Effect of slow compartments size in relation to NDL and DECO

[narke]

you disagree that the models should be based on half-lives

Nope. I postulate it could factor in size to be even better. I like the model. I will go sleep now 'coz its late and during the weekend I hope to come up with another way to show how I understand half life and then you tell me.

I am not afraid of being mistaken or proven wrong

 

[dmaziuk]

Lipid and sugar metabolism disorders usual with, but not limited to obesity, are linked to chronic inflammation and slower healing. The difference between bubble damage to already inflamed tissue that is not healing too well, and same amount of bubble damage to healthy tissue that heals fast, may well be the difference between clinical and sub-clinical DCS.

By your proposed model, a young 6'10 athlete in perfect health is at higher risk of bends than a 5'1 diabetic because the former has more tissue. By the above model, it's the opposite.

As @Blasto says, the actual processes are not well understood yet, so IRL if one of those two actually gets a DCS hit, it'll likely be written off to individual susceptibility, rather than to the amount of meat on their bones or to a (quite possibly undiagnosed) metabolic disorder.

 

[Blasto]

Why you brush it off like this? You make a great contribution first. Or I misunderstood your last statement.

Well, the above gives a conclusion that it's likely to actually matter if it's 1g or 10kg of tissue in a specific compartment. The difference also definitely isn't linear, maybe logarithmic if I had to guess.

But there's no real way to quantify it, because we lack models that link 1) body tissue type distribution with Haldanean compartment size (rough correlations only), 2) compartment size with DCS probability/severity (no idea). Both are needed to account for it in the deco schedule.

So, presently, simplified models are used, where set M-values are applied to each compartment, and individual differences are accounted for through an overall safety factor (GF).

 

[narke]

I promised @tbone1004 above so here one more time, I am sorry I could not be clearer before, at my best right now I say:

initial quantity (Q): 100
half-life (t1/2): 10
time (t): 10
quantity remains (Qt): 50

initial quantity (Q): 200
half-life (t1/2): 10
time (t): 10
quantity remains (Qt): 100

initial quantity (Q): 200
half-life (t1/2): 5
time (t): 10
quantity remains (Qt): 50

If you start with a higher quantity and the half-time is the same,
after the same time passes the remaining quantity is greater than if you start with a smaller quantity.
To get to the same quantity, the only way is that the half time is smaller.

This may well be the case of what is happening in the body and in two glasses of water of different sizes.
I don't know, this is my question.
Right now I can't think how to device an experiment to test that and can't find evidence for or against in literature.

Henry's law predicts what will be reached at equilibrium.
The model accounts for the change based the half-time concept, it does not consider the absolute quantities, just concentrations.

On the other hand it may well be that the initial quantities are not different enough for them to be relevant even after repetive dives and that other factors that have been exposed in the different interesting contributions may be more significant.

I may not find one answer but my thoughts are clearer (thanks all for this).

 

[narke]

Well, the above gives a conclusion that it's likely to actually matter if it's 1g or 10kg of tissue in a specific compartment. The difference also definitely isn't linear, maybe logarithmic if I had to guess.

But there's no real way to quantify it, because we lack models that link 1) body tissue type distribution with Haldanean compartment size (rough correlations only), 2) compartment size with DCS probability/severity (no idea). Both are needed to account for it in the deco schedule.

So, presently, simplified models are used, where set M-values are applied to each compartment, and individual differences are accounted for through an overall safety factor (GF).

I agree fully makes sense.

 

[narke]

As @Blasto says, the actual processes are not well understood yet, so IRL if one of those two actually gets a DCS hit, it'll likely be written off to individual susceptibility, rather than to the amount of meat on their bones or to a (quite possibly undiagnosed) metabolic disorder.

Agreed makes sense.

 

[100days-a-year]

All the math in the world can't predict the variability of any given individuals ability to perfuse gasses across the capillary bed to and from an imaginary analog of a class of tissue on any given day much less the variability between subjects,hence the need for empirical testing.And....since that involves humans,the data is scarce and biased towards the needs of the party doing the studies for the most part.

Don't let that be a hindrance to all the normal WWW pontification on the veracity of various models and outcomes.

 

[dmaziuk]

now that you mention it... if perfusion is the limiting factor, wouldn't the obese diver be less saturated after the same dive? With much more tissue per roughly the same amount of gas? And of course being less saturated, he's at lower risk of bubbles.

 

[Gessyget]

Well, the above gives a conclusion that it's likely to actually matter if it's 1g or 10kg of tissue in a specific compartment. The difference also definitely isn't linear, maybe logarithmic if I had to guess.

But there's no real way to quantify it, because we lack models that link 1) body tissue type distribution with Haldanean compartment size (rough correlations only), 2) compartment size with DCS probability/severity (no idea). Both are needed to account for it in the deco schedule.

So, presently, simplified models are used, where set M-values are applied to each compartment, and individual differences are accounted for through an overall safety factor (GF).

Thanks for your reply.Very useful.
So, for real no chance to quantify it?Sad.Gonna contine search solutions.

 

[100days-a-year]

now that you mention it... if perfusion is the limiting factor, wouldn't the obese diver be less saturated after the same dive? With much more tissue per roughly the same amount of gas? And of course being less saturated, he's at lower risk of bubbles.

Cause that's not how perfusion works and also,why I used the words " imaginary analog" and also highlights the lack of empirical data