blood pressure

BLOOD PRESSURE

DR NILESH KATE

MBBS,MD.

OBJECTIVESAt the end of this class, you should able to recollect. Definition of Blood Pressure Its variations. Measurement - Korotkoff sound Factors contributing to B.P Peripheral resistance Regulation of BP Immediate regulation Short term regulation Long term regulation. Applied - Hypertension - Hypotension Physiology of treatment.

ARTERIAL BLOOD PRESSURE Definition : Arterial blood pressure can be defined as the lateral pressure exerted by the moving column of blood on the walls of the arteries.

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SIGNIFICANCE 1. To ensure the blood flow To various organs.

2. Plays an important role in exchange of nutrients

and gases across the capillaries.

3. Required to form urine.

4. Required for the formationOf the lymph.

Normal Values

Normal Adult range Can fluctuate within a

wide range and still be normal

Systolic/diastolic 100/60 - 140/80

Systolic B.P (S.B.P)

Defined as the maximum B.P in the arteries Attainable during systole. Normal 120 + 20 mm Hg. This is mainly contributed by

1. Force of heart beat 2. Normal blood volume

3. Cardiac output.

Normal range 90-140 mm Hg.

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DIASTOLIC B.P (D.B.P)

Def--- as the minimum pressure that is obtained at the end of the ventricular diastole.Normal range 60 -90 mm Hg. 1. It represents a constant loadon the arterial walls with little or no fluctuation at all.2. It is an index to the peripheral resistance and decides the filling of the Coronary system.

Pulse Pressure (P.P)

Denotes the difference between systolic and diastolic pressure. PP= SBP - DBP = 40 mm Hg

MEAN ARTERIAL PRESSUREMean arterial .BP = DBP + 1/3 Pulse Pressure

normal = 95 mm Hg.

•Not the arithmetical mean but geometricalmean.

•It is because the period of the systole is only 0.3 sec when compared to 0.5 sec of the diastole.

ARTERIAL BLOOD PRESSURE

PHYSIOLOGICAL VARIATION IN BLOOD PRESSURE

A) AgeB) BuildC) ClimateD) Diurnal VariationE) ExerciseF) Fever

G) GestationH) high AltitudeI) Infusion/ IntakeJ) PainK) PostureL) SleepM) sex

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RECORDING OF B.P

Direct method

Indirect method

METHODS

Indirect Methods

1. Palpatory method 2. Auscultatory

method

PRINCIPLE INVOLVED IN RECORDING BLOOD PRESSURE

Slide 11.37

Measurement Device

Aneroid sphygmomanometer Simple mercury

sphygmomanometer

Automated bp device

3

RECOMMENDED BLOOD PRESSURERECOMMENDED BLOOD PRESSUREMEASUREMENT TECHNIQUEMEASUREMENT TECHNIQUE

2.• The cuff must be level with heart.• If arm circumference exceeds 33 cm,

a large cuff must be used.• Place stethoscope diaphragm over

brachia l artery.

2.2.•• The cuff must be level with heart.The cuff must be level with heart.•• If arm circumference exceeds 33 cm,If arm circumference exceeds 33 cm,

a large cuff must be used.a large cuff must be used.•• Place stethoscope diaphragm overPlace stethoscope diaphragm over

brachia l artery.brachia l artery.

1.• The patient should

be relaxed and thearm must besupported.

• Ensure no tightclothing constrictsthe arm.

1.1.•• The patient shouldThe patient should

be relaxed and thebe relaxed and thearm must bearm must besupported.supported.

•• Ensure no tightEnsure no tightclothing constrictsclothing constrictsthe arm.the arm.

3.• The column of

mercury must bevertical .

• Infla te to occlude thepulse. Deflate at 2 to3 mm/s. Measuresystolic (first sound)and diastolic(disappearance) tonearest 2 mm Hg.

3.3.•• The column ofThe column of

mercury must bemercury must bevertical .vertical .

•• Infla te to occlude theInfla te to occlude thepulse. Deflate at 2 topulse. Deflate at 2 to3 mm/s. Measure3 mm/s. Measuresystolic (first sound)systolic (first sound)and diastolicand diastolic(disappearance) to(disappearance) tonearest 2 mm Hg.nearest 2 mm Hg.

StethoscopeStethoscope

MercuryMercurymachinemachine

Tapping sound 1SBP

110 mm Hg

Banging sound 3

Muffing sound 4

DBP-

95 mm Hg

85 mm Hg

Recording of arterial BP by auscultatory method

Korotkovsounds

120 mm Hg

Murmurish 2

80 mm Hg No sound 5

AUSCULTATORY METHOD This method was introduced by a Russian physicianKorotkov

FACTORS MAINTAININGBLOOD PRESSURE

1. Cardiac output (CO= SV X PR) 2. Circulating blood volume

(This mainly affects systolic B.P)3. Elasticity of the vessel wall4. Viscosity of blood

Viscosity is affected by1. Cell count 2. Plasma proteins 3. Chemical composition like CO2, O2 content,PH.4. Temperature 5. Drugs like general anaesthetics. All these factors influence peripheral resistance through viscosity

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Peripheral Vascular Resistance

It is defined as the resistance offered to the flow of bloodby the blood vessels.

It is contributed by: The Smooth muscles of the arterioles in particular.

FACTORS AFFECTING BLOOD PRESSURE Disease Age Heredity Blood Volume Weight Diet Hormones Salt Caffeine

Environmental factors

Psychological factors Stress/Anxiety Gravity Drugs Alcohol Time of day

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BP = Cardiac output X PR

Peripheral resistance(PR) in a normal healthy youngadult is 20mm Hg/lit/mt.

Peripheral vascular resistance: depends upon

A) Velocity of blood

B) Viscosity of blood

C) Elasticity of the vessels wall

D) Lumen of the vessels

E) Length of the vessels F) Extra vascular compression

BLOOD PRESSURE

100 = 5X20

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Peripheral Resistance

Obsolute units: Dyne/sec/cm2

Pressure dyne/cm2 PR =

Flow cc/sec

= dyne/sec/cm2

P.R.U unit: (Relative unit) When there is a difference of 1 mm Hg and a flow of 1ml/sec then it is called one PRU unit.

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Ernest H. Starling in the dog lab (1915)

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FACTORS CONTRIBUTING TO BLOOD PRESSURE

1 Cardiac output-VR,HR,FOC—S.P 2. PERIPHERAL RESISTANCE

Elasticity Viscosity

Velocity

Length of BV Extra vascularcompression

Radius of BV DP

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CO TPRHR SV

ANSHormonesBrain

EDV

Venous Return

Kidney

AngiotensinAldosteroneADH

Respiratory pumpSkeletal muscle pump

ANSHormonesViscosityBlood vessel lengthBlood vessel diameterLocal factors

MAP

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REGULATION OF ARTERIAL BLOOD PRESSURE

Immediate mechanism Short term mechanism Long term mechanism

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ImmediateImmediate Regulatory Mechanisms:

Neural mechanisms

1. Baroreceptor reflexes

2. Chemo receptor reflexes 3. Cerebral ischaemic response

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BARORECEPTOR REFLEX

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BARO RECEPTOR REFLEXES (MAREY’S REFLEXES) BP Stimulation of baroreceptors (carotid sinus and aortic arch) Tractus solitarius stimulation

Inhibition of VMC Stimulation of CIC (nucleus ambiguous)

SNS Vagus

Symp tone Vagal tone

Blood Vessels Heart Rate Decreased - Vasodilatation- Venodilatation Bradycardia

BP

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Net effect

Peripheral resistance

Myocardial contractility

Heart rate (Bradycardia)

Fall in BP

BARORECEPTOR REFLEX

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BP <60 mm Hg

Hypoxia

Chemoreceptors

NTS Respiratory centre CIC VMC stimulation N ambiguus Vagus SNS action Vagaltone

Net effect Pulmonary ventilation, BP, Heart rate

Chemo receptor reflexes

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BP < 40 mm Hg (or) Intracranial pressure

Cerebra ischaemia Cerebral hypoxia

Direct effect on VMC

SNS action

Vasoconstriction

Cerebral Ischaemic Response

BP with reflex bradycardia

Cushing’s Reflex

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REGULATION OF ARTERIAL BLOOD PRESSURE

Short term regulatory mechanisms: These are again divided into a) acute regulatory mechanisms b) delayed regulatory mechanisms.

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Delayed or Intermediate Mechanism Capillary fluid shift phenomenonCapillary fluid shift phenomenon: Whenever there is an increase in blood pressure more fluid is filtered through the capillary wall into the interstitial space.

Blood volume decreases and so BP itself decreases.

Reverse changes take place when BP falls.

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Delayed or Intermediate Mechanism

Renin –Angiotensin System

Whenever there is a fall in B.P, there is a decrease in the blood flow to the kidney. This results is ischaemic kidney. Renin is released from J.G. cells

ReninAngiotensin Angiotensin I ACEAngiotensin I Angiotensin II

ACE - Angiotensin Converting Enzyme ( Present in the lungs)

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ACTION OF ANGIOTENSIN - II

1. Vasoconstriction2. Aldosterone secretion

3. Stimulation of the thirst centre

4. Increased absorption of Na+ from PCT by direct effect. As a result

. B.V , C.O . BP

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Stress Relaxation Phenomenon: BP Blood vessels are stretched

Stress relaxation

Increased capacity

Decreased effective blood volume

BP decreased relaxation

BP

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Long term Regulatory Mechanisms:

All the mechanisms that tend to alter the blood volume participate in Long term regulatory mechanisms

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Renal –body fluid system:

ECF or Blood volume - BP

B.P is brought back to the normal level

ECF or Blood volume - BP

B.P is slowly raised to the normal level.

GFR urine output GFR BP urine output

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HORMONAL REGULATIONS1) Catecholamines2) Mineralocorticocoid3) Glucocorticoid4) Thyroxine5) ADH6) Atrial Natriuretic Factor7) Nitric Oxide8) Histamine9) Angiotensin10) Serotonin

Hypertension Defined as an elevation of systolic

blood pressure Persistent hypertension very common 30% of people over 50 are

hypertensive Never diagnosed on one reading Indication of cardiovascular disease Trauma Side effect of medication

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BP is called Hypertension (Above 140/90 mm of Hg )

Primary(Essential 90%)

Secondary(10%)

Diseases Attributable to Hypertension

Hypertension

Heart failureStroke

Coronary heart disease

Myocardial infarction

Left ventricular hypertrophy

Aortic aneurysm

Retinopathy

Peripheral vascular disease

Hypertensive encephalopathy

Chronic kidney failure

Cerebral hemorrhage

Adapted from: Arch Intern Med 1996; 156:1926-1935.

AllVascular

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HypertensionPredisposing factors: Obesity Hereditary Alchoholism Stress Smoking Sedentary life

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Secondary HypertensionCauses: 1.Renal-Acute & Chronic

Glomerulonephritis,Nephrotic syndrome 2.Endocrine-

Cushings,Conns,Thyrotoxicosis, Pheochromacytoma 3.Vascular-Atherosclerosis Arteriosclerosis

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Treatment of HypertensionModification of lifestyle:

Cessation of smoking. Moderation in alcohol intake. Weight reduction. Programmed exercise. Reduction in Na+ intake. Diet high in K+. Relaxation technique – Yoga, TM

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Treatment of Hypertension Medications:

Diuretics: Increase urine volume.

Beta-blockers: Decrease HR.

Calcium antagonists: Block Ca2+ channels.

ACE inhibitors: Inhibit conversion to angiotensin II.

Angiotension II-receptor antagonists: Block receptors.

Prevention

Reduce the risk of developing High Blood Pressure by making lifestyle changes…..

Eat a healthy , well balanced diet Reduce salt and fat intake Exercise regularly Stop smoking Reduce alcohol and caffeine consumption to

recommended levels Reduce weight

Hypotension

Defined in adults as a systolic pressure below 100mm Hg

Rarely treated in this country

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BP is called Hypotension (Below 90/60 mm of Hg)

1. Hemorrhage2. Dehydration3. Vomiting4. Diarrhea5. Excessive sweating6.Adissons disease7.Hypothyroidism

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Treatment of Hypotension

Treat the causeBlood transfusionI.V. FluidsVasoconstrictors

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RECAPAt the end of this class, you should able to recall.1. Definition of Blood Pressure2. Its variations.3. Measurement - Korotkov sound4. Factors contributing to B.P5. Peripheral resistance 6. Regulation of BP7. Immediate regulation8. Short term regulation9. Long term regulation.10. Applied - Hypertension - Hypotension

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Success is one percent inspiration And ninety nine percent perspiration

Thank You