Causes of Cyanosis
| Central Cyanosis |
| Decreased arterial oxygen saturation |
| Decreased atmospheric pressure—high altitude |
| Impaired pulmonary function |
| Alveolar hypoventilation |
| Inhomogeneity in pulmonary ventilation and perfusion (perfusion of hypoventilated alveoli) |
| Impaired oxygen diffusion |
| Anatomic shunts |
| Certain types of congenital heart disease |
| Pulmonary arteriovenous fistulas |
| Multiple small intrapulmonary shunts |
| Hemoglobin with low affinity for oxygen |
| Hemoglobin abnormalities |
| Methemoglobinemia—hereditary, acquired |
| Sulfhemoglobinemia—acquired |
| Carboxyhemoglobinemia (not true cyanosis) |
| Peripheral Cyanosis |
| Reduced cardiac output |
| Cold exposure |
| Redistribution of blood flow from extremities |
| Arterial obstruction |
| Venous obstruction |