Dive planning and OTU's

[bamafan]

My dives seem to be getting longer and longer. I am on open circuit and having a problem with the CNS clock. I found this paper and was wondering what some others are doing for their dive planning and maximum OTU's for a single dive on a fresh diver. I have been told to try and keep the OTU's for a single dive below 300 but according to this paper "It had been observed that an
operationally acceptable daily exposure for a “fresh” diver
was 850 OTUs." What are others doing?

http://archive.rubicon-foundation.or...pdf?sequence=1

[patpicos]

I worry more about CNS loading than OTU.

To reduce CNS load, made your last stop at 10' rather than 20' where the cave allows.

Some cases, dial down the ppo2. 30% in ginnie Starts to load your CNS for long dives.

[Sludge]

Interesting post. That paper is pretty old, but the subject comes up on the forum from to time.

I read all these things and take them much more cautionary than most. Mainly, I'm no 21-year-old specimen of health. I'm old. The thought of an oxygen hit scares me. I could push the limits and probably get away with it, but I have no desire to do that. So as the years go by, I'm making shorter and shorter dives. I can't remember the last time I made a dive over 90 minutes. Certainly not in the past year. In fact, I've become so scared of an oxygen hit that I usually don't even take oxygen into the water any more. I would rather deco on nitrox for twenty minutes than on oxygen for ten.

I'm probably too cautious, and I'm sure there are plenty of people that disagree with me, but that's what this forum is for.

(My life used to be pretty good - now it's great! So I push fewer and fewer limits now. I still ride the crotch rocket, but never hit triple digits any more.)

[nakatomi]

I'm just curious, are there any documented cases of someone toxing during deco?

As to blowing the CNS clock through the roof, I have a hard time accepting that this would be a good idea. I'm always told that some WKPP people go way beyond 100%, but then in their case I assume everything that is well beyond 100% happens in a deco habitat where toxing may not be so much of an issue.
Also I'm getting told that some rebreather divers break 100% on a regular basis, but then we all know that there are mysterious cases of rebreather dives going wrong too.

[FW]

I'm just curious, are there any documented cases of someone toxing during deco?

Yes, and he was following the suggested PPO2 of the time. the max PPO2 for deco is about half of what it was back then.

[nakatomi]

Yes, and he was following the suggested PPO2 of the time. the max PPO2 for deco is about half of what it was back then.

So he was breathing O2 or Nitrox with a far higher PPO2 than 1.6?

How common is the practice of doing deco at say 10' or 15' with a corresponding PPO2 and the CNS loading getting pushed a long way beyond 100%, say 150% or 200%?

[PfcAJ]

I'm just curious, are there any documented cases of someone toxing during deco?

As to blowing the CNS clock through the roof, I have a hard time accepting that this would be a good idea. I'm always told that some WKPP people go way beyond 100%, but then in their case I assume everything that is well beyond 100% happens in a deco habitat where toxing may not be so much of an issue.
Also I'm getting told that some rebreather divers break 100% on a regular basis, but then we all know that there are mysterious cases of rebreather dives going wrong too.

Not always in habitats, especially not lately.

Low ppo2s on the bottom and gas breaks seems to be successful.

[bamafan]

I was taught that for every 20 minutes on O2 you are supposed to take a 5 minute "air" break. I always do this but I can not find any research where this would allow you to exceed 100% of your CNS clock. I have run numerous scenarios of a 4 hour dive at 90' on V Planner and unless I want some extreme deco I can't get the CNS % below 100%. What are others doing on dives like this?

OTU's vs CNS.pdf

[bent]

It must be must be one hell of an OC dive to worry about pulmonary oxtox. As far as I know its common practice to disregard your % for CCR divers on vacation.
Except from pat, you guys were all talking about CNS tox, but obamafan was asking for pulmonary tox, no? If I'm wrong I'd like to play the foreigner card.
BTW, there should be tons of info on that topic on CCR boards.

[bent]

Ok, bama just posted when wrote my post. Apparently I was wrong than.