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

[Diver-Drex]

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.

So the amount of inert gas absorbed during a dive is irrelevent?

A NDL is the duration of exposure to depth at which the volume of inert gas absorbed can not be eliminated in a continuous ascent with an acceptable rate of decompression injury.

If the volume of N2 absorbed is irrelevant to DCS then NDLs are meaningless? Breathing EAN is pointless? Decompression stops are a waste of time? Models that predict N2 tissue loading as a means to determine decompression obligation are wrong?

You previously said my statement was wrong. And now concede it is correct but it is irrelevant...

I made a very simple and accurate statement about EAN decreasing absorbed inert gas loading during a given dive. This decrease in gas loading is one way to reduce the risk of DCS. I will not stand in your way if you want to continue to argue against this.

 

[DevonDiver]

A NDL is the duration of exposure to depth at which the volume of inert gas absorbed can not be eliminated in a continuous ascent with an acceptable rate of decompression injury.

You do understand that it's based on statistics, not science right?

Henry's Law and dissolved gas just happens to be hanging out at the crime scenes... but no witnesses .

Likewise, even the role of bubbles in DCS isnt understood... that's if bubbles even do play a role in DCS... it's still not 'fact'. Until now, they're just guilty looking bystanders.

You previously said my statement was wrong. And now concede it is correct but it is irrelevant...

I said your description of Henry's Law was correct. I then stressed, again, that regurgitating a gas physics law was far short from proving a 'fact' relating to bubble growth, DCS and decompression stress.

This side-debate started because you used the F-word... I raised an issue with that.

As I said, re-visit the thread in a decade and review what you currently believe are 'facts' in our understanding of decompression science.

 

[archer1960]

Me - Nitrox allows for greater available bottom time or shorter surface intervals. The risk of DCS and any other harmful maladies while diving air is already so low in recreational diving that any reduction of nitrogen is negligible. 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.

If they feel better after using EAN, that IS evidence. Just not proof that it's the EAN that is doing it.

 

[dmaziuk]

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

do go on...

 

[tarponchik]

do go on...

It just get curioser and curioser with every post.

 

[Storker]

If they feel better after using EAN, that IS evidence. Just not proof that it's the EAN that is doing it.

Anecdote isn't evidence. Even the plural of anecdote isn't evidence. And without a plausible hypothesis, any correlation is worth nada. 15 Insane Things That Correlate With Each Other

However, the hypothesis that post-dive lethargy can be correlated with the choice of diving gas actually has a basis in theory. There are indications that post-dive lethargy can be caused by sub-clinical DCS, i.e. microbubbles. It's generally accepted in the scientific community that the generation of sub-clinical bubbles (microbubbles) is very much dependent on the individual, and on multiple issues before, under and after the dive. If we accept that sub-clinical bubbles are highly individual (both with regards to the person and to the depth profile), and that bubbles may be connected with post-dive lethargy (i.e. sub-clinical DCS), it's not particularly surprising that we see so differing opinions on the efficacy of nitrox and/or ascent profiles, and that there are serious problems with conducting proper, unequivocal studies showing the effect of nitrox on post-dive lethargy.

 

[PfcAJ]

You do understand that it's based on statistics, not science right?


Likewise, even the role of bubbles in DCS isnt understood... that's if bubbles even do play a role in DCS... it's still not 'fact'. Until now, they're just guilty looking bystanders.

Wut

 

[DevonDiver]

Wut

To expand.. DCS is 'probably' a multi-faceted ailment. The variety, spread and onset of symptoms expands beyond the pressure exerted by bubbles of a 'sufficient' size on tissues, or by retarding the cardiovascular system etc etc (hyperbaric injuries).

Of the spectrum of symptoms that can present with DCS, many characteristics are not yet proven in cause. Bubbles are the 'obvious' factor... but absolute medical understanding is not yet achieved nor proven.

The point, as per my side-track discussion, was that many divers assume that certain theories are inalienable facts... whereas the understanding in reality is much less developed.

 

[Diver-Drex]

The no decompression limits are based on statistical analysis of data collected on observed physical phenomenon. That most certainly is science.
Gas going into and coming out of a solution is described accurately by Henry's law. The problem with modeling this in humans is that the body is not a homogenous solution and diving is not a static environment. It is not because the gas laws somehow don't apply. It is correct that we do not know how the gases behave after leaving solution inside the body nor do we fully understand how the body reacts to those gases. But not knowing everything does not mean we don't know anything.
And for the record I still have not stated anything about bubble mechanics. You have done a good job at arguing against statements I have not made, while ignoring what I have said. Very plainly now, the less gas you put into solution means there is less gas that can come out of that solution. You can limit the amount of gas going into solution by decreasing depth, decreasing dive times or by decreasing the partial pressure of inert gas you are breathing. This whole discussion came about because statements were made by others that EAN can increase no decompression limits but somehow does not provide safety margin against decompression injury. It does both by reducing the partial pressure of nitrogen and subsequently it's absorption. Which is Henry's law. That is all I have stated is fact.

 

[tarponchik]

Anecdote isn't evidence. Even the plural of anecdote isn't evidence. And without a plausible hypothesis, any correlation is worth nada. 15 Insane Things That Correlate With Each Other

However, the hypothesis that post-dive lethargy can be correlated with the choice of diving gas actually has a basis in theory. There are indications that post-dive lethargy can be caused by sub-clinical DCS, i.e. microbubbles. It's generally accepted in the scientific community that the generation of sub-clinical bubbles (microbubbles) is very much dependent on the individual, and on multiple issues before, under and after the dive. If we accept that sub-clinical bubbles are highly individual (both with regards to the person and to the depth profile), and that bubbles may be connected with post-dive lethargy (i.e. sub-clinical DCS), it's not particularly surprising that we see so differing opinions on the efficacy of nitrox and/or ascent profiles, and that there are serious problems with conducting proper, unequivocal studies showing the effect of nitrox on post-dive lethargy.

I've already expressed my honest doubts in the existence of such "post-dive lethargy" a.k.a. fatigue.