Tissue stress associated with bubble formation; potential benefits of diving enriched air

[DevonDiver]

Arguing with someone who believes they feel better after diving nitrox is like telling a religious zealot that his beliefs are not based on any fact. You can't change their mind. They will continue to have faith in spite of no evidence.

There's been quite a bit of debate on the issue of nitrox and post-dive vitality.

On one hand you have a plethora of subjective testimonies alleging it improves vitality (or at least, prevents diminished vitality).

On the other hand, you have a minor study that was looking into the direct chemical effects of hyperbaric oxygen, rather than a decompression science based investigation.

I say this because the oft-quoted study didn't use dive profiles with the necessary potential to cause high bubble scores.

I believe that the jury is still firmly out as to whether oxygen can preserve post-dive vitality in scenarios where 'decompression stress' might otherwise cause perceivable diminished vitality.

That's what we're interested in....isn't it?

Not some fantasy that nitrox has some 'Red Bull' type property to improve our energy after surfacing...

 

[DevonDiver]

Andy, If there is less nitrogen absorbed there is less available to come out. You're going to dispute that, really? I understand there are many unknowns here. That's not one of them.

You seem unclear on the difference between inert gas diffusion and bubble mechanics.

Everything we're discussing is mathematical modelling, statistics and very little actual physiological understanding.

How many 'facts' have already been superceded? Many. . .

The factors that potentially play roles in bubble formation and DCS presentation are staggering: blood chemistry differences, cardio-vascular variances, gas solubility, critical tissues, immuno-reactivity. . . the list goes on. .

Does inert gas even diffuse to/from tissues in series or parallel?

So many things we don't know. . . but are accepted as 'fact' by some. Why? Because they've read something online?

The ONLY true consensus I've heard amongst the leading players in research is that they "don't really know". . .

People get bent on benign, fautless dives well inside no-stop limits. Others walk away clean after horrific ascents from heavily saturated dives. DCS is far more complicated than simplistic: inert gas in </> inert gas out = DCS/No DCS.

And that's before we consider whether NEW catagories, or sub-catagories, of DCS may be defined in the future as more understanding comes to light.

All we have are guesswork theories, known to be incomplete, that make minor differences over enormous sample sizes.

Re-visit this thread in a decade... and lets see what'd seem impossibly outdated, naive and wrong. . .

 

[Diver-Drex]

Andy, I think you're a knowledgeable person and you contribute a lot to the board. I have respect for that. But in this case I think you're just trying to be the smartest kid in class.
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That's what I said. I made no statement about inert gas diffusion or bubble mechanics, nor am I confused about the difference between them.

 

[DevonDiver]

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That's what I said. I made no statement about inert gas diffusion or bubble mechanics, nor am I confused about the difference between them.

No. What you said was...

". It's not a matter of harmless or harmful bubbles, it's less absorbed inert gas to potentially form any bubbles. This is again fact."

You might see why I assumed a bubble-related context to your 'fact"... There was definitely mention of bubble mechanics. Fact

And also why I asked if you were confused on the difference between diffusion and bubble mechanics... as your statement strongly seems to suggest saturated inert gas levels are the only influence on bubble formation.

 

[Diver-Drex]

If there is less inert gas absorbed how can there be anything but less gas absorbed?
Is the amount of inert gas absorbed into solution not the limit of how much gas can then come out of that solution?
Is the amount of gas that can come out of solution not the limit on much gas is available to potentially form bubbles?
Explain to me how what I am saying is incorrect?

 

[tarponchik]

tarponchik - What you are really saying is that there is no disadvantage to nitrox other than cost.

Not exactly since signs of oxidative stress were found in EAN divers.

 

[MaxBottomtime]

From Alert Diver;
Given an equal depth/time exposure, it is generally accepted that the higher the partial pressure of the inspired oxygen (PO2) and the lower the partial pressure of the inert gas (PN2), the less decompression stress will be experienced. It is then tempting to assume that lower decompression stress accompanies reduced perceptions of tiredness. However, a higher PO2 elicits more oxidative stress, and the PO2 of nitrox will be higher than that of air at a given depth.

Some studies of divers suggest that oxidative stress generated by nitrox's higher PO2 might cause mild endothelial dysfunction, which may itself lead to some vague symptoms that may be perceived as tiredness. Observations from hyperbaric-medicine clinicians, who report that greater oxidative stress during hyperbaric oxygen therapy is associated with greater fatigue following treatment, support these findings.

Alert Diver | Air, Nitrox and Fatigue

 

[tarponchik]

@Diver-Drex: The group was the issue, of course. My original point was that when diving with a group of random recreational divers, you are unlikely to extend your bottom time by choosing NITROX because they run out of gas too soon. I've seen this before many times, when half group including myself dives on air, half dives on NITROX, everyone follows the same profile and goes home save afterwards. But this time I gave up because otherwise I'd be the only one on air in the group.

Then this thread got hijacked by NITROX addicts

 

[DevonDiver]

Is the amount of gas that can come out of solution not the limit on much gas is available to potentially form bubbles?
Explain to me how what I am saying is incorrect?

Yes, it's the limit... but it's irrelevant when you consider the large volume of gas absorbed versus the small volume of gas needed to form catastrophic bubbles.

It's not a linear relationship. If only it were that simple...

There are more critical factors at play.

Is the amount of inert gas absorbed into solution not the limit of how much gas can then come out of that solution?

With regards to bubbles and DCS... where is that gas? Dissolved how? Henry's Law diffusion or inherent gas solubility? Lipid or liquid solubility?

What you're calling a fact is Henry's Law. Applying Henry's Law to decompression sickness (or stress) is extrapolating far beyond. . .

This debate has a context... that being 'bubble formation'. There's no facts about bubble formation in the body or how that applies to the malady - or maladies - we describe as decompression sickness. There's only guesswork. The popular guesswork is that which fits within 'acceptable' statistical parameters.

Here's a mind-bomb for you... it's not even proven that bubbles do cause all the symptoms... or harm... associated with DCS. We don't even know the full picture of what DCS actually is. . . only that bubbles are present. The 'usual suspects'. .

Facts... right?

I'd recommend a fun drinking game. Get together with diver friends and watch GUE's video 'The Mysterious Malady'.

Take a 1 finger shot whenever a world-leading deco scientist says the words: Unproven, Guess or Suspected.

Take a 2 finger shot whenever a world-leading deco scientist says the words: 'We don't know'.

Take a 3 finger shot whenever a world-leading deco scientist says something that's been clearly superceded in the decade since the video was shot.

See how sober you are by the end..

 

[DevonDiver]

.. , everyone follows the same profile and goes home save afterwards.

So... now you're categorically denying the occurrence of DCS in recreational divers?