What is "cyanosis"

Cyanosis \Cy`a*no"sis\ (s?`?-n?"s?s), n. [NL. See Cyanic.] (Med.) A condition in which, from insufficient a[eum]ration of the blood, the surface of the body becomes blue. See Cyanopathy.

"blue disease," the "blue jaundice" of the ancients, 1820, Medical Latin, from Greek kyanosis, from kyanos "dark blue color" (see cyan) + -osis.

n. (context pathology English) A blue discolouration of the skin due to the circulation of blood low in oxygen.

n. a bluish discoloration of the skin and mucous membranes; a sign that oxygen in the blood is dangerously diminished (as in carbon monoxide poisoning)

Cyanosis is the appearance of a blue or purple coloration of the skin or mucous membranes due to the tissues near the skin surface having low oxygen saturation. Based on Lundsgaard and Van Slyke's work, it is classically described as occurring if 5.0 g/dL of deoxyhemoglobin or greater is present. This was based on an "estimate" of capillary saturation based on a mean of arterial versus peripheral venous blood gas measurements. Since estimation of hypoxia is usually now based either on arterial blood gas measurement or pulse oximetry, this is probably an overestimate, with evidence that levels of 2.0 g/dL of deoxyhemoglobin may reliably produce cyanosis. Since, however, the presence of cyanosis is dependent upon there being an absolute quantity of deoxyhemoglobin, the bluish color is more readily apparent in those with high hemoglobin counts than it is with those with anemia. Also the bluer color is more difficult to detect on deeply pigmented skin. When signs of cyanosis first appear, such as on the lips or fingers, intervention should be made within 3–5 minutes because a severe hypoxia or severe circulatory failure may have induced the cyanosis.

The name cyanosis literally means "the blue disease" or "the blue condition". It is derived from the color cyan, which comes from kyanós, the Greek word for "blue".