Today I think i survived a CNS hit at depth

[TSandM]

Wow -- scary. If it hadn't been for the shaking, I'd say you had a combination of narcosis and a CO2 hit, especially with the depth and level of exertion. But CO2 can also potentiate O2 toxicity. If this really was an oxygen problem, it's one of the lowest ppO2 levels to have been documented as toxic, which is why 1.4 is generally regarded as safe. But this makes GUE's take on using 1.2 as the limit for bottom time, especially if working, look smarter rather than excessively conservative.

Glad you're okay.

 

[ianr33]

Obviously I don't know what this was, but IF it was due to CNS O2 then it's off the scale. The OP was only at 1.3 for a few minutes. Many divers (myself included) will happily run 1.3 for an hour on cave dives.

Very pleased it turned out OK for you.

 

[FoxHound]

Yeah it does sound like an ox tox but the numbers don't really add up, CNS OxTox is combo of both PPO2 and time at that PPO2......neither of which seem unreasonable at all......I'd def be interested to hear what DAN has to say. I was just looking at the NOAA chart for 24h exposure limits and none of your dives bring you too close to the limits at all.

I'm wondering what other factors such as a contaminated tank could be involved?

Glad you are ok!

 

[AaronRiot]

Very scary incident. Glad you made it up ok. Good on you for not panicking too and making it to the DM to thumb the dive right off the bat.

Jim mentioned that CNS is definitely not unheard of at 1.3, I'm wondering if the OP could personally just have a lower than average tolerance??

Thanks for the Deco Stop Link, that account and some of the replies were an incredibly interesting read having to do with an oil contamination in a tank.

 

[ianr33]

Jim mentioned that CNS is definitely not unheard of at 1.3, I'm wondering if the OP could personally just have a lower than average tolerance??

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Look at the time as well though. Toxing after a couple of hours at 1.3 is one thing, after a few minutes (almost/probably) unheard of.

---------- Post added ----------

My vision started to go weird too. It was like when you look through a thermocline, it's just a bit warped, and it started to narrow.

When you say "started to narrow" do you mean it was starting to close down to a point? Sheck Exley described something similar in his book.Happened to him on a really deep air dive (450' ??) Believe that's a pretty classic oxygen symptom.

 

[PfcAJ]

I wouldn't be surprised if it was or wasn't oxygen, there are just so many unknowns.

Days and days of nitrox diving add up, even with a break day here and there. I think there might be more accidents that are caused by oxygen than we're acutely aware of.There is huge inter and intra-subject variability in oxygen toxicity, and the causes and factors associated with it are poorly understood. A conservative approach is the only reasonable course of action because of this. Assuming it was oxygen related, this incident just goes to show that even conservative o2 management practices still carry some risk. If it wasn't oxygen related, it highlights how there are unknowns in diving, and having a good buddy with you can make the difference.

In any case, I'm glad everything panned out the way it did, and I'm glad you took the time to post about it.

 

[eelnoraa]

glad you are OK. this is very scary. And since you are OK, what I really want to know at this point is how would one prevent this from happening again?

 

[markmantei]

Scarry stuff, glad you were able to make it out of the water safely. It would be interesting to hear what DAN has to say.

 

[crispix]

Wow. Thanks for sharing this story. That tank needs to be re-tested to verify the contents and O2 levels. Please tell us what DAN says. I'd be wary of diving again without advice from DAN on how to proceed.

 

[flots am]

You would have been at 1.24, which is just a hair less than the lowest recorded O2 hit I was able to find, which was at 1.28.

You might be a new record holder.

I'd still get the tank tested.

flots.