hypoventilation

Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (hypo meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapnia) and respiratory acidosis. Hypoventilation is not synonymous with respiratory arrest, in which breathing ceases entirely and death occurs within minutes due to hypoxia and leads rapidly into complete anoxia, although both are medical emergencies. Hypoventilation can be considered a precursor to hypoxia, and its lethality is attributed to hypoxia with carbon dioxide toxicity.

==Causes== Hypoventilation may be caused by: A medical condition such as stroke affecting the brainstem Voluntary breath-holding or underbreathing, for example, hypoventilation training or the Buteyko method. Medication or drugs, typically when taken in accidental or intentional overdose. Opioids are a well-known cause of drug-induced hypoventilation due to their depressant effects on the central respiratory centers. Recent studies have highlighted patterns of postoperative opioid-induced respiratory depression that may help identify at-risk patients. Hypocapnia, which stimulates hypoventilation Obesity; see Obesity hypoventilation syndrome Chronic mountain sickness, a mechanism to conserve energy. Paralyzing venom, such as that of the blue ringed octopus.