Blood Pressure
Definition:
Blood pressure (BP) is a measurement of the pressure or force
exerted by the blood on the walls of the arteries in which it is contained.
Mechanism of Blood Pressure:
1. Each time the ventricles contract:
Blood is pushed out of the heart and into the aorta and
pulmonary aorta, exerting pressure on the walls of the
arteries.
This phase in the cardiac cycle is known as systole, and it
represents the highest point of blood pressure in the body, or
the systolic pressure.
The phase of the cardiac cycle in which the heart relaxes
between contractions is referred to as diastole.
The diastolic pressure (recorded during diastole) is lower
because the heart is relaxed.
2. Contraction and relaxation of the heart result in two different
pressures, systolic and diastolic.
Interpretation of Blood Pressure:
1. Blood pressure measurement is expressed as a fraction. The
numerator is the systolic pressure, and the denominator is the
diastolic pressure.
2. The standard unit for measuring blood pressure is millimeters of
mercury (mm Hg)
3. A blood pressure reading of 110/70 mm Hg means that there was
enough force to raise a column of mercury 110 mm during systole
and 70 mmduring diastole.
Based on guidelines from the National Heart, Lung, and Blood Institute
(NHLBI):
1. A blood pressure120/80 mm Hg is classified as normal.
2. Blood pressure should be:
Taken during every office visit to allow the physician to
compare the patient‘s readings over time.
This is a good preventive measure in guarding against
serious illness.
A single blood pressure reading taken on one occasion does
not characterize an individual‘s blood pressure accurately.
3. Several readings, taken on different occasions, provide a good
index of an individual‘s baseline blood pressure.
4. Blood pressure readings should always be interpreted using a
patient‘s baseline blood pressure.
5. An increase or decrease of 20 to 30 mm Hg in a patient‘s baseline
blood pressure is significant, even if it is still within the normal
accepted blood pressure range.
The most common condition that causes an abnormal blood pressure
reading is:
1. Hypertension, or high blood pressure, results from excessive
pressure on the walls of the arteries.
2. Hypertension: is determined by a sustained systolic blood pressure
reading of 140 mm Hg or greater or a sustained diastolic reading of
90 mm Hg or greater.
3. Hypotension, or low blood pressure, results from reduced pressure
on the arterial walls.
4. Hypotension is determined by a blood pressure reading less than
95/60 mm Hg .
Pulse Pressure:
1. The difference between systolic and diastolic pressure is the pulse
pressure.
2. It is determined by subtracting the smaller number from the larger.
If the blood pressure is 110/70 mm Hg, the pulse pressure would be
40 mm Hg.
3. A pulse pressure between 30 and 50 mm Hg is considered to be
within normal range.
Factors Affecting Blood Pressure:
1. Blood pressure does not remain at a constant value.
2. Numerous factors may affect it throughout the course of the day.
3. An understanding of these factors helps to ensure an accurate
interpretation of blood pressure readings.
Age: Age is an important consideration when determining whether a
patient‘s blood pressure is normal. As age increases, the blood
pressure gradually increases:
A 6-year-old child may have a normal reading of 90/60 mm
Hg, whereas a young, healthy adult may have a blood
pressure reading of 116/76 mm Hg, and it would not be
unusual for a 60-year-old man to have a reading of 130/90
mm Hg.
As an individual gets older, there is a loss of elasticity in the
walls of the blood vessels, causing this increase in pressure
to occur.
Gender: After puberty, women usually have a lower blood pressure
than men of the same age. After menopause, women usually
have a higher blood pressure than men of the same age.
Diurnal variations:
Fluctuations in an individual‘s blood pressure are normal
during the course of a day.
When one awakens, the blood pressure is lower as a result of
the decreased metabolism and physical activity during sleep.
As metabolism and activity increase during the day, the
blood pressure rises.
Emotional states:
Strong emotional states, such as anger, fear, and excitement,
increase the blood pressure.
If the medical assistant observes such a reaction, an attempt
should be made to calm the patient before taking blood
pressure.
Exercise: Physical activity temporarily increases the blood pressure. To
ensure an accurate reading, a patient who has been involved
in physical activity should be given an opportunity to rest for
20 to 30 minutes before blood pressure is measured.
Body position:
The blood pressure of a patient who is in a lying or standing
position is usually different from that measured when the
patient is sitting.
Notation should be made on the patient‘s chart if the reading
was obtained in any position other than sitting, using the
following abbreviations: L (lying) and St (standing).
Medications: Many medications may increase or decrease the blood
pressure. Because of this factor, it is important to record in
the patient chart all prescription and over-the-counter
medications that the patient is taking.
Other factors: Other factors that may increase the blood pressure
include pain, a recent meal, smoking, and bladder distention.
Assessment of Blood Pressure:
The equipment needed to measure blood pressure includes a
stethoscope and a sphygmomanometer:
1. The stethoscope amplifies sounds produced by the body and allows
the medical assistant to hear them. Stethoscope
2. The most common type of stethoscope used in the medical office is
the acoustic stethoscope.
It consists of four parts:
1. Earpieces. 2. Sidepieces known as
binaural
3. Plastic or rubber tubing 4. A chest piece.
Stethoscope Chest Piece:
1. Two types of chest pieces exist: a diaphragm, which is a large, flat
disc and a bell which has a bowl-shaped appearance.
2. The chest piece of a stethoscope consists of a diaphragm and a bell,
or just a diaphragm.
3. If a chest piece consists of a diaphragm and a bell, the medical
assistant ensure the desired piece is rotated into position before use.
4. Failure to do so would not allow the medical assistant to hear sound
through the earpieces.
Fig (40): Parts of a stethoscope and Types of chest pieces.
Patient Teaching Hypertension:
Answer questions patients have about hypertension.
What is high blood pressure?
1. Blood pressure is the force of blood against the walls of the
arteries.
2. High blood pressure, also called hypertension, means the pressure
in the arteries is consistently above normal (140/90 mm Hg),
resulting in excessive pressure on the walls of the arteries.
What are the symptoms of high blood pressure?
1. Approximately one third of people who have high blood pressure
are unaware of it because there are few or no symptoms and, as a
result, an individual with hypertension may go undiagnosed for
many years.
2. If symptoms do occur, they may include one or more of the
following: headaches, dizziness, flushed face, fatigue, epistaxis
(nosebleed), excessive perspiration, heart palpitations, frequent
urination, and leg claudicating (cramping in the legs with walking).
3. The only way to know for sure whether you have high blood
pressure is to have it checked regularly.
What causes high blood pressure?
1. In about 90% of cases, the precise cause of high blood pressure is
unknown.
2. This type of hypertension is known as essential or primary
hypertension.
3. Certain factors seem to increase the risk of developing essential
hypertension, however, including:
Heredity: A family history of high blood pressure increases
an individual‘s risk of developing high blood pressure.
Weight: Individuals who are overweight or obese are two to
six times more likely than the general population to develop
high blood pressure.
Ethnicity: Research has shown that more black than white
Americans develop high blood pressure.
Age: Blood pressure normally increases as one grows older.
Sodium intake:
Sodium, found in salt and processed, canned, and most
snack foods, does not cause high blood pressure;
however, it can aggravate high blood pressure.
Most Americans consume more sodium than they
need. The current recommendation is to consume less
than 2.4 g (2400 mg) of sodium per day.
This is equivalent to 6 g (about 1 teaspoon) of salt.
Stress: Research indicates that people who are under
continuous stress tend to develop more heart and circulatory
problems than people who are not under stress.
Smoking: Smoking tobacco constricts blood vessels, causing
an increase in blood pressure.
Alcohol consumption: Heavy alcohol consumption may
increase the blood pressure.
The remaining 10% of individuals with hypertension
have secondary hypertension.
This means that the high blood pressure can be linked
to a known cause, which includes chronic kidney
disease, adrenal and thyroid disease, narrowing of the
aorta, steroid therapy, oral contraceptives, and
preeclampsia associated with pregnancy.
What can happen if high blood pressure is not treated?
1. If high blood pressure is not brought under control:
It can cause severe damage to vital organs, such as the heart,
brain, kidneys, and eyes.
This damage can result in a heart attack or heart failure,
stroke, kidney damage, or damaged vision.
Early detection and treatment of high blood pressure can
prevent these complications.
2. High blood pressure is often discovered during a routine medical
examination or (less commonly) when an individual experiences
one of the complications of hypertension caused by damage to a
vital organ.
Can high blood pressure be cured?
1. Essential hypertension cannot be cured, but many treatments are
used to bring it under control.
2. These include lifestyle modifications, such as weight reduction, a
healthy diet rich in fruits and vegetables and low in saturated fat,
limitation of salt intake, regular aerobic exercise, cessation of
smoking, limitation or elimination of alcohol consumption, and
stress management.
3. If lifestyle modifications alone are not enough, medications are
available for reducing blood pressure, allowing the patient to lead a
normal, healthy, active life.
How long will I undergo treatment?
1. Treatment for essential hypertension is usually lifelong.
2. Even if you feel fine, you will probably have to continue treatment
for the rest of your life to maintain your blood pressure in a healthy
range.
3. If you discontinue your diet and lifestyle changes or stop taking
your medication, your blood pressure will increase again.
Encourage: patients with hypertension to adhere to the treatment
prescribed by the physician. Help patients remember to take
their medication by telling them to associate their medication
schedule with a daily routine, such as brushing their teeth or
having meals.
Provide: the patient with educational materials on high blood pressure
available from sources such as the American Heart
Association.
The diaphragm chest piece is more useful for hearing high-pitched
sounds, such as lung and bowel sounds, whereas the bell chest
piece is more useful for hearing low-pitched sounds, such as
those produced by the heart and vascular system.
Before using a stethoscope, the medical assistant should ensure that it is
in proper working condition.
Sphygmomanometers:
1. The sphygmomanometer is an instrument that measures the
pressure of blood within an artery.
2. It consists of a manometer, an inner inflatable bladder surrounded
by a covering known as the cuff, and a pressure bulb with a control
valve to inflate and deflate the inner bladder.
3. The manometer contains a scale for registering the pressure of the
air in the bladder.
The Two Types of Sphygmomanometers are the Aneroid and
Mercury:
The aneroid sphygmomanometer is lightweight and portable, but the
mercury sphygmomanometer is more accurate.
1. Aneroid Sphygmomanometer:
The aneroid sphygmomanometer (see figure 24) has a
manometer gauge with a round scale.
The scale is calibrated in millimeters, with a needle that
points to the calibrations (see figure 25).
To ensure an accurate reading, the needle must be positioned
initially at zero.
The manometer must be placed in the correct position for
proper viewing.
The medical assistant should be no farther than 3 feet from
the scale on the gauge of the manometer, and the manometer
should be placed so that it can be viewed directly.
At least once a year, an aneroid sphygmomanometer should
be recalibrated to ensure its accuracy.
Fig (41). The parts of an aneroid sphygmomanometer.
2. Mercury Sphygmomanometer:
The mercury sphygmomanometer (see figure 26) has a
vertical tube calibrated in millimeters that is filled with
mercury.
Although more accurate than the aneroid
sphygmomanometer, the use of the mercury
sphygmomanometer is being discouraged because mercury is
a hazardous chemical.
If a mercury manometer is used to measure blood pressure, it
must be placed in the correct position for proper viewing.
The medical assistant should be no farther than 3feet from
the scale of the manometer.
A portable mercury manometer should be placed on a flat
surface so that the mercury column is in a vertical position.
The wall model mercury manometer is mounted securely
against a wall, placing the mercury column in a vertical
position.
The Following Guidelines Must be Followed when Measuring Blood
Pressure with a Mercury Sphygmomanometer:
1. Before the blood pressure reading is obtained, the mercury must be
even with the zero level at the base of the calibrated tube:
Pressure created by inflation of the inner bladder causes the
mercury to rise in the tube.
The top portion of the mercury column, the meniscus, curves
slightly upward.
The blood pressure should be read at the top of the meniscus,
with the eye at the same level as the meniscus of the mercury
column.
.
Fig (42): The parts of a mercury sphygmomanometer.
2. Cuff Sizes:
Blood pressure cuffs come in a variety of sizes and are
measured in centimeters (cm).
Fig (43): Blood pressure cuffs: child, adult, and thigh.
The size of a cuff refers to its inner inflatable bladder, rather
than its cloth cover.
For accurate blood pressure measurement, the inner bladder
of the cuff should encircle at least 80% of the arm
circumference and be wide enough to cover two thirds of the
distance from the axilla to the antecubital space (see figure
28).
Child cuffs often must be used for adults with thin arms.
Fig (44): A Determination of proper site and cuff size.
The adult cuff is used for the average-sized adult arm, and
the thigh cuff is used for taking blood pressure from the
thigh or for adults with large arms.
If the cuff is too small, the reading may be falsely high, as it
would be, for example, when an adult cuff is used on a
patient with a large arm.
If the cuff is too large, the reading may be falsely low, as it
would be when an adult cuff is used with a patient with a
thin arm.
The cuff should fit snugly and should be applied so that the
center of the inflatable bag is directly over the brachial artery
to allow for complete compression of the artery.
The cuff has an interlocking, self-sticking substance (Velcro)
that facilitates closing and fastening the cuff in place
temporarily.
Korotkoff Sounds Korotkoff sounds are used to determine
the systolic and diastolic blood pressure readings.
When the bladder of the cuff is inflated, the brachial artery is
compressed so that no audible sounds are heard through the
stethoscope.
As the cuff is deflated, at a rate of 2 to 3 mm Hg per second,
the sounds become audible until the blood flows freely and
they can no longer be heard.
Fig (45): Inflation of cuff compresses and closes off brachial artery.
The medical assistant should practice listening to these sounds and be
able to identify the various phases.
1. Phase I: First faint but clear tapping sound is heard, and it
gradually increases in intensity. First tapping sound is systolic
pressure.
2. Phase II: As cuff continues to deflate, sounds have murmuring or
swishing quality.
3. Phase III: With further deflation, sounds become crisper and
increase in intensity.
4. Phase IV: Sounds become muffled and have soft, blowing quality.
5. Phase V: Sounds disappear.
N.B.This is typically recorded as diastolic pressure for an adult. Some
authorities believe that adult diastolic pressure falls midway between
phases IV and V; some physicians want the medical assistant to
record phases IV and V as the diastolic pressure (e.g., 120/84/80).
Prevention of Errors in Blood Pressure Measurement:
The following guidelines should be followed to prevent errors in blood
pressure measurement:
1. Instruct the patient not to consume caffeine or use tobacco for 30
minutes before blood pressure measurement.
2. The patient should be seated in a quiet room for at least 5 minutes
before blood pressure is taken:
Patient anxiety and apprehension can cause a spasm of the
brachial artery, which can increase the blood pressure
reading by as much as 30 to 50 mm/Hg.
This is known as the ―white coat effect,‖ which refers to the
white laboratory coat worn by the physician.
3. Always use the proper cuff size:
If the cuff is too small, it may come loose as the cuff is
inflated, or the reading may be falsely high.
If the cuff is too large, the reading may be falsely low.
The inner inflatable bladder of the cuff should encircle at
least 80% of the patient‘s arm and cover two thirds of the
distance from the axilla to the antecubital space.
4. Never take blood pressure over clothing:
Clothing interferes with the ability to hear the Korotkoff
sounds, which could result in an inaccurate blood pressure
reading.
Roll up the patient‘s sleeve approximately 5 inches above the
elbow.
If the sleeve is too tight after being rolled up, remove the arm
from the sleeve.
A tight sleeve causes partial compression of the brachial
artery, resulting in an inaccurate reading.
5. Position the patient‘s arm properly:
Position the arm at heart level, and ensure it is well
supported with the palm facing upward.
If the arm is above heart level, the blood pressure reading
may be falsely low.
If the arm is not supported or placed below heart level, the
blood pressure reading may be falsely high.
6. Avoid extraneous sounds from the cuff:
Position the cuff approximately 1 to 2 inches above the bend
in the elbow.
The cuff should be up far enough to prevent the stethoscope
from touching it; otherwise, extraneous sounds, which could
interfere with an accurate measurement, may be picked up.
7. Compress the brachial artery completely:
Center the inner bladder of the cuff directly over the artery to
be compressed.
Most cuffs are labeled with arrows indicating the center of
the bladder for the right and left arms.
Centering the inner bladder allows for complete compression
of the brachial artery.
8. Apply equal pressure over the brachial artery:
The cuff should be applied so that it fit smoothly and snugly
around the patient‘s arm.
This prevents bulging or slipping and permits application of
an equal pressure over the brachial artery.
A loose-fitting cuff can cause a falsely high reading.
9. Position the earpieces so that you can hear the sounds clearly:
Place the earpieces of the stethoscope in your ears with the
earpieces directed slightly forward.
This allows the earpieces to follow the direction of the ear
canal, which facilitates hearing.
10. Avoid extraneous sounds from the tubing:
Make sure the tubing of the stethoscope hangs freely and is
not permitted to rub against any object.
If the stethoscope tubing rubs against an object, extraneous
sounds may be picked up, which could interfere with an
accurate measurement.
11. Position the chest piece properly:
Palpate the brachial pulse to provide good positioning of the
chest piece over the brachial artery.
Place the chest piece firmly, but gently, over the brachial
artery to assist in transmitting clear and audible sounds.
Do not allow the chest piece to touch the cuff to prevent
extraneous sounds from being picked up, which could
interfere with an accurate measurement.
12. Release the pressure at a moderate steady rate:
Release the pressure in the cuff at a rate of 2 to 3 mm
Hg/sec to ensure an accurate blood pressure measurement.
Releasing the pressure too slowly is uncomfortable for the
patient and could cause a falsely high diastolic reading.
Releasing the pressure too quickly could cause a falsely low
systolic reading.
13. Avoid venous congestion:
If you need to take the blood pressure in the same arm again,
wait 1 to 2 minutes to allow blood trapped in the veins
(venous congestion) to be released.
Venous congestion can result in a falsely high systolic
reading and a falsely low diastolic reading.
14. Measure and record the blood pressure in both arms during the
initial blood pressure assessment of a new patient:
There may normally be a difference of 5 to 10 mm Hg
between the two arms.
During return visits, the blood pressure should be measured
in the arm with the higher initial reading.