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

[BlueTrin]

So? Why should it be? It is an empirical table.
https://www.scubaboard.com/community/threads/otus-where-do-the-limits-come-from.77221

I was just repeating what you said in a different manner. Please note that I only stated a fact, I don’t have an opinion about the shape.

It is actually linear in the middle part (at least when I glance at it quickly from my phone) but like you said they are just empirical results.

 

[tursiops]

I was just repeating what you said in a different manner. Please note that I only stated a fact, I don’t have an opinion about the shape.

It is actually linear in the middle part (at least when I glance at it quickly from my phone) but like you said they are just empirical results.

Yeah, and like many empirical results, I feel more comfortable NOT using it near the edges. Hence the 80% best practice recommendation.

 

[scubadada]

Ok, so you are saying that my decision to disregard the 02 warning mirrors your experience and strategy, you do it because you have determined that the Oceanic method of calculating 02 exposure is flawed?

I don't have any idea why you chose to disregard the Oceanic O2 warning, over 80% exposure, or the O2 alarm, over 100% exposure. I have chosen to follow an O2 tracking algorithm that allows for an elimination half life rather than one that does not. As a physician and scientist, the elimination half live makes considerably more physiological sense than the cliff credit given by NOAA. I have no good idea if the 90 min elimination half life is actually correct, maybe someone with more knowledge in the area can advise us. I tried to look for the data to support the chosen half life but was stymied in my search. You can find a previous attempt to look at the Seiko Epson O2 tracking calculation here Theory behind the half-life of CNS toxicity? Take a look at the abstract that is cited in my post.

Good diving, Craig

 

[pauldw]

Here's a little OT story that just popped into my head, so I'll share it. Once upon a time my wife and I were visiting the South Rim of the Grand Canyon, and the shuttle bus driver gave us all a little talk as he headed off along the rim with us (the shuttle lets you off wherever you want, including at places without fences, and picks you up when it comes back by). He said that some people think it's funny to stand on the edge and wave their arms like a bird. Occasionally a gust of wind will come along, or the earth will shift underfoot, and then they really will get to be a bird! For a few seconds. His suggestion was: don't stand next to the edge if you don't want to fall off.

 

[uncfnp]

I haven’t seen him post in awhile but maybe this from @Doppler can help here.

Daily Limits for CNS Oxygen Toxicity

His blog entry is from ‘09. Wondering too if his opinion has changed.

 

[scubadada]

I haven’t seen him post in awhile but maybe this from @Doppler can help here.

Daily Limits for CNS Oxygen Toxicity

His blog entry is from ‘09. Wondering too if his opinion has changed.

This is the NOAA table, I have wondered the same

 

[hroark2112]

The PO2 setting on your computer is only for the MOD alarm setpoint. It has nothing at all to do with any calculations or CNS calculations.

That being said, if you're going to ignore your computer, why carry it?

 

[JackD342]

Ok, so you are saying that my decision to disregard the 02 warning mirrors your experience and strategy, you do it because you have determined that the Oceanic method of calculating 02 exposure is flawed?

@scubadada is diving with two different computers, programmed with two different rule sets. Neither one is right or wrong, they are just different. He has made a personal decision to follow the more liberal rule set for O2 exposure. He has NOT decided to completely ignore all limits and warnings, the way that you did on that dive in question. I don’t think anyone is telling you to just ignore any and all O2 exposure limits and warnings. If you want to choose to follow a different, more liberal rule set, then go buy that other computer.

And at the risk of stating the obvious, for any given set of dive profiles the choice of device on your wrist doesn’t make the dives any safer or any more dangerous - the physics and physiology remain the same.

 

[tursiops]

It has nothing at all to do with any calculations or CNS calculations.

Try reading my post again. What you choose for PPO2 (e.g., 1.4 or 1.6) doesn't change the calculations, but it MAY change how you dive, and thus which CNS calculation is relevant to you.

 

[Lorenzoid]

To put it another way, the different methods all seem to keep divers from experiencing symptoms of CNS and pulmonary O2 toxicity. Sort of like how different deco algorithms seem to keep divers from getting bent. Follow whatever your computer tells you in this regard.