HYPERVENTILATION

rapid shallow breathing that provides the body with an excess of oxygen and a deficit of carbon dioxide. It most commonly occurs as a manifestation of anxiety or hysteria. It also occurs among pilots in unpressurized planes at high altitudes, who take short, rapid breaths rather than the normal slow, deep ones, in order to compensate for the smaller amount of available oxygen. Hyperventilation causes the body to expel more carbon dioxide than it does during normal breathing. When there are abnormally low levels of carbon dioxide in the blood the small arterial vessels tend to dilate, with a fall in blood pressure. The most apparent symptoms of hyperventilation are numbness or tingling of the hands, feet, and face. The person may also feel dizzy, giddy, or faint.