For patients whose hearts are in disrepair, cardiac surgery of some form may be the only effective means of correcting the situation. Until the 20th century, successful heart surgery was unthinkable because it was not possible to see inside a heart that was beating and filled with blood. Because of research on dogs and other animals, the 1950's saw an exciting blossoming of advances in cardiac surgery which continues to this day After decades of work, in 1953 a heart-lung machine was developed that was able to take over temporarily for the heart and lungs. Blood can be re-routed through this machine, bypassing the heart so that surgeons can work inside it.
Blood enters the machine from veins that empty into the heart.
This blood is returning from its circuit of the body, having given up its oxygen for carbon dioxide. Normally, the heart would pump it to the lungs, where carbon dioxide would be exchanged for fresh oxygen. The heart-lung machine performs this same exchange in an oxygenator. Since its development almost forty years ago, thousands of human and animal hearts have been repaired while this life-saving machine took over for them during surgery. When disease or injury impairs the heart's pacemaker, the heartbeat is disrupted, causing dizziness and sometimes even convulsions or death.