What is hypoxia?

Hypoxia is a deficiency of oxygen in body tissue.

Hypoxia is dangerous as this condition reduces mental function.  The primary causes of hypoxia are insufficient supply of oxygen, inadequate transportation of oxygen or inability of the body to use oxygen.  The four types of hypoxia are: hypoxic hypoxia, hypemic hypoxia, stagnant hypoxia and histotoxic hypoxia.

Hypoxic hypoxia is a result of insufficient oxygen available to the body as a whole.  Hypoxic hypoxia can occur with reduction in partial pressure of oxygen at high altitude.

Hypemic hypoxia occurs when the blood is not able to take up and transport a sufficient amount of oxygen to the cells in the body.  Hyperemic hypoxia may be caused by a variety of factors, such as lack of blood due to severe bleeding or diseases such as anemia.  The most common form of hypemic hypoxia is carbon monoxide poisoning, which prevents the blood’s hemoglobin from binding with and transporting the oxygen.

Stagnant hypoxia results when the oxygen-rich blood in the lungs is not moving adequately.  Stagnant hypoxia can occur with excessive acceleration of gravity or g forces.

Histotoxic hypoxia is the inability of the cells to effectively use oxygen.  Alcohol and other drugs can impair the body’s ability to use oxygen and can lead to histotoxic hypoxia.

Symptoms of hypoxia include cyanosis, headache, decreased response to stimuli and increased reaction time, impaired judgment, euphoria, visual impairment, drowsiness, dizziness, tingling in fingers and toes and numbness.  Treatment for hypoxia includes flying at lower altitudes and/or using supplemental oxygen.


FAA-H-8083-25B Pilots Handbook of Aeronautical Knowledge pg. 17-3

Other Aeromedical Factors

What is hyperventilation?

Hyperventilation is the excessive rate and depth of respiration which reduces the amount of carbon dioxide in the blood.

Hyperventilation can impair the pilot’s judgment and increase anxiety or stress aggravates the situation.  Hyperventilation seldom leads to unconsciousness, but the symptoms include dizziness, tingling in the lips, hands or feet, headache, weakness, fainting and seizures.  The systems of hyperventilation are similar to hypoxia so correct diagnosis is required.

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.


FAA-H-8083-25B Pilots Handbook of Aeronautical Knowledge pg. 17-4

Other Aeromedical Factors

What is spatial disorientation?

Spatial disorientation is when the pilot is unable to correctly determine his/her body position in space.

Spatial disorientation specifically refers to the lack of orientation with regard to the position, attitude, or movement of the airplane in space.  The body uses three integrated systems that work together to ascertain orientation and movement in space.

Vestibular system—organs found in the inner ear that sense position by the way we are balanced

Somatosensory system—nerves in the skin, muscles, and joints that, along with hearing, sense position based on gravity, feeling, and sound

Visual system—eyes, which sense position based on what is seen

Under normal flight conditions, when there is a visual reference to the horizon and ground, the sensory system in the inner ear helps to identify the pitch, roll, and yaw movements of the aircraft.  When visual contact with the horizon is lost, the vestibular system becomes unreliable.  Without visual references outside the aircraft, there are many situations in which combinations of normal motions and forces create convincing illusions that are difficult to overcome.

Prevention is usually the best remedy for spatial disorientation.  Unless a pilot has many hours of training in instrument flight, flight should be avoided in reduced visibility or at night when the horizon is not visible.  A pilot can reduce susceptibility to disorienting illusions through training and awareness and learning to rely totally on flight instruments.


FAA-H-8083-25B Pilots Handbook of Aeronautical Knowledge pg. 17-6

Other Aeromedical Factors