Back to Cardiovascular Procedures
A cardiac pump or cardiac bypass pump or heart-lung machine
temporarily takes over the function of breathing and pumping blood for
It generally has two parts, the pump and the aerator.
The pump is usually several motor-driven rollers that peristaltically
massage a tube made of silicone rubber. The massage pushes the blood
through the tubing.
The aerator varies, but usually is either a drip onto a sterile
surface, or passage through a silicone-membrane simulated lung.
Cardiac pumps are most often used in heart surgery, so that a
patient's heart can be disconnected from the body for longer than the
twenty minutes or so it takes a prepared patient to die. Although
unprepared patients get brain damage in three to four minutes, and
patient can be prepared by cooling and drugs so that no damage will
occur for twenty minutes or more.
Cardiac pumps are also sometimes used to keep babies with birth
defects alive, or to aerate bodies with transplantable organs.
Chronic use of cardiac pumps is contraindicated because the pressure
profile of most practical pumps is believed to cause circulatory
damage to the brain, especially in extended use. The pumps generate
continuous pressure. When this pressure is set high enough to aerate
tissues in the foot, it can easily damage tissue in the brain.
Likewise, if set low enough to avoid damaging the brain, it often
under-aerates some part of the body, such as the feet.
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