basics of taking a blood pressure

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6/16/22 Clinical Skills Resource Centre, University of Liverpool, UK 1 Blood pressure measurement tp://www.abdn.ac.uk/medical/bhs/tutorial/tutorial.h

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Page 1: Basics of Taking a Blood Pressure

May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 1

Blood pressure measurement

http://www.abdn.ac.uk/medical/bhs/tutorial/tutorial.htm

Page 2: Basics of Taking a Blood Pressure

May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 2

Blood pressure measurement Assessing arterial blood pressure is one of the

most common procedures undertaken in clinical medicine and, along with temperature, pulse and respiratory rate, is one of the vital signs recorded.

Accurate measurement of the BP is important in:· Assessment and management of hypotension (low blood pressure)

· The diagnosis and management of hypertension (high blood pressure)

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May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 3

HYPOTENSION Low blood pressure (hypotension) is a condition

where a person’s blood pressure is much lower than usual.

When the blood pressure is too low, there is inadequate blood flow to the heart, brain and other vital organs.

A BP that is borderline low for one person may be normal for another. The most important factor is how the BP changes from the baseline and how that change affects the person. It may indicate an improvement in a patients condition or deterioration

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May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 4

CAUSES OF HYPOTENSION Impaired cardiac output- Myocardial Infarction- Pericardial Tamponade- Massive Pulmonary Embolism- Acute Valve IncompetenceHypovolaemia- Haemorrhage- Diabetic pre-coma- Dehydration

Excessive Vasodilation- Anaphylaxis- Gram –ve Sepsis- Drugs (e.g. narcotic analgesics, alcohol,

diuretics, ß-blockers)- Autonomic failure

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May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 5

POSTURAL HYPOTENSION Postural hypotension is a fall in blood pressure that

occurs when changing position from lying to sitting or from sitting to standing. A fall of >20mmHg in systolic pressure on standing is classed as postural hypotension

It is also known as orthostatic hypotension. There are several causes of postural hypotension

which can require different treatment strategies e.g. Hypovolaemia, antihypertensive drug therapy, especially diuretics and vasodilators

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May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 6

POSTURAL HYPOTENSION 2 Symptoms :- Feeling dizzy and light-headed- Changes in vision- Feeling vague- Loss of consciousness – with or without warning- Pain across the back of the shoulders and neck- Pain in lower back and buttocks- Angina-type pain in the chest- Weakness- fatigue

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CAUSES OF POSTURAL HYPOTENSION

Venous pooling Impaired vasomotor toneReduced muscle toneHypovolaemiaDrugsAddison’s disease Idiopathic

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May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 8

HYPERTENSIONBlood pressure increases when large blood

vessels begin to lose their elasticity and the smaller vessels start to constrict, causing the heart to try to pump the same volume of blood through vessels with a smaller internal diameter.

A patient is considered to be hypertensive if blood pressure is equal to or greater than 140mmHg systolic, or over 85mmHg diastolic. (National Service Framework for Coronary Heart Disease 2000)

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CAUSES OF HYPERTENSION The majority of patients have Primary (Essential)

Hypertension, in other words there is no identifiable underlying cause.

The remainder suffer from Secondary Hypertension whereby the raised blood pressure arises from an identifiable disease.

Hypertension is usually asymptomatic. The exception is malignant hypertension usually characterised by a sustained diastolic equal to or greater than 120mmHg.

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MALIGNANT HYPERTENSION Characterised by a sustained diastolic blood

pressure of equal to or more than 120mmHg, with renal damage, retinal haemorrhages, infarcts and optic nerve swelling.

In this situation, many patients present with renal failure, heart failure or a stroke.

Most of these patients have proteinuria and left ventricular hypertrophy.

You should regard malignant hypertension as a medical emergency and immediately refer patients to hospital. Without effective treatment, fewer than 20% of patients survive for a year.

Page 11: Basics of Taking a Blood Pressure

May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 11

CAUSES OF SECONDARY HYPERTENSION

Aortic coarctationHormonal: Congenital - adrenal hyperplasia - ll hydroxylase deficiency Acquired - phaeochromocytoma - Conn’s syndrome - Cushings syndrome

Page 12: Basics of Taking a Blood Pressure

May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 12

CAUSES OF SECONDARY HYPERTENSION 2

Renal : - polycystic kidneys - renal artery stenosis - acute glomerulonephritis - chronic renal diseaseDrug related : - steroids - contraceptive pill - NSAIDs - cyclosporin

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May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 13

Systolic and diastolic pressure Systolic blood pressure is

the maximum pressure reached in the blood vessels and is due to ventricular systole when the heart pumps blood into the arterial circulation.

Diastolic blood pressure relates to the resting pressure within the blood vessels when the heart relaxes (diastole) to fill with blood prior to the next systole.

Blood pressure readings are traditionally recorded with the systolic value preceding the diastolic, usually separated by a slash e.g. 126/84

Systolic Diastolic

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Technique of BP measurement I Explain the procedure to patient Seat the patient for at least 3-5 minutes prior to the

measurement Gather equipment needed – stethoscope,

sphygmomanometer and steret. Expose the arm and make sure it is comfortably supported

at the same level as the heart. The upper arm should not be constricted by tight clothing.

Apply cuff - centre of bladder must be over brachial artery (the bladder should cover at least 80% of the circumference of the upper arm, but not 100%) and lower edge 2.5 cm above ante-cubital fossa.

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Brachial artery anatomy In the middle third of

the upper arm the brachial artery lies on the medial aspect of the humerus

The artery lies in the medial aspect of the antecubital fossa

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Positioning the cuff

The centre of the bladder should lie over the brachial artery on the medial aspect of the upper arm

The cloth cuff should lie at least 2.5 cm above the brachial artery in the ante-cubital fossa

Brachial artery

Cloth cuff

Bladder

Ulnar artery

Radial artery

Antecubital fossa

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The cuff and bladder The cuff is an

inelastic cloth with an inflatable bladder within

The cuff is secured with Velcro fastenings or by wrapping a tapering end around the arm and tucking it into the encircling material

Importance of bladder size If it is too short or too narrow,

BP falsely high if it is too long or too wide,

BP falsely low ideally it should encircle the

arm It is acceptable if it encircles

80% of the arm if it does not fully encircle,

then the bladder should be placed with its midpoint directly over the brachial artery in the upper arm

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CUFF SIZES(*The range for columns 2 and 3 are derived from the British Hypertension Society.

** Large bladders for arm circ. Over 42cm may be required)

INDICATION WIDTH (CM)*

LENGTH (CM)*

BHS GUIDELINESBladder width & length (cm)*

ARM CIRC. (CM)*

SMALL ADULT/CHILD

10-12 18-24 12 X 18 <23

STANDARD ADULT

12-13 23-35 12 X 26 <33

LARGE ADULT

12-16 35-40 12 X 40 <50

ADULT THIGH CUFF**

20 42 20 X 42 <53

Page 19: Basics of Taking a Blood Pressure

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Technique of BP measurement II

Palpate brachial (or radial) artery pulse in the antecubital fossa and inflate bladder to 30mmHg above the point of disappearance of the pulse then deflate the bladder slowly

Note the point at which pulse can be felt to reappear - this point approximates to systolic blood pressure

Deflate the cuff rapidly and completely Stethoscope is applied directly over the brachial artery, but

without too much pressure (which may alter the sound characteristics and produce sounds below the diastolic pressure). Either bell or diaphragm may be used

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Technique of BP measurement lll Re-inflate cuff to 20-30mmHg above palpated systolic

pressure and slowly deflate at a rate of 2-3mmHg/second The first sounds (2 consecutive clear tapping) you hear are

known as Korotkoff phase 1 this equates to SYSTOLIC pressure

You will then hear Korotkoff sounds 2,3 and 4 At the point you have complete disappearance of sounds

this is Korotkoff phase 5 and equates to DIASTOLIC pressure

After all sounds have disappeared the cuff should be fully deflated, even if another measurement is to be attempted

>15 seconds should lapse before attempting to repeat reading

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Why firstly estimate the systolic by palpation?

A period of silence below the initial systolic phase (Korotkoff 1) is found in some conditions.

This is known as the Auscultatory gap (period of silence) and may result in the systolic pressure being underestimated.

It is important to palpate the pulse whilst inflating the cuff and to continue 20 to 30mmHg above the point you felt it disappear.

The return of the palpable pulse on deflation equates to the estimated systolic pressure.

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The Korotkoff sounds Phase 1 First appearance of faint clear tapping

sounds which gradually increase in intensity Phase 2 The softening of sounds which may become

swishing Phase 3 The return of louder sounds Phase 4 Muffling of sounds Phase 5 The complete disappearance of sounds

Phase 1 = Systolic pressure Phase 5 = Diastolic pressure

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May 2, 2023 Clinical Skills Resource Centre, University of Liverpool, UK 23

Factors affecting blood pressure values

AgeGenderRaceTemperaturePain

Emotion / stressAlcoholSmokingExerciseObesity

Blood pressure should be measured after 5 minutes rest.No exertion, eating or smoking should take place for up to 30 minutes before measurement.

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Factors affecting blood pressure values

Age: About 70% of people aged over 75 have hypertension

Gender: Prevalence is higher among men than women up to age 64, over 64 it is higher in women

Race: Hypertension is more common in Afro-Caribbeans

Temperature: BP can increase with cold temperature

Pain: Linked with hypertension

Emotion: BP can be increased with stress

Alcohol: Regular heavy alcohol intake increases blood pressure.

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Page 25: Basics of Taking a Blood Pressure

Factors affecting blood pressure values

Smoking: Nicotine present in tobacco products causes increased blood pressure and heart rate

Exercise: regular activity helps to maintain the elasticity of the blood vessels which reduces BP

Obesity: Blood pressure associated with overall body mass. This is independent of errors in measurement due to obesity – cuff artefact.

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Sources of errorSphygmomanomet

er poor maintenance incorrect cuff

application incorrect bladder size tube/pump leakage

Patient Obesity Arrhythmias Arm position

The observer poor technique observer bias terminal digit preference

(e.g 120/70 or 125/75 instead of real pressure: 122/72)

note: the scale is graduated in 2s - there is no 5

distance from scale - should be <1m

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British Hypertension Society classification of blood pressure levels

Category Systolic blood pressure (mmHg)

Diastolic blood pressure (mmHg)

Optimal blood pressureNormal blood pressureHigh-normal blood pressure

Grade 1 hypertension (mild)Grade 2 hypertension (moderate)Grade 3 hypertension (severe)Isolated systolic hypertension (Grade 1)Isolated systolic hypertension (Grade 2)

<120<130130-139

140-159160-179≥ 180140-159≥ 160

<80<8585-89

90-99100-109≥ 110<90<90

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When should you take a BP? Lying and standing BP’s on first meeting the patient

if symptoms indicate postural hypotension Always on both arms when first meeting a patient.

The reasoning behind this practice is that there are sometimes important differences between the two readings, and that the lower blood pressure in one arm should be investigated as it may be a sign of an abnormality (coarctation, stenosis, dissection). A difference of equal to or less than 10mmHg is acceptable and needs no further investigation

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When should you take a BP? 2 Regular checks are also made on hypertensive

patients to assess treatment and lifestyle interventions.

WHITE COAT SYNDROME - 15-30% of patients have white coat syndrome

(O’Brien 1999) - This is a phenomenon where their blood

pressure is normal outside the GP’s surgery, but increases when measured in the surgery. Some patients with white coat hypertension develop target organ damage and all require close follow up.

Page 30: Basics of Taking a Blood Pressure

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Taking a BP 1• Ensure arm is at the

level of the heart, resting comfortably.

• Clean the stethoscope with a steret.

• Place the sphygmomanometer no more than 1 meter from you when you are recording the BP

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Taking a BP 2

Choose the right size cuff for the patients arm, ensuring at least 80% coverage with the bladder.

Brachialartery

Bladder, shown outside cuff

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Taking a BP 3 Bladder shown in

position on patient’s arm with the centre of the bladder in line with the artery and enclosing 80% of the arm

Brachial artery

2-2.5cm gap

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Taking a BP 4

Cuff may be placed on the arm with the tubes facing upwards (to minimise noise) or downwards.

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Taking a BP 5

Estimate the systolic by palpation.

Note point where no longerable to feelpulse

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Taking a BP 6Once you have felt the pulse disappear

continue to inflate for another 20-30mmHg, and then slowly deflate whilst feeling for the pulse’s return – note this figure = estimated systolic.

Deflate the cuff fully to allow arm to rest whilst you get ready to take the blood pressure.

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Taking a BP 7 • Place the stethoscope over the

Brachial artery. • Re-inflate the cuff to 20-

30mmHg over the estimated systolic

• Slowly deflate the cuff at 2-3mmHg/second whilst listening, with the stethoscope, for two consecutive taps (indicating systolic BP)

Remember the air should be continuously released – as if you stop and start, air removal sounds can be confused

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Taking a BP 8

SYSTOLIC PRESSURE DIASTOLIC PRESSURE

178mmHg

88mmHg

178/88

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Taking a BP 9Record your findings in the patient’s notes.Tell the patient about their BP reading – one

reading is insufficient to diagnose health, hypertension or hypotension.

If you were unable to identify either systolic or diastolic pressures, wait at least 15 seconds before doing another reading.

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ReferencesBritish Hypertension Society

http://www.bhsoc.org/ Douglas, G., Nicol, N. And Robertson, C.

eds., 2009, Macleod’s Clinical Examination 12th edition, London, Elsevier

National Service Framework for Coronary Heart Disease 2000

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