Heart-lung machine

The heart-lung machine is an essential component in open-heart surgery. Bloodfrom the veins is shunted via catheter to the machine, which introduces oxygen into the blood and then pumps the blood back into the patient's arteries.With the machine thus performing all the functions of the heart and lungs, the heart itself can be stopped while surgery is performed. Before the heart-lung machine, heart surgeons operated blindly, either with the heart still pumping, by slowly chilling the patient's body until circulation nearly stopped,or by connecting the patient's circulatory system to a second person's systemduring the operation. All of these methods were extremely risky.

While the idea of a heart-lung machine had been proposed as long ago as 1812,the device was not developed until American surgeon, John H. Gibbon, Jr. (1903-1974), decided in 1931 to build a heart-lung machine after a young femalepatient died of blocked lung circulation. At the time, experimental devices existed for pumping and oxygenating blood during perfusion (artificial circulation). Gibbon, who received his medical degree in 1927 from Jefferson MedicalCollege, began his heart-lung work in 1934 at Massachusetts General Hospitalduring a research fellowship with the assistance of research technician MaryHopkinson, who later became his wife. They found the action of roller pumpsgentle enough to minimize both clotting and damage to blood cells, and they employed centrifugal force to spread the blood in a layer thin enough to absorb the required amounts of oxygen. In 1935 the Gibbons went to the Universityof Pennsylvania School of Medicine and continued their experiments, reportingsuccessful results with animals by 1939. In 1946 John Gibbon became head ofthe surgical department at his alma mater and soon secured the backing of Thomas J. Watson, chairman of IBM. With the use of IBM laboratories and engineers, Gibbon's heart-lung machine was perfected after the introduction of wire-mesh screens to enhance oxygenation, filters to block air bubbles or clots, and monitoring devices. By 1952, the heart-lung bypass surgery had a ninety percent success rate on animals, and Gibbon decided to use the machine on a human patient. The first attempt failed, although the pump-oxygenator worked as required. On May 6, 1953, the second surgery using the heart-lung machine wassuccessfully performed on Cecilia Bavolek. Despite the deaths of two subsequent patients, the era of open-heart surgery had begun. The heart-lung machinewas rapidly improved: oxygenation, for example, was accomplished by more sophisticated methods. Once patients could be kept alive during heart surgery, awhole new range of operations became possible. Congenital heart defects couldbe repaired, diseased or damaged valves could be replaced, and coronary bypass surgery became possible through sewing in a replacement blood vessel to carry blood flow around a blocked section of artery. Thanks to Gibbon'sheart-lung machine, open-heart surgery--especially coronary bypass--has become routine throughout the world.

By the late 1990s, a laser system being used in many protocols across the United States, allowed traditional bypass surgery without the heart-lung machine. This surgery requires only a small incision between the ribs (no cutting ofthe chest bone as with traditional bypass surgery) to expose the heart muscle. The laser is aimed at the portion of the heart starved for oxygen and, synchronized with the heartbeat, fires automatically when the ventricle is fullof blood until about 20 to 40 new channels are created through the wall of the heart muscle. The outside of these channel heals almost immediately while the inside remains open. As the heart pumps, blood is forced from the left ventricle into these new channels, providing oxygenated blood to the previouslystarved section. This surgery takes one-to-two hours as opposed to the four-to-six required for traditional bypass surgery.

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