BLOOD PRESSURE
Lecture – 10
Dr. Zahoor Ali Shaikh
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ARTERIAL BLOOD PRESSURE
What is Blood Pressure?
• It is the pressure or force exerted by the blood
against the vessel wall.
Systolic Pressure - It is maximum pressure exerted
in the arteries during systole of ventricle. Average
120mm Hg.
Diastolic Pressure – Minimum pressure within the
arteries during the diastole of ventricle. Average
80mm Hg.
• Unit of Measurement of BP is mm Hg.
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ARTERIAL BLOOD PRESSURE
Normal BP
• Systolic - 120
• Diastolic - 80
(100 —140 mmHg)
(60 – 90 mmHg)
What is Pulse Pressure ?
• Difference between systolic and diastolic
blood pressure.
• Normal Range - 30 to 60 mm Hg
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ARTERIAL BLOOD PRESSURE
What is Mean Arterial Blood Pressure ?
• It is the average pressure which keeps blood
flowing through blood vessels throughout the
cardiac cycle.
• Normal B.P – 120/80 mmHg
• Mean Arterial B.P = DiastolicB.P+1/3Pulse pressure
= 80 + 1/3 × 40 = 93.3mmHg
• It is Mean Arterial Blood Pressure that is regulated
in the body.
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BLOOD PRESSURE [BP]
• Routine BP measurements record systolic and
diastolic blood pressure, which is used to
assess the Mean Arterial Blood Pressure.
• We use instrument Sphygmomanometer to
take the blood pressure.
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DETERMINANTS OF MEAN ARTERIAL
PRESSURE
Mean Arterial Pressure
= Cardiac Output × Total Peripheral Resistance
• Cardiac Output depends on Stroke Volume
and Heart Rate.
CO = SV × HR
• We have discussed the Cardiac Output.
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PERIPHERAL RESISTANCE
• Total Peripheral Resistance depends on Radius of
all arterioles and blood viscosity.
• Arteriolar radius is more important and
influenced by intrinsic metabolic factors which
control blood flow.
• It is also influenced by extrinsic control that is
sympathetic activity, vasopressin and angiotensin
II, which are vasoconstrictors.
• We have discussed factors affecting the Radius of
arteriole.
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REGULATION OF BLOOD PRESSURE
1. Short Term {Operates in seconds}
– Baroreceptors
– Chemoreceptors
– CNS Ischemic Response
2. Intermediate {Operates in Minutes}
– Renin-Angiotensin-Aldosterone Mechanism
3. Long Term {Operates in few hours to days}
– Kidney- Regulation of Na+ and H2O
Two Important Mechanisms are:
1- Baroreceptor Reflex
2- Renin-Angiotensin Mechanism
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MECHANISM FOR
REGULATION OF
ARTERIAL
PRESSURE
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BLOOD PRESSURE REGULATION
• We will discuss Short Term Mechanisms:
BARORECEPTORS
Baroreceptors are stretch receptors present in
the walls of blood vessels—CAROTID SINUS
and AORTIC ARCH, for short term regulation of
B.P.
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BLOOD PRESSURE REGULATION
BARORECEPTORS
• If blood pressure changes that is, increases or
decreases Baroreceptors try to bring it back to
normal value by adjusting cardiac output and
peripheral resistance by working through ANS
influences on heart, veins and arterioles.
• They work in seconds.
• Baroreceptors reflex is very important for
regulation of Mean Arterial Pressure.
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BLOOD PRESSURE REGULATION
BARORECEPTOR REFLEX
• It has following components:
Receptors
Afferent Pathway
Center
Efferent Pathway
Effector Organ
RECEPTORS – Carotid Sinus and Aortic Arch, they are
nerve endings and generate action potential in
response to pressure present in the arteries.
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BARORECEPTOR REFLEX
Afferent Pathway – Afferent nerve which carry impulse from
carotid sinus is IX [Glassophyrangeal] and from aortic arch
is X [Vagus].
Center – Cardiac Center is located in medulla [brain stem].
Efferent Pathway – From Cardiac center, we get Efferent ANS,
Sympathetic and Parasympathetic fibers to heart and blood
vessels.
Effector Organ – Sympathetic causes increase heart rate and
force of contraction of heart, vasoconstriction, therefore,
increase CO and BP.
Parasympathetic causes decrease heart rate, decrease
force of contraction of heart, therefore, decreased cardiac
output and decreased BP.
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CHEMORECEPTORS
• They are located in the carotid artery and
aorta.
• They are called Carotid body and Aortic body.
• They are sensitive to low O2 and increased CO2
and increased H+ ion in blood.
• They are mainly for the regulation of
respiration but reflexly increase blood
pressure by sending excitatory impulses to
cardio vascular center in medulla.
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CNS ISCHEMIC RESPONSE
• CNS Ischemia occurs when blood pressure is
very low [below 60 mmHg], there is increased
sympathetic discharge from cardiac center in
medulla to increase blood pressure.
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RENIN-ANGIOTENSIN SYSTEM
• It works in minutes and fully active in 20mins.
• Renin is enzyme released by kidneys when
arterial blood pressure becomes low.
• Renin is synthesized by Juxta glomerular [JG
cells] of the kidneys.
• Renin enters the blood and acts on
Angiotensinogin.
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FACTORS AFFECTING
BLOOD PRESSURE
• BLOOD PRESSURE is affected by the following factors:
- Age – BP increases with age
- Sex
- Height, Weight
- Posture—Supine, Standing
- Emotions
- Exercise – there is increased cardiac output and
decrease in peripheral resistance, {due to vasodilation
in skeletal muscle}, therefore systolic BP increases and
diastolic BP decreases. Pulse pressure is increased.
- Ethnic Background
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APPLIED
Hypertension [High BP]
•
•
•
•
•
Mild — 140-160/90-100mmHg
Moderate — 160-180/100-110mmHg
Severe — 180-200/110-120mmHg
Malignant — When Diastolic BP > 140mmHg
Blood Pressure should be measured on more
than Two occasions to make high blood
pressure.
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HYPERTENSION
• Primary or Essential Hypertension—90%
Cause is Not known.
• Secondary Hypertension—10%
Renal Cause—80%
Endocrine Cause—5%
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PRIMARY HYPERTENSION
• Life Long Drugs are advised.
Aetiology – although cause is NOT known, but
Genetic Factors, Positive Family History may be
there.
Factors which worsen the Hypertension:
- Obesity
- Increased Sodium Intake
- Smoking
- Stress
- Increased Alcohol Intake
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SECONDARY HYPERTENSION
• When increased B.P is due to other known
problem.
Causes Of Secondary Hypertension
1. RENAL DISEASES
• E.g. Diabetic Nephropathy
• Adult Polycystic Kidney Disease
• Renal Artery Stenosis
2. CARDIOVASCULAR CAUSE
• E.g. Coarctation Of Aorta
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Causes Of Secondary Hypertension
3. ENDOCRINE CAUSES
• E.g. Pheochromocytoma
• Conn Syndrome
• Cushing Syndrome
4. DRUGS
• E.g. Oral Contraceptive Pill
5. PREGNANCY
• PRE-ECLAMSIA - Increased BP during 2nd half
of pregnancy
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Hypertension Complications
•
•
•
•
Eye -- Retinal Changes
Chronic Renal Failure
Heart Failure
C V A (Cerebro Vascular Accidents)
 IMPORTANT
Hypertension may be detected on routine examination.
WHY?
Because Hypertension may be symptomless, until
complication occur.
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PRE-HYPERTENSION
• Normal BP 120/80
• Hypertension 140/90
• Now we use the word Pre-Hypertension when systolic is
between 120 to 140 and diastolic is between 80 to 90.
Advice for Pre-Hypertension
• Diet
• Exercise
Advice for Hypertension
• Diet
• Exercise
• Medication – Angiotensin Converting Enzyme Inhibitors,
Vasodilator, Diuretic, Beta-blocker, Calcium blocker
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BLOOD PRESSURE PRACTICAL
• Normal BP = 120/80 mmHg (In Adults)
• Range
Systolic = 100-140 mmHg
Diastolic = 60-90 mmHg
• Equipment
Stethoscope
Sphygmomanometer
A Bicycle ergometer and/or a treadmill
• Methods Of Measurement BP
1-Palpatory Method
2-Ausculatatory Method
 Note: Palpatory method gives estimate of
Systolic BP only
• Ausculatory method allows Both Systolic and
Diastolic BP to be measured.
• KOROTKOFF Sounds
• Laminar Flow, Turbulent Flow
We will discuss in Practical.
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WHAT YOU SHOULD KNOW FROM
THIS LECTURE
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•
•
•
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Definition of Blood Pressure
Normal Value for Blood Pressure
Pulse Pressure
Mean Arterial Blood Pressure
Factors which determine Blood Pressure
{CO × Peripheral Resistors}
• Factors which regulate Blood Pressure
• Baroreceptor, Renin-Angiotensin Mechanism
• Hypertension – Primary & Secondary
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THANK YOU
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