michigan hypertension core curriculum - State of Michigan

of the wrist. Additionally, there is difficulty creating an accurate algorithm to estimate BP as there
are two arteries at the wrist contributing to the oscillometric signal. 4 Wrist devices are not currently
recommended for routine clinical practice or decision making. 3,4 Ambulatory BP monitoring (ABPM),
another type of ocillometric measurement, may be done when there is the possibility of white-coat
hypertension or other concerns of measurement error. White-coat hypertension (persistent elevation
in BP when measured in a clinical setting, but normal BP when the measurement is taken at home),
affects as many as 1 in 3 in the general population but is higher in the elderly and pregnant women. 3,5
ABPM records BP every 15 to 30 minutes (or when triggered at the patient’s request) for a 24 to 48
hour period. The data is stored in the device’s memory until downloaded to a computer for interpretation
by the physician. 5,6 The multiple recordings may provide greater diagnostic accuracy than isolated
clinic measurements. However, when proper, standardized procedures are followed, the average of
4 duplicate clinic BP readings is as reliable as 24hr ABPM. 7 A third method of BP measurement uses
hybrid sphygmomanometers which combines the features of both ausculatory and ocillometric
devices. The hybrid combines manual BP measurement techniques but replaces the mercury column
with an electronic pressure detection system. 3 These are relatively new devices with only a few
certified to meet established standards.
BP measurements taken with ocillometric devices (automated or ABPM) are usually lower than
with ausculatory methods. This difference must be reconciled with the fact that BP treatment guidelines
are based on epidemiologic data obtained using ausculatory methods. Thus, lower thresholds for
treatment should be considered if treatment decisions are based on automated measurements. BP
measurements > 135/85 mmHg obtained with an ocillometric device (e.g., ABPM, home monitors)
should be considered abnormal (hypertensive) and treated as such. 4
Measurement Protocol
Accuracy of BP measurement requires careful attention to detail when any BP reading is
obtained. Table 1 contains guidelines that should be followed to achieve maximal accuracy.
Measurement Locations
Blood pressure may be measured in numerous locations including professional settings (e.g.,
out-patient clinics, hospitals); community sites (e.g., pharmacies), and in patients’ homes. In all of
these locations, principles of accurate measurement must be followed including the use of appropriate
equipment and adherence to BP measurement protocols. It is important that the individual measuring
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