informations on tissues half times and m values

[TeaBag]

hello doctors!
i'm divecon instructor and i'm working on a decompretion modle
for my students, that shows the nitrogen tention in a tissue
according to depth and the fraction of the nitrogen in the mixture
and the decompration stops according to m values.
i want to improve this modle by adding more tissues half times
for nitrogen and offcourse adding information on other inert
gasses if i can and especially on helium.
my question is: if someone can send me the tissues half time and
m values on other inert gasses or guide to the availble text books.
thanks alot: TeaBag

 

[Liquid]

TeaBag-this mess sure explains why you don't have a "ptor" from english. Let me try and help you:

What teabag looks for is M-values and tissue half time for variouse tissues for use of other gasses than niterox (i.e- Helium, Neon and so forth).

P.S- Did you ask Issac for guidance for the right literature? he might clue you.

 

[Liquid]

Teabag-
Let me know if the info I gave you helped. Gimme a call when you read this (ever since your cell got stollen it's damn hard to get to you!!!!).

 

[BRW]

As a starting point, inert gas M-values
can be assumed pretty much the same for N2,
He, H2, etc. On other gases the jury is still out, and not enough diving data on Ne, Ar, Kr,
etc has been amassed from divers assuming same.

By Graham's law, all gas diffusivities
are inversely proportional to the square root
of their atomic weight. Lighter gases penetrate
(diffuse) more quickly than heavier gases. If
a set of nitrogen half-times, t(N2), is given,
the corresponding set for any other gas, t(gas),
follows from,
1/2
t(gas) = t(N2) [ A(gas)/28]

with A(gas) the atomic weight of the arbitrary gas, and 28 the atomic weight of N2. For He,
A(He) = 4, and

t(He) = t(N2)/2.7

and for H2, A(H2) = 2, and

t(H2) = t(N2)/3.7

and so on with Ne, Ar, Kr. By the way, don't
dive on Ne, Ar, and Kr for both medical and other
reasons.

Bruce Wienke
LANL Counterterror Dive Team Ldr

 

[Liquid]

Hello BRW, great to have you on board here!

I just called Teabag and talled him you answered his thread, so I'm going to leave further questions for him. We work on some algorithms, and got a lot of questions.

P.S-

I will really apreciate it if you could P.M me your personnal e-mail adress (though I will really understand if you'd rather not to).

P.S.S-

Teabag- dont forget to ask about the anomaly with the half-times from Baker's essaey.

 

[TeaBag]

thanks alot
i've managed to infer the comparison between (N) & (He) by comparing "Buhlmann ZH-L12" for helium & nitrogen Mv's & T1/2's but i don't understand why they're not using the same M'vs in compartment (10-16) more then that i'd like to know why in workman's table they ignore the nitrogen 1st compartment T1/2=5 M=31.7 from in the helium tabel T1/2=5 M=26.2 & add a slow compartment that's not calculated in the nitrogen table.
also in "Buhlmann ZH-L16"the same compartments for nitrogen
and helium have different M values.

 

[BRW]

On physics, there is NO reason to assume that
M-values should be same for all inert gases. But
that is where data fits to exposure profiles
started. And of course, M-values are bogus
limit points anyway, And halftimes are arbitary.
Any set of NDLs, halftimes, and M-values can
be backfitted to data -- given two, the third emerges consistently. See TDID -- pages 39 - 44.
Actually, M-values scale as solubility times
diffusivity as chemical limit points for partial
gas separation at metastable equilibrium -- NOT
a case in the body and hence my comment about M-values being bogus to begin with.

The variance in USN and Buhlmann M-values
for He and N2 merely reflects this from both
the data fitting and basic principles side.
And same said for halftime assignments. This is
data fitting mostly, not basic biophysics. The
amount of permissible gas scales as the product
of gas solubility times gas diffusivity (mass
transport coefficient), and halftimes coupled to
M-value only really touch on the diffusivity side
(hence only half correct). Dual phase models
like RGBM touch on both. Nothing more or less
noteworthy here on differences.

For recreational diving, M-values are OK as
mix independent (nitrox and trimix) to lowest order and halftimes consistently scale as
the square root of the ratio of atomic/molecular
masses. But for deco diving, this is not true.
Dual phase models also do not use M-values, but
Haldane models still MUST. The EAD method, tried
and tested for recreational nitrox (and we did helitrox too), attests to the lowest order assumption of equal mix M-values, and halftime
scaling ala Graham's law.

Bruce Wienke
Counterterror Dive Team Ldr.

PS -- Pardon all typos in last postings since I am
on the fly.