Basics of Taking a Blood Pressure

21-Jan-16 Clinical Skills Resource Centre, University of Liverpool, UK 1
Blood pressure
measurement
http://www.abdn.ac.uk/medical/bhs/tutorial/tutorial.htm

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)

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

CAUSES OF HYPOTENSION
 Impaired cardiac output
- Myocardial Infarction
- Pericardial Tamponade
- Massive Pulmonary
Embolism
- Acute Valve Incompetence
Hypovolaemia
- Haemorrhage
- Diabetic pre-coma
- Dehydration
 Excessive
Vasodilation
- Anaphylaxis
- Gram –ve Sepsis
- Drugs (e.g. narcotic
analgesics, alcohol,
diuretics, ß-blockers)
- Autonomic failure

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

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

CAUSES OF POSTURAL
HYPOTENSION
 Venous pooling
 Impaired vasomotor tone
 Reduced muscle tone
 Hypovolaemia
 Drugs
 Addison’s disease
 Idiopathic

HYPERTENSION
 Blood 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)

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.

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.

CAUSES OF SECONDARY
HYPERTENSION
 Aortic coarctation
 Hormonal: Congenital
- adrenal hyperplasia
- ll hydroxylase deficiency
Acquired
- phaeochromocytoma
- Conn’s syndrome
- Cushings syndrome

CAUSES OF SECONDARY
HYPERTENSION 2
 Renal : - polycystic kidneys
- renal artery stenosis
- acute glomerulonephritis
- chronic renal disease
 Drug related : - steroids
- contraceptive pill
- NSAIDs
- cyclosporin

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

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.

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

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

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

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 GUIDELINES
Bladder 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

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

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

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.

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

Factors affecting blood pressure values
 Age
 Gender
 Race
 Temperature
 Pain
 Emotion / stress
 Alcohol
 Smoking
 Exercise
 Obesity
Blood pressure should be measured after 5 minutes rest.
No exertion, eating or smoking should take place for up to
30 minutes before measurement.

 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.

 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.

Sources of error
 Sphygmomanometer
 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

British Hypertension Society
classification of blood pressure levels
Category Systolic blood
pressure
(mmHg)
Diastolic
blood
pressure
(mmHg)
Optimal blood pressure
Normal blood pressure
High-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
<130
130-139
140-159
160-179
≥ 180
140-159
≥ 160
<80
<85
85-89
90-99
100-109
≥ 110
<90
<90

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

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.

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

Taking a BP 2
Choose the right size cuff for the patients arm, ensuring at least 80% coverage with
the bladder.
Brachial
artery
Bladder, shown outside cuff

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

Taking a BP 4
Cuff may be placed on the arm with the tubes facing upwards (to minimise noise) or
downwards.

Taking a BP 5
Estimate the systolic by palpation.
Note point
where no
longer
able to
feel
pulse

Taking a BP 6
 Once 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.

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

Taking a BP 8
SYSTOLIC PRESSURE DIASTOLIC PRESSURE
178mmHg
88mmHg
178/88

Taking a BP 9
 Record 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.

References
 British 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

Basics of Taking a Blood Pressure

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