What Is a Membrane Oxygenator?

A membrane oxygenator is a device that mimics the function of the lungs, pulling carbon dioxide out of the blood and infusing it with oxygen. This equipment can be used for short term cardiopulmonary bypass in surgical procedures. It is also available in the form of extracorporeal membrane oxygenation (ECMO), which can be used for up to ten days to support a patient who lacks normal heart and lung function. The origins of this technology may be traced back to the 1930s, when researchers began experimenting with ways to sustain patients with limited circulatory function.

This equipment requires a pump to circulate the blood and push it into the membrane oxygenator. A semipermeable membrane pulls out carbon dioxide while allowing oxygen to flow through before the blood is returned the body. The technology required substantial research and development before working models were successfully created, as there were a number of challenges for researchers. Successful membrane oxygenator devices were a significant development for medicine in the 20th century, providing more options to support patients and perform complex medical procedures.

One concern with early designs involved clotting. Blood exposed to air can clot, and the circulation in some equipment couldn’t prevent clots, posing a clear risk to patients. The very earliest designs required exposing blood to air to work, which created an unacceptably high level of clots. Another concern was gas bubbles, which could cause problems for patients, and required the development of carefully calibrated equipment that could allow for the injection of oxygen without the creation of bubbles.

In cardiopulmonary bypass, the membrane oxygenator is operated by a technician with specific training in the technology and its safe operation. Cannulas are placed to bypass the heart and lungs while the machine takes over for them. This allows surgeons to work in the chest, performing surgeries that would not otherwise be possible. When the procedure is over, the patient can be taken off bypass to allow the heart and lungs to resume normal function.

People with degraded heart and lung function who are waiting for surgery, recovering from surgery, or preparing for transplant may benefit from the use of a membrane oxygenator. The machine cannot keep someone alive indefinitely, but it can provide support for several days. These patients typically need to be hospitalized for monitoring and support. If they reach the edge of the safety window beyond which ECMO might be dangerous, their care providers may need to reassess to determine the best approach.