What is "hypoventilation"

n. (context medicine English) respiratory depression, occurring when ventilation is inadequate to perform the necessary gas exchange, which may be caused by certain medical conditions, by hold one's breath, or by drug overdose.

In medicine, hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (hypo meaning "below") to perform needed gas exchange. By definition it causes an increased concentration of carbon dioxide ( hypercapnia) and respiratory acidosis.