Pathophysiology
Clinical meaning
Extracorporeal membrane oxygenation (ECMO) provides temporary cardiopulmonary support by diverting blood from the body through an external circuit containing a membrane oxygenator (gas exchanger) and a centrifugal pump, then returning oxygenated blood to the patient. Two configurations exist: venovenous (VV) ECMO drains deoxygenated blood from a large vein (typically femoral or internal jugular), passes it through the oxygenator, and returns it to the venous system near the right atrium, providing respiratory support only while the patient's native cardiac output continues; venoarterial (VA) ECMO drains from the venous system and returns oxygenated blood to the arterial system (typically femoral artery), providing both cardiac and respiratory support by bypassing both the heart and lungs. The membrane oxygenator contains microporous hollow fibers across which gas exchange occurs: oxygen diffuses into the blood while carbon dioxide diffuses out, controlled by adjusting the sweep gas flow rate (FiO2 and CO2 removal) and blood flow rate. The circuit requires systemic anticoagulation (typically unfractionated heparin) to prevent clot formation on the artificial surfaces, creating a continuous balance between thrombosis and hemorrhage. Complications include hemorrhage (most common, 30-50%),...