3.2.8 Cardiac Output

Question 1

Cardiac Output

Answer 1

Cardiac output (CO) is a term used to describe the volume of blood that is pumped by the heart (the left and right ventricle) per unit of time
An average adult has a cardiac output of roughly 4.7 litres of blood per minute when at rest
Individuals who are fitter often have a higher cardiac output due to having thicker and stronger ventricular muscles in their hearts
Cardiac output increases when an individual is exercising
- this is so that blood supply can match the increased metabolic demands of the cells
The CO of an individual can be calculated using their heart rate and stroke volume
Heart rate is the number of times a heart beats per minute
- this can also be described as the number of cardiac cycles per minute
Stroke volume is the volume of blood pumped out of the left ventricle during one cardiac cycle

Question 2

Calculating Cardiac Output

Answer 2

Cardiac output is found by multiplying the heart rate by the stroke volume:
Cardiac output = heart rate x stroke volume
The equation can be rearranged to find the heart rate and stroke volume if required
- heart rate = cardiac output / stroke volume
- stroke volume = cardiac output / heart rate