Heart-lung Machine Functionality

Until the early 1950’s, operations on the heart were fairly limited in nature. Rectification of congenital abnormalities, or surgery on valves and arteries were almost impossible. Modern day technologies and medical advancements have developed to allow for the heart to come to a complete stop for hours - in a safe way - with the heart-lung machine supporting the systemic circulation; taking over the function of both the heart and lungs. The evolution of the heart-lung machine has forever changed the landscape of the surgery room: offering extended time to the surgeon, with an increased possibility to focus specifically on the surgery at hand.

How the heart-lung machine functions: The surgical lights are on, the patient is sleeping and the breathing, heartbeat, oxygen levels and blood pressure are all being monitored by the anaesthetist. Medicine is administered to reduce chances of blood clotting and soon, the heart will lose its responsibility to pump. The heart is now connected to the iron heart, via a tube that is placed in the right side of the heart, which will move blood away from the heart and carry blood to the machine. The body temperature of the patient has been lowered to a state of hypothermia - a state the body can maintain without blood flow for at least 45 minutes, and most appropriately, a state that is considered safe when it comes to cutting off blood supply. Permanent brain damage is often the result of blood flow cut off at a normal body temperature, which is followed closely by death. Blood enters the heart-lung machine and the waste or carbon dioxide from the blood is absorbed into the machine. An oxygenator injects the red blood cells with oxygen to carry back to the body. On its way out, the blood additionally passes through a heat exchanger - an advancement that gives the perfusionist control over the body temperature of the patient and allows for a constant temperature to be maintained. Once a pump completes the flow of blood back to the left side of the heart - into the aorta - blood circulates the body and the same process is repeated when the blood from the upper and lower parts of the body reaches and tries to enter into the right atrium of the heart. The enter process sees empty heart chambers and motionless lungs - an optimal situation for heart defects to be assessed and operated on. “The heart–lung machine has made virtually all the advances in cardiac surgery possible.” (D.J. Wheatley).

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© Maboneng Heart and Lung Institute 2017 | Featured Image: National Heart, Lung and Blood Institute Sources: https://www.nhlbi.nih.gov/health-topics/heart-surgery http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/blood-circulation http://www.encyclopedia.com/medicine/divisions-diagnostics-and-procedures/medicine/heart-lung-machine