Surface Breathing of Nitrox After a Dive

[jscott099]

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.

 

[David P]

ok, if breathing 100% has been studied and confirmed, why would breathing <100% but still >21% be bogus? The only real question would be how big of a benefit is breathing <40%. If I was hurting and there was no O2, I'd suck on a bottle of 36... but other than that, I don't think Id spend my time...

 

[ClayJar]

Well, looking at it from simple physics, there's a lower f_N2 in the nitrox compared to air, so it will certainly increase offgassing of N₂. We were even taught that if you don't have O₂ (or don't have enough) that you use whatever nitrox you have available (the higher the O₂ content, i.e. the lower the N₂ fraction, the better).

As for how much it helps, I have not run any numbers on that. Does VPlanner or another allow you to model offgassing on the surface? (A few inches below would work fine for a demonstration.)

 

[DA Aquamaster]

The theory is solid and it would be much like the difference between using 36% rather than air during a deep deco stop in that you would off gas more efficiently. But you are not going to find specific medical research to support it nor are you going to get anyone's blessing to shorten your SI by X amount.

Deco planners like V-Plan or Palm VPM are just that - planners designed for use in specific situations and while you could get an idea of the benefits of 100% O2 during surface intervals, you would be using them outisde your intended use. The closest you would get to related medical research would be studies on pre-breathing of 100% O2 by astronauts and high altitude pilots to avoid DCS in low pressure environments.

Practically speaking it's not uncommon for a diver just surfaced from a deco dive to stay on 100% 02 or their highest deco mix for a while after surfacing and it is not unknown for 100% O2 to be used by a diver as a precaution after a rapid ascent, etc and most dive boats have 100% O2 on board. And administration of 100% O2 is the emergency treatment of choice for suspected DCS cases (and what ever you have for nitrox is better than nothing if 100% O2 is not available.) But given the ready availability of 100% O2 and suitable demand masks there is not much reason to use a lower percentage mix.

If you are interested in this as a way to increase a safety margin with repetetive dives (rather than shorten an SI), it would be worth your while to take an advanced nitrox course and perhaps buy your own O2 system.

 

[Gene_Hobbs]

The only research we have done at Duke was the work on surface interval oxygen that you have seen. I am not aware of any other work out there though we have done some interesting work in the hypobaric literature using a 10.2 psi stage with blow by oxygen to simulate suit donning prior to shuttle EVA (4.3 psi). Note: this is starting at 14.7 psi.

But this is getting into Dr. Deco's work so I'll stop before I hit my limits.

You may find this older thread interesting as well.

Good luck!

 

[robertarak]

Would o2 therapy post dive decrease the time to fly window?

Hypotheticly of course.

 

[Charlie99]

Yes. The limiting factor in flying is the loading of the slower tissues. 100% O2, whether on the surface or at 10' or 20' underwater has the equivalent air depth of -33' (negative 33') for purposes of calculating the average depth of the dive. If you compare the end result of a technical dive with deco gases to repetitive NDL diving using a single air or nitrox mix, in many cases the technical diver will be in better shape as far as time-to-fly limitations.

The gotcha is that while O2 does a very good job of washing out dissolved N2, any bubbles that have formed will offgas much more slowly.

The danger is that you have minor bubble formation in tissues that the O2 doesn't clean out, and that these bubbles then expand with an increase in altitude.

 

[jscott099]

Thanks for the replies. I suggested to him, that while it wouldn't hurt, that there is not enough compelling evidence available to show that it is going to help a great deal. Thus I would be deciding whether to sit there with a reg in my mouth for an undetermined amount of time vs. getting my wetsuit/drysuit off, getting something to drink and eat, and bragging about the sharks I saw on my dive, and taking a nap.

 

[tc]

My only concern would be that breathing the higher PPO2 at the surface could possibly mask minor DCS symptoms during the initial period at the surface. Any thoughts Dr. Deco?

 

[nereas]

My only concern would be that breathing the higher PPO2 at the surface could possibly mask minor DCS symptoms during the initial period at the surface. Any thoughts Dr. Deco?

Masking those minor DCS symptoms would certainly put you in a dilemma.

After all, if your dive plan and execution was so shoddy as to give you DCS in the first place, it would certainly seem like further poor judgment to mask those symptoms, by such things as breathing nitrox or O2 on the surface or on shore after the dive.

I say, why not let the minor DCS symptoms manifest themselves first completey into major DCS symptoms before you take any preventive action such as breathing nitrox or O2 at the surface on on shore? How nice!


i·ro·ny &#8211; noun, plural -nies. 1.the use of words to convey a meaning that is the opposite of its literal meaning: the irony of her reply, &#8220;How nice!&#8221; when I said I had to work all weekend.