This presentation is apt for Physiotherapy students or students of basic medical school.

1. CARDIAC OUTPUT
Dr. Blessy Joel (PT)
MPT (Cardio Respiratory diseases)

2. • DEFINITION
• NORMAL VALUE
• DETERMINANTS
• STROKE VOLUME AND ITS REGULATION
• HEART RATE AND ITS REGULATIONS
• ITS VARIATIONS

3. • Cardiac output (CO) is a measurement of the
amount of blood pumped by each ventricle in one
minute.
• To calculate this value, multiply stroke volume
(SV), the amount of blood pumped by each
ventricle, by heart rate (HR), in contractions per
minute (or beats per minute, bpm).
• It can be represented mathematically by the
following equation:
• CO = HR × SV

4. • Stroke volume is expressed in mL/beat and
heart rate in beats/minute.
• Therefore, cardiac output is in mL/minute.
Cardiac output may also be expressed in
liters/minute.
• Stroke volume depends on–
• End diastolic volume
• Contractility

6. • Cardiac Output is an excellent example to
exhibit the efficiency of the human heart.
• It is related to the amount of blood pumped
by the heart per minute.
• A normal cardiac output would be about five
litres (5 litres) of blood per minute in a
healthy individual.

7. FACTORS AFFECTING CO
• Cardiac output is maintained by four
factors:
Venous return
Force of contraction
Heart rate
Peripheral resistance

8. 1.Venous Return
• This is the amount of blood that enters the
Right Atrium through the veins per minute.
After a certain time interval, the venous
return becomes equal to the cardiac output.
• Venous return in turn, depends on following
factors:
Respiratory pump
Muscle pump
Gravity
Venous pressure

10. 2.Force of Contraction
• The stroke volume and the cardiac output
increases with the increase in the force of
contraction.
• Frank -Starling law of the heart states that
when increased volume of blood flows into
the heart, the cardiac muscle contracts with
increased force and this empties the extra
blood that has entered from the systemic
circulation leading to
--- increased cardiac output.

12. PRELOAD
• •It is stretching of cardiac muscle fibre at
the end of diastole, just before contraction
• •Cardiac output is directly proportional to
pre-load.
AFTERLOAD
• •It is the force against which ventricles must
contract and eject the blood.
• •Force of contraction and cardiac output is
inversely proportional to after-load.

13. 3.Heart Rate
• The cardiac output increases with the
increase in heart rate.
• Any factor which changes heart rate will
also change Cardiac output.
• Cardiac Output Formula
• The equation for cardiac output is:
• Cardiac Output (CO) = HR x SV

14. 4. Peripheral Resistance
•Peripheral resistance is the resistance offered
to blood flow at the peripheral bloodvessels.
•Peripheral resistance is the resistance or load
against which the heart has to pump
theblood.
•Cardiac output is inversely proportional to
peripheral resistance.

16. • 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.

17. • Some of the methods to measure cardiac
output are listed below:
• Doppler ultrasound
• Echocardiography
 Transcutaneous
 Transoesophageal
• Low output results in heart failure, a severe
infection or heart diseases.
• The high output may be an indicator of
blood infections.

18. • Cardiac Index
• “Cardiac index is defined as the cardiac
output divided by the body surface area.”
• It is a hemodynamic parameter that relates
the cardiac output from the left ventricle in
one minute to the body surface area.
• Cardiac Index = Cardiac
Output/Body Surface Area
• Stroke volume index is the stroke volume
divided by the body surface area.

19. The average
human being who
weighs 70 kg has a
body surface area of
about 1.7 sq meters,
which means
that the normal
average cardiac
index for adults is
about 3 L/min/m2 of
body surface area.

20. • Major Factors Influencing Cardiac Output:
• Cardiac output is influenced by heart rate
and stroke volume, both of which are also
variable.

21. • SVs are also used to calculate ejection
fraction, which is the portion of the blood
that is pumped or ejected from the heart
with each contraction.
• To calculate ejection fraction, SV is divided
by EDV.
• the ejection fraction is normally expressed as
a percentage. Ejection fractions range from
approximately 55–70 percent, with a mean
of 58 percent.

22. EJECTION FRACTION
• Ejection fraction (EF) is a
measurement, expressed as
a percentage, of how much
blood the left ventricle
pumps out with each
contraction.
• Ejection fraction refers to
the fraction (or portion) of
enddiastolic volume (see
below) that is ejected out
by each ventricle per beat.
• From 130 to 150 mL of
enddiastolic volume, 70
mL is ejected out by each
ventricle (stroke volume).
Normal ejection fraction is
60% to 65%.

24. • Exercise and Maximum Cardiac Output
• In healthy young individuals, HR may
increase to 150 bpm or higher during
exercise.
• SV can also increase from 70 to
approximately 130 mL due to increased
strength of contraction.

25. • This would increase CO to approximately 19.5
L/min, 4–5 times the resting rate. Top
cardiovascular athletes can achieve even higher
levels.
• At their peak performance, they may increase
resting CO by 7–8 times.
• Since the heart is a muscle, exercising it
increases its efficiency.
• The difference between maximum and resting
CO is known as the cardiac reserve. It measures
the residual capacity of the heart to pump blood.

26. • What controls heart rate?
• Heart rate controlled by the two branches of the
autonomic (involuntary) nervous system. The
sympathetic nervous system (SNS) and the
parasympathetic nervous system (PNS).
• The sympathetic nervous system (SNS) releases the
hormones (catecholamines - epinephrine and
norepinephrine) to accelerate the heart rate.
• The parasympathetic nervous system (PNS) releases the
hormone acetylcholine to slow the heart rate.
• Such factors as stress, caffeine, and excitement may
temporarily accelerate your heart rate, while meditating
or taking slow, deep breaths may help to slow your
heart rate.
• Exercising for any duration will increase your heart rate
and will remain elevated for as long as the exercise is
continued.

27. VARIATIONS IN CARDIAC OUTPUT
PHYSIOLOGICAL CAUSES
•Age-↑ses with age
•Sex-less in females more in males
•Body build-↑ses with body build
•Exercise-↑ses with exercise
•High altitude-↑ ses
•Pregnancy-↑ ses
•Sleep-↓ ses

28. PATHOLOGICAL CAUSES
•Increase in-
1.Fever
2.Anemia
3.Hyperthyroidism
•Decrease in-
1.Shock
2.Hypovolumia
3.Hemorrhage
4.Congestive cardiac failure
5. Hypothyroidism