Explain Cyanosis - histotoxic hypoxia

Cyanosis is a physical sign for causing bluish discoloration of the skin & mucous membranes. Cyanosis is caused by a lack of oxygen in the blood capillaries containing more than 5 g of reduced haemoglobin in 100 ml of blood. Cyanosis is associated with the cold temperatures, heart failure, and lung diseases and smothering.

It is seen in infants at birth as a result of heart defects, respiratory distress syndrome, or lung and breathing problems. If the blood does not absorb enough oxygen during its passage through the lungs, then the arterial blood appears bluish in color.