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What's minimum safe O2 level?

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Old November 7th 04, 03:20 AM
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Default What's minimum safe O2 level?

I took my Arrow up to 10,500 today to check out my fingertip O2
measuring device. I can maintain 90-93% saturation with deep
breathing and no supplemental O2. Anybody know what the minimum safe
level is for daytime? I guess it might be cumulative, i.e. the longer
you go at 92% the less safe it is? Dropped down to about 88% when I
got distracted with some cockpit chores and started normal sea level
Old November 7th 04, 03:41 AM
Peter Duniho
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"PaulH" wrote in message
I took my Arrow up to 10,500 today to check out my fingertip O2
measuring device. I can maintain 90-93% saturation with deep
breathing and no supplemental O2. Anybody know what the minimum safe
level is for daytime?

It all depends on the individual, but 90% saturation is considered about the
safe minimum.

The effects ARE cumulative over time, hence the 30 minutes granted for
operations without oxygen between 12,500' and 14,000'. However, IMHO at a
safe saturation level the main effects of extended time without supplemental
O2 have to do with fatigue, leading to secondary impairment, rather than
impairment due directly to hypoxia.

All that said, the bottom line is that even at 10,000' anyone can benefit
from supplemental oxygen. If nothing else, you'll feel better after a long
flight, and you may find that mental tasks are actually easier.


Old November 7th 04, 04:55 AM
Mike Rapoport
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On mountaineering trips we would often have O2 saturation levels in the 80s
(some people low 80s) upon reaching a new altitude. After a day (or three
sometimes) it would recover to the low 90s. Then we could go up another
thousand meters. This went on for weeks. I don't think that it is


"PaulH" wrote in message
I took my Arrow up to 10,500 today to check out my fingertip O2
measuring device. I can maintain 90-93% saturation with deep
breathing and no supplemental O2. Anybody know what the minimum safe
level is for daytime? I guess it might be cumulative, i.e. the longer
you go at 92% the less safe it is? Dropped down to about 88% when I
got distracted with some cockpit chores and started normal sea level

Old November 7th 04, 11:54 AM
Ron Rosenfeld
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On Sun, 07 Nov 2004 06:20:01 -0500, Cub Driver

I have been skiing at Ajax (Aspen Mountain) on a regular basis for
nearly forty years and have never noticed any effect on mental acuity
at 11,000 feet. Of course it may be that skiers are mentally inacute
to begin with.

Relying on yourself to "notice" a change has been shown to be an
exceedingly UNreliable assessment method. There have been numerous
experiments in altitude chambers demonstrating that. The subjects were not
aware of their errors in, for example, performing simple mathematical
computations, until they were returned to sea level pressure and could view
what they had written.

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)
Old November 7th 04, 01:22 PM
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In general for a patient in a hospital we try to keep the O2 sat at or above
92%, and will give supplemental oxygen if it falls below.

On a recent trip at 10,000 feet I felt bad after around three hours, and
checked my sat, which was in the low 80's. My eight year old son complained
of a headache and nausea, and after putting on the oxygen we both felt a lot
better as our sats returned to the 90's.

I had recently undergone refresher training for the Air Force in the signs
and symptoms of hypoxia in the altitude chamber, and for anyone flying at
altitude I would strongly recommend a chamber ride. The symptoms of hypoxia
can be subtle, and can vary from individual to individual.

Old November 7th 04, 01:42 PM
Larry Dighera
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On Sun, 07 Nov 2004 13:22:54 GMT, "Viperdoc"
wrote in

On a recent trip at 10,000 feet I felt bad after around three hours, and
checked my sat, which was in the low 80's.

This happened to me after about 3-1/2 hours at 12,500'; I felt okay,
but was apparently impaired. Upon arrival at the destination airport,
I found myself a bit confused by ATC's instructions. Everything came
out alright, but I couldn't understand why I was having difficulty
with simple arrival procedures until I realized that it must have been
a result of mild hypoxia sustained over a prolonged period.

Now I carry a small O2 bottle to refresh myself for arrival:

Here's some information on the subject:

Many of today's home built aircraft capable of transporting man to
high altitudes in near record time, with the average age of the pilot
base at well over 50 years old, a practical knowledge of physiological
human principals and atmospheric physics are not only desirable, but
necessary in order to sustain safe operating parameters. Therefore,
the pilot should have a firm understanding of the relationships
between oxygen, altitude and the body.

The various gases that the atmosphere is made of consists of about 78%
nitrogen, about 21% oxygen and about 1.1% carbon dioxide and other
gases. These three main gases are very important to the body
physiologically. Due to the constant mixing of winds and other
meteorological factors, the percentages of each gas in the atmosphere
are normally constant to about 70,000 ft. throughout a wide range of
temperature and barometric changes.

Nitrogen, present in a high percentage, is responsible for the major
portion of the atmosphere's pressure or weight. Some nitrogen is
dissolved in and is carried by the blood, but this gas does not enter
into chemical combinations as it is carried throughout the human body.
Each time we breathe, the same amount of nitrogen is exhaled as was

Oxygen is a colorless, odorless, tasteless gas, but is absolutely
essential to all life on earth. Each time man breathes, approximately
21% of that breath is oxygen. In the lungs, a portion of this oxygen
is absorbed into the blood-stream where it is carried to all parts of
the body. It is used to "burn" or oxidize food material and produce
energy transformations in the body.

Man can live for weeks without food and for days without water, but
only a few minutes without oxygen. Because man can not store oxygen in
his body, as he can food and water, he lives a breath-to-breath
existence. He continues to live only as long as he can continually
replenish the oxygen consumed by his metabolic process. Air is a
relatively heavy substance. It weighs 14.7 pounds per square inch at
the earth's surface sea level. That is the pressure created by one
column of air one inch square that is about 100 miles high (the
approximate total thickness of the layer of free air or atmosphere
covering the earth). Because the air pressure is equal from all sides
one does not notice the atmosphere's weight in pressure.

The weight of the atmosphere does not remain the same from to bottom.
In one respect the atmosphere can be viewed as an ocean where a person
finds that the absolute pressure around him increases the deeper (or
closer to the earth's surface) he goes. The composition of the
atmosphere always remains the same, but is more dense at the bottom or
at the surface).

The pilot should recognize that atmospheric pressure does not diminish
at a uniform (linear) rate with altitude. Although the atmosphere
covers the earth to a height of about 100 miles, three-fourths of the
molecular destiny of the atmosphere rests just below our tallest
mountain, Mt. Everest.

At an altitude of 18,000 feet above sea level the absolute air
pressure has decreased by 1/2, to only about 7 psia. (pounds per
square inch absolute). Deep interstellar space would be near zero
psia. In other words 18,000 ft. MSL is half way through the density of
the atmosphere. At 34,000 feet, the pressure has been cut in half
again to a mere 3.5 psia. At 65,000 ft. there is only 1 psia. and only
0.15 at 100,000 ft. Beyond that, the atmosphere is largely a vacuum.

The principal purpose of respiration is to supply the cells of the
body with oxygen and remove the carbon dioxide, a biological waste
product, produced by cellular activities. Three basic processes are
involved with respiration phases. The first process (external) is
ventilation, or breathing, the movement of air between the atmosphere
and the lungs. The second and third processes (internal) involve the
exchange of gases within the body through the blood stream. External
respiration is the exchange of gases between the blood and lungs.
Internal respiration is the exchange of gases between the blood and
tissue cells throughout the body.

The respiration cycle begins with inhalation of air into the lungs.
Inhalation is produced by the contraction of the diaphragm, the large
muscle separating the thoracic and abdominal cavity.

Ordinarily, a person breathes 12 to 16 times a minute, although the
rate will be slower when resting and faster when exercising. The
average, quiet, resting man inhales about a pint (400 ml) of air for
each breath, or six to eight quarts (8 liters) per minute.

Oxygen used in the body is inhaled through the nose or mouth, passes
through the trachea and bronchial tubes, and is directed into the
lungs where it transfers to the blood. The blood then carries this
oxygen to living cells where energy is obtained by molecular cellular
transfer for all body functions. This energy transfer produces carbon
dioxide (CO2), a biological waste product. As carbon dioxide is
produced, blood then carries it back to the lungs to be released to
the atmosphere through the exhaling respiration phase back through the
nose or mouth. fig xx

Within the lungs, there are millions of tiny air sacs called alveoli
which inflate like tiny balloons. The number of alveoli in the lungs
is estimated to be around 750 million with a surface area between 700
and 800 square feet, or about the size of a tennis court.

Blood is pumped from the heart through arteries to microscopic
capillaries, or tiny tubes, through which blood is constantly flowing.
The walls of the alveoli have micro-capillaries in which the oxygen is
diffused into the blood. Pressures inside and outside, (the natural
molecular tensions of body fluids and pressure altitude) play an
important factor in the effectiveness of the entire respiration
system. Once these differential pressures are reversed or placed below
a certain point, life-giving gases may not properly exchange through
the lungs or tissues.

The Pilot's Oxygen Needs & Availability The amount of oxygen consumed
by the body during the respiratory cycle depends primarily upon the
degree of physical or mental activity of the individual. A person
walking at a brisk pace will consume about four times as much oxygen
than at rest. In the course of an average day, a normal adult male
will consume about 35 cu. ft. of oxygen or 2.5 lb. This is
approximately equivalent to the weight of solid food consumed daily.
An oxygen supply which might be adequate for a person at rest would be
inadequate for the same individual while piloting an aircraft under
severe weather conditions or under mental stress.

It should be noted that since only 21% of the atmosphere inhaled is
oxygen, added to the fact that we only benefit from only 1/5 to 1/8 of
the total volume of oxygen inhaled per breath, one can see that the
actual volume of air used per day can be 80 to 90 Lbs. This number can
be quite a bit higher by the respiration quality factor that
individual has, i.e. asthma, physical damage and age.

Oxygen becomes more difficult for your body to obtain with altitude
because the air becomes less dense, and the total (absolute) air
pressure decreases compromising your primary (lungs) and secondary
(bloodstream) respiratory systems the ability to transport and
exchange oxygen throughout the body, even though the percentage of
oxygen (21%) remains constant with respect to the atmosphere. As
altitude is increased and the pressure of oxygen is reduced, the
amount of oxygen transferred in the lungs alveoli is reduced which
results in a decrease in the percentage of oxygen saturation in the
blood. This causes a deficiency of oxygen throughout the body, and,
for this reason, supplemental oxygen is required if the body is to
receive adequate oxygen for proper mental and physical functions.

In a relatively simplistic term "oxygen saturation" is defined as the
percentage of available oxygen-carrying hemoglobin that are carrying
oxygen in your tissue and/or bloodstream. Another simplistic, but
fair, example would be if a given volume of blood has 100 hemoglobin
cells and 95 of them are carrying oxygen, then the oxygen saturation
level is 95%.

The total effect on an oxygen-deprived individual is the result of
both altitude and amount of time exposed. Every cell in the body is
affected by the lack of oxygen, but the primary effects are on the
brain and the body's nervous system. Above 10,000 ft. deterioration of
physical and mental performance is a progressive condition. This
degenerative condition becomes more severe with increased altitude or
prolonged exposure. A person who is flying at 10,000 ft. for 5 hours
can be equally affected as a person who went to 16,000 ft. for only
one hour.

Oxygen pressure is about 1/5 that of actual atmospheric pressure.
Therefore, at a pressure altitude of 10,000 ft., for a standard day
i.e. 70° F @ 29.92 In. Hg., the absolute pressure would be about 10
psia. while the working pressure for oxygen would only be 2.0 psia.
It's no wonder why of all our critical life-support organs our lungs
are the largest for their function.

Hypoxia or Hypoximia - As Webster defines it:
hyp-ox-emia \,hip-,äk-'se-me-a, ,hi-,päk-\ n [NL, fr. hypo- + ox-+
-emia]: deficient oxygenation of the blood - hyp-ox-emic \-mik\ adj

hyp-ox-ia \hip-'äk-se-a, hi-'päk-\ n [NL, fr. hypo- + ox-]: a
deficiency of oxygen reaching the tissues of the body - hyp-ox-ic
\-sik\ adj

The effects of an insufficient supply of oxygen on the body that
includes mental any physical degradation is generally called hypoxia.

Some of the most common indications (symptoms) of hypoxia a
1. An increased breathing rate
2. Lightheadedness or dizzy sensation
3. Tingling or a warm sensation
4. Cold chills and/or cold extremities
5. Sweating and increased heart rate
6. Reduced color vision and visual field
7. Sleepiness, insomnia and/or nervousness
8. Blue coloring of skin, fingernails and lips
9. Behavior change, giddiness, belligerence, cockiness, anxiousness or

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.

Commercial aviation pilots are required to be on supplemental oxygen
for flights lasting 30 minutes or more at 10,000 ft. At 15,000 ft.
drowsiness, headaches, weariness, fatigue and a false sense of
well-being will most likely be experienced in 1 to 2 hours without
oxygen. Most important and less evident to the individual is the
psychological impairment which could cause judgment errors, poor
coordination and difficulty in performing simple, let alone, important
piloting tasks.

At 20,000 ft. the absolute pressure altitude drops to 6.75 psia. and
the oxygen pressure drops to 1.38 psia. This is less than half that at
sea level. Oxygen saturation of the blood drops to 62 to 64% at this
pressure altitude. Unconscious collapse and/or convultions will result
within 10 to 15 minutes of exposure. Death is not uncommon as a result
of complications acquired from long or quickly changing exposures to
low partial pressures (high altitudes) without supplemental oxygen or
pressurized cabins.

At a pressure altitude of 34,000 ft. the lungs are compromised so much
in the ability to transfer gases to the blood and air that the oxygen
saturation level will drop to only 30%. Total unconsciousness will
result in 3 to 4 minutes. At this point a person breathing 100% oxygen
would not benefit from the supply because pressures in water vapor and
tissues will be the same as the absolute pressure of oxygen (0.76
psia) where nearly nothing is transferred. One would need to be using
a full pressure-demand-type oxygen mask.

It is true that susceptibility to hypoxia varies from person to
person, and there are some who can tolerate altitudes well above
10,000 ft. without suffering from the effects. It is equally true that
there are persons who develop hypoxic effects below 10,000 ft. As a
general rule, individuals who do not exercise regularly or who are not
in good physical condition will suffer from the effects of hypoxia
more readily. It is also true that even with tip-top shape athletes
the effects of hypoxia are still the same as a person who is in good
physical condition, but they simply have the ability to tolerate the
effects much better.

Individuals who have recently over-indulged in alcohol, who are
moderate to heavy smokers, or who take certain drugs will be
considerably more susceptible to the effects of hypoxia.
Susceptibility to the effects of hypoxia can also vary in the same
person from day to day or from morning to evening.

High altitude acclimation can be an improving factor at moderate
altitudes, i.e. 10,000 to 15,000 ft., however, once again, at high
altitudes the laws of physics prevail and even the most acclimated
will still suffer the effects of hypoxia from the exposure.

While not all of the known symptoms listed occur in each individual,
any given person will develop the same symptoms in the same order for
each time he becomes hypoxic. For this reason, a person, having once
experienced hypoxia is usually better prepared to recognize the onset
of hypoxic symptoms the next time around. One can participate in a
controlled hypoxic awareness program through an altitude chamber that
is offered by many commercial and/or university flight medical
training programs.

Because hypoxia affects the central nervous system, the general
effects of hypoxia are almost identical to alcoholic intoxication. A
typical individual suffering from hypoxia, induced by exposure between
15,000 and 20,000 ft. will be comparable to an individual who has
consumed five to six ounces of whiskey. The most hazardous feature of
hypoxia, as it is encountered with aviation, is its gradual and rather
insidious onset. Its production of a false sense of well-being called
euphoria is particularly dangerous. Since hypoxia obscures the
victim's ability and desire to be critical of himself, he generally
does not recognize the symptoms even when they are very obvious to
others. The hypoxic individual commonly believes things are
progressively getting better as he nears total collapse. There are
some false indicators of a hypoxic condition which should be
considered. The "blueness" color test of the finger nails has been
suggested by some as a guide to determine the degree of hypoxia, but
this approach is usually invalid because any hypoxic individual should
consider himself an unreliable observer that has all the appearances
to himself of operating effectively. Almost all of the symptoms of
hypoxia are useless for self-diagnosis, but have proven to be a
life-saver from the standpoint of an unaffected observer.

So remember, don that oxygen system before the effects of hypoxia can
manifest themselves. This will help you to arrive at your destination


You placed a great deal of emphasis on the quality and integrity of
your equipment and flying skills. Now it's time to put emphasis on the
integrity of the most important, yet weakest, link in your system, . .
yourself. While you are piloting your craft (whichever type that might
be) you are performing a rewarding yet demanding task. This is a time
when you can't afford any performance compromise from the most
important component of your system. . . YOU !.

Whether you're standing at the Gold Hill launch, 12,500 feet above sea
level in Telluride Colorado, or 12,500 feet msl in the cabin of your
plane, you need air. To be specific, you need supplemental breathing
oxygen. Without it, your brain (YOU), the most important component of
the system, will operate at only a fraction of its capacity. You will
loose your precious mental capabilities at a time when you need them
most, during some competition or simply free flying, when judgment is
important to your and others' safety. This phenomenon, in which
altitude affects your physical and mental abilities, is known by many
proficient pilots as hypoxia.

What is hypoxia ? As Webster (in his dictionary) defines it; "hypoxia
\hip–'äk–se–ah, ª–'päk–\n [NL, fr. hypo– + ox– + –emia ]: deficiency
of oxygen reaching the tissues of the body - hyp o ox o ic \–sik\

As many medical reference manuals and books define it;
Hypoxia : the effects of an insufficient supply of oxygen pressure on
the body and tissues that includes the loss of mental judgment and
cause of physical dysfunction.

The word "hypoxia" is derived from "hypo" meaning "under" and "oxia"
referring to "oxygen". Hypoxia is a relatively new word not in many of
the older dictionaries still in use today. The medical aspects of
hypoxia are also somewhat new and still a very good subject for
undergraduate studies. The advent of the Air Force has been
responsible for almost all we know about it. What is known is that it
is real, dangerous, and most of all, not something to ignore. You can
live for weeks without food, days without water, but only minutes
without oxygen. You do not store oxygen in your body, therefore, you
live only as long as you can replenish the oxygen consumed by your
metabolic process. Oxygen is the most important element for your
survival and quality of personal performance. See How does aoxygen
work? on AVweb.com

Recognition of hypoxia and its dangers Hypoxia does not hit you all at
once. It comes on slowly, at a speed that is mainly a function of your
altitude and somewhat of your condition. The higher you go, the faster
hypoxia will take effect. Experiencing any of the effects indicating
the onset of hypoxia is just as, if not more, insidious as the
condition itself. Simply put, once you have convinced yourself you are
experiencing hypoxia, it's simply to late. You are now mentally and
physically operating at a fraction of your capacity and losing more at
a fast rate. Oxygen is needed now. Oxygen will prevent this dangerous

A list of the most common indications (symptoms) of hypoxia pilots may
or may not recognize:
1 an increased breathing rate
2 lightheadedness or dizziness.
3 tingling or false warm sensations in appendages
4 sweating
5 reduced field of view, tunnel vision
6 blue coloring of skin, fingernails and lips
8 behavior changes
9 inability to warm extremities

If you think you can detect and control the effects of hypoxia without
oxygen, think again; you're wrong, potentially dead wrong. The two
most dangerous aspects of hypoxia encountered by all types of aviation
are its gradual onset and the false feeling of well-being called
euphoria. Since this obscures the pilot's ability and desire to be
critical of himself (his judgement), he most likely will not recognize
the symptoms that would otherwise be obvious. The hypoxic pilot
commonly believes he and things are getting progressively better as
he, unfortunately, nears total collapse.

Many high altitude chamber experiments have shown that a person
affected by hypoxia may recognize only a fraction of its known
indications. In fact, some experienced pilots don't even report
experiencing any effects at all while they are obviously
incapacitated. This is where the insidious nature of hypoxia is so
dangerous. Many pilots black-out or faint in flight each year from
hypoxia. In reviewing many of the so-called pilot error deaths and
serious accidents, in which no tangible explanation was found for
cause, they may in fact have been caused by hypoxia. The only answer
to preventing or reversing the effects of hypoxia is oxygen.

Prevention and factors of hypoxia Pilots have found that a good way to
protect themselves from hypoxia is to be constantly aware of the
problem and use the altimeter as the primary guide for the use of
oxygen. It is recommended that pilots use oxygen as they fly at
altitudes over 10,000 feet. Many factors influence when, how, where
and what the indication of hypoxia will be. Your diet and health play
an important role in your altitude tolerance. What you eat or drink is
also a factor. Some foods and beverages, mostly the junk and
pre-processed variety, may 'out-gas', from your digestive track an
oxygen-depleting agent resembling the properties of carbon monoxide,
lowering the ability of your blood system to absorb and deliver
oxygen, thus lowering your altitude tolerance. Although there is not
much medical data on this subject, many serious pilots have indeed
noticed a difference when they eat a good balanced diet.

Recovery from hypoxia Recovery from mild hypoxia can be rapid, usually
within 15 to 20 seconds, after oxygen is administered you will witness
a remarkable change. Dizziness from head and body motion may occur
during the recovery making piloting a craft more difficult. A pilot
recovering from moderate to severe hypoxia is usually quite fatigued
and can suffer from a degradation in mental and physical performance
for many hours. Headache and nausea may also occur. The continued use
of oxygen helps recovery many times over.

At what altitude will I get hypoxia ? This is the most difficult
question to answer. You can suffer from the effects of hypoxia at
almost any altitude where there is a quick altitude gain of about
8,000 feet. Quick in this case is about 150 ft/min. It's the loss of
oxygen (pressure) on your body that causes your blood to lose some of
its ability to absorb oxygen and possibly out-gas (lose oxygen),
resulting in hypoxia.

Many who live at lower altitudes have blood that is conditioned to a
point where the oxygen collecting factor is lower than what is needed
for the altitude gain. This can be compensated by "high altitude
conditioning". The mechanism of this conditioning is not well
understood, but does seem to work where moderate altitude exposure and
exercise are performed. Many proficient pilots have become (somewhat)
conditioned through their flying and can withstand more exposure
without ill effects. It would be a good and responsible practice for
you, the pilot in command, to follow the FAA 'recommendation' for
non-registered pilots and craft to use oxygen starting at pressure
altitudes of 10,000 feet above sea level.

What can I do to limit the effects of hypoxia ? This is the second
most asked question and is also just as difficult to answer. We can't
spell out a definitive set of do's and don'ts, but we can point out a
few factors that are medically known to affect one's altitude
tolerance. If you smoke and drink alcohol or generally are not in good
health, hypoxia will be a danger and should be considered. Where you
live can also be a factor to how sensitive you will be in experiencing
hypoxia. Being in good health and practicing healthful habits may
limit the effects of hypoxia.

It's really quite simple; if you take good care of yourself and eat
well you will be able to withstand and tolerate more altitude exposure
with less effects. You will also gain faster recovery from general
exposure. If you use oxygen, you will be adding invaluable insurance
to your safety, health and sense of well-being. In addition, you will
be adding to your confidence and show responsibility to your fellow

Many very good publications are available at almost any public library
or general aviation airports or flight schools regarding the FAA
rules, regulations and medical aspects of aviation. The FAA does not,
at present, enforce, but recommends rules regarding 'pilot physiology'
with our type of flight. We should, however, show responsibility
regarding this, as we have with other issues, and at least be aware of
them and fly with oxygen whenever we will be at these altitudes. Fly
safe for yourself and your fellow pilots.

About the author:
Patrick L. McLaughlin is a veteran hang gliding and general aviation
pilot. His profession is computer hardware and software engineering.
He also enjoys keeping up with the medical technological arts and
human physiology.
Old November 7th 04, 04:37 PM
Ron Natalie
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Posts: n/a

PaulH wrote:
I took my Arrow up to 10,500 today to check out my fingertip O2
measuring device. I can maintain 90-93% saturation with deep
breathing and no supplemental O2. Anybody know what the minimum safe
level is for daytime? I guess it might be cumulative, i.e. the longer
you go at 92% the less safe it is? Dropped down to about 88% when I
got distracted with some cockpit chores and started normal sea level

Are we talking about the pilot or the passengers. 90% is fine for
passengers, even the 80's would be fine for most passengers.

90% is not so good for the pilot.

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