ArgOx as decompression gas

[deepmaxim]

Hi folks,

I do have a question regarding your experiences and theoretical thoughts on the use of ArgOx (Argon+Oxygen mixes) for improvement of decompression.

We know from different sources that the solubility of Argon in fat is expected about 2,25 times the one of nitrogen. Other experiments with mice have shown narcosis potential of about 2-3 times of nitrogen.
Anyway, last weekend our team has tried the use of Argox50 (50% Oxygen +50% Argon) on decompression (only 35 mins) from 21m upwards without noticing any strong effects of higher narcosis in real life. Work of breathing also seemed to be at reasonable levels without increasing risks of CO2 hits.

So far so good. As you may imagine our idea behind using Argon for decompression is eliminating any inert gases with which our tissues are already loaded (but O2) from the breathing mix. This is to increase the Delta partial pressures of gases in the tissues and in the breathing gas to speed up off-gasing for faster/safer decompression. Replacing EAN50 or TX50/25 with Argox50 seemed to be the best way to introduce ArgOx in decompression planning as it’s then used widely in the range where it still makes sense from narcosis point of view.

Now I want to know from you if you have any practical experience or theoretical thoughts on the use of Argon. This would especially be interesting when it comes to the calculation of decompression times. Our first idea was to modify Bühlman with gradient factors and to introduce argon besides nitrogen and oxygen as a third gas. Calculation of factors a and b is in this case would be something that I would be interested in your thoughts. Would it be an safe alternative to just “skip” Argon calculation, use EAN50 for calculation and profit from additional safety margins or do I miss something (e.g. the argon-load itself creating potential risk)? Is it safe (probably not) to just skip argon calculation and use only 50%O2 without any other gas in the deco calculation as argon on-gasing would be so slow it would practically not contribute to decompression calculation as other factors will be leading the calculation?

I’m looking forward to a good discussion.

Thanks and best regards

Maxim Vasiljev and Michael Protogerakis
​

 

[pisoiu]

From me only some theoretical thougts:
-from decompression point of view, I would imagine it is best to modify decompression algorythms according to argon parameters, as you would do with helium, since each gas has its own solubility parameters. I would not count on an algorythm adjusted for one gas or mixture of gases (nitrogen on EAN or mixture nitrogen/helium) to be used on another gas.
-I would pay some attention to isobaric counterdiffusion. I don't know the numbers to see if can be a potentian problem, but somewhere during the dive, probably you will switch between different mixtures with big difference in partial pressures. AFAIK, this is not a very well understood problem and it can cause sometimes problems in vestibular system.

 

[deepmaxim]

@Pisoiu
Thx for your post. We think, that Ar has about 2x slowly difussion speed as nitrogen in tissue and (?) the same lipid solubility. But sadly we have not more information about possible coefficient for calculating modified decompression time... If anybody has more information, plese tell us!

 

[Nirvana]

This is an interesting discussion. I'm sorry I can't contribute much, except by pointing to this previous thread where using argox was debated:

http://www.scubaboard.com/forums/te...8338-accelerated-decompression-argon-mix.html

 

[Akimbo]

I was on a project in the 1970s that used the same tissue theory. We alternated air and 80/20 HeO2 up to four dives/day for several weeks. Zero hits… but we had a chamber and hyperbaric doc onboard. The depth, bottom time, and decompression time were essentially the same for each dive.

Scuba divers switched to pure O2 at a 20'; their only water stop. O2 was supplied by hose from a chase boat while we drifted in strong currents. Meanwhile the support vessel came along side. The dive supervisor yanked us from the water stop and recompressed us to 60' in a chamber within 5 minutes (standard Sur-D-O2 procedure). We did a couple of 20 minute O2 periods on BIBs masks. Surfaced at 60'/minute and geared up to do it again. The surface interval was less than 20 minutes sometimes.

Argon is typically the least expensive diluent gas after Nitrogen, but is very dense. CO2 build-up in the depths where 50/50 would be used is an issue.

 

[Rhone Man]

This is an interesting discussion. I'm sorry I can't contribute much, except by pointing to this previous thread where using argox was debated:

http://www.scubaboard.com/forums/te...8338-accelerated-decompression-argon-mix.html

I remember that thread. There was an extremely good anecdote that someone produced from a tec diving conference, where a few guys were discussing a previous ad hoc experiment doing their deco on argox and, in their own words, pretty much everybody got bent.

 

[Akimbo]

...There was an extremely good anecdote that someone produced from a tec diving conference, where a few guys were discussing a previous ad hoc experiment doing their deco on argox and, in their own words, pretty much everybody got bent.

Ahh, the devil is in the details. Juggling tissue tensions of different gasses can work to your advantage… or against you. The difference can be a very narrow corridor.

 

[deepmaxim]

Hey guys! Thanks a lot for your reply! We have used last time the 50% ArgOx on 21m depth. I can not say, that the narcosis effect was much greater than with 50EAN. And WOB was (thx to good regulator) equivalent to EAN. On the end, i had no problem with a density, narcosis or DCS... But it was "try and error" , without any realy serious information about diffusion speed from Argon...And that is what i need... Interesting, that Argon helps tissue under hypoxic condition...