|ICD9= |_}}In medicine, hyperventilation (or overbreathing) is the state of breathing faster and/or deeper than necessary, thereby reducing the carbon dioxide concentration of the blood below normal. Hyperventilation can, but doesn't necessarily always cause symptoms such as numbness or tingling in the hands, feet and lips, lightheadedness, dizziness, headache, chest pain, slurred speech and sometimes fainting, particularly when accompanied by the Valsalva maneuver. Sometimes hyperventilation is… (More on Hyperventilation)