1. Literally, the absence of carbon dioxide; however, the term is used to indicate less than the normal amount of carbon dioxide in the blood and tissues: The doctor was concerned about the acapnia in the patient’s blood.

Symptoms of acapnia include depressed respiration, giddiness, paresthesia (abnormal sensation like "burning"), cramps, involuntary contraction of the fingers, and occasionally convulsions.

Acapnea is a misspelling of acapnia.

2. Etymology: from Latin acapnos, "without smoke"; from Greek akapnos, a-, "not" + kapnos, "smoke" (carbon dioxide).