Hypocapnia (from the Greek words ὑπό meaning below normal and καπνός kapnós meaning smoke), also known as hypocarbia, sometimes incorrectly called acapnia, is a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation. Hypocapnia is the opposite of hypercapnia. Short term hypocapnia does not usually have any adverse effects. It is sometimes used as lifesaving treatment for conditions such as neonatal pulmonary-artery hypertension and for people with severe intracranial hypertension. If the state of hypocapnia persists or is prolonged, adverse outcomes may occur. Source: Wikipedia (en)