Gerhard,

I bought a Nonin oxymeter about four years ago and really like having
one for several reasons:

* Even when using O2 it's nice to be able to check occasionally and
make sure the system is working as it should. Without an oxymeter,
there's no feedback if the system started to malfunction. Admittedly
the oxymeter is enough of a hindrance that I cannot leave it on all the
time, so a sudden failure would likely go un-noticed by the oxymeter
(but hopefully caught by me!), but a slow degradation or an error will
be caught.

* When not legally required to use O2, my need for it depends on many
factors and it'snice to be able to measure and see.

* An anesthesiologist friend who flew with me taught me a technique for
getting O2 saturation up significantly and the oxymeter lets me see
whether I've done it enough and if it's working. The technique (helps
with and without supplemental O2): take a deep breath and, when
exhaling, purse your lips or otherwise create a back pressure. This
inflates some of the air sacs in your lungs that are collapsed (some
always are), increasing your lung capacity. The increase in O2 shows up
within 20-30 seconds, but unfortunately goes away just as quickly and
the breathing method takes a lot of energy and concentration. So it's
not the thing to do for a long period of time, but is useful if you're
getting a bit higher than normal for a short period of time or should
your O2 system fail, it could help you while you descend to a safe
altitude.

Martin