Hypoxia causes impaired brain and organ functions, which results in a reduction in mental capacity and potentially life-threatening errors in the cockpit.
Hypoxia is defined as a lack of oxygen in the body. The FAA recognizes four types of hypoxia:
Hypoxic hypoxia is caused by a reduction in the partial pressure of oxygen. Hypoxic hypoxia is the most likely type of hypoxia to be encountered while in flight and can begin to occur at altitudes as low as 5,000ft.
As an aircraft climbs the outside atmospheric pressure decreases resulting in a lower atmospheric pressure. Lower atmospheric pressure results in a decreased amount of air molecules in any given space. However, the ratio of oxygen to other gases, 21%, remains the same.
This causes pilots and passengers to experience a state of oxygen deprivation with less oxygen available for normal functions.
Hypoxic hypoxia can also be caused by blocked airways, drowning, and blood loss.
Hypemic hypoxia occurs when the blood in the body cannot bind to, and transport, oxygen to cells in the body. A failure in the blood causes hypemic hypoxia, not a lack of oxygen.
In the flight environment, hypemic hypoxia is most likely to occur due to carbon monoxide.
Carbon monoxide, undetectable by humans and produced by combustion engines, can bind to blood 200 times more easily than oxygen. As a result, blood will bind to carbon monoxide and not oxygen if given the choice.
Stagnant hypoxia is caused by oxygen-rich blood being unable to travel to parts of the body that require. Similar to hypemic hypoxia, stagnant hypoxia is not caused by a lack of oxygen.
A great example of stagnant hypoxia is g-LOC. g-LOC, or G-force induced loss of consciousness, describes a loss of consciousness from excessive and sustained g-forces draining and pulling blood away from the brain.
Other causes of stagnant hypoxia can include frostbite, heart issues, and blood clots.
Histotoxic hypoxia is caused by a reduction in the efficiency of the body's cells. With histotoxic hypoxia, oxygen is being transported to the body's cells; however, the cells cannot use it.
Histotoxic, meaning poisoned cells, can be caused by alcohol, drugs, and other narcotics. Research has shown that the human body will perform as if it was 2000ft higher than it is for every ounce of alcohol consumed.