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Pilot's Handbook of Aeronautical Knowledge
Aeromedical Factors

Health and Physiological Factors Affecting Pilot Performance

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Pilot's Handbook of Aeronautical Knowledge

Preface

Acknowledgements

Table of Contents

Chapter 1, Introduction To Flying
Chapter 2, Aircraft Structure
Chapter 3, Principles of Flight
Chapter 4, Aerodynamics of Flight
Chapter 5, Flight Controls
Chapter 6, Aircraft Systems
Chapter 7, Flight Instruments
Chapter 8, Flight Manuals and Other Documents
Chapter 9, Weight and Balance
Chapter 10, Aircraft Performance
Chapter 11, Weather Theory
Chapter 12, Aviation Weather Services
Chapter 13, Airport Operation
Chapter 14, Airspace
Chapter 15, Navigation
Chapter 16, Aeromedical Factors
Chapter 17, Aeronautical Decision Making

Appendix

Glossary

Index

Pilots encountering an unexpected stressful situation may
subconsciously increase their breathing rate. If flying at
higher altitudes, either with or without oxygen, a pilot may
have a tendency to breathe more rapidly than normal, which
often leads to hyperventilation.

Since many of the symptoms of hyperventilation are similar
to those of hypoxia, it is important to correctly diagnose and
treat the proper condition. If using supplemental oxygen,
check the equipment and .ow rate to ensure the symptoms are
not hypoxia related. Common symptoms of hyperventilation
include:
• Visual impairment
• Unconsciousness
• Light headed or dizzy sensation
• Tingling sensations
• Hot and cold sensations
• Muscle spasms

The treatment for hyperventilation involves restoring
the proper carbon dioxide level in the body. Breathing
normally is both the best prevention and the best cure for
hyperventilation. In addition to slowing the breathing rate,
breathing into a paper bag or talking aloud helps to overcome
hyperventilation. Recovery is usually rapid once the breathing
rate is returned to normal.

Middle Ear and Sinus Problems
During climbs and descents, the free gas formerly present in
various body cavities expands due to a difference between
the pressure of the air outside the body and that of the air
inside the body. If the escape of the expanded gas is impeded,
pressure builds up within the cavity and pain is experienced.
Trapped gas expansion accounts for ear pain and sinus pain,
as well as a temporary reduction in the ability to hear.

The middle ear is a small cavity located in the bone of the
skull. It is closed off from the external ear canal by the
eardrum. Normally, pressure differences between the middle
ear and the outside world are equalized by a tube leading from
inside each ear to the back of the throat on each side, called
the Eustachian tube. These tubes are usually closed, but open
during chewing, yawning, or swallowing to equalize pressure.
Even a slight difference between external pressure and middle
ear pressure can cause discomfort. [Figure 16-2]

During a climb, middle ear air pressure may exceed the
pressure of the air in the external ear canal, causing the
eardrum to bulge outward. Pilots become aware of this
pressure change when they experience alternate sensations
of "fullness" and "clearing." During descent, the reverse
happens. While the pressure of the air in the external ear
canal increases, the middle ear cavity, which equalized with
the lower pressure at altitude, is at lower pressure than the
external ear canal. This results in the higher outside pressure,
causing the eardrum to bulge inward.

The Eustachian tube allows air pressure to equalize in the middle ear.
Figure 16-2. The Eustachian tube allows air pressure to equalize
in the middle ear.

This condition can be more difficult to relieve due to the
fact that the partial vacuum tends to constrict the walls of
the Eustachian tube. To remedy this often painful condition,
which also causes a temporary reduction in hearing
sensitivity, pinch the nostrils shut, close the mouth and lips,
and blow slowly and gently in the mouth and nose.

This procedure forces air through the Eustachian tube into the
middle ear. It may not be possible to equalize the pressure in
the ears if a pilot has a cold, an ear infection, or sore throat.
A flight in this condition can be extremely painful, as well as
damaging to the eardrums. If experiencing minor congestion,
nose drops or nasal sprays may reduce the risk of a painful
ear blockage. Before using any medication, check with an
AME to ensure that it will not affect the ability to fly.

In a similar way, air pressure in the sinuses equalizes with
the pressure in the flight deck through small openings
that connect the sinuses to the nasal passages. An upper
respiratory infection, such as a cold or sinusitis, or a nasal
allergic condition can produce enough congestion around an
opening to slow equalization. As the difference in pressure
between the sinuses and the flight deck increases, congestion
may plug the opening. This "sinus block" occurs most
frequently during descent. Slow descent rates can reduce
the associated pain. A sinus block can occur in the frontal
sinuses, located above each eyebrow, or in the maxillary
sinuses, located in each upper cheek. It will usually produce
excruciating pain over the sinus area. A maxillary sinus
block can also make the upper teeth ache. Bloody mucus
may discharge from the nasal passages.

 

16-4