Deep diving accident

[fierodiver]

Heres a recent accident that ended well. This story is out of the OC Register. SAN DIEGO – A San Clemente man nearly drowned off San Diego after going into convulsions while underwater Sunday afternoon, authorities said.

The man was 15 feet from the surface and about 1.5 miles from the coast when he started reacting to an air mixture he was using for diving deep into the ocean, said Sans Diego Lifeguard Lt. Andy Lume.

The man's diving partner noticed he was having convulsions and gave him his regulator to supply air, Lume said.

The quick action saved the diver's life, Lume said.

The diver, who has not been identified by authorities, had been diving off La Jolla Shores when the accident occurred at 12:15 p.m. The two divers went underwater to a depth of about 200 feet.

To make the dive, they used a mixture of oxygen and nitrogen called Nitrox, an advanced diving technique to prolong the amount of time a diver is underwater.

The two divers were on their way to the surface and making decompression stops along the way, Lume said. During the stops, the diver seemed to be having a hard time keeping his buoyancy and was kicking hard to stay underneath, Lume said.

"He was inhaling more oxygen than he should," Lume said.

Both divers had experience doing extended dives, but this was the longest dive he'd done.

The San Clemente man is believed to have reacted to oxygen toxicity, where a diver takes in excess amounts of pure oxygen, Lume said.

The man's partner took him up to their boat and lit a flare to alert lifeguards. When lifeguards arrived, the diver had regained consciousness.

The diver was transported to UCSD Medical Center to be treated.

My understanding is that Nitrox typically would not be used for a deep dive like the one described. Am I correct about this? Is Nitrox desirable for very deep dives?

 

[rigdiver]

Probably was on pure O2 at his shallow stops and toxed. Article states he was "having trouble staying down." Exertion increases the risk.

 

[JAMIE MCG]

fierodiver, you are correct, typically not used. On HLplanner @ 200' your PPO on 21% is 1.48, on 22% is 1.55, on 23% is 1.62. If they were using nitrox, that might explain the oxtox.

 

[caveseeker7]

My understanding is that Nitrox typically would not be used for a deep dive like the one described. Am I correct about this?

Yes you are. Nitrox is used to lower the partial pressure of nitrogen in the gas mix, which reduces tissue loading. Less nitrogen, longer no deco times, shorter deco duration should you get into deco. Hence Nitrox is also used as deco gas.

There are sport diving limits for both the partial pressure of oxygen and nitrogen.
Per ANDI they are 1,45 ata pO2 and 4.0 ata pN2. At higher partial pressures of those gases oxygen can be toxic (hyperoxia) and nitrogen becomes narcotic.

200 feet depth equals about 61 meters, so the ambient pressure is about 7,1 ata.
Easier to do the math metric, every 10 m equals a 1 ata, plus the 1 ata at the surface.

Air as a breathing gas at 200 feet has a pO2 of 1,49 ata, a pN2 of 5,61 ata.
Chances are you're narked out of your skull.

While any gas with a fO2 over 21% is considered nitrox, there are some standard mixes, like EAN32 for example (Enriched Air Nitrox 32% O2). At 200 feet/7,1 ata the partial pressures would be 2,27 ata pO2 and 4,83 ata PN2. Slightly narcotic and quite toxic for the average diver.

Using the ANDI limits, the max depth you would want to dive EAN32 would be 35,5 meters, or 116 feet. At that depth the pO2 is 1,45 ata, the pN2 is 3,08 ata. Compared to air you can see the advantages: air's pO2 would be 0,95 ata, the pN2 3,57 ata. Less narcotic, longer NDL.

Without knowing what gas mix was in their tank it's hard to say just how toxic/narcotic the mix was, but it was wrong for the depth in any way.

Is Nitrox desirable for very deep dives?

No, as explained above. Trimix is usually used for deep diving.
Helium is mixed into the gas to keep both pO2 and pN2 reasonably low and safe.

 

[wedivebc]

Per ANDI they are 1,45 ata pO2 and 4.0 ata pN2. .

Did ANDI change this recently? It used to be 4.5pN2

 

[caveseeker7]

Don't know, that's what I remember, and now after dinner I'm way too lazy to look it up. Or ask padiscubapro, Joe's knows the correct value to the 5 digit past the comma.

 

[divebri]

anybody but the people involved don't know the mixtures they were on, and I go by one credo when listening to the news: If it doesn't seem to make sense, it didn't happen that way.

Nobody nitrox-trained, doing deco, would go to 200 on anything more O2-enriched than air, and even that, based on the calculations, is very questionable.

Everything is pure speculation, but I would venture a guess that they were carrying nitrox as a deco gas, then maybe 100% O2 for the 15 ft stop.

But it does raise several questions: were they diving tri-mix? what was their deco gas? were they breathing 100% O2 @15FSW? Was he breathing 100% @15 and through bouyancy issues hit some lower depth and then get oxy-toxed?
And, the most important questions, did they analyze their gases prior to the dive?

It would be interesting to have one of the participants in this sagagive us a detailed post so we really, truly knew.

But, nice recovery by the buddy, that's for sure. Sounds like everything went right when everything went wrong, so to speak.

 

[drbill]

Well, one thing I'd question is if they were doing La Jolla Shores and were 1.5 miles from shore, they should be in some pretty deep water.

Although my physiological response to nitrogen may be quite unusual (after all, everything else about me is), I can dive air to 200 ft and be quite able to function as judged by my videotaping (ability to frame subject, follow subject if moving, etc). Not saying I'm not narc'ed at that depth, just still quite functional.

 

[VooDooGasMan]

The OP story says, he was inhaling more oxygen than he should, During stops noticed problems, fighting to stay down.

Not enough weight ,current, We all know that within 1 minute of any constant movement,you will fight boyuancy even harder, and suck more air (o2).

They said done similiar dives before, So remember your allowed 100% o2 exposure a day.
From this info given on dive they more than likely had there own dive plan, like jamie said, a 22, 23, 24, or who knows 25, planned to 185 went to 200 for 40 seconds (plan the dive dive the plan) so they exceeded there plan a little, one made it the other ran in trouble.
Its possible they were bending the rules of exposure. Extra o2 on deco took it over the top.

Caveseeker, Brought up 32%. The IANTD table 32% 130' 40 min (deco on air 5 min 30'- 3 min 20'- 23 min 15') 50% o2 ( 3 min 20'- 18 min 15,).

With computers and multilevel diving, A diver could think he is in the safe range doing the above dive with a accelerated deco, Then having sucked in to much o2 causing a oxtox hit.

I can see this to be a learning accident, If the divers post there incident.

I'M VERY HAPPY THERE ALIVE MERRY XMAS TO THEM AND HAPPY NEW YEAR.
AND YOU TOO DR.BILL.

 

[drbill]

Certainly would like to see more information on this dive. I've only done depths to about 140' off LJS (I'm an old guy so the surface swims are a PITA!). Likewise, VooDooGasMan!