In an otherwise healthy human being, the oxygen content (as measured as
a partial pressure of gas) of blood starts dropping off pretty abruptly
below 90-92% (Im omitting co-factors such as temperature, blood counts,
blood pH and such for non-medical people). In the in-hospital
population, we treat saturations below 92% in major medical
center/teaching hospital intensive care units that I work in, and below
90% in persons with SEVERE lung disease (again, Im keeping it simple for
the non-medical people).

I would avoid sats in the 80's as a general rule, if you are going to
titrate your oxygen flow based on a portable pulse ox. You will have
less fatigue, less headache, and less cardiovascular stress. You will
FEEL better.

If your sat is below 92% on the ground, without oxygen, I would
recommend talking to a doctor to find out why.

When I did flight nursing, we dealt with cabin altitudes of 5-7k feet
and it wasnt uncommon for patients to drop from 95% down to the high
80's.. as a result we routinely placed ALL of our patients on low flow
supplemental oxygen.. usually 2 liters per minute as a minimum, and gave
more as needed to keep the saturation up. Keep in mind, these are sick
people with little cardiovascular reserve, so we were minimizing patient
stressors that the healthy flight crew could readily tolerate. I have no
idea what the equivalent settings are on aviation oxygen systems - the
ones I have seen are labelled with altitudes rather than their
corresponding flow rates. But if you are using a pulse ox, adjust it
until you get the desired result.

As for "chamber rides" I dont have any resources on how to set that up.
I know that some NASA facilities can accomplish this, but I dont have
any contact info with regards to that.

Dave, PPASEL, RN/Paramedic

O. Sami Saydjari wrote:

I just bought a FlightStat Fingertip Pulse Oximeter as an added measure
of safety when flying at oxygen altitudes (with oxygen, obviously).
Anyway, the device does not really come with any guidelines on threshold
levels below which you should be concerned.

1. A little background reading suggests that 93% is good; 89% seems to
be OK, but the lowest one would want to go to avoid any imapirment.
Does anyone know definitive values?

2. Does anyone have experience with Oximeters like this? What values do
you see at the higher altiutudes (non-cabin pressure aircraft...just
supplemental oxygen).

3. I read that, at least at one time, one could find places (often
military bases) where pilots could go and experience O2 deprivation in a
controled environment to learn about its effects and how better to
notice them. Does anyone know where on goes to try this out and how one
finds the nearest place to do this. Seems like a good safety exercise.