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>Hrm, ok, what I guess I am driving at is this.  At least as I understand
>them, the simple Haldanean tables (Navy, PADI RDP) assume exponential
>ingassing and offgassing with the same time constants(in/out), but it
>is exponential, not linear, so maybe the gradients aren;t the *same*
>but supposing that diver A offgasses more slowly, and he also ingassed
>more slowly (so his tissue loadings were lower than would have been expected)

Hi Folks !

I'd like to add something to the discussion of linear/exponential
relationship. There is a big difference in the nature of the
linear and exponential phenomeneons, from the point of how nature works.
The following will contain some math, but don't worry
about the details if you do not understand it. It will be explained
later.

So, let's assume time t to be variable here, then a linear relation
would look something like n(t) = at + b where a and b are some
constants, but the exponential one will look like
n(t) = exp(at)+b, a and b being again some constants. We'll get
to rates by derivation giving dn(t)/dt = a for a linear and
dn(t)/dt = an(t) for exponential.

Here it can be seen what is the main issue here: for a linear
relation the rate (that is dn(t)/dt in the example) is depending
only of the constant but the exponential depends of the constant
AND the original function.

If we'll put this into diving it means that if n(t) tells us
how much we have nitrogen in our body during the dive, the dn(t)/dt
tells how it is changing with time. So, "linear" means the rate does
not depent of the content of nitrogen in the body, while "exponential"
means that the rate depends also of the content already dissolved in
the tissues. This sounds natural to a diver, right  ?

I do not mean that the in- and outgassing is this simple. I just
wantted to tell about the nature of the exponential phenomenas.
The in- and outgassig are much more complicated matters.

Terho.Kaikuranta@nm*.no*.co*
diver and physicist

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