Subtle hypoxic effects begin at 5,000 ft., particularly noticeable at
night. In the average individual, night vision will be blurred and
narrowed. Also, dark adaptation will be compromised. At 8,000 ft.,
night vision is reduced as much as 24% without supplemental oxygen.
Some of the effects of hypoxia will be noticed during the daylight at
these altitudes without supplemental oxygen during long flights, i.e. 3
to 5 hours.

At 10,000 ft. the oxygen pressure in the atmosphere is about 10 psia.
Accounting for the dilution effect of water vapor and carbon dioxide in
the alveoli, this is not enough to deliver a normal (or less than
needed) supply of oxygen into the lungs. This mild deficiency is
ordinarily of no great consequence. However, flying at an altitude of
about 10,000 ft. (not taking density altitude into account) for 3 to 5
hours will more likely than not cause fatigue in which the pilot may
have compromised performance once he enters his destination. Since the
beginning of powered flight, pilots have reported experiencing
difficulty in concentrating, reasoning, judging, solving problems and
making precise adjustments of aircraft controls under prolonged flight
conditions at altitudes as low as 8,000 ft. MSL.

Please see my website for the entire article

http://www.craggyaero.com/o2_systems.htm

I turn on my Mountain High EDS system to the D5 setting which starts
delivering O2 at 5000 and continues the correct protocol as you climb.

I like to keep my O2 level above 92%. Things like breathing through
you mouth and holding you breath are common and show immediately on a
pulse oximeter.

Richard
www.craggyaero.com

On Jan 26, 9:09 am, "Udo" wrote:
How long does it take for the blood oxygen level to normalize at 15000
ft, after one discovers the flow meter was not adjusted correctly?
Also at what altitude does Oxygen become beneficial, assuming an
average person? Are there any factors, other then altitude it self,
that can lower Blood oxygen level during flight assuming supplemental
oxygen is not used between 5000 and 10000 ft and the pilot has a normal
cardio vascular health? What oxygen level is considered optimum at sea
level and 10000ft to 15000ft?
Udo