What is a heart-lung machine?

The heart-lung machine is also called a cardiopulmonary bypass machine. It takes over for the heart by replacing the heart's pumping action and by adding oxygen to the blood. This means that the heart will be still for the operation, which is necessary when the heart has to be opened (open heart surgery). Because the heart-lung machine takes over the work of the heart, surgeons can operate on a heart that is not moving or full of blood.

When you are connected to the heart-lung machine, it does the same job that your heart and lungs would do. The heart-lung machine carries blood from the upper-right chamber of the heart (the right atrium) to a special reservoir called an oxygenator. Inside the oxygenator, oxygen bubbles up through the blood and enters the red blood cells. This causes the blood to turn from dark (oxygen-poor) to bright red (oxygen-rich). Then, a filter removes the air bubbles from the oxygen-rich blood, and the blood travels through a plastic tube to the body's main blood conduit (the aorta). From the aorta, the blood moves throughout the rest of the body.

The heart-lung machine can take over the work of the heart and lungs for hours. Trained technicians called perfusion technologists (blood flow specialists) make sure that the heart-lung machine does its job properly during the surgery. Even so, surgeons still try to limit the time that patients must spend hooked up to the machine.