Freedive Experience with Pure O2?

[wes]

Has anyone experimented with freediving on pure O2. I was taught in my SCUBA course it was (could be) toxic below 10 meters. This I assume is with the diver continuously breathing oxygen. I was wondering if any trials have been done with only taking one breath of O2 on surface and then freediving? I also realize this is potentially very very dangerous to try and greatly appreciate a the DB forum where we can talk about these things!!

Cheers Wes

[naiad]

There is a discussion about that here...
http://forums.deeperblue.net/freediv...00-oxygen.html
Probably dangerous, due to O2 toxicity and CO2 narcosis.

Lucia

[wes]

Thanks Naiad, That thread you linked to was very interesting. As far as actual experiences, it included accounts of Navy divers using first generation pure O2 rebreathers and also one account of lifeguards breathing up on pure 02 and then swimming a bit and waiting at depth of about 5m.

I was wondering if anyone has expericence (that they are willing to share) of actually freediving to some depths beyond the accepted safe depth limit (of continuous breathing) with pure O2 or for that matter other mixed gases.

Cheers Wes

[trux]

Originally Posted by wes

I was wondering if anyone has expericence (that they are willing to share) of actually freediving to some depths beyond the accepted safe depth limit (of continuous breathing) with pure O2 or for that matter other mixed gases.

The toxicity of O2 is influenced by two principal factors: the time you breath the gas, and the partial O2 pressure (combination of percentage of O2 in the gas mixture you breath - in case of pure O2 it is equal to the environmental pressure). You will find tables showing times for which you can breath O2 at different depth in many sources. Check out for example WikiPedia:
Oxygen toxicity - Wikipedia, the free encyclopedia
Maximum operating depth - Wikipedia, the free encyclopedia
The second link shows for example that you could breath pure oxygen for 45min in the depth of 6m, while you could breath safely pure air (~21% of O2) at the dept of 66m for the same time (45min). Apnea times are much shorter (even if on pure O2), so you could afford going deeper - that's why freedivers can go far below the depth that may be already toxic for scuba.

Additionally, the toxicity of O2 due to hyperoxia is reduced by the consumption of O2 in the tissue during apnea, so the tables would be different for apnea (but I doubt you'll find any more precise data anywhere). As already told by others, at apnea on O2, the CO2 toxicity may be often setting on before the O2 toxicity.

[wes]

Thanks Trux, that confirmed my general understanding from reading the older post Naid had linked to. It is pretty fascinating stuff. Makes you wonder how seals and whales avoid O2, CO2 and N toxicity on thier deep and long dives. Seems a very good test would be to implant a device to measeure all those gases in thier blood over time and store data from a long dive. Seems would be a treasure trove of info though technically a very very difficult experiement to do, especially to not injure the animal at the same time. Maybe if we could learn whale or dolphin language we could just ask them?

Cheers

[efattah]

I have thought a lot about this over the years. In fact, I developed what I think is an entirely new system of diving. It involves 'packing' from an O2 cylinder at depth, just one pack every 10-20 seconds. Although 100% O2, no toxicity would be incurred, because you would be consuming the O2 at the same rate as your would be packing it in. Doing this on a full exhale would virtually eliminate any N2 narcosis or DCS, and if done with lots of hyperventilation (20+ minutes) before hand, then CO2 toxicity could be delayed until 15-25 minutes into the breath-hold. WARNING: Please do not attempt this!

Hypothetically, this method could allow 'no-decompression' dives to 400m+, with no narcosis. Chest squeeze would be the only limiting factor.

[wes]

Eric,

Yeah that is a great insight, thanks for sharing it!! I was thinking of something like that but couldn't clarify the details in my head. Do you have any idea how seals or whales deal with gas toxictity (assuming they aren't taking hits off of hidden O2 bottles that we don't know about)?

Cheers Wes

[Jon]

There are many out there that believe that 02 is at LEAST as narcotic as nitrogen- if not more. Since your body is using it up as you breath it you run into other problems- like inner ear DCS.

I've never freedove on it, but I do use 02 to clean myself out after a very long day in the water- like up at Freedive-a-palooza where I am in the water for over 10 hours at a time. The 02 at the end of the day helps me to stay awake long enough to eat my dinner. I use a bottle of pure 02 and just hang out on the fish cribs at 20' for about 10 minutes or so after my last freedive of the day.

For normally long days in the water, like spearing, I don't use anything except a cup of coffee if I have a long drive home.

Jon