In intensive care medicine, extracorporeal membrane oxygenation (ECMO) is a technique of providing oxygen to patients whose lungs are so severely diseased that they can no longer serve their function.

An ECMO machine is similar to a heart-lung machine. To initiate ECMO, cannulas are placed in large blood vessels to provide access to the patient's blood. Anticoagulant drugs (usually heparin) are given to prevent blood clotting. The ECMO machine continuously pumps blood from the patient through a "membrane oxygenator" that imitates the gas exchange process of the lungs, i.e. it removes carbon dioxide and adds oxygen. Oxygenated blood is then returned to the patient.

ECMO can provide sufficient oxygenation for several days or even weeks, allowing diseased lungs to heal while the potential additional injury of aggressive mechanical ventilation is avoided. It may therefore be life-saving for some patients. However, due to the high technical demands, cost, and risk of complications (such as bleeding under anticoagulant medication), ECMO is usually only considered as a last resort therapy.