What is cardiac output and how is it calculated?

What is cardiac output and how is it calculated?

• A. Cardiac output is the total blood volume in the vascular system at a given moment.
• B. Cardiac output is the rate of blood flow through a single artery.
• C. Cardiac output is the volume of blood pumped by the heart each minute, calculated as CO = heart rate × stroke volume.
• D. Cardiac output equals the product of systolic blood pressure and heart rate.

Answer: (C)

Cardiac output is the amount of blood the heart pumps each minute. It depends on two factors: heart rate, which is how many times the heart beats per minute, and stroke volume, the amount of blood ejected with each beat. The relationship is simple: cardiac output = heart rate × stroke volume, giving units of liters per minute. For example, if the heart beats 75 times per minute and each beat moves about 70 milliliters of blood, the cardiac output is 75 × 70 mL = 5250 mL per minute, roughly 5.25 L/min. This value can rise during exercise because both heart rate and stroke volume typically increase to meet higher demands for oxygen and nutrients by the body's tissues. The other descriptions don’t represent how much blood the heart pumps per minute. Total blood volume is the full amount of blood in the circulatory system at a moment, not the rate of pumping. The rate of blood flow through a single artery reflects local flow, not overall cardiac output. And multiplying systolic blood pressure by heart rate mixes a pressure measure with a rate, which does not yield volume per time.

Cardiac output is the amount of blood the heart pumps each minute. It depends on two factors: heart rate, which is how many times the heart beats per minute, and stroke volume, the amount of blood ejected with each beat. The relationship is simple: cardiac output = heart rate × stroke volume, giving units of liters per minute.

For example, if the heart beats 75 times per minute and each beat moves about 70 milliliters of blood, the cardiac output is 75 × 70 mL = 5250 mL per minute, roughly 5.25 L/min. This value can rise during exercise because both heart rate and stroke volume typically increase to meet higher demands for oxygen and nutrients by the body's tissues.

The other descriptions don’t represent how much blood the heart pumps per minute. Total blood volume is the full amount of blood in the circulatory system at a moment, not the rate of pumping. The rate of blood flow through a single artery reflects local flow, not overall cardiac output. And multiplying systolic blood pressure by heart rate mixes a pressure measure with a rate, which does not yield volume per time.