Download B2.17 Calculating cardiac output

B2.17 Calculating cardiac output
Cardiac output is the volume of blood pumped out by the heart
in a given time, usually one minute.
It is calculated using two values:
•
heart rate
•
stroke volume.
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B2.17 Calculating cardiac output
Heart rate is the number of contractions of the heart in a given
time, usually given per minute.
Average resting heart rate for an adult is around 70 bpm
(beats per minute).
Children and some people who are ill have a higher resting
heart rate significantly higher than 70 bpm.
In the short-term, activity and stress increase heart rate.
Exercise training over a long period usually decreases the
resting heart rate.
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B2.17 Calculating cardiac output
Stroke volume is the volume of blood pumped out by the heart
by one ventricle during each contraction.
Average resting stroke volume is around 70 cm3 for an adult
man.
Women have a smaller average resting stroke volume
because they have smaller bodies and smaller hearts.
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copyright free. This document may have been altered from the original.
B2.17 Calculating cardiac output
Disease of the heart and blood vessels may decrease stroke
volume.
Activity usually increases stroke volume a little during the
period of exercise.
Exercise training over a long period usually decreases the
resting stroke volume.
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copyright free. This document may have been altered from the original.
B2.17 Calculating cardiac output
Cardiac output is calculated as:
•
heart rate × stroke volume
So the resting cardiac output for an average adult man is:
•
70 bpm × 72 cm3
= 5040 cm3/minute
= c. 5 dm3/minute
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copyright free. This document may have been altered from the original.
B2.17 Calculating cardiac output
In a healthy but untrained man, during vigorous exercise,
heart rate increased to 160 bpm and stroke volume increased
to 120 cm3.
Calculate the cardiac output for a man during vigorous
exercise.
© Pearson Education Ltd 2011. Copying permitted for purchasing institution only. This material is not
copyright free. This document may have been altered from the original.
B2.17 Calculating cardiac output
In a healthy but untrained man, during vigorous exercise,
heart rate increased to 160 bpm and stroke volume increased
to 120 cm3.
Calculate the cardiac output for a man during vigorous
exercise.
160 × 120
= 19 200 cm3/min
= about 19 dm3/min
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copyright free. This document may have been altered from the original.
B2.17 Calculating cardiac output
A trained athlete has a resting heart rate of 54 bpm and a
resting stroke volume of 110 cm3.
Calculate the cardiac output for a trained athlete.
© Pearson Education Ltd 2011. Copying permitted for purchasing institution only. This material is not
copyright free. This document may have been altered from the original.
B2.17 Calculating cardiac output
A trained athlete has a resting heart rate of 54 bpm and a
resting stroke volume of 110 cm3.
Calculate the cardiac output for a trained athlete.
55 × 100
= 5500 cm3/min
= 5.5 dm3/min
© Pearson Education Ltd 2011. Copying permitted for purchasing institution only. This material is not
copyright free. This document may have been altered from the original.