1. Blood pressure & cardiac output
PREPARED BY: Dr. Jaishree Tiwari (P.T)

3. • Upon completing this chapter students should be able to:
1.Define Blood pressure
2.Describe Pulse and Cardiac Output
3
Learning Objectives

4. BLOOD PRESSURE
 Blood pressure (BP) is a measure of the
 force that the circulating blood exerts
 against the arterial wall.
4
SYSTOLIC PRESSURE
• Systolic pressure is the maximum pressure exerted by the blood against the arterial walls.
• It results when the ventricles contract (systole )

5. 5
DIASTOLIC PRESSURE
• Diastolic Pressure is the lowest pressure in the artery.
• It result when the ventricles are relaxed (diastole )
Blood Pressure measurement
•Office BP measurement:
Two readings, 5 minutes apart, sitting.
•Ambulatory BP monitoring:
For white coat hypertension.
•Self-measurement of BP:
Information on response to therapy, may improve adherence to therapy.
Time of measurement
• Use multiple readings at different times during the waking hours of the patient.
• For patient taking antihypertensive medications monitoring of blood pressure should be done
before taking the scheduled dose.

6. 6
Patient position
• BP should be measured in sitting position. Patient should sit for 5 minutes before measuring BP.
• In elderly, supine and standing position can be used to detect postural hypotension.
Selecting the most accurate blood pressure cuff
• The length of the bladder should be at least 80% of the circumference of the upper arm.
• The width of the bladder should be approximately 40% of the circumference of the upper
arm.

7. 7Where to listen for blood pressure
sounds
1- Locate the antecubital fossa of the patient’s arm
and palpate the brachial artery. This location is the
point over which the stethoscope is placed to listen for
Korotkoff sounds later.
2-Wrap the cuff approximately 2.5 inch above the
antecubital fossa.

8. 8Determining the palpated systolic pressure
and the maximum inflation level
3. While palpating the radial pulse, inflate the cuff until
you feel the radial pulse disappear.
Note the pressure on the manometer at this point and rapidly
deflate the cuff.

9. 9Measurement of BP
4- Place the stethoscope lightly over the brachial artery and inflate the cuff to a pressure 30 mm Hg
greater than estimated systolic pressure.
5- Deflate the cuff slowly at a rate of 2 mm Hg per heartbeat.
6- Systolic pressure equal the pulse first heard by auscultation
7- Deflate the cuff until the sounds become muffled and then disappear.The
disappearance of sound estimate the diastolic pressure.
8- Record the blood pressure reading in even numbers. Note patient’s position, cuff
size, and arm used for measurement.

10. 10

11. CARDIAC OUTPUT
 Cardiac output is defined as amount of
 blood pumped out of each ventricle per
 minute.
 Cardiac output is expressed in two forms,
 1)stroke volume
 2) minute volume
 Unit – litre (ml) / min
11

12. 12CO = SV x HR
cardiac output = stroke volume X heart rate (ml/minute) (ml/beat) (beats/min)
a.Average heart rate = 70 bpm
b.Average stroke volume = 70−80 ml/beat
c.Average cardiac output = 5000 ml/minute
Cardiac output varies widely with the level of activity of the body.
FACTORS EFFECTING CARDIAC OUTPUT
Heart rate
When heart rate increases ,cardiac output also increases. Any factor which changes heart rate
will also changes cardiac output.
Force of contraction of heart
When the force of contraction of the heart increases, stroke volume will increase. Therefore
cardiac output will increase.
Blood volume
When blood volume increases cardiac output increases.
Venous return

13. 13

14. STROKE VOLUME
 Stroke volume ( SV ) is the volume
 of blood pumped out of each ventricle per
 beat or contraction .
 As the stroke volume increases the
 cardiac output also increases.
 Stroke Volume depends upon
 1. End diastolic Volume
 2. Contractility
 SV = EDV – ESV
14

15. 15The stroke volumes for each ventricle are generally equal, both being approximately 70
ml in a healthy 70 kg man.
Men, on average, have higher stroke volumes than women due to the larger size of their
hearts.
Physiological variations of cardiac output
1. Age: Cardiac output is more in adults than in children because blood volume is more.
2. Gender: cardiac output is more in male than females.
3. Altitude: cardiac output increases at high altitude places.
4. Pregnancy: cardiac output increases during pregnancy
5. Exercise: cardiac output increases during exercise
6. Emotion: cardiac output increases during emotional expressions.

16. 16
PATHOLOGICAL VARIATION OF CARDIAC OUTPUT
Pathological increase:
1. Hyperthyroidism
2. Fever
Pathological decrease:
1. Hypothyroidism
2. Hypovolemia
3. Haemorrhage
4. Myocardial infarction
MEASURING CARDIAC OUTPUT
1. The Fick principle
2. Dilution methods
3. Pulmonary artery thermo dilution (trans right- heart Thermo dilution)
4. Doppler ultrasound method
5. Impedance cardiograph

17. RELATIONSHIP WITH BP
 As Cardiac output is made up of heart rate and stroke volume - at rest
these are relatively constant.
 With exercise the heart beats faster - more
 blood is pumped out with each beat
 contributing to a rise in BP.
 Changes in the volume of blood within the cardiovascular system will also
affect Bp.
17

18. 18
 A person was severely dehydrated or lost a large quantity of blood through a wound,
there would be less blood for the heart to pump, thereby reducing cardiac output and
BP.
 For a typical, fit young person, the cardiac output might go up to about 20 litres/min at
the peak of exercise.
 For a world-class athlete in an endurance sport, the maximum cardiac output might be
around 35 litres/min.
REGULATION OF CARDIAC OUTPUT
It means maintaining a constant cardiac output around 5 litres/min under normal
conditions and adjusting the cardiac output as per the physiological demands.
It has to be regulated to have an optimum cardiovascular efficiency.

19. REFERENCES
 Reference Books : BD chaurasia Vol 3 anatomy
 https://teachmeanatomy.info/thorax/organs/heart/atria-ventricles/
19