Weird experience today - ox tox warning

[Scubaholic]

First dive 139 fsw, 32% EAN. Kept no deco, turned dive with one minute bottom time.

Second dive, about 45 minutes later 128 fsw, 32% EAN.

Computer alarm = 100%OLF after a few minutes on bottom of second dive, but wrist computer in failure mode, and had been showing only 60%. Tingline in lips, nausea, a brief sound in my head (I may have been mildly narced, I thought I heard my name called, and then a breif high pitched noise). I meandered up off the bottom and slowly made my way up. Console unit showed me at 100% OLF all the way to the top. I don't think there was a snowball's chance that I was at 100%, and I think computer penalized me big time for a fairly high PPO on that first deep dive. Still , the combination of symtoms with a computer telling me 100% causes me to want to analyze it better.

Those mixes were a little rich for my liking. I don't mind necessarily planning a 1.6 PPO, but the first stop was supposed to be 130, and yada yada yada, it wasn't.

Still, I can't see oxygen toxicity with this scenario, but it got my attention. Does anyone know if DAN would be willing to look at the computerized profiles of the dives?

 

[miketsp]

Those mixes were a little rich for my liking. I don't mind necessarily planning a 1.6 PPO, but the first stop was supposed to be 130, and yada yada yada, it wasn't.

Still, I can't see oxygen toxicity with this scenario, but it got my attention. Does anyone know if DAN would be willing to look at the computerized profiles of the dives?

You were over 1.6 on first dive and nearly 1.6 on second while all major agencies recommend 1.4 max and you wonder why you had problems?
These things are statistical & not binary.

 

[Diver0001]

<snip>

Those mixes were a little rich for my liking. I don't mind necessarily planning a 1.6 PPO, but the first stop was supposed to be 130, and yada yada yada, it wasn't.

This part of your post is very telling. You're ok to *plan* for 1.6 but then admit to being unable or unwilling to dive your plan..... The 1.6 contingency was made for people like you. You should be planning for 1.4 the way you were taught.

You know what. Do yourself a favour and stop diving Nitrox. You're clearly unable to do so responsibly and I would hate to be "learning" from your mistakes the next time we read about one of your dives.....

R..

 

[divenut2001]

Max depth for 32% is 130 ft @ 1.6 bar, 110 ft @ 1.4 bar is what were taught to use. After that ox tox is very likely. Also a tingling sensation IS a sign of ox tox as well as dci. Did a simulated dive of your profile on my computer and it started going off immediately upon reaching 129 ft so I'm sure your's did too!. With in 5 min I was at 100% olf. I was still @ 100% olf after a 45 min simulated si, I'll bet you were too. You said you turned the dive with one min bottom time? Do you mean to say you reached that depth and ended the dive in one min or am I mis reading that? How long were you at depth on each dive? You're very lucky you didn't convulce.

 

[pipedope]

Oxtox is not something that you can predict accurately. The tolerance to O2 is highly variable and an exposure that is fine one day may cause convulsions the next week.

In rec scuba gear convulsions are a very bad thing. If you have no buddy you are almost certain to drown. If your buddy is really excellent then you have a fairly good chance of surviving. Of course a really good buddy would not let you dive these profiles.

If the buddy is so-so he might kill you with AGE if he starts bringing you up while you are still convulsing. Or you might still drown if you get a big shot of water when you take that first breath after the convulsion.

Often, there is NO WARNING before the convulsions start.

There are good reasons for the limits being set where they are. Please review what the limits are and WHY they are what they are. While you are hitting the books check on the other factors that increase the risk of CNS O2 tox.

Once you have a good understanding of the risks you can do what you want, but don't expect us to be any happier about your reported dive profile than your computer was.

 

[BubbaFetta]

First dive 139 fsw, 32% EAN. Kept no deco, turned dive with one minute bottom time.

Second dive, about 45 minutes later 128 fsw, 32% EAN.

Computer alarm = 100%OLF after a few minutes on bottom of second dive, but wrist computer in failure mode, and had been showing only 60%. Tingline in lips, nausea, a brief sound in my head (I may have been mildly narced, I thought I heard my name called, and then a breif high pitched noise).

I'll skip the bash fest on you (as the others have already ragged on you hard enough). But you should treat yourself to a nice meal for being lucky enough to escape unscathed from such a profile.

You need to read up on the max exposure to O2 under NOAA guidelines.
As well as the half-life of O2 exposure (off-gasing).
Please also read up on the MOD (Maximum Operating Depth) of EANx mixtures.

Do not assume that everyone can tolerate 1.6 PPO2 for 45 minutes in a 24 hour period without convulsing. Certain foods, medications can increase your susceptibility--and lower your tolerance--to a CNS Otox event.

Dive safe, dude.


-BubbaFetta

 

[SueMermaid]

Dude! My instructor would slap me silly if he saw that profile on my computer!
Count yourself among the lucky and don't do that again. Okay? You need to get MUCH more conservative about your EAN/dive profile. Seriously.

 

[archman]

Good heavens Scubaholic, I HOPE you're a relative newcomer to nitrox. Seems like you got some of your safety margins confused. Thank goodness you're computer checked ya', else you might still be on the bottom! It's frightening to hear somebody relate symptoms of oxygen toxicity firsthand, wow.

 

[Rick Murchison]

You cannot think of oxygen like nitrogen (well, you can, but it would be a mistake). Nitrogen is inert; it's mere presence - though it has an effect - narcosis - doesn't do damage so long as it stays in solution and is off-gassed on a safe schedule so that no damaging bubbles grow.
Oxygen, on the other hand, is active and poison in high doses or even moderate doses with long exposure. If you're overexposed it does damage. The body must have time to recover from the damage - it must heal. That's why there's a 24 hour sliding window for oxygen exposure rather than a table that starts giving you credit for time out of the water immediately. That's why 100% doesn't start going away in 45 minutes.
Do not trivialize oxygen limits. Oxygen will bite you if mishandled.
Rick

 

[pasley]

Scubaholic,
Thank you for having the courage to share your story with us. From the sounds of things (your dive computer and your friends here on the board) now it is time to revisit your course in EAN and perhaps take a refresher before somthing tragic happens.

I an not EAN certified, so I rally can not comment, but do have to ask if you are EAN certified? From what I have heard both here and in my readings, EAN has depth limits that are NOT just guidelines. It sounds like you pushed the envelope and pushed it more than you realised.

Revisit your training mannuels and learn from the experience, and live to dive another day.