Does 100% O2 on deco provide a greater benefit than other deco mixes?

[FloridaMan1974]

I understand that the greater the difference between the Nitrogen in your system and the Nitrogen in the mix the faster you will off gas. (Big simplification, but you get the point)

What I'm wondering is if pure O2 has any additional benefits because there is absolutely no Nitrogen in the mix. I recently read that it did, but haven't been able to find any science to back this up.

Is 100% O2 substantially better than 90% or 80%

Thanks,
Max

 

[BRT]

Problem is you can't start on the 100% until you are shallower.

 

[PfcAJ]

Yes, the whole point of a deco gas is to reduce the inert gas you're breathing. Oxygen has the least amount of that.

 

[lermontov]

I understand that the greater the difference between the Nitrogen in your system and the Nitrogen in the mix the faster you will off gas. (Big simplification, but you get the point)

What I'm wondering is if pure O2 has any additional benefits because there is absolutely no Nitrogen in the mix. I recently read that it did, but haven't been able to find any science to back this up.

Is 100% O2 substantially better than 90% or 80%

Thanks,
Max

do you mean additional benefits other than reducing nitrogen %? e.g. shorter deco times than on 21% - less deco gas required?

 

[The Chairman]

You have to wait until 18ft to use O2.
I can jump on 50% at 50 ft.

So, the gas I carry usually depends on where I will be starting my deco. More often than not, I'm using pure O2.

Unless I'm on a breather, then it does all of the mixing as I dive.

 

[PfcAJ]

You have to wait until 18ft to use O2.
I can jump on 50% at 50 ft.

So, the gas I carry usually depends on where I will be starting my deco. More often than not, I'm using pure O2.

Unless I'm on a breather, then it does all of the mixing as I dive.

20ft and 70ft for everyone else.

 

[lermontov]

20ft and 70ft for everyone else.

at what Po2 ?

 

[DevonDiver]

The % O2 doesn't necessarily correlate to shorter deco time. Depending on the dive parameters and ascent profile, lower mixes... breathed from deeper... can cut deco more.

I'd only use 100% for relatively shallow deco dives (30-40m), as there's virtually no stops below 6m. Using a lesser mix would be inefficient, relevant to time at stops.

As dives get deeper, it can make sense to go for a leaner mix. Deeper still and you'd use 2 deco gasses... O2 again becomes an option.

One benefit of 100% is that (above 6m/1.6ppo2) it doesn't matter where you do your stop... from a deco perspective. The only factor is your O2 tracking.

100% is easier to obtain than a blended mix. That's a distinct advantage. All that's really needed is a transfill whip from a medical regulator to a DIN connection.

Obviously, 100% has numerous drawbacks... expecially in regard to O2 tax and otu/CNS tracking.

 

[Kevrumbo]

The use of 100% Oxygen maximally increases the partial pressure gradient for off-gassing supersaturated inert gas slow tissue tensions, along with any pathogenic DCS causing gas bubbles, and also prevents new uptake of inerts -obviously using 100% O2 has zero inert N2 and is more efficient compared to Eanx80 as your last 6m/20' deco stop gas.

In treating acute DCS/AGE in a Recompression Chamber, O2 counteracts the hypoxia of affected tissues and reduces blood sludging; the vasoconstriction caused by oxygen also counteracts the associated edema, which can be of extreme importance in case of edema affecting the Central Nervous System in consequence of type II Neurologic DCS.

 

[kotik]

One "special property" of 100% O2 vs others is that you offgass equally quickly regardless of your depth. So once you switch, your deco time will be the same whether you do all remaining time at 20ft vs moving up to the 10ft stop once cleared to do so. The theoretical advantage there is that if there are micro bubbles in the system there's a better chance they will stay micro if you stay at 20ft, whereas moving to shallower depth with lower ambient pressure could trigger them to start growing.

It's not free though- toxicity of course starts to become a concern when staying at PPO2 1.6 for a while.