free diving on 100% o2

[eternaljonah]

question 1:
if i were to breath 100% o2 on the surface would i reduce my chances on a black out.
question 2:
if i dived down to 40 meters after having breathing 100% o2 on the surface could i suffer oxygen toxicity. as i swim down my body would use o2 and reduce the % in my lungs.

 

[DivemasterDennis]

No to the oxygen toxicity question. Don't know the answer to the first question.
DivemasterDennis

 

[emoreira]

The shallow water blackout is produced because the PPO2 (Oxygen Partial Pressure) at the end of the dive reduces beyong 10%, forming a gas mixture in your lungs of 79 % N2, 10 % O2 and 11 % CO2. If you breath 100 % Oxygen, that 79% N2 is replaced with O2, so, at the end of your dive your lings will have something like 11% CO2 and 89 % O2. No blackout should occur. At least this is my thought. Any way, that 11 % CO2 will make you hungry to breathe. CO2 buildup is the breathing trigger.

 

[lowviz]

I wouldn't try that for another reason. This may cause partial lung collapse by having nothing left to keep the lungs inflated. http://www.scubaboard.com/forums/diving-medicine/294739-age-deco-diving-pure-oxygen.html#post4564096

 

[nimoh]

No to the oxygen toxicity question. Don't know the answer to the first question.
DivemasterDennis

are you sure about that?

I am not sure, butin thinking about it, it seems to be that as you swim down, the air in your lungs will be compressed to a smaller volume resulting in a higher partial pressure of oxygen (i.e. 1.0 on the surface 2.0 at 33'). Wouldn't this cause more oxygen to be absorbed into the surrounding tissues, and isn't this what causes oxygen toxicity?

However, since you wouldn't be able to stay down there very long, I'm guessing the O2 toxicity risk is very low.

Just to be clear, I am not trying to explain anything here...I don't know the answer.

 

[BluewaterSail]

Maybe if this was in the Freediving forum, it would be more likely to be seen by someone who was knowledgeable in freediving. Its in Advance Scuba now.

 

[ianr33]

I don't know the answer either but, if you totally filled your lungs with O2 then rapidly dropped down to 40 m, that's going to give you a pO2 of 5. (Smaller volume for sure, but the pO2 will be 5) Presumably you will only be there a few seconds,and the pO2 will gradually drop as O2 is absorbed and CO2 and N2 is offgassed, but it still sounds dodgy to me!

 

[lowviz]

You will probably tox long before anything else happens, you can't get around an MOD by holding your breath.

 

[Rhone Man]

I very much doubt that you could tox. Even if you breathe oxygen at a partial pressure of 4.5 ATA (and you would have to be a pretty damn good free diver to get that deep.... most casual free divers struggle to get too far beyond 3.0 ATA (or 66 feet)) it is still going to take several minutes for seizures to set in, and you would only be at max partial pressure for a second, and would spend over half of your hundred-and-eighty-odd seconds at 2.2 ATA or less. And your onset would be slower because you are not continuously breathing it - you have a single lungful of gas.

More to the point... why in God's name would you want to do that? It won't allow you to go deeper or stay longer. The CO2 buildup is the respiratory trigger.

 

[nimoh]

I very much doubt that you could tox. Even if you breathe oxygen at a partial pressure of 4.5 ATA (and you would have to be a pretty damn good free diver to get that deep.... most casual free divers struggle to get too far beyond 3.0 ATA (or 66 feet)) it is still going to take several minutes for seizures to set in, and you would only be at max partial pressure for a second, and would spend over half of your hundred-and-eighty-odd seconds at 2.2 ATA or less. And your onset would be slower because you are not continuously breathing it - you have a single lungful of gas.

More to the point... why in God's name would you want to do that? It won't allow you to go deeper or stay longer. The CO2 buildup is the respiratory trigger.

good point, I didn't initially consider the difference of not continuously breathing. The whole time during the dive, you would be using 02, further reducing the PP02.

I also agree with you on why you would ever want to do this, but I think we are just talking in theory...it's a fun discussion.