Surgery of the heart usually involves opening the heart muscle. For operations of short duration it is possible to apply hypothermy (deep cooling) and thus temporarily stopping the blood circulation altogether. However, for major operations it is necessary to maintain the circulation, and this is achieved by means of the heart-lung machine. This has the twofold function of keeping the replacement blood in circulation by means of a pumping system and enriching with fresh oxygen the blood of low oxygen content coming from the patient’s body.

It is the function of the heart to provide circulation of blood at all times. It pushes blood out into the body and through the lungs. It must function every minute of every day of life to maintain the health of the tissues throughout the body.

In 1953, at Jefferson Medical College in Philadelphia, Dr. John Gibbon connected the circulatory system of an 18 year old female to a new machine, stopped the woman's heart, and for 26 minutes he performed surgery to close a hole in the wall of the heart between the left and right atria. It was the first successful use of a heart-lung machine and the beginning of a new era in cardiac surgery. The machine was not a sudden inspiration by anyone, but rather was the culmination of many years of dedicated research in many laboratories to find the means to oxygenate the blood and circulate it through the body.

To function, the heart lung machine must be connected to the patient in a way that allows blood to be removed, processed, and returned to the body. Therefore, it requires two hook-ups. One is to a large artery where fresh blood can be pumped back into the body. The other is to a major vein where used blood can be removed from the body and passed through the machine.

The venous blood, before it enters the right auricle of the heart, is diverted out of the vena cava and passed into the plastic tubes (a). This blood, which has already circulated through the body and consequently has a low oxygen content, is circulated through an artificial lung (b). In a horizontal glass cylinder partly filled with blood a number of steel discs rotate, which thus become wetted with blood. The blood on the surface of these discs forms a thin films of large area, which is exposed to a stream of oxygen in the upper part of the glass cylinder. The red blood cells are thus able to absorb oxygen in much the same way in which they do this in the human lung.

The heart-lung machine is a device used to provide blood circulation and oxygenation while the heart is stopped. It is a means of keeping a patient alive while his heart is stopped or even removed from his body. Usually called the heart-lung machine, the device also is referred to as cardiopulmonary bypass, indicating its function as a means to substitute for the normal functions of the heart (cardio) and lungs (pulmonary).