<unk>  (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.<unk>  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.<unk>  can be considered a precursor to hypoxia and its lethality is attributed to hypoxia with carbon dioxide toxicity.
Hypoventilation
Hyperventilation
Permissive hypercapnia
Hypoxic ventilatory response
Hyperoxia
Pseudohypoxia
Expiratory apnea
Cerebral hypoxia