cyanosis (central)
Last reviewed 01/2018
Central cyanosis only occurs when the oxygen saturation of arterial blood is less than 85%. Causes include:
- decreased PO2 of inspired air - high altitude
- hypoventilation
- parenchymal lung disease - massive pulmonary embolism, chronic airflow limitation with cor pulmonale
- right to left cardiac shunt - congenital cyanotic heart disease
Central cyanosis may be simulated by methaemoglobulinaemia and sulphaemoglobulinaemia. Also, a patient with polycythaemia may present with central cyanosis.