1. Clinical Science Applied to Nursing
Blood Pressure
Clinical Science Applied to Nursing
Copyright CSAN 2011 Cardiff University

2. Why is theory and practice of Blood Pressure important?
How can we relate it to clinical practice?

3. ARTERIAL BLOOD PRESSURE-
Too low a value of arterial blood pressure
hypotension
blood flow to the tissues will be reduced
(for example to the brain and induce a faint
Too high a value of arterial blood pressure
hypertension
this may cause excessive capillary pressures and damage
e.g heart (myocardial infarction) kidneys, brain (stroke) and eyes

4. Effects of High Blood Pressure on Your Body
Food for thought
Artery Damage

5. Effects of High Blood Pressure on Body
Food for thought
Effects of High Blood Pressure on Body
Hardening of the arteries
Stroke
Heart attack
Kidney damage
Blindness

6. Blood Pressure and Pregnancy
Food for thought
Blood Pressure and Pregnancy
Gestational hypertension
The effects of high blood pressure for mother and foetus can be dangerous.
High blood pressure can:
harm the mother's kidneys and other organs
cause low birth weight and early delivery
Some mothers can develops preeclampsia which can threaten the lives of both the mother and the foetus

7. Blood Pressure and Children
Food for thought
Blood Pressure and Children
One in three children in Wales are above a healthy weight (WAG, 2010)
The Health Behaviour in School-Aged Children (HBSC) Survey found that among 13-year-olds 22% of boys and 17% of girls are classed as overweight, and 4% of boys and 2% of girls classed as obese
Obese children have approximately a 3-fold higher risk for hypertension than non obese children (Sorof and Daniels, 2002).
Hypertension in childhood is due to renal causes and only occasionally drug treatment (eg steroids)

8. Food for thought
An adult’s blood pressure is considered high when the readings are greater than 140 mm Hg systolic or 90 mm Hg diastolic (BHS, 2004)
Non-modifiable Risk Factors:
Age
male sex
family history
Primary cause of raised cholesterol (genetic)
diabetes mellitus (autoimmune)
Modifiable Risk Factors
Excess alcohol (43 units/day)
Excess salt intake
Lack of exercise
Environmental stress
smoking
Overweight (obesity)
Type II -Diabetes
(Type II can often coexists with obesity, dyslipidaemia, hypertension)

9. Learning Outcomes Define blood pressure
State why its important to study normal mechanism of blood pressure – for example what is the effect of hypertension
State the function of blood pressure
Explain how blood pressure is commonly measured
Name factors that influence blood pressure.
Define cardiac output and state how it is calculated
Discuss the factors that are involved in cardiac output
 Describe the main control mechanism for regulation of the blood pressure

10. What is Blood Pressure
The blood pressure is the force that causes blood to flow through the arteries, capillaries, and finally veins back to the heart

11. What is Blood Pressure?
Blood pressure is the amount of force exerted by the blood against the walls of the blood vessel
Arterial Blood pressure
Blood must circulate through the body and organs to maintain life
E.G.
To carry oxygen and nutrients to the cells
To remove waste products from the cells
The Heart is the pump that circulates the blood
Pressure difference in the vascular system ensures that blood flows around the body
That is why pressure varies in arteries, veins and capillaries

12. Arterial Blood Pressure
Expressed as systolic/diastolic
Adult
Normal – 120/80 mmHg
High – 140/90 mmHg
Systolic pressure (top number)
Pressure generated during ventricular contraction
Diastolic pressure
Pressure during cardiac relaxation

13. Blood Pressure
Each blood vessel has a blood pressure value – e.g. arterial blood pressure 120 mm Hg systolic
Capillary blood pressure averages 25 mm Hg
The pressures in the pulmonary system are much lower than systemic circulation
Blood flows from an area of high to an area of low blood pressure - there must be a difference in pressure for the blood to flow.

15. Blood Pressure Pulse Pressure (PP) Mean Arterial Pressure (MAP)
Difference between systolic and diastolic
PP = systolic - diastolic
Mean Arterial Pressure (MAP)
Average pressure in arteries
MAP = diastolic + 1/3 (systolic – diastolic)

17. Blood Pressure is generated by Ventricular Contraction

19. Blood pressure
Blood pressure is different in blood vessels and varies from minute to minute dependant on factors such as stress

20. Blood Pressure A blood pressure reading consists of two numbers:
Systolic pressure - the first, highest number
Indicates pressure when the ventricles contract to push blood out to the body
Diastolic pressure- the second, lower number
Indicates when the heart relaxes between beats

21. How can we measure Blood Pressure?
Blood Pressure can be measured in two ways:
Indirectly, using a sphygmomanometer and ausculating (listening) with a stethoscope, the sounds you hear are called Korotkoff sounds
Directly, using an arterial cannula (only used in Critical Care Areas, Operating Theatres).
(l00k up this reference: British Hypertension Society )

22. Measuring BLOOD PRESSURE
External blood pressure measurements:
We apply a cuff to the arm & apply pressure to the cuff to form a constricting band around the arm and around internal arteries.
The pressure in the cuff is initially above Blood pressure in the arteries– as the cuff pressure falls, it ‘meets’ the blood pressure & 1st Korotkof sound is heard.
When the cuff pressure falls below the blood pressure, the Korotkof sound disappears

23. Blood Pressure

25. Making sense of what we hear

27. Function of blood pressure
Systemic BP maintains the essential flow of substances into and out of organs

28. Function of blood pressure
Systemic blood pressure maintains the essential flow of the substance into and out of the organs
Control of blood pressure especially to the vital organs is essential for the maintenance of homeostasis
Control of BP is essential for the maintenance of homeostasis

29. Blood flow through the vessels
vessels is directly
proportional to the
difference in pressure
between the ends
of the tube

30. Healthy young adults: Resting
Arterial Blood Pressure the driving force for blood in the circulatory system
Healthy young adults: Resting
Systolic pressure = 120 mmHg
Diastolic is about 80 mmHg
Healthy children values vary (see Whaley & Wong 2000):
Rough Guide
Systolic pressure
1 –7years: age in years + 90:
8-18 (2 x age in years) + 83 &
Diastolic pressure:
1-5 years 56mmHg,
6-8years: age in years + 52

31. Blood Pressure measurement in adult

32. Blood Pressure in Pregnancy
Blood pressure during pregnancy is checked at every antenatal appointment
Blood pressure change a little over whole pregnancy. This is perfectly normal.
The pregnancy hormone progesterone relaxes the walls of blood vessels.
This causes blood pressure fall during first and second trimesters
This lower blood pressure may cause a woman to faint if they stand for too long or when getting up too quickly
Blood pressure is at its lowest between 18 and 20 weeks of pregnancy
In that period a woman will have produced an extra 1 to 2.5 litres of blood, which your heart has to pump around your body
Blood pressure returns to its pre-pregnancy levels in the last few weeks before baby is born.

33. What are the reasons for monitoring BP during Pregnancy
May help to identify:
High blood Pressure
Pre-eclampsia,
gestational hypertension
Blood pressure change in pregnancy?
The effects of high blood pressure range from mild to severe. High blood pressure can:
In the most serious cases, the mother develops preeclampsia which can threaten the lives of both the mother and the foetus.

34. Factors to consider when taking BP measurements
Cold Exposure
Bowel/Bladder Distension
Caffeine
Physical Activity
Stress

35. Making sense of what we hear

37. Factors which influence BP
Cardiac output (and venous return)
Blood volume and viscosity
Peripheral resistance
Elasticity of the blood vessels

38. Factors influencing blood pressure
Blood Pressure = Blood Volume × Peripheral Resistance
Cardiac Output = circulating blood volume
Cardiac Output = Heart Rate × Stroke Volume
Cardiac output affects circulating blood volume. * Any increase in circulating blood volume * will cause a corresponding increase in cardiac output. * The increased cardiac output * will increase blood volume * causing an increase in the blood pressure.
As cardiac output is determined by multiplying the heart rate times the stroke volume, * any increase in either of them * * will increase cardiac output * and effect an increase in blood pressure.
* For instance, an increased heart rate due to the release of epinephrine by the adrenal glands into the blood during an emergency, * will increase blood pressure. *

39. Factors which influence blood pressure
Cardiac output (CO)
Total Peripheral Resistance (TPR) Or
BP = CO x TPR

40. Cardiac output
Cardiac Output = Heart Rate x Stroke Volume l/min bpm mL In a healthy adult this is 70 bpm x 75mL= 5L/min

41. Terms, Definitions & Units
BP = CO x TPR
Cardiac Output (CO) - the amount of blood pumped by a ventricle per minute.
Units may be in Liters per minute
Heart Rate (HR)- number of cardiac cycles per minute. Normal beat per minute
Stroke Volume – (mls) amount of blood pumped out of a ventricle each beat.
Average resting stroke volume = 70 ml.
Cardiac output * refers to the amount of blood pumped by a single ventricle per minute. It may be reported in milliliters or Liters per minute.
Heart rate * is the number of cardiac cycles per minute. The average heart rate for adult males is from beats/minute. The average heart rate for adult females varies from 72-80/minute.
Stroke volume * refers to the amount of blood pumped out of a ventricle with each beat (contraction). The average stroke volume for an adult is around 70 ml.
Knowing the heart rate and the stroke volume, one can calculate the cardiac output by simply multiplying the two. For instance, if the heart rate is 70/minute and the stroke volume is 70 ml, what would be the cardiac output?
70/minute x 70ml = 4,900 ml (4.9 L.) *

42. Factors that influence cardiac output
Stroke volume – the amount of blood ejected from each ventricle at each heartbeat.
Heart Rate – regulated by the autonomic nervous system (ANS)
Increased heart rate caused by the release of epinephrine into blood by the adrenal glands = increased cardiac output, which increases circulating blood volume, to increase blood pressure.

43. Stroke Volume Preload Afterload Contractility
Stroke volume is determined by three factors:
Preload 
Afterload
Contractility

44. Preload Blood volume Venous return The vasomotor tone
- related to the volume of blood in the ventricle
at the end of diastole:
- End Diastolic Volume
Factors affecting preload are:
 Blood volume
Venous return
The vasomotor tone

45. Factors Aiding Venous Return
Venous blood pressure alone is too low to promote adequate blood return and is aided by the:
Respiratory “pump” – pressure
changes created during breathing
suck blood toward the heart by
squeezing local veins
Muscular “pump” – contraction
of skeletal muscles moves blood
toward heart
Valves prevent backflow during venous return

46. Preload: Factors which influence Venous return to the heart
Muscle pump
Respiratory Pump
Valves in the vein

47. Afterload
Described as the resistance against which the ventricle must work.
Whilst Preload is a major determinant of myocardial contractile power
Afterload is mainly mechanical factor that affects performance

48. Total Peripheral Resistance (TPR)
Peripheral Vascular Resistance
resistance exerted by the action of the walls of the resistance vessels impeding blood flow 
most resistance is provided systemically by the arterioles,and small and medium sized arteries –
exert a powerful influence in the control of blood pressure.

49. Factors which influence TPR
The length of the vessel the blood
The diameter of the lumen of the vessel
The viscosity of the blood

50. Pulse and Mean Arterial Pressures
Mean arterial pressure (MAP) = Diastolic + 1/3 pulse pressure
MAP is considered to be the perfusion pressure seen by organs in the body.
It is believed that a MAP that is greater than 60 mm Hg is enough to sustain the organs of the average person. MAP is normally between 70 to 110 mm Hg
If the MAP falls significantly below this number for an appreciable time, the end organ will not get enough blood flow, and will become ischaemic
The difference between the systolic and diastolic pressure is known as pulse pressure
Pulse pressure = Systolic–Diastolic

51. Control of Blood Pressure
Short term control - mainly involves:
First Response by:
Autonomic Nervous System.
The receptors which monitors changes in BP are:
Baroreceptor reflex
Chemoreceptor reflex
Circulating hormones
(They are Responsible for maintaining BP homeostasis)
Second or Indirect Adaptive Response by :
Renin-angiotensin Mechanism
Long term control involves regulation of Blood Pressure by the kidneys.

53. MECHANISMS OF B/P CONTROL
Higher brain stimulus
Baroreceptors
Chemoreceptors

54. Control of Blood Pressure
Short term control - mainly involves:
Baroreceptor reflex
Chemoreceptor reflex
Circulating hormones
Long term control involves regulation
Of blood Pressure by the kidneys.

56. Control of the Heart

57. Vasoconstrictors and Vasodilators
Epinephrine and Norepinephrine
Angiotensin II
Vasopressin
Vasodilators
EDRF (NO) endothelium derived relaxing factor- is produced and released by the endothelium to promote smooth muscle relaxation

58. Cardiovascular centers of the brainstem
Medulla oblongata is essential to Cardiovascular centers.

60. Second or Indirect Adaptive Response by Renin-angiotensin Mechanism
When BP 
Renin is released by the kidney into the blood
Renin stimulates Angiotensinogen (in lungs) to convert to Angiotensin I (mild constrictive hormone)
Angiotensin I is then converted by (ACE) Angiotensin Converting Enzyme
to Angiotensin II
When Angiotensin II causes
1 Vasoconstriction
2. Release of aldosterone from the adrenal cortex.
Prevents excretion of Na+ water in kidneys  reduce water loss from
circulation and this increases Blood Volume which in turn increases Blood Pressure 

61. Homeostatic Blood Pressure Regulation Mechanisms
Baroreceptors * in aortic arch & carotid sinuses:
sensitive to changes in blood pressure.
Reflex Centers in Medulla
Cardioacceleratory - increases heart rate
Cardioinhibitory - decreases heart rate
Vasomotor - changes diameter of vessels
BP* - Stimulates Cardioinhibitory center to heart rate & Vasomotor center to diameter.
Homeostatic mechanisms for the regulation of blood pressure include the following reflex centers in the medulla oblongata: *
* the Cardioacceleratory center, which increases heart rate,
* the Cardioinhibitory center, which decreases heart rate, and
* the vasomotor center in the aortic arch and the carotid sinuses, which can change the diameter of the arteries and arterioles causing vasoconstriction or vasodilation.
In addition to the reflex centers in the medulla, there are peripheral baroreceptors * in the walls of the aortic arch , the carotid sinuses and nearly every other elastic artery in the heck and thorax which are sensitive to changes in blood pressure. *
* A sudden increase in blood pressure * will cause the Cardioinhibitory center * to decrease heart rate * and will stimulate the vasomotor center * to increase the diameter of arterioles, thus reducing the blood pressure.
* A sudden drop in blood pressure noted by the baroreceptors * will stimulate the Cardioacceleratory center to increase heart rate * while stimulating the vasomotor center to decrease * the diameter of arterioles to increase blood pressure. *
BP* - Stimulates Cardioacceleratory center to heart rate &
Vasomotor center to diameter.

62. Anti Diuretic Hormone (ADH)
Released from Posterior Pituitary gland in
response to low blood volume and low BP
conserves body water by reducing the loss
of water in urine
vasoconstriction of mainly Splanchnic
circulation & fluid retention
WHAT is the Splanchnic circulation?

63. Atrial Natriuretic Peptide (ANP)-
released from the atria by large atrial stretch
Produces diuretic responses from kidney, also vasodilation and decrease in renin release.

65. Fluid Exchange
85% of fluid that leaves blood is returned at venous end
What about the other 15%?

69. References Fox S. (2009) Human Physiology, (11th Ed), McGraw-
Hill International Edition
Saladin K. (2010) Anatomy & Physiology, (5th Ed)
McGraw-Hill International Edition
Sorof J and Daniels S (2002), Hypertension. 2002;40:441
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