no nitrogen breathing gas ?

[caribou]

We all know about how nitrogen loading at depth limits our bottom time (more than our air consumption.

at recreational depth (say 120 feet), if we were to breath 21% oxygen, 79% helium (or any other inert gas, excluding nitrogen), asides from the problem of getting such a fill, would it eliminate NDL ?

Or would we see the same problem, i.e. the helium goes into solution in the bloodstream, and creates bubbles as the pressure decreases, prompting the need to create tables again...

if not then, since 21% oxygen isn't toxic at this depth (120 feet), what else could prevent us from staying down as long as the gas supply allows and then ascend slowly back up.

Is there physiological problems I don't see or is it just that creating such a mix is not practical, or not stable ?

 

[chickdiver]

Heliox mixes are easy to make- if a bit overkill for these depths. They do not, however, solve the problem of inert gas loading. In the example you cite, helium would be absorbed into the tissues just as nitrogen is, as would any inert (non-metabolized) gas.

 

[daniel f aleman]

Mmmmm.......... cookies.

 

[roakey]

Or would we see the same problem, i.e. the helium goes into solution in the bloodstream, and creates bubbles as the pressure decreases, prompting the need to create tables again...

You'd see the same problem. Helium ingasses and outgasses faster than N2, but the key word is "ingasses" -- just like N2.

Helium is used in diving gasses, but to reduce nitrogen narcosis at deeper depths.

Roak

 

[PerroneFord]

Helium is used in diving gasses, but to reduce nitrogen narcosis at deeper depths.

Roak

Oh. I thought Helium was a ploy to fill the coffers of dive shops who were losing money on air fills. Another way to vacuum the money out of the wallets of the common man.

And now you tell me it's being foisted on the dive community to take away the only cheap high left in the world..

WHEN WILL IT END!

 

[RumBum]

I haven't taken any courses yet for air mixing, but let me take a stab at this and y'all tell me if I have it all wrong...

if we were to breath 21% oxygen, 79% helium (or any other inert gas, excluding nitrogen), asides from the problem of getting such a fill, would it eliminate NDL ?

essentially, there is Nitrox, Heliox, and Trimix. They are used to extend NDL and/or to allow safety with deeper dives (depending on the mix). Each mix has its own set of tables. You are still loading on gasses that your body cannot metabolize so you have to have deco time to offgas before surfacing.

if not then, since 21% oxygen isn't toxic at this depth (120 feet), what else could prevent us from staying down as long as the gas supply allows and then ascend slowly back up.

You can stay underwater as long as you have air supply. But the longer you stay down the longer it will take you to come up. Like in The Abyss - they were down on the u/w station for weeks but had to spend a few days in decompression before they could get back on the surface. That's essentially what a decompression chamber does - brings your body back to the pressurization of a certain depth and over several hours allows you to "ascend" to regular atmospheric pressure.


Correct me if I'm wrong...

 

[PerroneFord]

RumBum, sounds good to me. But I don't know anything. I like your avatar.

 

[chickdiver]

That's essentially what a decompression chamber does - brings your body back to the pressurization of a certain depth and over several hours allows you to "ascend" to regular atmospheric pressure.


Correct me if I'm wrong...

Technically- it is a RECOMPRESSION CHAMBER rather than a "decompression chamber". The individual is recompressed to a specified depth and then slowly decompressed to resolve any DCS issues. The term "decompression chamber" though common, is a misnomer with regard to treating injured divers. There are decompression chambers, but they are used more specifically for other hyperbaric usages (training pilots, altitude studies, etc).

 

[caribou]

all right it makes sense. Then the main benefit to use heliox is to reduce nitrogen narcosis and allows greatest depths (as long as oxygen content is reduced).

 

[daniel f aleman]

Then the main benefit to use heliox is to reduce nitrogen narcosis and allows greatest depths (as long as oxygen content is reduced).

Right now, this is an assumption.