Surface Breathing of Nitrox After a Dive

[tc]

DCS doesn't always result from shoddy dive plans or shoddy execution. It occasionally occurs with very good dive plans and execution too.

I've had one dive leader recommend breathing 100% O2 at the surface after ANY dive over 60 fsw. I felt that was a bit much.

Not trying to discourage anyone but it is something to consider.

DCS treatment is most effective and has much lower incidence of long term disabilities if treated within the first few hours of the symptom onset.

If you breathe O2 right after the dive it's possible that you could reduce the severity of a DCS case and that would be great. Or you could simply mask the symptoms enough that it was not even noticed till much later, not so great. Maybe even a bit ironic.

And where did I state or even imply withholding O2 from someone with ANY DCS symptoms?

 

[BarryNL]

I have a friend who suggests that surface breathing Nitrox (<40%) after a dive could be beneficial for reducing DCS exposure, decreasing SI's, etc.

While I have seen research about surface breathing 100% O2 after deco diving, I have not seen anything that would back up his claim.

Does anyone know if this has been a topic of research by DAN, NOAA, etc.

Well, it will certainly help remove nitrogen from the blood faster. The higher the pressure gradient the faster gas will move across it. Normally, air has a nitrogen PP of 0.79 - breathing nitrox reduces this and so helps increase the pressure gradient between your blood gas and the air in your lungs.

Of course, that's the science. Whether there's any real world benefit from doing it, I don't know. Probably not much.

Though, as an aside, I think there was a famous bug with the Aladdin computers that was getting people bent. Basically when diving nitrox the computer was assuming they kept breathing the same mix during surface intervals and so were removing nitrogen from their blood faster than they actually were.

 

[nereas]

DCS doesn't always result from shoddy dive plans or shoddy execution. It occasionally occurs with very good dive plans and execution too.

I've had one dive leader recommend breathing 100% O2 at the surface after ANY dive over 60 fsw. I felt that was a bit much.

Not trying to discourage anyone but it is something to consider.

DCS treatment is most effective and has much lower incidence of long term disabilities if treated within the first few hours of the symptom onset.

If you breathe O2 right after the dive it's possible that you could reduce the severity of a DCS case and that would be great. Or you could simply mask the symptoms enough that it was not even noticed till much later, not so great. Maybe even a bit ironic.

And where did I state or even imply withholding O2 from someone with ANY DCS symptoms?

[Credibility issue of 1000+ dives deleted].

Technical divers are routinely taught to breathe O2 at the surface after a deco dive. The issue is not "delaying signs of DCS." The object is PREVENTING DCS.

 

[nereas]

Nice comeback, do you actually have anything to add to the discussion or would you rather just toss around personal insults?

I'm always amazed by the folks that take a simple question thats tossed out for discussion and immediately condemn the poster.

Aren't you worried about the inherent danger in your suggestion of delaying surface nitrox or O2 administration?

What if somebody actually takes your advice??

 

[dumpsterDiver]

I have a similar question: A friend of mine decided to breath 100 % oxygen at the END of his surface interval and entered the water and made a rapid descent to around 100 feet. He said that it was only about 2 minutes from when he spit out the oxygen reg on the boat and the time he descended.

Immediately upon reaching the bottom he felt very bad and dizzy etc, which he interpreted as impending oxygen toxicity. He immediately aborted the dive. He is a commercial diver who dives 3 tanks of nitrox each day and he was convinced there were no ther causes of him feeling really bad..

Is there a recommended interval from when someone should delay diving after breathing pure oxygen?

 

[nereas]

I have a similar question: A friend of mine decided to breath 100 % oxygen at the END of his surface interval and entered the water and made a rapid descent to around 100 feet. He said that it was only about 2 minutes from when he spit out the oxygen reg on the boat and the time he descended.

Immediately upon reaching the bottom he felt very bad and dizzy etc, which he interpreted as impending oxygen toxicity. He immediately aborted the dive. He is a commercial diver who dives 3 tanks of nitrox each day and he was convinced there were no ther causes of him feeling really bad..

Is there a recommended interval from when someone should delay diving after breathing pure oxygen?

Yes, there are special CNS Ox Tox exposure tables to determine this, and it is built into many tech software programs as well. The CNS tables used for an ordinary NDL nitrox course are largely the same as those for tech.

However, breathing O2 at the surface entails a ppO2 of 1.0 ATAs, and it is hard to imagine, although entirely possible, that CNS Ox Tox symptoms could be brought on by doing so.

CNS exposure limitations are reset by breathing ordinary air during your surface interval. Therefore after someone has finished breathing O2 or nitrox at the surface, they would begin to measure their surface interval for CNS purposes from the time they stopped the O2 or nitrox and started breathing ordinary air.

It is not a good idea to try to reduce a surface interval, which is normally 1 hour for NDL scuba, and 3+ hours for tech deco scuba. The scheme to use O2 to reduce it can come back and bite you in the form of CNS Ox Tox. Maybe that is what happened to your friend?

 

[tc]

Aren't you worried about the inherent danger in your suggestion of delaying surface nitrox or O2 administration?

What if somebody actually takes your advice??

I don't see where I actually offered that advice. I simply pointed out that it would concern me and asked if Dr. Powell had any thoughts on the topic.

I simply wanted to point out a possible but unlikely consequence of administering O2 on a routine basis after dives and to see if Dr. Powell had an opinion on the subject. That's all. Really.

 

[tc]

Technical divers are routinely taught to breathe O2 at the surface after a deco dive. The issue is not "delaying signs of DCS." The object is PREVENTING DCS.

I agree and did not intend to suggest otherwise.

To clarify, the point I'm wondering about is the routine use of O2 after non-technical dives.

 

[Dr Deco]

Oxygen at he surface is always valuable for off gassing and reducing the size of tissue bubbles. You can not tell the quatitative effect of this, however. If you treat the oxygen breathing [or partially elevated oxygen] as if it were air-breathing time- eg, for time at surface interval - it will not do any harm.

 

[nereas]

Thanks Doc!