Cardiac Output

The term of Cardiac Output (CO) has been discussed as that part of cardiac physiology that shows the heart pumping blood in term of volume either through the right or left ventricles measured by their unit times. There are different ways in which CO could be measured like the L/min and dm3/min.

Cardiac Output

The amount of blood output by the left ventricle in one compression is called the stroke volume. Both, the heart rate and the stroke volume determine the cardiac output.

Cardiac Output is an excellent example of how the human heart does efficient work for maintaining the human body. It is related to the amount of blood pumped by the heart per minute. A normal cardiac output would pump about five to six litres of blood per minute when a person is resting.

The cardiac output comprises 2 vital components viz. SV – Stroke Volume and HR – Heart Rate.

  • Heart rate refers to the number of times the heart beats every minute (bpm).
  • Stroke volume refers to the quantity of blood pumped out of the left ventricle with every heartbeat.

Cardiac Output Formula

The equation for cardiac output is:

Cardiac Output (CO) = HR x SV

Cardiac Output Formula

Cardiac Output Calculation

For example: If the heart rate is 70 bpm and stroke volume is 70 ml.

Using the formula: HR X SV

= 70 X 70

= 4900 ml/min or 4.9 liters per minute.

Cardiac Output Measurement

There are different merits and demerits of measuring CO using methods in an invasive and non-invasive manner. At present, there is no standard comparison system available for comparing these methods using a reference measurement or standards.

The invasive systems are well accepted, but there is progressing evidence that these systems are neither accurate nor effective in guiding therapy activities like:

  • Doppler ultrasound
  • Echocardiography
  • Transcutaneous
  • Transoesophageal

Low output results in heart failure and this also could happen after the lost too much blood cells, or having a severe infection, or had heart damage.

The high output results in blood infections which leads to a dangerous fall in the blood pressure and failure of several organs. The high output is many caused by the lack of oxygen-rich blood cells and hyperthyroidism.

Important Questions for You:

  • What is Cardiac output?

The cardiac output is cardiac physiology term which describes the functioning of a human heart, and also about the total volume of blood (5 to 6 litres) being pumped every minute. Normal cardiac output is said when a person is resting.

  • When does the body need a higher cardiac output?

During exercise, running, tensed and other workouts, our body requires three or four times more than the normal cardiac output.

  • What happens during a higher cardiac output?

During the higher cardiac output, our heart functions faster and stronger to increase the pumping of blood into our body. This is because our body cell, tissues and muscles need more oxygen when we exert ourselves.

  • How is cardiac output calculated?

As we all know, Cardiac output is the total volume of blood that heart pumps every minute.

The formula used to calculate cardiac output is given as CO = HR × SV.


CO – Cardiac output

HR – Heartbeat rate per minute

SV- Stroke volume — the amount of blood circulated by the heart with each beat.

  • Is it important to maintain cardiac output?

Yes. Because, an adequate cardiac output helps to keep our blood pressure at the normal levels, which is required to supply oxygen-rich blood to our brain and other vital parts of our body.

Stay tuned with BYJU’S to learn more about the Cardiac Output and other related topics @ BYJU’S Biology

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