Effect of slow compartments size in relation to NDL and DECO

[narke]

While one may have more gas in him, it's because he took it in faster, ergo he can get rid of it faster.

This is giving me something to think about, thanks.
I don't know.
Where and how is all this adipose tissue distributed in the body?

 

[stuartv]

Yes they start with the same concentration but different quantity.

The culprit is that should they take the same time to reach new equilibrium at P change then they have different half-times (they start off with different quantities). I demonstrated that above.

I said this before. I'll say it one more time.

If they have the same half-time, then they will achieve saturation at the same time and they will return to equilibrium with the surface at the same time. That is by definition of the term "half time".

If you compare two blobs of tissue and you assert that they don't return to equilibrium with the surface at the same time, then, by definition, they do not have the same half-time. In which case, you are comparing apples to oranges.

Nothing about the model asserts that two physically identical types of tissue (e.g. adipose tissue in diver 1 and adipose tissue in diver 2) have the same half-time. You are constructing your hypothesis on the basis that tissues that are physically the same must correlate to model compartments with the same half-time. That is incorrect.

 

[tbone1004]

Would you know if an a body, due to whatever reason - say they way it is distributed, more adipose tissue would need more time to decompress, i.e. effects would not be due to to simple scaling up the quantity?

This is giving me something to think about, thanks.
I don't know.
Where and how is all this adipose tissue distributed in the body?

fat tissue is not necessarily a specific "compartment" you have to factor in every single compartment in the body and it's not like "compartment 11=brain" "compartment 1=skin" "compartment 8=fat" so you can't quantify it that way.
More importantly, regardless of the composition because it is based on the concept of half-lives, it doesn't matter whether you start with 1g or 1 tonne, if the half-life is 30 minutes, then it will lose half of the "quantity" in 30 minutes. I suggest you do some reading on half-times and how they are applied in decompression theory. At that point you may realize it is not the quantity of tissues, just the quality of the tissues

Go hear and scroll about a third of the way down to "Decompression model concepts"
Decompression theory - Wikipedia

 

[Blasto]

What I think is being missed in this simplification (and it is one, like all models have to be) is that the damage caused by specific decompression rates will still vary with the amount of tissue.

If we go beyond the pass/fail logic of end-user models, you don't actually come up from a dive simply bent or not bent. You come up with a specific amount of bubble damage in each of your tissues, which beyond some minimal level produces symptoms of varying severity, which at some point become clinical.

Tying it back to the deco models, at the end of a dive you are "10% bent" in 25% of your tissues, 45% in another 6.3%, etc. The symptoms certainly aren't just a linear function, but it's reasonable to expect them to vary with the amount of damaged tissue.

Since NDL and max GF are just points of acceptable risk and symptom severity, they, and even the perfect deco schedule, should actually vary slightly (maybe very slightly) with body tissue distribution. Of course, since we don't have a verified (if any) model to account for it, it's just written off as part of personal susceptibility. But for less-practical purposes, such as splitting hairs...

 

[narke]

since we don't have a verified (if any) model

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

 

[narke]

if the half-life is 30 minutes, then it will lose half of the "quantity" in 30 minutes

Yep!

 

[tbone1004]

Yep!

so with you agreeing about half-lives, and that is what our favored decompression model is based on and has been for decades, and even the bubble models are based on bubble size, not quantity, what is your current stance on your original post regarding size of the compartments and the effect on decompression stress?

 

[narke]

If they have the same half-time, then they will achieve saturation at the same time and they will return to equilibrium with the surface at the same time. That is by definition of the term "half time".

Nope.
This is what is happening in the model because in the model the compartments have no size.
I don't know if this is happening in real life because the divers start with different absolute amounts of the same tissue and different absolute amounts of N2 and different distribution of the tissues.
In common they will have the same same concentration of N2 to start off with.

 

[tbone1004]

Nope.
This is what is happening in the model because in the model the compartments have no size.
I don't know if this is happening in real life because the divers start with different absolute amounts of the same tissue and different absolute amounts of N2 and different distribution of the tissues.
In common they will have the same same concentration of N2 to start off with.

so you disagree that the models should be based on half-lives? the whole concept of a half-life or half-time in this case is that the size is irrelevant

 

[narke]

fat tissue is not necessarily a specific "compartment"

Yep. This is actually where the model is very strong.