number of repetitive Nitrox dives over 3 days.

[Madacub]

I've thought that toxicity due to very high partial pressures is more idiosyncratic, not so tightly linked to time of exposure

How about "ALL manifestation of oxygen toxicity, CNS/pulmonary/ocular are time and/or oxygen partial pressure dependent."?

 

[uncfnp]

I've thought that toxicity due to very high partial pressures is more idiosyncratic, not so tightly linked to time of exposure

Obviously all I know is what I read. Everything I have read links at least some degree of time exposure along with partial pressure. It obviously takes some time for the process to develop in both instances. But yes, the time/pressure variable for CNS toxicity is unique to each occurrence but it is still present. It’s why some of us feel comfortable briefly exceeding MOD when needed.

Have I missed something?

 

[Madacub]

MOD for nitrox is something I have never exceeded. (Deco, I'll sometimes deliberately go into depending on the situation) A PPO2 of 1.4 has a fair bit of buffer built in, maybe even 1.6 has a small bit. Maybe that's why you feel comfortable (?). I would not feel comfortable at all.

Convulsions based on CNS toxicity can come on without warning, even at a MOD you have safely been to earlier. That's why I have been perhaps belaboring the point trying to figure out if time exposure to PPO2 can bring about CNS toxicity, even at depths less than the given PPO2 MOD.

 

[Jay]

I’ve not kept up with the posts but I think some of your questions from reading this post might be found here (I don’t think it has been linked yet).

Alert Diver | Understanding Oxygen Toxicity

ALL manifestation of oxygen toxicity, CNS/pulmonary/ocular are time and oxygen partial pressure dependent.

That a good article. Thanks. One highlight for me was:

which make it surprising to me that SW only looks at CNS.

MOD for nitrox is something I have never exceeded. (Deco, I'll sometimes deliberately go into depending on the situation) A PPO2 of 1.4 has a fair bit of buffer built in, maybe even 1.6 has a small bit. Maybe that's why you feel comfortable (?). I would not feel comfortable at all.

Convulsions based on CNS toxicity can come on without warning, even at a MOD you have safely been to earlier. That's why I have been perhaps belaboring the point trying to figure out if time exposure to PPO2 can bring about CNS toxicity, even at depths less than the given PPO2 MOD.

FYI a while ago I asked this: OxTox (CNS) on Nitrox - what if you briefly exceed MOD significantly.

 

[rjack321]

which make it surprising to me that SW only looks at CNS.

Well anyone doing a 10+hr dive knows where they are OTU-wise and doesnt really need SW to remind them of that.