nitrox at surface to improve off gassing?

[rebelrph]

I'm on my 14 day of a 16 day trip in Cozumel. While here in December I had the thought of instead of discussing the "who say what" while bobbing at the surface and waiting for the boat to pick us up, why not continue to breathe as much 32% nitrox as possible to facilitate off gassing nitrogen and CO2? I've done it each dive this trip and have (after some strange looks and questions) have encouraged other enriched air divers on the boat to do the same. We've been making 60+ minute dives (HP steel 120's) and I'll surface with between 1200 and 1500psi usually. I'll breath from the tank for 8-10 minutes a the surface or down to 1000psi, which ever comes first. The 1000psi is just an arbitrary level I chose to keep the tank as pressurized as possible to prevent oxidation.

Anyway, IS THERE ANY REASON WHY THIS SHOULD NOT BE DONE?

 

[Tortuga68]

It may help with off-gassing nitrogen, although once you take your mask off you're not going to get the full benefit (minimal as that may be) anyway, and since it's only 32%, probably not a huge difference to breathing ambient air IMO

I can't think of any reason why it shouldn't be done, so long as you don't mind the funny looks/questions - whether it has any tangible benefit is another question

Aside from off-gassing faster, what is it that you are you hoping to achieve? Shorter SI, reduced DCS risk, 'value for money' on EAN fills or what?

There's no reason not to breathe your tank down further BTW

 

[Insta-Gator]

Wouldn't continued use of >21% potentially increase your risk of CNS on the next dive?

 

[Tortuga68]

Not really... breathing EAN32 at suraface pressure isn't going to add to your CNS clock or OTUs (assuming that's what you're referring to), especially not for such a short period of time and followed by a SI

 

[TSandM]

You'd get a small advantage in offgassing, and I cannot think of any reason why it should not be done. Your ppO2 on 32% at the surface is really too low to have a significant impact on CNS or OTUs.

 

[doctormike]

Anyway, IS THERE ANY REASON WHY THIS SHOULD NOT BE DONE?

Medical News: EuroPRevent: Diving May Damage Blood Vessels - in Meeting Coverage, EuroPRevent from MedPage Today

I don't know if this is a statistically valid study, or if the conclusions are clinically relevant. But when faced with a question like this, I always ask myself: "Do I want to be in the experimental group or the control group?"

 

[Tortuga68]

I don't know if this is a statistically valid study...

Given that the study was 10 divers across 36 dives, I would suggest not

Either way, I wouldn't have thought that breathing EAN32 for 8-10 minutes on the surface post-dive would make much difference when the entire dive was conducted on the same gas. By diving EAN in the first place, you're already in the experimental group

 

[ianr33]

Anyway, IS THERE ANY REASON WHY THIS SHOULD NOT BE DONE?

No reason at all not to do it, although the benefit using 32% is pretty marginal.

As already stated,the CNS exposure is a non issue.

 

[knowone]

Anyway, IS THERE ANY REASON WHY THIS SHOULD NOT BE DONE?

Only, if you feel left out, and lonely, not being involved with
the others yelling and snorting and squawking and drowning

 

[doctormike]

Given that the study was 10 divers across 36 dives, I would suggest not

True dat!

Either way, I wouldn't have thought that breathing EAN32 for 8-10 minutes on the surface post-dive would make much difference when the entire dive was conducted on the same gas. By diving EAN in the first place, you're already in the experimental group

Double true!