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cardiac output  
The volume of blood pumped per minute by each ventricle of the heart. Cardiac output is equal to the stroke volume (the amount of blood pumped from a ventricle in a single heartbeat) times the heart rate. It is used as a measure of the overall health of the heart.
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Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
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cardiac output

in human physiology, volume of blood expelled by either ventricle of the heart. It is customarily expressed as minute volume, or litres of blood per minute, calculated as the product of stroke volume (output of either ventricle per heartbeat) and the number of beats per minute. Maintaining and regulating cardiac output, which is usually proportional to the tissues' need for oxygen and other nutrients, is one of the circulatory system's most intricate functions. In the healthy human adult, resting (or basal) output is estimated to be slightly over five litres per minute. Normally, it decreases somewhat when a person changes from recumbent to upright position. It may be increased 50 to 100 percent by anxiety and excitement and as much as fivefold by exercise. Measurement of cardiac output, as first described by the German physiologist Adolf E. Fick in 1870, makes possible an evaluation of respiratory exchange, i.e., the delivery of oxygen to the tissues.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Cardiac output is a major limiting factor for prolonged exercise.
Over time, patients may lose muscle weight due to low cardiac output and a significant reduction in physical activity.
As cardiac output falls, the kidneys try to make up for the reduced blood flow by retaining fluid, thus boosting blood pressure.
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