Hi TC

It was another Nick who set up the forum (it seems you thought it was me,
but I wasn't sure).

[However, if breathing is JUST the balance between atmospheric pressure
and elasticity of the organ structure, the natural outcome should be
eventually (I do not mean death, though it is a natural event) a static
balance between two. The movement cannot perpetual by itself.]

The main thing I was trying to emphasise was that the actual movement in and
out of breath is caused by a non-doing sort of process (inhaling is
atmospheric pressure, exhaling is elasticity of muscle).

It's true that if the pressure on the inside of your chest is equal to
atmospheric pressure, no air moves and you don't breathe. The traditional
theory is that we contract our diaphragms and the muscles between our ribs,
which increases the volume in our chests and therefore reduces the pressure
to below what's outside, causing the air to rush in from outside. And
breathing out is the reverse, the diaphragm and the muscles between the ribs
relaxing, which increases the pressure inside our chests to above what's
outside, and this forces the gases out.

So from this traditional viewpoint there does need to be a do-ing (although
it's automatic) to start the whole cycle off, that first expansion of the
diaphragm and ribs to drop the pressure inside you. Although I wouldn't mind
betting that the traditional picture misses something here - it doesn't talk
a lot about how much that first expansion is in fact assisted by the air as
it begins to rush in, and also it's a fairly static two-component model,
with no sense of what happens at the two ends of this cycle. Breathing is a
continuous process, but this traditional model says nothing at all about the
'apogee' points if you like at the beginning and end of each breath. It
wouldn't surprise me at all if the process becomes self-sustaining once
you've started it - that first expansion is like a starter motor, which then
becomes unnecessary as the alternating pressure and elasticity drives the
cycle. But that's just a hunch - I should see if there's anything in the
literature!

Cheers
Nick