Which statement best defines hypoxia?

• A. A state of oxygen deficiency in the body
• B. A state of excess oxygen in the body
• C. A condition of low carbon dioxide
• D. A condition of high altitude only

Answer: (A)

Hypoxia means the body's tissues are not receiving enough oxygen to meet their needs. In flight, this can happen as you climb because the air has less oxygen and the blood delivers less usable oxygen, so brain and muscle function can be impaired if oxygen delivery falls. There are several forms—oxygen delivery can be reduced by low ambient oxygen (hypoxic hypoxia), by the blood’s reduced carrying capacity (hypemic hypoxia), by poor circulation (stagnant hypoxia), or by the body's cells being unable to use oxygen (histotoxic hypoxia). The statement that best defines hypoxia is that it is a deficiency of oxygen reaching the body's tissues. The other choices describe conditions that aren’t what hypoxia means: excess oxygen is hyperoxia, a low carbon dioxide level isn’t hypoxia, and hypoxia isn’t limited to high altitude—although altitude is a common cause, it can occur in other situations as well.