Decompression chamber question

[Duke Dive Medicine]

Sounds like we are saying the same thing. Convulsions can be the first recognizable symptom, just very rarely. A factor that may put a little space between our experiences is I have only dealt with healthy commercial and military divers who are acutely aware of oxygen toxicity symptoms and have lots of time on a BIBs mask. They are usually the first to raise the red flag, even when caused by too much Tabasco on their corn flakes.

After re-reading, it would have been clearer by writing “I have never witnessed a confirmed or likely O2 hit”. Maybe 1 out of 50-75 runs a symptom was suspected by the diver or super and the mask removed. In every case, the diver went back on the mask after 10-15 minutes and completed the run without further incident. Sorry if there was any confusion.

Hi Akimbo,
I think we're saying different things. I've seen a number of O2 hits in the chamber, and almost without exception, the diver or patient went straight into convulsions. Certainly other symptoms can occur, and maybe these convulsions were preceded by symptoms that the person either didn't recognize or report, but in my experience, it's not the case that convulsions occur more rarely than the other symptoms of O2 toxicity. Thanks for a good discussion.
Best,
DDM

 

[CuNanoTube]

My mother was receiving hyperbaric oxygen treatment for a severe sinus fungal infection and was run at 2.2Ata. (off topic, she dove 60 times last year in the chamber, more than me in the water)

 

[Tigerman]

60 chamber treatments?
I guess shes pretty fed up with sitting in a metal box then..

 

[CuNanoTube]

60 chamber treatments?
I guess shes pretty fed up with sitting in a metal box then..

Fortunately were new acrylic "coffin" style chambers, the hospital put a tv on the outside and had an oxygen proof speaker on the inside, she watched a lot of movies. I also feel inclined to mention the Canadian government covered the full cost of the treatment (which worked).

 

[Tigerman]

They would over here as well (Well, the norwegian one, not the canadian one), but Im not sure if theire doing hyperbaric treatments on that kinda stuff here - But they should as we have the chambers in a few of the larger cities.


Edit: After looking around a bit I see they do infact do hyperbaric treatments for various infections and circulary disorders here. The random facts one finds out from discussions on the internet..

 

[Blastman4444]

My last treatment was in one of the smaller chambers where the whole thing fills with 100% 02 after they put the ground strap on my wrist I was thinking about the Apollo 1 astronauts who burned up after a spark in 100% 02.

 

[Tigerman]

Thats the same typep they use for medical hyperbaric treatment over here as well it seems. For some reason they forbid bringing ignition sources to the chamber

 

[Akimbo]

Hi Akimbo,
I think we're saying different things. I've seen a number of O2 hits in the chamber, and almost without exception, the diver or patient went straight into convulsions.…

Interesting. How much of a factor do you believe or suspect that physical conditioning plays? Here is why I ask: Military non-combat divers are usually in pretty decent shape (excluding alcohol), but nothing compared to SEALs. Commercial divers are usually strong but often have lower cardio fitness.

Some of the guys I worked with were ex-Seals and British Commandos. They often talked about dropping below their 25' limit on O2 rebreathers — the deepest at 25 Meters/82' — pushing 3½ ATA. Considering that they were deep because they concluded the alternative was much more dangerous, the stress level had to be pretty high. I always wondered how much their extraordinary physical condition may have protected them from oxygen toxicity.

Also, have you noticed or suspect a correlation to the first symptom being convulsions at higher PPO2 levels? Max was 2.8 ATA/60' in my career, except for the French divers I observed and described earlier.

 

[Blastman4444]

Do they use full face masks to keep them from spitting the regulator out?

 

[Akimbo]

Do they use full face masks to keep them from spitting the regulator out?

On military pure oxygen rebreathers? No second stage regulators are in their mouth. Modern models have corrugated hoses like mixed gas rebreathers that connect to breathing bags and a chemical CO2 scrubber/canister. There is a HP pure O2 bottle and first stage regulator for manually and/or automatically re-filling the bag(s). The official, and safe limit is 20-25'. The primary purpose is no bubbles and secondarily long duration.

I have seen old photos of facemasks used by Military swimmers but not in years. They might use them in very cold waters or for swimmer delivery vehicle pilots for hard-wire communications. A face mask is a two edged sword in terms of oxygen toxicity. It would be good for convulsions, a problem for vomiting. A hat with a neck seal would be a safer choice but their mass makes them impractical once their heads exit the water. All the ones I have seen were fitted with mouthpieces.