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lottie
06-16-2008, 04:19 AM
I was reading an article in the DAN Alert Diver Magazine that was to do with a diver (not recreational) who had oxygen toxicity. It mentioned about the rescue operation of getting the diver out the water and back onto the boat, where they gave him oxygen.

Now, i've done the rescue course and know that giving someone oxygen to inhale will help them, and I know that oxygen is toxic at depth.

What I can't get my head around is why would giving someone who has oxygen toxicity oxygen???

Any insight into this would be appreciated as i'm confused :confused:

The Publisher
06-16-2008, 04:47 AM
Oxygen does not become toxic until partial pressures start to exceed 1.8.

However in chamber therapy under tightly controlled conditions my understanding is they may exceed P02's of 2.0. The reason being having an oxygen convulsion in the chamber cannot result in drowning compared to underwater.

rubber chicken
06-16-2008, 05:29 AM
If somebody suffers an Oxygen toxicity hit underwater then it is a fair bet that they were rescued straight to the surface ignoring any possible decompression obligations and risking lung overexpansion injury.
Once on the surface, the risk of Ox Tox is removed and standard diving first aid takes over, hence putting the casualty onto O2.

At least that is my reading of the situation. Unless anyone knows different?

dalehall
06-16-2008, 06:59 PM
Also remember that Ox Tox can only happen at depth. At the surface there is no retaining of O2 or Nitrogen in the tissues because you are not under pressure.

lars2923
06-17-2008, 12:33 AM
I would hope my buddy would secure the reg in my mouth,
keep my head tilted upwards, make a slow, safe, steady ascent.
I believe I would come out of the tox, and resume breathing on my own.
If I was in Deco, and if I was feeling up to it, stay as long as safely possible.

While on a trip in Mexico, the last day of a 7 day trip, first dive of the day,
at around 70 feet, my body began to tingle and hum all over...
I notified the DM, I was heading up to a shallower level.. I thought at least I was still diving..
The humming and tingling stopped... then at about 40 feet, it began to hum and
tingle all over, head to toe again... Oh, not good.. So I head up to the
safety stop level and it stopped.. hanging at the safety stop level, the body
began to hum and tingle again.. Oh boy, time to exit the water before something worse happens.
VENTID..
I was diving Nitrox AM on this last day.. During the week, I was diving air
(cause I was diving 130-150 range)in the AM, then nitrox in the afternoon.
Near the end of the week I went to Nitrox all day and kept the dive more shallow... until the last day... Bzzzzzzzz...
Everyting turned out OK... The recompression chamber was contact and when we made it back to the dock, OMG... didn't know the boat called it in.
They were waiting for me at the dock... I decided not to go to the chamber and decided to just relax...
Chill out.. Have a beer (like a dumb ass) and lay down...
I felt better after the beer :-)

The Publisher
06-17-2008, 12:42 AM
Well, I trust you are doing follow up beer treatments.

seasnake
06-17-2008, 12:44 AM
Interesting ... do you think there could've been a possibility of just dehydration?

lars2923
06-17-2008, 02:48 AM
I threw the beer story in there to lighten it up a bit..
I canceled the 3 remaining dives and rested.
I was flying out the next day...

lars2923
06-17-2008, 02:51 AM
Well, I trust you are doing follow up beer treatments.

As required.. Flashbacks you know... Bzzzzzzz

lars2923
06-17-2008, 03:16 AM
I would hope my buddy would secure the reg in my mouth,
keep my head tilted upwards, make a slow, safe, steady ascent.
I believe I would come out of the tox, and resume breathing on my own.


I want to correct myself. One does not stop breathing when one is in O2
Toxicity, one stops breathing after expiring. When my buddy has secured and position my head, I am implying the regulator never fell out of my mouth.

We know the higher the partial Pressure O2, PPO, the longer the bottom time yet the shallower the Target Operating Depth, TOD.

Then there is time to deco.

When you figure out where the time line for O2 clock and the time line for
Deco intersect. This is your O2 limit and no deco max bottom time.

Your objective it to maximize bottom time, minimizing exposure. When the lines cross past the time you take to consume your air supply. Now you begin
working on your Surface Air Consumption, SAC rate. When all the time lines for all the variables converge at around the same point, you would have reach a pinnacle.

bottlefish
06-17-2008, 11:00 AM
A CNS tox hit has two stages, tonic, where the body goes in to spasm and clonic where the body relaxes. During the tonic phase, the airway will be blocked, so ascending the diver at that stage would probably lead to baura traumas. Once the diver goes to clonic phase the airway will reopen, it would then be safe to surface.

If a diver gets a CNS hit then they probably ingest water, and could also suffer some form of baura trauma, in either case oxygen would be the treatment of choice.

CNS tox will generally come from increased PO2 levels, however it can also occur through long exposure to O2. Increased pressure will increase the rate at which this can occur, however this can still happen on the surface (happened to a friend of mine a few weeks back...). It's not really an issue though, getting a CNS tox hit on the surface, whilst undesirable, is not going to cause any long lasting problems. It's also rare, and would require a very long exposure, not something that should be considered when providing O2.