High Blood Pressure / Hypertension

Monitoring of Blood Pressure: Alternative Site Measurement

By Cardiologist on February 1st, 2010

Alternative Site Measurement

Manufacturers have developed blood pressure monitors that work on the wrist and the finger. These devices are gaining popularity because of their perceived advantages of greater portability, ease of use, and comfort. However, devices that work on the upper arm are still preferable to wrist and finger monitors because of superior accuracy.

Wrist: Wrist measurement of blood pressure using the oscillometric technique has shown generally good agreement compared with the upper arm measurement using auscultatory or oscillometric methods. However, wrist measurement has shown high variability in individual cases and the correlation coefficients generally are not as high as those using the upper arm methods. The wrist measurements are very dependent on position of the device in relation to heart level. Error due to flexion or hyperextension of the wrist during measurement can occur also.

Finger: It is widely agreed that finger blood pressure monitors are not accurate for home use.These devices measure BP by occluding a digital artery in the finger. Limb position is even more critical with finger monitors, and there is the additional problem of peripheral vasoconstriction affecting accuracy.

Special Features

The major advances in technology have been oriented toward how data are displayed, printed, stored, or transmitted. Some digital monitors feature measurement readouts on extra-large display panels. Other monitors have self-contained printers that provide data both digitally and in bar graph form. Talking monitors that announce the blood pressure and pulse are also available. Memory functions such as last-reading and multiple-reading recall are available on some monitors. Some monitors also add the time and date to the measurement record. Other types of special features pertain to control of inflation, i.e., some automatic-inflation products come with “fuzzy logic,” which anticipates the systolic blood pressure to reduce overinflation of the cuff. Some monitors allow the user to preset the inflation level. Cuff overinflation can cause patient discomfort. Features of home BP monitors are listed in Tables 1 and 2.

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