to breathe rapidly and deeply; to breathe excessively; as, The mountain climber started to hyperventilate.

When going into trance a medium's respiration may be abnormally fast or deep, seemingly absorbing excessive quantities of air. As the state of trance ends a relieving expulsion of breath, hypoventilation, may occur.

A rapid series of quick, deep, and forceful breathes causing over oxygenation of the blood with accompanying dizzyness or light headedness.

produce hyperventilation in; "The nurses had to hyperventilate the patient"