Normally triggered by stress or fear, hyperventilation refers to excessive breathing. As a person breaths, they exhale carbon dioxide. If a person begins to breath too rapidly and deeply, they excessively vent carbon dioxide.

When the carbon dioxide content in the body is sufficiently reduced, it triggers a feeling of suffocation. This feeling results in continued hyperventilation.

The symptoms of hyperventilation are similar to those of hypoxia, including headache, drowsiness, lightheadedness, dizziness, numbness of the fingers and toes, and euphoria. The skin often appears pale and clammy, and muscle spasms may result.

However, because there is no oxygen deficiency, a person who is hyperventilating will not show cyanosis.

Recovery from hyperventilation requires the individual to consciously slow their breathing. If hyperventilation is not controlled, it can result in unconsciousness. In this case, the brain will regulate breathing at a normal rate and recovery is normally rapid.