US Pharm. 2008;33(2):14-17.
Blood pressure measurement is
critical in diagnosing hypertension and managing the efficacy of
antihypertensive medications.1 Home blood pressure monitoring
(HBPM) is a useful tool to allow consumers to participate in their health
care. Its popularity has risen in the past decade for a number of reasons.
However, its use is not free of risk. There are many precautions patients
should observe in taking their blood pressure at home. If done carefully,
however, HBPM can provide physicians and other health care providers with
compelling information about their patients' health status.
The Gold Standard
For many years, the
gold standard to which all other methods were compared was blood pressure
taken in the office by a trained health care provider using a mercury
sphygmomanometer and the auscultatory technique.1-4 This method,
generally credited to Riva-Rocci/Korotkoff, yields a pair of numbers (systolic
and diastolic).3,5 It was an inexpensive, simple, and reliable
method, and the equipment did not have to be periodically readjusted.3,6
In addition, research on the prognosis of hypertension (e.g., the risk of
cardiovascular events) has been based largely on readings taken in a
physician's office, using mercury or nonmercury methods.3
Inadequacies of the Office
over the toxic effects of mercury in the environment has led to apprehension
about mercury in sphygmomanometers. The drive to replace them in the United
States began in 1998, pursuant to an agreement between the Environmental
Protection Agency and the American Hospital Association to limit mercury waste
issued from hospitals to the greatest extent possible by 2005.7
Their use is decreasing in the U.S., and they are banned in several European
Office blood pressure
measurement is subject to a high degree of variation.3 To increase
accuracy of office measurement, operators should be regularly retrained in the
methods, and patients must be properly prepared and positioned.
However, concerns about
mercury and operator error or inconsistency aside, there are other criticisms
of office blood pressure measurement. They are of such gravity that office
readings are characterized as "poorly reproducible and unable to diagnose
hypertension."2 Office readings yield inaccurate results in
one half of attempts and may not justify the time and effort needed to take
Office readings do not detect
patients with nocturnal hypertension, a common occurrence in posttransplant
patients and those undergoing dialysis.9 They are also associated
with problems in patients with white-coat hypertension and masked
A major concern with office blood pressure measurement revolves around the
phenomenon of white-coat hypertension, also referred to as the white-coat
effect or as isolated clinic hypertension.2,3,6,10 Investigators
have long recognized that blood pressure measurements taken in medical offices
are higher than those taken at home or at work, perhaps due to an exaggerated
stress response to physicians and other medical personnel.9,11
Systolic blood pressure measurements can be 9 to 23 mmHg higher and diastolic
readings can be 3 to 10 mmHg higher than those obtained at home or with the
use of ambulatory blood pressure measurement.11 An estimated 15% to
20% of patients with stage 1 hypertension may experience white-coat
White-coat hypertension does
not occur with equal frequency in all patients. Men exhibit higher readings in
the office than women, and patients not taking antihypertensive medications
show more elevated readings than those who are on a regimen of
antihypertensives.11 Increasing age raises the likelihood of
white-coat hypertension, as does anxiety.
White-coat hypertension can be
identified if a patient has had persistently elevated clinic blood pressure
readings of 140/90 mmHg or higher on three or more visits, while having
obtained two or more readings less than 135/85 when awake in settings outside
of the clinic.4,12 The patient must not have had target organ
It is vital to identify
patients whose hypertension is triggered by blood pressure readings being
taken in a clinic setting. This is because such patients are at low risk for
sequelae from the apparent high blood pressure readings and are not generally
considered candidates for antihypertensive medications, as their ambulatory
blood pressure is actually normal.12 In fact, administration of
antihypertensives has been demonstrated to lower the blood pressure in the
office, but does not affect the normal, ambulatory blood pressure.4
Masked hypertension has received increased recognition in recent years. This
occurs in patients who experience the reverse of white-coat hypertension.4
That is, readings taken in the clinic are normal, but those taken in
nonclinic settings are abnormal.12 The dangers of this are readily
apparent. Patients remain undiagnosed, or the severity of their condition is
underestimated. As a result, they experience a relative risk of cardiac events
that is 2.3 times higher than patients who receive adequate treatment,
increasing the risk of target organ damage.12 The percentage of
patients with masked hypertension may be as high as 10%.12
The reasons for masked
hypertension are somewhat obscure. However, when trained clinic observers take
blood pressures correctly, they are instructed to prepare patients by asking
that they refrain from caffeine, exercise, and smoking for at least 30 minutes
before measurements are taken.8 Further, patients are seated
quietly in a chair for at least five minutes with their feet on the floor. At
home, patients may not comply with these instructions. Thus patients'
lifestyle choices (i.e., their level of physical activity or alcohol, tobacco,
and caffeine use) may not follow clinical recommendations.4 These
patients are at increased risk of target organ damage, as they may remain
undiagnosed and untreated for longer periods than patients whose clinic
readings are more reflective of the actual blood pressures.
Advantages of Home
HBPM has several
advantages over office methods. It is inexpensive, more reproducible, and may
help negate white-coat hypertension.13 When the values obtained are
compared to office measurements, HBPM may detect masked hypertension, allowing
those patients to be treated appropriately.14 It also compensates
for the paucity of clinic or office measurements by providing information for
a variety of time windows.5,15 When patients are placed on an
antihypertensive regimen, performing HBPM can improve their compliance and
increase the data needed to guide the physician's decision in modifying the
regimen.14 HBPM is superior to clinic measurements in predicting
sustained hypertension in borderline patients and in identifying patients at
risk of target organ damage and cardiovascular mortality.11 There
is often a memory in home devices, increasing the quality of information
gained.3 Because of its many advantages, HBPM is characterized as
the "optimal method for long-term follow-up of treated hypertension."
Types of Monitors
Monitors: HBPM monitors come in a variety of choices. The first
generation consisted of aneroid sphygmomanometers with a pressure-registering
gauge, now commonly used in offices and clinics. The patient was required to
use a stethoscope to hear the Korotkoff sounds.7 These devices
require patient instruction and are poorly suited for patients who have
difficulty hearing the subtle Korotkoff sounds.
Electronic Home Monitors:
Electronic devices comprise the majority of today's market. Product lines
include HoMedics, Invacare, LifeSource, Lumiscope, Mabis, and Omron. Patients
should be encouraged to purchase devices with accuracy validated through an
agency such as the American National Standards Institute, British Hypertension
Society, or the Association for the Advancement of Medical Instrumentation.
16 The advertisement or package insert for each monitor usually mentions
its validation status. If it does not, a note or call to the manufacturer
before purchase should reveal its status. Web sites can also provide this
information. For example, Omron Healthcare's Web site lists certain monitors
and the protocol used to validate them.17
Instructions for HBPM
There are no
universally accepted guidelines for how often a patient should perform HBPM,
nor is there agreement on an optimal schedule. However, one regimen suggests
beginning with measurements taken twice daily (morning and evening) for seven
consecutive days.6 The patient should ignore readings taken in the
first 24 hours. The average of 12 or more readings is acceptable.
The upper arm is the standard location to measure blood pressure, using an
occluding cuff placed at the crease of the elbow over the brachial artery.
4,16,18 However, some devices claim accuracy when using measurements
derived from the wrist or finger.11 This may appeal to patients
because of the reduced weight and size of these devices, which increase
portability and comfort level.3,18 The accuracy of wrist/finger
devices has been questioned, as they are generally considered to be less
reliable than those using the upper arm as the measurement site.3
The major reason is that blood pressure varies depending on which part of the
anatomy is being measured. As measurements move from the upper arm downward to
the finger, vascular resistance changes.16 The net effect is an
overestimation of blood pressure. Thus, the use of finger monitors is
generally discouraged.4 Wrist measurement devices are subject to
variations caused by such factors as wrist anatomy, degree of dorsal or ulnar
flexion, and incorrect limb position. If the pharmacist offers them for sale,
it would be wise to restrict the models to those with full approval via
1. Graves JW, Grossardt BR, Gullerud
RE, et al. The trained observer better predicts daytime ABPM diastolic blood
pressure in hypertensive patients than does an automated (Omron) device.
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2. Stergiou GS. How to cope with
unreliable office blood pressure measurement? Am J Hypertens.
3. Parati G, Bilo G, Mancia G. Blood
pressure measurement in research and in clinical practice: recent evidence.
Curr Opin Nephrol
4. Pickering TG, Hall JE, Appel LJ,
et al. Recommendations for blood pressure measurement in humans and
experimental animals: part 1: blood pressure measurement in 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.
5. Pickering TG. New ways of
measuring blood pressure. Am J Hypertens. 2006;19:988-990.
6. Vilaplana JM. Blood pressure
measurement. J Ren Care. 2006;32:210-213.
7. Lewis C. Checking up on blood
pressure monitors. FDA consumer magazine. Available at:
www.fda.gov/FDAC/features/2002/502_hbp.html. Accessed December 18, 2007.
8. U.S. Department of Health and
Human Services. The Seventh Report of the Joint National Committee on
Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC
7). Available at: www.nhlbi.nih.gov/guidelines/hypertension. Accessed December
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Ambulatory blood pressure monitoring: what a pediatrician should know. Curr
Opin Pediatr. 2007;19:178-182.
10. Tochikubo O, Kura N, Tokita H,
et al. Estimation of blood pressure by using a new device in the outpatient
clinic. Hypertens Res. 2006;29:233-241.
11. Taylor JR, Campbell KM. Home
monitoring of glucose and blood pressure. Am Fam Physician.
12. Pickering TG, Shimbo D, Haas D.
Ambulatory blood-pressure monitoring. N Engl J Med. 2006;354:2368-2374.
13. Stergiou GS, Jaenecke B, Giovas
PP, et al. A tool for reliable self-home blood pressure monitoring designed
according to the European Society of Hypertension recommendations: the
Microlife WatchBP Home monitor. Blood Press Monit. 2007;12:127-131.
14. Nolly H, Romero M, Nolly A, et
al. Clinical evaluation of the Braun BP 3000 Easy Click according to the
ANSI/AAMI SP 10:2002. Blood Press Monit. 2006;11:91-95.
15. Parati G, Hernandez-Hernandez R,
Velasco M. Home blood pressure monitoring in general practice: expectations
and concerns. J Hypertens. 2006;24:1699-1701.
16. Scolaro KL, Stamm PL, Lloyd KB.
Devices for ambulatory and home monitoring of blood pressure, lipids,
coagulation, and weight management, part 1. Am J Health Syst Pharm.
17. Omron Healthcare, Inc.
Validation standards & testing for home blood pressure monitors. Available at:
December 18, 2007.
18. Altunkan S, Oztas K, Altunkan E.
Validation of the Omron 637IT wrist blood pressure measuring device with a
position sensor according to the International Protocol in adults and obese
adults. Blood Press Monit. 2006;11:79-85.
19. Yosefy C, Vaturi M, Levine RA.
An acute hypertensive episode triggered by an ambulatory
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