However, in polycythemia, cyanosis is detectable at a higher value of SaO2, whereas in anemia, the reverse is true. Thus, in severe anemia, cyanosis cannot be detected by observation. Another type of cyanosis, called peripheral cyanosis, involves a bluish discoloration of the skin but sparing of the mucus membranes & tongue. In this type, a normal PaO2 value is detected. In this case, increased oxygen extraction due to sluggish movement through the capillaries leads to increased deoxygenated blood on the venous side.