Actual O2 Tox at 1.4 PPo2?

[Web Monkey]

Does anybody know if there have been any actual cases of O2 Tox at 1.4 PP O2?

Is that a reasonable number, or should it actually be lower?

Terry

 

[skresch]

Depends, for recreational diving a Po2 of 1.4 is reasonably safe and the accepted value. If you look at NOAA tables, it allows 1.4-1.6. Now when you move over to the technical arena I can think of several divers who have oxtoxed at or below 1.4 although it is still a very small percentage. (Halbach being the most recent/ check TDS for details) Therefore, I guess the answer is it depends…

 

[firemedic1015]

The Deco Stop

 

[lamont]

so what is the difference between someone who oxtoxes, and someone with a undiagnosed/subclinical seizure disorder who has their seizure threshold lowered by a 1.4 ppO2?

 

[skresch]

Intresting reading about Po2 limits for CCR but still relevant to OC.

CNS toxicity in closed-circuit oxygen diving: symp...[Aviat Space Environ Med. 2006] - PubMed Result

 

[skresch]

I look at it as each person has their own po2 limit and then medications of all types and other factors effect that limit rising or lowering it. I do want to say that I am not an expert on hyperbaric medicine nor a tech diver. TDS has a lot of information on this though; it would be a great source to gain more understanding along with that link.

so what is the difference between someone who oxtoxes, and someone with a undiagnosed/subclinical seizure disorder who has their seizure threshold lowered by a 1.4 ppO2?

 

[gcbryan]

so what is the difference between someone who oxtoxes, and someone with a undiagnosed/subclinical seizure disorder who has their seizure threshold lowered by a 1.4 ppO2?

The same difference between someone who oxtoxes and someone with an undiagnosed/subclinical seizure disorder who has their seizure threshold lowered by a 1.1 ppO2.

You have to draw the line somewhere.

 

[DA Aquamaster]

It's more than just the PPO2, it's also the total exposure time as well as other predisposing factors (Co2 retention, high levels of exertion, caffenine, etc.).

As a general number I think 1.4 is "reasonable", but that has the same meaning as a dive table being "reasonable" for safe decompression. People still get bent now and then even within the table limits, especially if they push the limits, use the table beyond what it was designed to do (week long multi-day repetitive dive profiles, etc.) and add some predisposing factors such as dehydration, etc.

In short there are a lot of unknowns and it makes sense to recognize what may increase your suceptibility, be aware of symptoms of an imminent O2 hit and adjust your conservatism accordingly.

 

[Notso_Ken]

Does anybody know if there have been any actual cases of O2 Tox at 1.4 PP O2?

Is that a reasonable number, or should it actually be lower?

Terry

PPO2 is only one factor involved. If you stay all day long at 1.4 PPO2, your total O2 exposure is going to go astronomical. You have to track that for the duratrion of all the dives, just like your computer tracks total nitrogen loading till you've been able to totally de-saturate.

You can actually max out your total O2 at a PPO2 much below 1.4. Calculate and track all the relevant figures. Now that I've got my curiosity up, I might check out the tables to see what dives it would take to max out O2 exposure with a PPO2 of 0.5!


Ken

 

[Web Monkey]

The Deco Stop

Thanks, that was interesting.

I think I'll drop my magic number down to 1.3 . . .

Terry