Heart-lung machine. Image 12 of 24 Heart-lung machine being used during heart surgery. This machine takes over the function of the heart and lungs while the heart is temporarily stopped during surgery, allowing more time to operate. The machine oxygenates the blood and removes carbon dioxide. It also heats the blood to the correct temperature before pumping it back into the patient's body. In this case it is being used during heart valve replacement surgery. For a sequence showing the operation, see images M560/494 to M560/517.