Transcript Arterial Blood Pressure (BP)

BLOOD PRESSURE
Arterial Blood Pressure (BP)
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Is a measure of the force that the circulating
blood exerts against the arterial wall OR
The pressure force generated by the
pumping action of the heart on the wall of
aorta & arterial blood vessels per unit area.
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It tells us how hard the heart is working.
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Too high means the heart is working extra
hard and this could be very dangerous!
Blood pressure almost always is measured
in millimeters of mercury (mmHg).
Occasionally pressure is measured in
centimeters of water ( cm H O)
2
1 mmHg = 1.36 cm H2O
In normal adult  120/80 mmHg.
Factors determining BP
Blood Pressure = Cardiac Output X Peripheral Resistance
(BP)
(CO)
Flow
BP depends on:
1. Cardiac output.
2. Peripheral resistance.
3. Blood volume.
(PR)
Diameter of
arterioles
Cardiac Output
Is the volume of blood being pumped by the heart, in
particular by a Left or Right ventricle in the Time interval
of one minute
Cardiac Output (Q) = SV × HR
Peripheral Resistance
The sum of resistance to flow that must be overcome to
push blood through the circulatory system
-- combined resistance of all vessels
-- vasodilation  resistance decreases
-- vasoconstriction  resistance increases
Stroke Volume
Is the volume of blood pumped from one ventricle of the
heart with each beat
Blood Pressure
Is the measured
pressure placed on
the blood vessels
while the heart is
contracting.
Is the measured
pressure placed on
the blood vessels
while the heart is
at rest. (not
contracting)
NOTE !!!
Pulse pressure
Systolic BP – Diastolic BP
The most important determinant of pulse pressure is
STROKE VOLUME.
Mean arterial pressure
Diastolic BP + 1/3 Pulse press
Is a term used in medicine to describe an average blood pressure in
an individual
How is Blood Pressure Taken?
Blood Pressure
Non-Invasive
Palpatory Method
Auscultatory Method
Ultrasonic Method
Oscillometric Method
Invasive
Tonometry
Extravascular Sensor
Intravascular Sensor
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Is your patient ready?
If your patient has finished a cigarette or an
alcoholic beverage within the last 15 minutes the
readings will be altered.
If they haven’t sat quietly for at least 5 minutes or
are talking during the procedure, the readings will
be altered.
Systolic and diastolic BP's in hypertensive and
normotensive patients increase with talking
And if you have placed the cuff over a shirt sleeve
the readings will not be reliable
Brachial artery is the most common
measurement site
Close to heart
Convenient measurement
1. Use appropriate size BP cuff

Is the cuff you are using sized for the patient? A cuff
too large can cause reading to be lower than actual
and a cuff too small can cause reading to be higher
than actual.
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2. Position patient
Patient should be seated with back and
arms supported, feet on floor, and legs
uncrossed with upper arm at heart level
3.Measure baseline BP bilaterally
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Cuff applied 1 inch above crease at elbow
Locate brachial artery
Palpate radial pulse
Inflate cuff until pulse disappears
Types Of BP Apparatuses
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Mercury Type
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Aneroid Type
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Digital Type
A- Palpatory Method
Feel the radial pulse.
 An occlusive cuff is placed on arm and inflated
above the level at which the pulse become
impalpable.
 Gradually deflate it.
 The level at which the pulse become palpable
again is taken as systolic pressure.
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ADVANTAGES
The blood pressure can be measured in noisy
environment too
Technique does not require much equipment
DISADVANTAGES
Only the systolic pressure can be measured (not DP)
The technique does not give accurate results for
infants and hypotensive patients
B- Auscultatory Method
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Apply the cuff one inch above the elbow
Palpate the brachial artery
Place the stethoscope lightly over it
Inflate the cuff above the systolic level determined
by the palpatory method
Lower the pressure in the cuff
The level at which Korotkoff sound are heard is the
Systolic pressure.
The level at which sound disappear is diastolic
pressure.
ADVANTAGES
Auscultatory technique is simple and does not require much
equipment
DISADVANTAGES
Auscultatory tecnique cannot be used in noisy environment
The observations differ from observer to another
A mechanical error might be introduced into the system e.g.
mercury leakage, air leakage, obstruction in the cuff etc.
The technique does not give accurate results for infants and
hypotensive patients
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Pulse waves that propagate through the
brachial artery, generate Korotkoff sounds.
There are 5 distinct phases in the Korotkoff
sounds, which define SP and DP
The Korotkoff sounds are ausculted with a
stethoscope
Korotkoff sound
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The first Korotkoff sound is the snapping sound first heard at
the systolic pressure. Clear tapping, repetitive sounds for at
least two consecutive beats is considered the systolic
pressure.
The second sounds are the murmurs heard for most of the
area between the systolic and diastolic pressures.
The third = A loud, crisp tapping sound.
The fourth sound, at pressures within 10 mmHg above the
diastolic blood pressure, were described as "thumping" and
"muting".
The fifth Korotkoff sound is silence as the cuff pressure
drops below the diastolic blood pressure. The disappearance
of sound is considered diastolic blood pressure -- two mm
Hg above the last sound heard.
RECOMMENDED BLOOD PRESSURE
MEASUREMENT TECHNIQUE
2.2.
••The
Thecuff
cuffmust
mustbe
belevel
levelwith
withheart.
heart.
••IfIfarm
armcircumference
circumferenceexceeds
exceeds 33
33cm,
cm,
aalarge
cuff
must
be
used.
large cuff must be used.
••Place
Placestethoscope
stethoscopediaphragm
diaphragmover
over
brachial
artery.
brachial artery.
1.1.
••The
Thepatient
patientshould
should
be
relaxed
be relaxedand
andthe
the
arm
arm must
mustbe
be
supported.
supported.
••Ensure
Ensureno
notight
tight
clothing
constricts
clothing constricts
the
thearm.
arm.
3.3.
Stethoscope
Mercury
machine
••The
Thecolumn
columnofof
mercury
mercurymust
mustbe
be
vertical.
vertical.
••Inflate
Inflatetotoocclude
occludethe
the
pulse.
Deflate
pulse. Deflateatat22toto
33mm/s.
mm/s.Measure
Measure
systolic
systolic(first
(firstsound)
sound)
and
anddiastolic
diastolic
(disappearance)
(disappearance)toto
nearest
nearest 22mm
mmHg.
Hg.
3
Common problem in BP measurement
Wrong cuff size
 Excess pressure of stethoscope
 Patient arm at the wrong level
 White coat effect
 Auscultatory Gap (silent gap)
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Auscultatory Gap
In some hypertensive patients the
Krotokoff sound disappear for some time
between systolic and diastolic pressure.
 So there is a risk of either recording a
low systolic or high diastolic .
 Avoid it by using palpatory method before
the Auscultatory method.
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Factors affecting BP
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Sex M > F …due to hormones/ equal at menopause.
Age Elderly > children …due to atherosclerosis.
Emotions  due to secretion of adrenaline & noradrenaline.
Exercise  due to  venous return.
Hormones … (e.g. Adrenaline, noradrenaline, thyroid H).
Gravity  Lower limbs > upper limbs.
Race Orientals > Westerns … ? dietry factors, or weather.
Sleep  due to  venous return.
Pregnancy  due to  metabolism.
Hypertension
Sustained raised in BP which require medical
interventions.
JNC 7 Guidelines (2003)
Category
SBP
 Normal
< 120
 Prehypertension 120-139
 Stage 1
140-159 or
 Stage 2
≥ 160
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DBP
or
< 80
or
80-89
90-99
or
≥ 100
Causes Of Hypertension
Essential hypertension 95%
 Secondary hypertension 5%
 Renal
 Endocrine
 Pregnancy
 Drugs
 Coartation of aorta
 Others
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Treatment
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Treatment goal <140/85 mmHg
(130/80 mmHg in diabetic)
Lifestyle changes include :
Drugs:
Stop smoking
Low fat diet
Low salt intake
Exercise
Reduce wt
ACE inhibitor
B-blocker
Ca channel blocker
Diurtics
Postural Hypotension
Drop in systolic BP>20 mmHg OR
diastolic BP>10 mmHg after standing for
3 minutes.
 Causes:
Hypovolemia
Antipsychotics
Addison‘s disease
hypopituitarism
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