Hypocapnia or hypocapnea also known as hypocarbia, sometimes incorrectly called acapnia,'s a state of reduced carbon dioxide in the blood. Hypocapnia usually results from deep or rapid breathing, known as hyperventilation. Hypocapnia's the opposite of hypercapnia. Effects Even when severe, hypocapnia's normally well tolerated. However, hypocapnia causes cerebral vasoconstriction, leading to cerebral hypoxia and this can cause transient dizziness, visual disturbances, and anxiety. A low partial… (More on Hypocapnia)