Evan's CFI Notebook

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====== Aeromedical Factors (General) ======


===== Physiological Aspects of Night Flight =====


===== Spatial Disorientation, Motion Sickness and Inflight Illusions =====

See [[topics:spatial_disorientation_illusions|Spatial Disorientation and Illusions]]
===== Hypoxia, Hyperventilation, and Carbon Monoxide Poisoning =====

**Hypoxia** means “reduced oxygen” or “not enough oxygen.” 

Hypoxia can be caused by several factors, including an insufficient supply of oxygen, inadequate transportation of
oxygen, or the inability of the body tissues to use oxygen.

==== Symptoms of Hypoxia ====

High-altitude flying can place a pilot in danger of becoming hypoxic. Oxygen starvation causes the brain and other vital organs to become impaired. The first symptoms of hypoxia can include euphoria and a carefree feeling. With increased oxygen starvation, the extremities become less responsive and flying becomes less coordinated. The symptoms of hypoxia vary with the individual, but common symptoms include:

  * Cyanosis (blue fingernails and lips)
  * Headache
  * Decreased response to stimuli and increased reaction time
  * Impaired judgment
  * Euphoria
  * Visual impairment
  * Drowsiness
  * Lightheaded or dizzy sensation
  * Tingling in fingers and toes
  * Numbness

As hypoxia worsens, the field of vision begins to narrow and
instrument interpretation can become difficult. Even with all
these symptoms, the effects of hypoxia can cause a pilot to
have a false sense of security and be deceived into believing
everything is normal. 

===== Oxygen Requirements =====

See [[topics:oxygen_requirements|Oxygen Requirements]]
===== Middle Ear and Sinus Problems =====

<note>PHAK Ch. 17 p. 17-5</note>

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 17-2]
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.
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 into 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 usually produces 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.
Sinus block can be avoided by not flying with an upper
respiratory infection or nasal allergic condition. Adequate
protection is usually not provided by decongestant sprays
or drops to reduce congestion around the sinus openings.
Oral decongestants have side effects that can impair pilot
performance. If a sinus block does not clear shortly after
landing, a physician should be consulted.

===== Decompression Sickness =====


===== Stress, Fatigue, and Dehydration =====

 The body’s reaction to stress includes releasing chemical hormones (such as adrenaline) into the
blood and increasing metabolism to provide more energy to the muscles. Blood sugar, heart rate, respiration, blood
pressure, and perspiration all increase. The term “stressor” is used to describe an element that causes an individual to experience stress. Examples of stressors include physical stress (noise or vibration), physiological stress (fatigue), and psychological stress (difficult work or personal situations).

**Acute Stress** -- short term, "flight or fight" response. Normal person can cope with this stress and prevent overload.

**Chronic Stress** -- ongoing, long-term, intolerable burden, exceeding the ability of the individual to cope, causes performance to fall sharply.

Pilots experiencing this level of stress are not safe and should not exercise their airman privileges. Pilots who suspect they are suffering from chronic stress should consult a physician.
===== Drugs, Alcohol and Medication =====
Evan's CFI Notebook

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