Summerson JH, Pearce KA, Evans GW
Blood pressure determination using the random zero and
standard mercury sphygmomanometers
12th Annual ASH Meeting
Am J Hypertens
(Apr) 10:65A 1997
The random zero blood pressure sphygmomanometer was developed to
remove bias and error from blood pressure measurement. The device is
supposed to remove bias by randomly allowing the operator to blindly
dial in an amount of mercury to the reading which is later subtracted.
There are several versions of the machine which have been used in many
epidemiological studies over the past 20 years. Recently, many
authors have questioned the accuracy of this machine and consistently
reported that it underestimates blood pressure.
The authors of this study compared the random zero and the standard
mercury sphygmomanometer in 75 older adults using a set of six
readings. The patients were randomly selected from their primary care
clinic. They found that the initial value of mercury dialed in (zero
levels) were non-uniform in distribution and found a significant
negative correlation between them and the measured systolic blood
pressure. The random zero device recorded lower systolic and
diastolic blood pressure when compared to the standard mercury device.
Comment: The issue of the whether the device should continue to
be used remains unsettled. Many researchers have now stayed away from
using it because of the concerns about error. A detailed review of
these issues is found in
Brown et al , J Human Hypertens , 1997: 11:73-93. However,
the argument
that despite the presence of a systematic
error we should continue to use it because so much data has been
collected with it is weak one. We will hear more about these issues in
the future. (George Mansoor, M.D., University of
Connecticut)
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12th Annual ASH Meeting
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