Publications

Objectives

Blood pressure measurements taken by doctors and practice nurses are the cornerstone of many
prescribing and management decisions in general practice. We surveyed blood pressure monitors in
use in general practice in Oxfordshire.
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Method

34 general practices, with a total of 604 blood pressure monitors in use, agreed to take part. We used
the Omron-PA350 and the PMS Instruments Pressure Tester to evaluate readings of each monitor at
50, 100, 150, 200 and 250 mm Hg.

Results

194 aneroid, 305 digital and 80 mercury devices were in use. At each of 50, 100 and 150 mm Hg the
mean absolute error was greatest in the aneroid devices and least in the mercury devices (p<0.05), but
there were no significant differences between these types at 200 mm Hg (p=0.2) or 250 mm Hg
(p=0.4). In aneroid, digital and mercury devices respectively, 16% (95% confidence interval 11% to
24%), 10% (95% confidence interval 7.3% to 16%) and 2.5% (95% confidence interval 0.7% to 5.9%)
of measurements were more than 3 mm Hg from the true value. Within aneroid devices, instruments
manufactured by Accosson, Welch-Alleyn and other manufacturers had 11% (95% confidence interval
6% to 19%) , 2.2% (95% confidence interval 0.4% to 6.9%) and 32% (95% confidence interval 22% to
49%) of errors worse than 3 mm Hg.

Conclusions

Aneroid and digital blood pressure devices in use in general practice in Oxfordshire are less accurate,
on average, than devices using the older, mercury-based technology. Devices from poorly-known
brands may be particularly unreliable.