BLOOD PRESSURE
Orbán-Kis Károly, Száva Iringó, Mureșan Simona
I. THEORETICAL BACKGROUND
Blood pressure (BP) is the pressure of the blood. It is closely related to the force and rate of
the heartbeat and the diameter and elasticity of the arterial walls.
1. Blood pressure parameters
1.1. Systolic blood pressure (SBP): the highest value of the BP during the cardiac cycle;
occurs immediately after the systole of the left ventricle. It depends mainly on the
contraction force of the left ventricle and arterial wall compliance.
1.2. Diastolic blood pressure (DBP): the lowest value of the BP during the cardiac cycle;
occurs during the ventricular diastole. It depends mainly on the stroke volume of the heart
and the resistance of the arterial system.
1.3. Mean arterial pressure (MAP): the average pressure throughout the cardiac cycle. It
can replace the SBP and the DBP with one single value that would characterize the same
circulatory volume in case of continuous blood flow. It is considered a better indicator of
perfusion to vital organs than SBP. The value of the MAP only depends on the volume of
blood found within the arterial system, and therefore on the stroke volume (dictating the
amount of blood that enters the system) and on the resistance of the arterial system
(dictating the amount of blood that leaves the system), but is not influenced by the elastic
properties of the arterial walls.
MAP  DBP 
SBP  DBP
3
Arterial hypertension refers to persistently increased values of the blood pressure. The
current standards, based on large population studies, have been defined by the European
Society of Cardiology (ESC; Table 1).
Table 1. Normal values for the BP and arterial hypertension classification (ESC Guideline on
the Management of Arterial Hypertension, 2013).
SBP (mmHg)
< 120
120-130
130-140
140-160
160-180
>180
DBP (mmHg)
< 80
80-85
85-90
90-100
100-110
>110
Interpretation of result
optimal
normal
high normal
mild hypertension (grade 1)
moderate hypertension (grade 2)
severe hypertension (grade 3)
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2. Blood pressure measurement
2.1. Direct (invasive) methods: the measurement is done by introducing a catheter inside
an artery; the catheter is then connected to a device that measures and records the BP (for
detailed description please refer to the Cardiac Catheterization practical)
2.2. Indirect (noninvasive) methods: the measurement is done after compressing the
artery with an inflatable cuff in which we generate pressure. Pressure in the artery is
determined by comparison to the pressure within the cuff using several methods (Figure 1).
Figure 1. Principles of noninvasive blood pressure measurement. ABP - arterial blood
pressure, SBP - systolic pressure, DBP - diastolic pressure, CuffP - pressure of the inflatable
cuff placed around the arm.
The auscultatory method (Korotkoff method): both the SBP and the DBP can be measured
using a stethoscope placed over the brachial artery (listening for the sounds caused by
turbulent circulation in a partially compressed artery). Blood pressure should be measured
both in orthostatic and standing position and on both sides of the body (both arms).
Differences between the two arms should be carefully noted as they can suggest stenosis or
occlusion of the arterial system or aortic dissection (tear in the inner wall of the aorta
causing blood to flow between the layers of the wall of the aorta, forcing the layers apart
and often occluding the origin of one or several aortic branches such as the left subclavian
artery).
Repeated measurement may also be necessary, as errors given by vasomotor reactivity due
to anxiety can be reduced / excluded in this way.
The palpation method (Riva Rocci method): measures only the SBP. While the pressure is
gradually reduced in the cuff placed around the arm, the examiner checks for the first radial
pulsation (the value obtained represents the SBP).
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Measurement description:
- choose a cuff with a proper size (cuffs are different for adults and children)
- place the inflatable cuff around the upper arm so that its lower edge is at 2-3 cm
above the crease of the elbow. The cuff should NOT be placed over the clothing of
the patient.
- palpate the brachial artery in the crease of the elbow and place the stethoscope over
it (never place it under the inflatable cuff)
- squeeze repeatedly the rubber bulb to raise the pressure in the cuff at a level of 3040 mmHg over the pressure that makes the pulsations disappear
- open the adjusting screw and deflate the cuff gradually
- for the auscultatory method (Korotkoff method) - the pressure at which a sound is
first heard represents the value of the SBP. The cuff pressure is further released until
no sound can be heard; this is the moment when the DBP is measured.
- for the palpation method (Riva Rocci method) - the pressure at which a first radial
pulsation can he felt represents the value of the SBP. The DBP cannot be measured
using this method.
Figure 2. Measuring blood pressure by palpation (A) and by the auscultatory (B) method.
Non-imaging Doppler techniques. The ankle brachial pressure index (ABPI)
Doppler frequency shift (see the ‘Echocardiography’ chapter) depends on the velocity of the
blood flow and is within audible ranges (approximately 2 kHz). By placing a Doppler
transducer in the axis of an artery and connecting it to a speaker, the presence of blood
flow can be heard by the examiner. The characteristics of the sound will change if there is
laminar (musical tonality, low intensity) or turbulent blood flow (stiff, sharp, high intensity).
There are several non-imaging Doppler techniques which may be used for the evaluation of
arteries; among them, the most frequently used are the ankle brachial index and the
segmental pressure measurement.
The ankle brachial pressure index (ABPI)
This parameter relies on the calculation of the ratio of SBP between the upper and lower
limbs, offering information about the presence and the severity of vascular pathology.
It is measured by placing the inflatable cuff of the manometer at the level of the calf and on
the upper arm. Blood pressure measurement in the legs is performed with a pencil-shaped
ultrasound transducer which uses continuous wave Doppler.
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By using this method we measure:
- the highest value of SBP on the upper limb (after measuring on both arms)
- the highest value of SBP on any of the following arteries: anterior tibial artery,
posterior tibial artery, dorsalis pedis artery (for both lower limbs)
- finally, the ratio of brachial SBP / lower limb BP is computed and analyzed.
Interpretation of data:
- normal: ABPI ≥1
- vascular pathology (decreased blood flow): ABPI = 0.5-0.9
- critical ischemia: ABPI < 0.5.
Segmental pressure measurement
For this test, two or three blood pressure cuffs are placed on the lower limb - one cuff is
placed just below the knee and two other cuffs are placed above the knee and on the upper
thigh. Measurements are performed identically to ABPI. A difference of more than 20
mmHg between two sequential cuffs is proof of severe stenosis.
Ambulatory Blood Pressure Monitoring (ABPM)
ABPM is a convenient method to continuously monitor the BP of a patient outside the
hospital. By using a cuff secured on the patient's arm and connected to an electronic
device, the physician can obtain data regarding the SBP and the DBP recorded
continuously for at least 24 hours.
Usually, measurements are done at 20-minute intervals during the day (at least 14 values
during daytime) and every 30 minutes during the night (at least seven values by night). The
results can be expressed as numerical values for both SBP and DBP or as MAP. All data can
be represented in graphical format.
ABPM is used:
- when there is a suspicion for ’white-coat hypertension’: a common (15-30% of the
general population) clinical entity in which the blood pressure is over 140/90
mmHg in the doctor's office, but lower than 135/85mmHg in extra-hospital
environment (out-of-office)
- when there is large variability of BP during the same visit or different visits of the
patient
- in case of suspicion of autonomic, postural, postprandial or drug-induced
hypotension
- in case of pregnant women with suspicion of preeclampsia (a disorder of
pregnancy characterized by high blood pressure and proteinuria)
- for the identification of drug-resistant hypertension
- when there is suspicion of nocturnal hypertension
- in order to obtain guidance for the treatment of elderly patients with difficulties in
BP monitoring.
The criteria for establishing the diagnosis of arterial hypertension based on ABPM
monitoring have been defined by the European Society of Cardiology (ESC; Table 2).
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Table 2. Definition of hypertension based on Ambulatory Blood Pressure Monitoring (ECS
Guideline on the Management of Arterial Hypertension, 2013).
Category
SBP (mmHg)
DBP (mmHg)
Daytime (or awake)
≥135
≥85
Nighttime (or asleep)
≥120
≥70
24-h
≥130
≥80
3. Blood pressure regulation
The detailed mechanisms involved in BP regulation are discussed in the Lecture notes. The
efficiency of BP regulating systems can be monitored with the help of various stress tests
and posture tests.
The Schellong I test
It is a positional test assessing the efficacy of baroceptor reflexes in adjusting BP at the
moment of standing up from recumbent position.
First, pulse rate and BP are measured in supine every minute until constant values are
detected. Then, the subject stands up and remains standing for 10 minutes; the pulse rate
and the BP are taken immediately after standing up and afterwards minute by minute. At
the end, the subject lies down again and the pulse rate and the BP are measured after 1, 2,
and 3 minutes.
Interpretation of results: in normal conditions, there is minimal change in pulse rate and BP
when standing up. Variations considered normal:
- heart rate: rise of 10-20 bpm (30 bpm in the young)
- SBP: decreased by 15 mmHg followed by normalization, and then followed by
increase (around 10 mmHg)
- DBP: increase by 5 mmHg.
Variations outside normal values might be classified in three major categories:
- hypotonic – adjustment mainly by rise in the heart rate
- hypertonic – adjustment mainly by increase in the BP
- hypodynamic – lack of adjustment in the heart rate or in the BP
In case of sensation of faintness and dizziness at standing up abruptly, the subject
should recline immediately with feet passively elevated at 45 degrees.
The Crampton test
It is a positional test assessing changes in pulse rate and SBP at patients in supine position
and standing.
First, the subject is lying down for 2 minutes and the pulse rate and SBP are measured.
Then, the patient stands up without being supported; after 2 minutes, the pulse rate and
SBP are measured. At the end of the test, the Crampton index is computed:
Crampton index  25  (3.15 
BP P

)
10
20
where: ΔBP - difference of SBP measured in mmHg, ΔP - difference of pulse rate/min
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Interpretation of the result:
- insufficient adjustment < 50
- weak adjustment 50-75
- good adjustment 75-100
- excellent adjustment >100
In case of sensation of faintness and dizziness at standing up abruptly, the patient
should recline immediately with feet passively elevated at 45 degrees.
II. EXPERIMENTAL OBJECTIVES AND PROCEDURES
1. Experimental objectives:
 to use the auscultatory method for the indirect determination of SBP and DBP and to
correlate the appearance and disappearance of vascular sound with SBP and DBP,
respectively
 to measure and compare systemic BPs in the right arm and the left arm of the same
subject under identical conditions
 to measure and compare systemic BPs in the same subject under different
experimental conditions: standing, sitting, and supine position
 to calculate the ABPI
 to compare the systemic BPs detected audibly to those recorded by the stethoscope
microphone
 to compute and compare pulse pressure and MAP under different experimental
conditions
 to compute the pulse pressure wave velocity by measuring the time between the R
wave of the ECG and the Korotkoff sounds.
2. Materials
 for manual BP measurement: manometer with cuff and gauge, stethoscope,
continuous wave Doppler
 for recording:
 BIOPAC recording system (BIOPAC data acquisition unit connected to a computer)
 transducers for recording ECG (SS2L) and BP (SS19L and SS30L)
 clock with a second hand
3. Experimental methods
3.1. Manual measurement of blood pressure
A.1. Students should form pairs. Measure the BP using the manometer and the
stethoscope in sitting position on both the right and left arms. Switch places so that
everybody measures the BP. Complete the tasks in the corresponding section of the
Worksheet.
Do not inflate the cuff higher than is needed. Never leave the cuff on the subject at
high pressure (more than 120 mmHg) for more than 1 minute.
A.2. This section should be performed on a single volunteer. Measure the BP using the
manometer and the stethoscope only on the right arm, under different circumstances:
standing, sitting, and supine position. Complete the tasks in the corresponding section of
the Worksheet.
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A.3. This section should be performed on a single volunteer. Place the inflatable cuff of the
manometer at the level of the calf and on the upper arm, first on the right then on the left
side. Measure BPs at all sites and calculate the ABPI. Complete the tasks in the
corresponding section of the Worksheet.
A.4. This section should be performed on a single volunteer. First the pulse rate and the BP
are measured in supine every minute until constant values are detected. Then the subject
stands up and remains standing for 10 minutes; pulse rate and BP is taken immediately
after standing up and afterwards minute by minute. At the end the subject lies down again
and pulse rate and BP is measured after 1, 2 and 3 minutes. Complete the tasks in the
corresponding section of the Worksheet.
In case of sensation of faintness and dizziness at standing up abruptly, the subject
should recline immediately with feet passively elevated at 45 degrees.
A.5. This section should be performed on a single volunteer. First the subject is lying down
for 2 minutes and the pulse rate and BP is measured. Then the subject stands up without
being supported; after 2 minutes pulse rate and BP is measured. Calculate the Crampton
index and complete the tasks in the corresponding section of the Worksheet.
In case of sensation of faintness and dizziness at standing up abruptly, the patient
should recline immediately with feet passively elevated at 45 degrees.
3.2. Recording of blood pressure
During this recording the BIOPAC system will be used to record simultaneously ECG (Lead
II) and the BP. The recording system will be set up by lab assistants. In order to record, the
transducers must be connected according to Figure 3.
Figure 3. The electrode cable for Lead II must be connected to Channel III; electrodes will
be placed on both lower limbs and right upper limb: red to left leg (positive), white to right
arm (negative) and black to right leg (ground). For BP recording the cuff will be placed on
the right arm and connected to Channel I of the system whereas the stethoscope should be
connected to Channel II.
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After connecting the transducers follow the lead of the lab assistant who will guide you
through the necessary steps of the recording. For a proper recording the subject must be
seated in a relaxed fashion, always facing away from the monitor.
The subject must not have had or now have any disorder such as arterial hypertension,
heart surgery, stroke, or any history of cardiovascular disease. The subject should not
have consumed caffeine, smoked, or performed heavy exercise within one hour of the
recording.
B.1. Record with the subject seated and relaxed, arms supported, breathing normally,
facing away from the monitor. Record first on the left arm. Release pressure at a constant
rate of 2 - 3 mmHg/second (time yourself with a watch). Monitor Korotkoff’s sounds on the
same arm and mark promptly (by pressing F4) their appearance and disappearance. The
recording should look like Figure 4. Repeat the recording (two trials).
Figure 4. Top trace: gradual reduction of the pressure inside the cuff; middle trace: heart
sounds recorded using the stethoscope; bottom trace: ECG tracing.
B.2. Repeat the previous recording, but this time record on the right arm. Repeat the
recording (two trials).
B.3. The subject is supine (lying down, face up). Repeat the previous recording on the right
arm (two trials).
B.4. Unclip the leads and remove the cuff to allow the subject to perform moderate
exercise to elevate his/her heart rate (e.g. several squats). After the exercise, the recording
is performed as quickly as possible on the right arm in sitting position.
Review your data. Complete the tasks in the corresponding section of the Worksheet. For
the pulse wave velocity measure from the R wave on the ECG to the start of the Korotkoff
sound recorded with the stethoscope.
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TEST YOUR KNOWLEDGE
1. If the blood pressure at the right brachial artery is 120/80 mmHg, at the left brachial
artery is 140/80 mmHg, at the anterior tibial artery is 130/90 mmHg and at the posterior
tibial artery is 125/85 mmHg, choose the correct answer(s):
a. the ankle brachial pressure index (ABPI) is greater than 1
b. the ankle brachial pressure index (ABPI) is lower than 1
c. the ABPI is normal
d. the ABPM (ambulatory blood pressure monitoring) is >135 mmHg
e. the calculated ABPM can be due to arteriopathy
2. The blood pressure of a patient is 120/80 mmHg. The pressure in the cuff placed over the
brachial artery is 115 mmHg. Choose the correct answer(s):
a. the heart sounds cannot be heard with the stethoscope
b. palpation at the level of the radial artery reveals pulsations
c. the velocity of the pulse wave will be faster than normal
d. the heart sounds can be heard with the stethoscope
e. mean arterial pressure (MAP) is 100 mmHg
3. If the blood pressure is 150/90 mmHg, calculate:
The mean arterial pressure: ___________________________ mmHg
The pulse pressure: __________________________________ mmHg
4. If the blood pressure measured at the right brachial artery is 120/80 mmHg, at the left
brachial artery is 140/80 mmHg, at the left posterior tibial artery is 130/90 mmHg, and at
the right posterior tibial artery is 125/85 mmHg, calculate the ABPI:
ABPI: ______________________________________________
Interpret the result: __________________________________
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