Weird experience today - ox tox warning

[rcain1]

Great topic, great answers, great view points, great topic!

Question. Has anybody dove NITROX with the Sherwood Wisdom computer yet and how did it do? I got mine because of NITROX and want to know forehand shat to watch out for. I never want to see 1.6 PPO2 on it!!!!

Thanks

 

[H2Andy]

You stated it clearly; but it's wrong.

i have looked through your post and i can't find where you
show that my statement was wrong.

please try to explain it again? specifically, which of my
sentences is wrong and how?

remember, if i say "New York City is in New York State,"
you can't say "You're wrong. So is Albany."

while your later statement is true, it does not negate
my prior statement.

 

[pipedope]

In the days of deep air we normally exposed ourselves to PPO2's of 2.0 and higher for 10-15 minutes. How we lived, I am not sure?

I have a few ideas.

We were so narced that the CNS didn't have a chance.
No, this is actually not a joke because high PPN2 reduces the likelyhood of a CNS hit.
Increased PPCO2 increases the likelyhood of a CNS hit, this is part of the reason for a higher limit for the resting part of a dive than for the working part of the dive.

Everything in diving has advantages and disadvantages.
Diving a high HE mix reduces the problems of nitrogen narcosis but increases the risk of O2 CNS tox. Generally a good trade because you can control the PPO2 pretty easily.

 

[MikeFerrara]

But that doesn't explain why two different Suunto computers came up with two different results. I thought maybe I had forgot to plug in the right gas on one of them, but not the case. I'd like for Suunto to explain that to me. As it is, the Cobra is history. There are far better designs on the market that actually enable you to see the OLF data. On the Cobra, if you can see that you have all the bars, then you have better eyes than me, and I am 20/20 bilat.

It's what you get when you use some of these computers. Using a computer to help you make decisions is one thing but it's not always easy to know what the computer is saying. I think some computers, especially the recreational computers, are designed to just be followed by a diver. I'd rather not.

 

[Spectre]

please try to explain it again? specifically, which of my
sentences is wrong and how?

"there are two things you can not exceed: max PO2 for
a mix AND max time at that PO2 for that mix."

My point is that there is -no- max Po2 for the mix; it's a max time at a set po2 that you choose. e.g. you go from 1.6 to 1.7 you don't instantly tox; your clock just changes. going the other direction; if you say 1.4 is your max po2 [150 minutes iirc], then going to 1.6 after 50 minutes; that leaves you with 30 minutes, not 100. likewise going from 1.6 to 1.7 or 1.8 or whatever is the same thing. It's all about the time and there is no magic max PO2.. that's the first point I'm trying to make.

The second point is that it's all subjective; theoretical, and a calculated risk sort of thing. The 1.6 max is a calculated risk for the masses. And that's actually at rest. The 1.4 max is the calculated risk for the masses on a working dive. Some have adjusted that to 1.3 or even 1.2. I believe the constant ppo2 rebreather folk adjust it down even lower.. maybe .8 for working and 1.2 for deco? *shrug* They can comment on what they use.

 

[H2Andy]

My point is that there is -no- max Po2 for the mix; it's a max time at a set po2 that you choose.

well... there is a max po2 for the mix. it is set as 1.6 by my training agency for my diving level. 1.6 is my max PO2.

The second point is that it's all subjective; theoretical, and a calculated risk sort of thing.

agreed, but how does that make what i said wrong?

 

[Spectre]

well... there is a max po2 for the mix. it is set as 1.6 by my training agency for my diving level. 1.6 is my max PO2.

Nevermind... you're right; there is two different things you have to be careful of... :icorolley

 

[reubencahn]

A couple times in this thread, the subject of repetitive multi-day diving on liveaboards has come up. I've never seen a good thread discussing sensible dive planning for such circumstances. How about a thread where some of you lay out your views on what would be the most sensible way to plan such diving? How many dives would you do per day? Max depths? Use computer or no? Vplanner? Break after so many days? Anything else you think should go into good planning?

 

[Jeddah Aquanaut]

Wow, the thread that Scubaholic started was entertaining, to say the least. Just having done the EANx speciality myself, the thread in question was pretty wild at times, but informative. I agree with the majority of responders, that ppO2's are not to be messed with. If he wanted to go to 139 feet, which is of course beyond normal recreational depths, then why was he using nitrox? Should have used air. Either his instructor didn't make it clear enough to him about limits with nitrox, or he ignored them. Scubaholic might think it's cool and aggressive, but who's he trying to impress? I have my own level of what I consider risky, but I want to make it home alive after. I don't make my computer angry. I take care of it and it takes care of me. It's possible to be a cool and pro diver without having to dive 7 times in a day to below 100 feet. You can be Rec or Tec, but not a RecTec. I don't know about him, but dying would really mess up my day, ya' know? Being a paralytic veggie would be worse. I'd like for Scubaholic to 1. not get so defensive and 2. make some of his wonder multi-multi dive day's profiles available for people to peruse for themselves. After all, stories like his are great examples as How-not-to's. Otherwise, he'll end up in Dive Training magazine, in the section where they talk about an accident and why it happened. :11:

 

[Atticus]

Have you manually calculated your oxygen exposure? Can you post your manual calculations and your exact dive profiles? (Not just the total time from your computer)

This would help us understand the dives and would give us a baseline to compare to the computer.

As to the Cobra that you no longer want - I'd be happy to provide you with a shipping address...

Best Regards,
Merlin