Jose wrote:

It's been reported that for some, especially at night, altitudes above
5000 feet cause noticable impairment.

I didn't really believe it either until I bought a portable system and
experimented at night; the difference is indeed noticeable (and I am not a
smoker); even when not flying high, it also makes a noticeable difference
I noticed on long cross country flights (you arrived much less tired at
the end)

I bought the system after coming back from a high altitude
training at Beale AFB and I would recommend this training to any pilot:

http://www.faa.gov/pilots/training/a...ce_physiology/

Nonin makes a fingertip device
(pulse oxymeter) to measure blood oxygen saturation. I'm curious myself
as to what my readings would be. However, it's a $300 device, and I
don't often fly that high anyway.

You now find devices -- different brand called Check Mate -- for half
that price. Refilling costs varies considerably from one location to
another one;

--Sylvain