cyanosis 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)
- Webster 1913
Cyanosis is a blue coloration of the skin and mucous membranes due to the presence of deoxygenated hemoglobin in blood vessels near the skin surface. It occurs when the oxygen saturation of arterial blood falls below 85-90% (1.5g/dl deoxyhemoglobin).
Although human blood is always a shade of red (except in rare cases of hemoglobin-related disease), the optical properties of skin distort the dark red color of deoxygenated blood to make it appear blueish.
The elementary principle behind cyanosis is that deoxygenated hemoglobin is more prone to the optical bluish discoloration, and also produces vasoconstriction that makes it more evident. The scattering of color that produces the blue hue of veins and cyanosis is similar to the process that makes the sky and large bodies of water appear blue: some colors are refracted and absorbed more than others. During cyanosis, tissues are uncharacteristically low on oxygen, and therefore tissues that would normally be filled with bright oxygenated blood are instead filled with darker, deoxygenated blood. Darker blood is much more prone to the blue-shifting optical effects, and thus oxygen deficiency - hypoxia - leads to blue discoloration of the lips and other mucous membranes.
The name is derived from the color cyan, the Greek word for blue.
TypesCyanosis can occur in the fingers, including underneath the fingernails, as well as other extremities (called peripheral cyanosis), or in the lips and tongue (central cyanosis).
Central cyanosisCentral cyanosis is often due to a circulatory or ventilatory problem that leads to poorer blood oxygenation in the lungs or greater oxygen extraction due to slowing down of blood circulation in the skin's blood vessels.
Acute cyanosis can be a result of asphyxiation or choking, and is one of the surest signs that respiration is being blocked.
Common causes of central cyanosis
Peripheral cyanosis is the blue tint in fingers or extremities, due to inadequate circulation. The blood reaching the extremities is not oxygen rich and when viewed through the skin a combination of factors can lead to the appearance of a blue color. All factors contributing to central cyanosis can also cause peripheral symptoms to appear, however peripheral cyanosis can be observed without there being heart or lung failures. Small blood vessels may be restricted and can be treated by increasing the normal oxygenation level of the blood.
Common causes of peripheral cyanosis
cyanosis in Czech: Cyanóza
cyanosis in German: Zyanose
cyanosis in Persian: کبودی پوست
cyanosis in French: Cyanose
cyanosis in Italian: Cianosi
cyanosis in Dutch: Cyanose
cyanosis in Japanese: チアノーゼ
cyanosis in Norwegian: Cyanose
cyanosis in Norwegian Nynorsk: Cyanose
cyanosis in Polish: Sinica
cyanosis in Portuguese: Cianose
cyanosis in Slovak: Cyanóza
cyanosis in Slovenian: Cianoza
cyanosis in Swedish: Cyanos
cyanosis in Ukrainian: Ціаноз
cyanosis in Chinese: 發紺
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