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body due to the poor circulation of the blood.
Several different situations can lead to stagnant
hypoxia, such as shock, the heart failing to pump
blood effectively, or a constricted artery. During
flight, stagnant hypoxia can be the result of pulling
excessive positive Gs. Cold temperatures also
can reduce circulation and decrease the blood
supplied to extremities.
HISTOTOXIC HYPOXIA
The inability of the cells to effectively use oxygen
is defined as histotoxic hypoxia. The oxygen may
be inhaled and reach the cell in adequate
amounts, but the cell is unable to accept the oxygen
once it is there. This impairment of cellular
respiration can be caused by alcohol and other
drugs, such as narcotics and poisons. Research
has shown that drinking one ounce of alcohol can
equate to about an additional 2,000 feet of
physiological altitude.
High-altitude flying, which glider pilots encounter
when mountain wave soaring or thermal soaring
at high elevations, can place you in danger of
becoming hypoxic. Oxygen starvation causes the
brain and other vital organs to become impaired.
One particularly noteworthy attribute of the onset
of hypoxia is the fact that the first symptoms are
euphoria and a carefree feeling. With increased
oxygen starvation, your extremities become less
responsive, and your flying becomes less coordinated.
The following are common symptoms of
hypoxia.
• Headache
• Decreased Reaction Time
• Impaired Judgment
• Euphoria
• Visual Impairment
• Drowsiness
• Lightheaded or Dizzy Sensation
• Tingling in Fingers and Toes
• Numbness
• Blue Fingernails and Lips (Cyanosis)
• Limp Muscles
As hypoxia worsens, your field of vision begins to
narrow, and instruments can start to look fuzzy.
Even with all these symptoms, the intoxicating
effects of hypoxia can cause you to have a false
sense of security and deceive you into believing
you are flying as well as ever. The treatment for
hypoxia includes flying at lower altitudes and/or
using supplemental oxygen.
All pilots are susceptible to the effects of oxygen
starvation, regardless of your physical
endurance or acclimatization. When flying at
high altitudes, it is paramount that you carry aviator’s
breathing oxygen in your glider and have
it readily accessible. The term “time of useful
consciousness” is used to describe the maximum
time you have to make rational, life-saving
decisions and carry them out at a given altitude
Figure1-12. This illustration shows the symptoms of hypoxia and
time of useful consciousness as altitude increases.
1-12
without supplemental oxygen. As altitude
increases above 10,000 feet, the symptoms of
hypoxia increase in severity, while the time of
useful consciousness rapidly decreases.
[Figure 1-12]
Since symptoms of hypoxia vary in an individual,
the ability to recognize hypoxia can be
greatly improved by experiencing and witnessing
the effects of it during an altitude chamber
“flight.” The FAA provides this opportunity
through aviation physiology training, which is
conducted at the FAA Civil Aerospace Medical
Institute (CAMI) and at many military facilities
across the United States. To attend the
Physiological Training Program at CAMI telephone
(405) 954-6212 or write:
FAA/AAM-400
Aerospace Medical Education Division
P.O. Box 25082
Oklahoma City, OK 73125
HYPERVENTILATION
Hyperventilation occurs when you are experiencing
emotional stress, fright, or pain, and your breathing
rate and depth increase although the carbon dioxide
is already at a reduced level in the blood. The
result is an excessive loss of carbon dioxide from
your body, which can lead to unconsciousness due
to the respiratory system’s overriding mechanism to
regain control of breathing.
Glider pilots encountering extreme, unexpected
turbulence, or strong areas of sink over rough
terrain or water, may unconsciously increase
their breathing rate. If you are flying at higher
altitudes, either with or without oxygen, you 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 you are using supplemental oxygen, check the
equipment and flow rate to ensure you are not suffering
from hypoxia. The following are common
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Glider Flying Handbook(14)
