During an open-heart surgery (such as valve or bypass surgery), the heart-lung machine is used to take over the functions of the heart and lungs. Also known as a cardiopulmonary bypass machine, it allows the surgeon to carefully stop the heart while the vital organs continue to receive blood and oxygen. When patients are on the heart-lung machine, very delicate work can be performed by surgeons without interference from bleeding or the heart’s pumping motion.

When first used successfully in humans in 1955, the machine was a revolutionary piece of equipment. Today, the heart-lung machine is used in about 1 million cardiac surgeries every year, including surgeries to the coronary arteries, heart valves and other structures of the heart. The heart-lung machine has a very low complication rate, approaching 1 percent for certain surgeries.

Newer medical technology is being developed that may someday replace the heart-lung machine in some circumstances. These technologies include systems that allow surgeons to operate on a beating heart, without use of the heart-lung machine. Known as off-pump surgery, this is used when surgeons are operating on the coronary arteries.