Aeronautical Information Manual (AIM), page 549

Index   548 -- Page 549 -- 550

easily committed to memory is being distributed by
the FAA in the form of a wallet-sized card.
i. PERSONAL CHECKLIST. I'm physically
and mentally safe to fly; not being impaired by:







8-1-2. Effects of Altitude

a. Hypoxia.
1. Hypoxia is a state of oxygen deficiency in the
body sufficient to impair functions of the brain and
other organs. Hypoxia from exposure to altitude is
due only to the reduced barometric pressures
encountered at altitude, for the concentration of
oxygen in the atmosphere remains about 21 percent
from the ground out to space.

2. Although a deterioration in night vision
occurs at a cabin pressure altitude as low as
5,000 feet, other significant effects of altitude
hypoxia usually do not occur in the normal healthy
pilot below 12,000 feet. From 12,000 to 15,000 feet
of altitude, judgment, memory, alertness, coordina-
tion and ability to make calculations are impaired,
and headache, drowsiness, dizziness and either a
sense of well-being (euphoria) or belligerence occur.
The effects appear following increasingly shorter
periods of exposure to increasing altitude. In fact,

pilot performance can seriously deteriorate within

15 minutes at 15,000 feet.
3. At cabin pressure altitudes above 15,000 feet,
the periphery of the visual field grays out to a point
where only central vision remains (tunnel vision). A
blue coloration (cyanosis) of the fingernails and lips
develops. The ability to take corrective and protective
action is lost in 20 to 30 minutes at 18,000 feet and

5 to 12 minutes at 20,000 feet, followed soon
thereafter by unconsciousness.
4. The altitude at which significant effects of
hypoxia occur can be lowered by a number of factors.
Carbon monoxide inhaled in smoking or from
exhaust fumes, lowered hemoglobin (anemia), and
certain medications can reduce the oxygen-carrying
capacity of the blood to the degree that the amount of
oxygen provided to body tissues will already be
equivalent to the oxygen provided to the tissues when
exposed to a cabin pressure altitude of several
thousand feet. Small amounts of alcohol and low
doses of certain drugs, such as antihistamines,
tranquilizers, sedatives and analgesics can, through
their depressant action, render the brain much more
susceptible to hypoxia. Extreme heat and cold, fever,
and anxiety increase the body's demand for oxygen,
and hence its susceptibility to hypoxia.
5. The effects of hypoxia are usually quite
difficult to recognize, especially when they occur
gradually. Since symptoms of hypoxia do not vary in
an individual, the ability to recognize hypoxia can be
greatly improved by experiencing and witnessing the
effects of hypoxia during an altitude chamber
"flight." The FAA provides this opportunity through
aviation physiology training, which is conducted at
the FAA Civil Aeromedical Institute and at many
military facilities across the U.S. To attend the
Physiological Training Program at the Civil
Aeromedical Institute, Mike Monroney Aeronautical
Center, Oklahoma City, OK, contact by telephone
(405) 954-6212, or by writing Aerospace Medical
Education Division, AAM-400, CAMI, Mike
Monroney Aeronautical Center, P.O. Box 25082,
Oklahoma City, OK 73125.
To attend the physiological training program at one of the
military installations having the training capability, an
application form and a fee must be submitted. Full
particulars about location, fees, scheduling procedures,
course content, individual requirements, etc., are con-
tained in the Physiological Training Application, Form
Number AC 3150-7, which is obtained by contacting the

accident prevention specialist or the office forms manager
in the nearest FAA office.
6. Hypoxia is prevented by heeding factors that
reduce tolerance to altitude, by enriching the inspired
air with oxygen from an appropriate oxygen system,
and by maintaining a comfortable, safe cabin
pressure altitude. For optimum protection, pilots are
encouraged to use supplemental oxygen above

Fitness for Flight 8-1-3

Page 549 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   548 -- Page 549 -- 550