Cyanosis is the change of body tissue color to a bluish-purple hue, as a result of decrease in the amount of oxygen bound to the hemoglobin in the red blood cells of the capillary bed.

[1] Cyanosis is apparent usually in the body tissues covered with thin skin, including the mucous membranes, lips, nail beds, and ear lobes.

Furthermore, mongolian spots, large birthmarks, and the consumption of food products with blue or purple dyes can also result in the bluish skin tissue discoloration and may be mistaken for cyanosis.

While patients with increased amounts of red blood cells (e.g., polycythemia vera) can appear cyanotic even with lower concentrations of deoxyhemoglobin.

However, cyanosis can still be diagnosed with careful examination of the typical body areas such as nail beds, tongue, and mucous membranes where the skin is thinner and more vascular.

[5][6] Signs of severe anemia may include pale mucosa (lips, eyelids, and gums), fatigue, lightheadedness, and irregular heartbeats.

In patients with significant respiratory distress, supplemental oxygen (in the form of nasal canula or continuous positive airway pressure depending on severity) should be given immediately.

[12] It is postulated by Dr. Christen Lundsgaard that cyanosis was first described in 1749 by Jean-Baptiste de Sénac, a French physician who served King Louis XV.

[13] De Sénac concluded from an autopsy that cyanosis was caused by a heart defect that led to the mixture of arterial and venous blood circulation.