2015年职称英语卫生类概括大意练习（11）

Surgery Involving the Heart

　　1. The heart-lung machine (pump-oxygenator1) is a valuable addition to the modern operating room. This machine has made it possible to perform many operations on the heart and other thoracic organs which could not otherwise be done. There are several types of machines in use, all of which serve as2 a temporary substitute for3 the patient’s heart and lungs.
　　2. The machine siphons off4 the blood from the large vessels entering the heart on the right side so that no blood passes through the heart and lungs. The blood is returned to the general circulation for body distribution through one of the large arteries. While passing through the machine, the blood is oxygenated by means of5 an oxygen inlet, and carbon dioxide6 is removed by various chemical means. These are the processes that normally take place between the blood and the air in the lung tissue. While in the machine, the blood is also “defoamed” to be sure that all air bubbles are removed, since such bubbles could be fatal to the patient by obstructing blood vessels. An electric motor in the machine serves as a pump during the surgical procedure to distribute the processed blood throughout the body by means of the artery mentioned above.
　　3. Diseased valves may become deformed and scarred from endocarditis so that they are ineffective and often obstructive. In some cases a special small knife can be inserted into the heart chamber and the valve can be cut so that it no longer obstructs the blood flow. The valve may even become partially functional. In other cases there may be so much damage that replacement is the only resort. Substitute valves made of7 plastic materials have proved to be a lifesaving measure for many patients. Very thin butterfly valves made of dacron or other synthetic material have also been successfully used.
　　4. Artificial hearts or parts of hearts designed to assist the ventricles in their pumping function have not proved as successful as the artificial valves. However, research continues and it is quite possible that an effective device may soon be ready for use. More spectacular is the transplantation of a human heart from the body of a person who has recently died. Tissues of the donor and the recipient should be as closely matched as possible to avoid rejection by the recipient’s antibody mechanism. This rejection syndrome is the most serious problem related to heart transplants.

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