basics of taking a blood pressure
TRANSCRIPT
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
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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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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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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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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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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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.
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CAUSES OF SECONDARY HYPERTENSION
Aortic coarctationHormonal: Congenital - adrenal hyperplasia - ll hydroxylase deficiency Acquired - phaeochromocytoma - Conn’s syndrome - Cushings syndrome
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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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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
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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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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.
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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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.
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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.
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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