How does cardiac output affect the blood pressure?

Cardiac output is the amount of blood per minute pumped out by each of the two ventricles of the heart. A typical value in an adult at rest is 5 litres per minute. The output of each ventricle is the product of the stroke volume (about 70 ml) and the heart rate (about 70 per minute). The output increases with muscular activity, in work or exercise perhaps to a maximum of 4-5 times the resting rate in an average healthy person, or up to 6-7 times in athletes; heart rate increases by a greater factor than stroke volume.

The more blood pumped from the heart per minute (that is, the larger the cardiac output), the higher the blood pressure—as long as resistance to blood flow in the arteries remains constant. The body can change the amount of blood pumped during each heartbeat by making each contraction weaker or stronger.

The higher the volume of blood in the blood vessels, the higher the blood pressure—as long as resistance to blood flow in the arteries remains constant. To increase or decrease blood volume, the kidneys can vary the amount of fluid excreted in urine.

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