Cyanosis << `sy` uh NOH sihs >> is a medical condition involving a bluish tint of the skin and mucous membranes. Cyanosis results if the blood flowing through vessels in the skin and mucous membranes contains too much reduced hemoglobin—that is, hemoglobin not combined with oxygen. Hemoglobin is the compound in red blood cells that carries oxygen. When combined with oxygen, hemoglobin makes blood bright red. Blood containing large amounts of reduced hemoglobin appears bluish when seen through the skin and mucous membranes.
Cyanosis may occur among people who live at high altitudes, where the air pressure is low and less than the normal amount of oxygen is available. It may result from abnormalities in hemoglobin or heart and lung ailments that prevent blood from combining properly with oxygen. For example, blue babies have cyanosis because a heart defect prevents some blood from entering their lungs to receive oxygen (see Blue baby). Cyanosis also can occur when blood circulates poorly after a person goes into shock or suffers heart failure.
Cyanosis resulting from too little oxygen may be treated by improving the patient’s respiration or by using an oxygen tent or mask. Physicians treat cyanosis caused by poor circulation by increasing the rate of the blood flow.
