A heart–lung machine takes over the function of the heart and the lungs. This allows the surgeon to operate on the heart during certain major chest operations, such as coronary artery bypass grafts, a heart transplant, or heart valve replacements. The heart is cooled and paralysed to stop it beating during surgery, and blood is diverted to the heart–lung machine, which oxygenates the blood, removes carbon dioxide, and then returns the blood to the body. Afterwards, the heart is restarted with an electric shock and the circulation is restored.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.