Deco Gas Question

[detroit diver]

TheDecoStop once bubbled...
Here is some interesting info that I have come accross while doing a little extra research on this subject.

"Furthermore, trying to maintain high partial pressures of oxygen with multiple mixtures results in
vasoconstriction (a reduction in off-gassing potential), increased pulmonary irritation (likely with reduced
diffusion efficiency), and increased CNS toxicity risk."

Just a portion of the story, but interesting. The rest of the story points towards using minimal gases with the best calculated results.

I always like to hear peoples practices and the reasons behind them, so keep them coming.

Rick

When using high o2 gasses, many divers break to back gas at set intervals so that the irritation that you mention above does not occur. That gives them full benefit of the high Po2's without the dangers of irritation and it's problems.

 

[Tampico_ED]

Hi Guys,

Excuse my ignorance. If I understood from other readings...When you go deco TDI 150ft. you can only use EAx21 (Air). Right? ...Also, Am I wrong saying that if you have doubles you put two different Nitrox gases?

I promise to take the TDI courses soon !

 

[Azza]

If high partial pressure is you answer then what is the difference between 36% at 113 feet and 50% at 72 feet. which ever gas you choose to use double your stop time at the gas switch were the PO2 is the highest

That’s great for the initial gas change but what about your ascent from the first gas switch to the second switch? You start running consistently lower and lower PPo2 and consistently higher and higher PP of inert gasses.
You spend more time between 70ft and 20 ft than you do between 113 ft and 70 ft. Surely it’s better to have the advantage of those higher PPo2 before your second gas switch?

as for feeling better, I will pressume you are talking about nitrogen loading, perfect reason to get onto the 80% shallower, and flush that out. do the balance of your deco at the 30 foot stop, and just your added safety deco time at the 20 foot stop.with the 80% there is no back switching required for those longer stop times.

Well you wont be flushing it out as well as jumping on O2 at 20 ft because you are still taking in 20% of inert gasses, as Doppler stated.
Staying on 02 at 20ft for the remainder of deco you have the added benifits of a higher PPo2 and no inert gasses entering your system.

36% and 80% are better choices for deeper diving, until it is time to add in that intermediat trimix, but consideration then is given to added tanks to carry and beyond his question

I don't believe so for the reasons already stated in this thread. However it is up to you how you want to deco...

 

[wedivebc]

Hi Brandon: should have been "VACANT partial pressure effect... also known as Oxygen Window... sorry for the mis-type... gotta start sense-checking this stuff!!! Very, very simply put in the current context... why breathe something that contains 20% of the stuff you are trying to eliminate?

I have not read an understandable explaination of oxygen window from a credible source. Steve, could you point me in a direction that will help me understand this. (other than you know who's rant on the subject)

 

[Lil' Irish Temper]

Just in case,

the last comment from detroit diver was 2 1/2 years ago.

Now back into the secret bat cave I go

 

[wedivebc]

Just in case,

the last comment from detroit diver was 2 1/2 years ago.

Now back into the secret bat cave I go

Doh! (again)

 

[boomx5]

I have not read an understandable explaination of oxygen window from a credible source. Steve, could you point me in a direction that will help me understand this. (other than you know who's rant on the subject)

Boy, I haven't seen this thread in...years. Anyway, Maiken has some good stuff on decompression you might find interesting. I think this the article I'm thinking of. I'll do a bit more searching and see what I can find for you Dave.

 

[Azza]

last comment from detroit diver was 2 1/2 years ago.

Now back into the secret bat cave I go

Doh!!!

 

[BigJetDriver]

Dave,

Try Bennett and Elliot's Diving Medicine for a good explanation.

As for this gas switching nonsense, get a good ECCR and an RGBM wetcomputer, run heliox surface to surface, and forget dragging all these tins of odd mix arround. HA!

As Mr. Natural once said: "Get the right tool for the job, kids!"

 

[eanxgirl]

Wow, Mr. Natural. Talk about a blast from the past!