From: jim@spitws117.sbil.co.uk (James Gillespie)
Newsgroups: rec.arts.sf.science
Subject: Re: Gills and Continuous-flow breathing
Date: 25 Aug 92 17:27:52 GMT
Reply-To: jim@spitws117.sbil.co.uk
Organization: Salomon Brothers International Limited

In article 77913@ut-emx.uucp, dillard@ccwf.cc.utexas.edu (Alex Dillard) writes:
>   Actually, there are already two holes, the nose and the mouth.  You could
>take air in through the nose and send it out through the mouth.  When you
>want to eat, just switch to in-and-out breathing through your nose.  The only
>other thing you need is to re-plumb the lungs so that they are connected in 
>series, rather then parallel.  With this set-up, the air goes in through the 
>nose, through the (say) left lung, into the right lung and out the 
>mouth.  The individual lungs could pump the air like the heart does, 
>requiring valves at either end of each lung.  Finally, you could just 
>put a divider in the trachea to divide the incoming and outgoing 
>airstreams.  For eating a valve allowing exhalation through the nose is 
>needed, but this is not much more complicated than the epiglottis 
>which we use to close the trachea when we swallow.
>
>A rough flow diagram:  (where = represents plumbing and =/= is a valve)
>
>   Nose=left trachea=/=left lung=/=right lung=/=right trachea=mouth
>

I don't think this would work exactly as you have described without
extensive reengineering of the lungs themselves.  The lungs are not the
simple bags by which they are often represented.  They are more like a
3D binary tree:  each bronchus subdivides into smaller and smaller
passages until it terminates in millions of tiny alveoli, past which
the blood flows and is oxygenated.

Thus the lungs as they stand can't be set up for a simple flow-through
arrangement.  But do not despair!  With a somewhat fancier set of
valves, not to mention plumbing, maybe the lungs could be hooked up
more like the human heart:

		|    |    |
		| R  |  L |
		|    |    |
		|    |    |
          ------+    |    +------
                 \   |     \
                 /   |     /
          R'   ------+------    L'
                     /
                     \
          -----------------------

L and R are the left and right tracheas, L' and R' are the left and
right lungs (L and R are reversed because the patient is lying on his
back ;-).  Following a breath through a full cycle: inhale left; exhale
left & inhale right; exhale right.

This leaves the problem of how to separately inflate and deflate each
lung, presumably by splitting the chest cavity and diaphgram
(diaphragm?) down the centreline of the body.  Hmmm.  The wall dividing
the chest would have to be rigid.  I think the ribs are independent on
each side anyway, but watching one of these guys breathe would look
pretty weird :-)

There is also the fact that the right lung would get "used" air, i.e. less
O2 and more CO2.  Maybe the right lung would become more efficient (some
hope), or maybe bigger.  Lopsided people.

---
Jim Gillespie ----------------------------------------------------
jim@sbil.co.uk              Salomon Brothers International Limited
+44 71 721 2672             ---------------------------------------------------
"Open your wallets and repeat after me: 'help yourself'" - Major Denis Bloodnok