How To Check Your Blood Pressure

How To Check Your Blood Pressure
How To Check Your Blood Pressure
Picking the Best Monitor for You
•
•
•
•
Choose a proper size arm cuff . You should be able to slide one finger under the cuff and the lower edge
should be one inch (2.5 cm) above your elbow. Larger/smaller cuffs may be ordered.
Choose the type that best suits your needs:
1. Automatic arm cuff: fits around the upper arm and automatically inflates. This type may not work
for some people who have irregular heartbeats.
2. Manual arm cuff: readings automatically display, but you must inflate the cuff by pumping a bulb.
3. Wrist monitors: very convenient, but usually more expensive than other monitors, and slightly less
consistent. Works well for people with big arms that may not fit well with arm cuffs.
4. Fingertip monitors: not as reliable as other models and are not recommended.
Ask your pharmacist to help you choose a reliable monitor. Some reputable brands include Omron,
Lifesource, etc. Many generic store brand monitors are made by the same brand name companies.
Other things to consider: Is the digital display large enough for you to read easily? Does the machine
have the ability to store blood pressure values in its memory or will you need to keep these records?
Before Taking Your Blood Pressure
•
•
•
Sit quietly for at least five minutes with your upper arm at heart level.
Sit up straight with feet flat on the floor and your back supported. Do not cross your legs or your ankles.
Wait at least half an hour after eating, smoking, or exercising to get the most accurate reading. You’ll
need to wait a couple of hours after ingesting caffeinated products.
Taking Blood Pressure
•
•
•
•
•
Roll up the sleeve on your arm or remove any tight-sleeved clothing.
For arm models, rest your arm on a table with your palm facing upwards. For wrist models keep your
wrist level with your heart.
Avoid talking while taking your blood pressure.
May repeat after a few minutes. Record the average of three consecutive readings.
It is important to check the blood pressure reading from your home machine with your healthcare
provider at least once or twice a year, or more frequently if the machine is dropped or if the blood
pressure readings change suddenly.
What Blood Pressure Numbers Mean
The readings from the blood pressure machine show how hard your heart is working to pump blood. The
top number (systolic pressure) is the pressure while the heart pumps and the bottom number (diastolic
pressure) is the pressure between heartbeats. People who have high blood pressure have a greater chance of
developing heart disease, stroke, kidney disease, and blindness.
Blood pressure readings are generally lower with home monitors compared to readings from your
healthcare provider’s office. Your healthcare provider will decide whether to adjust your medications based
on your home readings or office readings. Talk with your healthcare provider if you’re concerned about
your readings.
What You Can Do To Reduce Your Blood Pressure
There are several dietary and lifestyle changes you can make to decrease blood pressure. These include
weight loss, decrease sodium intake, increase exercise, smoking cessation, drinking alcohol in moderation,
and increase intake of fruits and vegetables. There are many other things you can do to help control your
blood pressure, just ask your healthcare provider. If lifestyle changes alone do not lower your blood
pressure, your healthcare provider may also have you take blood pressure lowering medication(s).
Prepared for the subscribers of
Pharmacist’s Letter / Prescriber’s Letter to give to their patients.
Copyright © 2008 by Therapeutic Research Center
Phone: 209-472-2240 ~ Fax: 209-472-2249
www.pharmacistsletter.com ~ www.prescribersletter.com
Detail-Document #240304
−This Detail-Document accompanies the related article published in−
PHARMACIST’S LETTER / PRESCRIBER’S LETTER
March 2008 ~ Volume 24 ~ Number 240304
Blood Pressure Monitoring
—Information about Validated Blood Pressure Monitors is
located in the “Home Blood Pressure” section of this document—
Background
An estimated one-quarter of Canadian adults
and nearly one-third of U.S. adults have
hypertension.1,2 Another one-quarter of U.S.
adults
have
blood
pressure
in
the
‘prehypertension’ range. Blood pressure is one of
the most important clinical measurements since
hypertension is a major risk factor for coronary
heart disease, kidney failure, heart failure, stroke,
and other conditions.3 The accuracy of blood
pressure measurement can be affected by
instrumentation, observer error, and patient error.
This document reviews the proper way to measure
blood pressure and provides a comparison
between different blood pressure measurement
methods. A patient handout on proper blood
pressure measurement is also provided.
Monitoring Blood Pressure
The seventh report of the Joint National
Committee on Prevention, Evaluation, and
Treatment of High Blood Pressure (JNC-VII)
classification for blood pressure in adults is as
follows:3
Classification
Normal
Prehypertension
Stage 1
Hypertension
Stage 2
Hypertension
SBP (mmHg)
<120
120 to 139
140 to 159
DBP (mmHg)
And <80
Or 80 to 89
Or 90 to 99
>160
Or >100
The Canadian Hypertension Education
Program (CHEP) does not endorse the label of
Blood
“prehypertension” (>120/80 mmHg).
pressure in the range of 130 to 139 mmHg/85 to
89 mmHg is classified as high normal. A patient
is considered hypertensive if the initial office
blood pressure is >180/110 mmHg or blood
pressure ranges between 140 to 179/90 to 109
mmHg in patients with target organ damage,
diabetes, or chronic kidney disease. A patient is
also considered hypertensive if the blood pressure
average over the first three office visits is SBP
>160 mmHg or the DBP >100 mmHg, OR if the
SBP averages >140 mmHg or the DBP averages
>90 mmHg after five visits.2
Hypertension is a major risk factor for
coronary heart disease, kidney failure, heart
failure, stroke, and other conditions.3 Therefore, it
is important to have blood pressure checked on a
regular basis and initiate lifestyle management
and/or drug therapy if hypertension is detected.
The blood pressure treatment goal is usually
<140/90 mmHg for hypertension patients or
<130/80 mmHg for patients with diabetes or
chronic kidney disease.2,3
Blood pressure measurement can be done with
various devices in various settings (e.g., home
monitoring devices, blood pressure measuring
kiosks located in pharmacies, blood pressure
measured in healthcare clinics, and ambulatory
blood pressure monitoring). Studies have shown
that blood pressure measurement can vary
depending on the monitoring device, technique,
and the setting in which the blood pressure is
measured.1,3 Home blood pressure readings are
consistently lower (by approximately 5 mmHg)
than clinic pressures in most hypertensive
patients.3 There are many factors that may affect
clinic blood pressure readings, including the
inherent variability of blood pressure, the
tendency for blood pressure to increase in the
presence of a healthcare provider (white coat
effect), and inaccuracies in the methods used to
measure blood pressure.
Because of this
variability, controversy exists as to which blood
pressure reading clinicians should base
hypertension treatment on.
More. . .
Copyright © 2008 by Therapeutic Research Center
Pharmacist’s Letter / Prescriber’s Letter ~ P.O. Box 8190, Stockton, CA 95208 ~ Phone: 209-472-2240 ~ Fax: 209-472-2249
www.pharmacistsletter.com ~ www.prescribersletter.com
(Detail-Document #240304: Page 2 of 6)
Proper Blood Pressure Measurement
There are many factors that may affect blood
pressure readings. Room temperature, exercise,
alcohol, caffeine, or nicotine consumption, arm
position, muscle tension, bladder distension,
talking, and background noise can all affect blood
pressure reading.1 It is important to control factors
that may affect blood pressure reading prior to
blood pressure measurement. At least three
measurements should be made at least one minute
apart and the average should be recorded.1,3
The current guidelines recommend that the
patient should be instructed to relax as much as
possible with both feet on the ground, not crossed,
arms supported and free of constrictive clothing at
heart level for at least five minutes prior to blood
pressure measurement.1-3 However, the optimal
rest time before blood pressure measurement is
still undefined. A recent study suggests a ten
minute resting time may improve the precision
and accuracy of blood pressure measurement to
match the patient’s true blood pressure.6 In that
study, the authors found that systolic blood
pressure may drop almost 11 mmHg after a 16
minute resting time.6 Whether resting for five
minutes or ten minutes before blood pressure
measurement, it is recommended the wait time to
be consistent. Consider recording the wait time
with blood pressure records to better interpret
blood pressure readings.6
JNC-VII recommends that caffeine, exercise,
and smoking should be avoided for at least 30
minutes prior to measurement.3 But some experts
now question whether 30 minutes is long enough
after caffeine consumption. A recent review
states that caffeine has been found to elevate
blood pressure acutely (by as much as
15 mmHg/13 mmHg), with blood pressure values
increasing within 30 minutes and peak effect
evident between one to two hours, persisting for
four or more hours.4 Based on this finding, some
experts suggest measuring blood pressure before
ingestion of caffeinated products, waiting a couple
of hours after caffeine ingestion, or interpret the
result with prior coffee ingestion in
consideration.4 It’s been reported that ingestion of
one to four and a half cups of coffee per day can
increase blood pressure by 0.1 mmHg systolic and
1 mmHg diastolic. Ingestion of five or more cups
of coffee a day can increase blood pressure by as
much as 3.2 mmHg systolic and 1.4 mmHg
diastolic.4 Note that the effect of caffeine is
different for each individual.
Cigarette smoking generally raises blood
pressure acutely, but the level generally returns to
baseline about 15 minutes after smoking.3
Chronic smokers are at a higher risk for
developing “masked hypertension,” where office
blood pressure measurements (when not smoking)
are generally lower than daytime home blood
pressure measurements (when smoking).5 There
is evidence that patients with untreated masked
hypertension are at higher risk for cardiac
morbidity.5 For this reason, home blood pressure
monitoring or 24-hour ambulatory blood pressure
measurement may be especially useful in chronic
smokers.3
Posture also affects blood pressure. Blood
pressure tends to increase from the lying to the
sitting or standing position.7 However, in most
people, as long as the arm is supported at heart
level, posture is unlikely to lead to significant
error in blood pressure measurement.7 The arm in
which blood pressure is being measured should be
supported and horizontal at the level of the heart.
Blood pressure readings tend to be higher in an
unsupported arm. Arm at a level lower than the
heart may lead to overestimation of blood
pressure, whereas arm at a level higher than the
The
heart may lead to underestimation.1,3,7
magnitude of error can be as high as 10 mmHg in
systolic and diastolic blood pressure.1,7 Blood
pressure is most commonly measured in a sitting
or supine position. It is recommended that the
patient be seated with back supported, both feet
touching the ground and upper arm bared without
constrictive clothing. An unsupported back and
crossing the legs may increase the blood
pressure.1 If blood pressure is measured in a
supine position, the arm should be supported with
a pillow so it is not below heart level.1
Studies have shown significant differences in
blood pressure readings between arms.1,7
However, there is no clear pattern and the
difference does not seem to depend on whether
the patient is right- or left-handed.1 It is
recommended that blood pressure be checked in
both arms at the first examination.1 If blood
pressure is consistently higher in one arm, the
higher reading should be used to determine
antihypertensive therapy.1
It is important to use the correct cuff size to
ensure the accuracy of readings. The blood
More. . .
Copyright © 2008 by Therapeutic Research Center
Pharmacist’s Letter / Prescriber’s Letter ~ P.O. Box 8190, Stockton, CA 95208 ~ Phone: 209-472-2240 ~ Fax: 209-472-2249
www.pharmacistsletter.com ~ www.prescribersletter.com
(Detail-Document #240304: Page 3 of 6)
pressure cuff should encircle at least 80% of the
arm circumference.1 If a cuff is too small, blood
pressure tends to be overestimated and vice
versa.1 The magnitude of error can be as great as
30 mmHg.8
in clinic blood pressure measurement.
The
potential advantages of automated measurement
in the office include elimination of observer error,
minimizing the white coat effect, and increasing
the number of readings.1
The recommended cuff sizes are:1
Arm
Cuff Size
Cuff
Circumference
dimension
22 to 26 cm
Small Adult
12 x 22 cm
27 to 34 cm
Adult
16 x 30 cm
35 to 44 cm
Large Adult
16 x 36 cm
45 to 52 cm
Adult Thigh
16 x 42 cm
Home Blood Pressure
The midline of the cuff bladder (usually
marked) should be placed over the arterial
pulsation over the patient’s bare upper arm. For
clinic blood pressure measurement, the lower end
of the cuff should be two to three centimeters
above the antecubital fossa to allow room for
stethoscope placement.1 The cuff should be
inflated rapidly to about 30 mmHg above the
palpated systolic pressure.7 The deflation rate
should be no greater than 2 mmHg to 3 mmHg per
second. Deflation rate >2 mmHg per second can
lead to significant underestimation of blood
pressure.1,7
Clinic Blood Pressure
Auscultatory
clinic
blood
pressure
measurement has been used by most for the
diagnosis and treatment of hypertension.
However, it’s been shown that clinic blood
pressure measurement may not be representative
of the patient’s true blood pressure, which is the
average blood pressure over prolonged periods of
time.1 There is evidence that clinic blood pressure
measurement may not correlate as well to target
organ damage and cardiac morbidity compared to
The
home blood pressure measurement.1
inaccuracy may be due to poor technique,
defective device, inherent blood pressure
variability, or white coat effect.1
The gold standard device for clinic blood
pressure measurement has been the mercury
sphygmomanometer, but these are being removed
from clinics due to environmental concerns.1
Aneroid and hybrid sphygmomanometers are
often
used
in
place
of
mercury
sphygmomanometers. Automated oscillometric
blood pressure devices are increasingly being used
Home blood pressure monitoring is a
convenient and relatively inexpensive way to
monitor blood pressure over long periods of time.
Home blood pressure readings are useful to help
monitor efficacy of antihypertensive therapy. In
addition, studies have shown that home blood
pressure may predict target organ damage and
morbid events better than clinic blood pressure.3
Since home blood pressure readings are generally
lower than clinic blood pressure readings, 135/85
mmHg (instead of 140/90 mmHg) is generally
accepted as the upper limit of normal for home
blood pressure.1-3 A lower home blood pressure
goal is recommended for diabetic patients,
pregnant women, and patients with renal failure.3
It is helpful to get blood pressure readings from
early morning and the evening.1 Advise patients
to take three consecutive readings at least one
minute apart and record the average.1
There are various home blood pressure
monitors available on the market. Electronic
blood pressure monitors are becoming more
popular and take blood pressure from the upper
arm, wrist, or finger. They are easy to use and
correlate well with the auscultatory method.3
However, they may be more expensive than
aneroid monitors (those with dial gauge and arm
cuff with a stethoscope attached to the cuff). The
standard location for blood pressure measurement
is the upper arm. The wrist monitors are smaller
than arm devices and can be used in obese people
since wrist diameters are rarely affected by
obesity. However, they may not be as accurate as
arm monitors. The finger monitors have been
found to be inaccurate and are not recommended.3
Recommend a home blood pressure monitor
that has been approved or validated by the British
Hypertension Society (BHS), the U.S. Association
for the Advancement of Medical Instrumentation
(AAMI), the American National Standards
Institute (ANSI), the Canadian Hypertension
Society (CHS), or the International Protocol
(IP).9,10 Home monitor devices should be checked
for accuracy every one to two years.1,2 Encourage
patients to compare home blood pressure readings
More. . .
Copyright © 2008 by Therapeutic Research Center
Pharmacist’s Letter / Prescriber’s Letter ~ P.O. Box 8190, Stockton, CA 95208 ~ Phone: 209-472-2240 ~ Fax: 209-472-2249
www.pharmacistsletter.com ~ www.prescribersletter.com
(Detail-Document #240304: Page 4 of 6)
with readings from their primary care provider’s
office.
Some of the reputable brands of automatic
blood pressure monitors include Microlife,
Lifesource, A&D, Omron, etc. Each company
manufactures multiple models of blood pressure
monitors. The prices of automatic arm blood
pressure monitors range from $60 to $120 U.S.
depending on the model. For an up-to-date survey
of validated blood pressure monitors, go to
http://www.dableducational.org/sphygmomanome
ters/recommended_cat.html.
Blood pressure monitors endorsed by CHS
include:
A&D or LifeSource monitors
Models: 705, 767, 767PAC, 767Plus, 774,
774AC, 779, 787, 787AC
Omron monitors
Models: HEM-705 PC, HEM-711, HEM741CINT
Microlife or Thermor monitors (also sold as
‘private label brands’)
Model: BP 3BTO-A, BP 3AC1-1, BP 3AC1-1 PC,
BP 3AC1-2, BP 3AG1, BP 3BTO-1, BP 3BTO-A
(2), BP 3BTO-AP, RM 100, BP A100 Plus, BP A
100.
For the most up-to-date information about the
CHS
endorsed
monitors,
go
to
http://hypertension.ca/chs/deviceendorsements/de
vices-endorsed-by-chs/.
More
information
about
hypertension
management in Canada can be found at
http://www.hypertension.ca.
Pharmacy Blood Pressure Kiosks
Blood pressure kiosks are available in most
retail pharmacies. These blood pressure kiosks
are generally not as accurate as mercury
sphygmomanometers or validated home meters.11
One major factor that may affect the accuracy of
these blood pressure kiosks is inappropriate cuff
size. Kiosks come with a standard size cuff and
may underestimate blood pressure reading in
obese people or overestimate in thin people. As
with home blood pressure monitors, blood
pressure readings from kiosks are generally lower
than clinic blood pressure readings. The cuff size
may be too small for more than half of the
hypertensive population.11 Due to the high chance
of inaccuracy, blood pressure readings from
kiosks cannot replace other forms of blood
pressure monitoring.12,13 It is recommended to
calibrate blood pressure kiosks every six to 12
months to improve accuracy.14 Patients should be
advised to have their blood pressure checked by a
healthcare professional if they suspect they have
high blood pressure based on kiosk reading.
Ambulatory Blood Pressure Measurement
Twenty-four hour ambulatory blood pressure
monitoring may better predict a patient’s true
blood pressure than clinic blood pressure
measurment.15 However, it is not commonly used
due to the relatively high expense.15 Ambulatory
blood pressure may be used to identify patients
with nondipping blood pressure pattern (blood
pressure does not decrease during sleep), white
coat hypertension, or masked hypertension.1,3,5
Individuals with nondipping pattern appear to be
at increased risk for blood pressure related
complications compared with those with a normal
dipping pattern. In addition, there is evidence
suggesting that nighttime blood pressure may be
the best predictor of risk.1
During an ambulatory blood pressure
measurement session, blood pressure is typically
measured every 15 to 30 minutes over a 24-hour
period (preferable on a workday). The blood
pressure readings are stored in the monitor and
can be converted into a report that provides mean
values by hour and period (e.g., daytime,
nighttime, and 24-hour values).
Studies have shown that the average level of
ambulatory blood pressure predicts risk of morbid
events better than clinic blood pressure.1,15 In
addition, certain ambulatory blood pressure
patterns may predict blood pressure-related
Ambulatory blood pressure
complications.1
monitoring may be considered if:3
• White coat effect suspected in patients with
hypertension and no target organ damage
• Drug resistance is apparent in clinic
• Hypotensive
symptoms
present
with
antihypertensive medications
• Patient experiences episodic hypertension
• Autonomic dysfunction is present
The upper limit of normal is set at
135/85 mmHg for ambulatory blood pressure
monitoring since readings are generally lower
The Canadian
than clinic blood pressure.1
More. . .
Copyright © 2008 by Therapeutic Research Center
Pharmacist’s Letter / Prescriber’s Letter ~ P.O. Box 8190, Stockton, CA 95208 ~ Phone: 209-472-2240 ~ Fax: 209-472-2249
www.pharmacistsletter.com ~ www.prescribersletter.com
(Detail-Document #240304: Page 5 of 6)
Hypertension Education Program classifies
ambulatory blood pressure measurements as
hypertensive if awake SBP is >135 mmHg or the
DBP is >85 mmHg, or if the mean 24 hour SBP is
>130 mmHg or the DBP is >80 mmHg.2
3.
4.
Conclusion
Accurate blood pressure measurement is the
key to determining appropriate therapy.
Controversy exists as to whether drug therapy
should be initiated or adjusted based on clinic
blood pressure reading or home blood pressure
reading. Since home blood pressure levels seem
to better correlate to patient’s risk for morbidity,
home blood pressure monitoring is now strongly
encouraged by experts. For accurate blood
pressure readings, patients should be instructed on
the proper way to measure blood pressure and
they should use a blood pressure monitor that has
been validated.
Users of this document are cautioned to use their own
professional judgment and consult any other necessary
or appropriate sources prior to making clinical
judgments based on the content of this document. Our
editors have researched the information with input
from experts, government agencies, and national
organizations. Information and Internet links in this
article were current as of the date of publication.
Project Leader in preparation of this DetailDocument: Wan-Chih Tom, Pharm.D.
5.
6.
7.
8.
9.
10.
11.
12.
13.
References
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2.
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Recommendations
for
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humans: a statement for professionals from the
Subcommittee of Professional and Public
Education of the American Heart Association
Council on High Blood Pressure Research.
Circulation 2005;111:697-716.
2007 Canadian Hypertension Education Program
recommendations for the management of
hypertension.
http://www.hypertension.ca/chep
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2008;24(3):240304.
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National Institutes of Health. National Heart, Lung,
and Blood Institute. The seventh report of the Joint
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Treatment
of
High
Blood
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http://www.nhlbi.nih.gov/guidelines/hypertension/jn
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Mort JR, Kruse HR. Timing of blood pressure
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Ann Pharmacother 2008;42:105-10.
Pickering TG, Eguchi K, Kario K.
Masked
hypertension: a review.
Hypertens Res
2007;30:479-88.
Sala C, Santin E, Rescaldani M, Margrini F. How
long shall the patient rest before clinic blood
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Am J Hypertens
2006;19:713-7.
Beevers G, Lip GY, O’Brien E.
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techniques. BMJ 2001;322:981-5.
Parati G, Mendis S, Abegunde D, et al.
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settings. Blood Press Monit 2005;10:3-10.
Anon.
2007 Public recommendations on
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http://ww2.heartandstroke.ca/images/english/CHEP
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Pickering TG. Measurement of blood pressure and
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Graves JW. Blood pressure measurement in
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American Family Physician
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Lewis JE, Boyle E, Magharious L, Myers MG.
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CMAJ
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Staal EM, Nygard OK, Omvik P, Gerdts E. Blood
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Personal communication. Service Department.
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Pickering TG, Shimbo D, Hass D. Ambulatory
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Canadian Hypertension Society.
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http://hypertension.ca/chs/deviceendorsements/dev
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2008).
Blood pressure monitoring. Pharmacist’s Letter/Prescriber’s Letter
More. . .
Copyright © 2008 by Therapeutic Research Center
Pharmacist’s Letter / Prescriber’s Letter ~ P.O. Box 8190, Stockton, CA 95208 ~ Phone: 209-472-2240 ~ Fax: 209-472-2249
www.pharmacistsletter.com ~ www.prescribersletter.com
(Detail-Document #240304: Page 6 of 6)
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Copyright © 2008 by Therapeutic Research Center
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