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When it comes to hi-tech methods of measuring blood
pressure, newer may not be better.
Some 50 million
Americans suffer from high blood pressure, or hypertension,
a major risk factor for cardiovascular disease.
For more than a century, the mercury gravity (blood
pressure measurement device) has been the gold standard for indirect measurement
of blood pressure.
However, in recent years modern, hi-tech devices
have begun to replace the mercury manometer. These include electronic
instruments such as home pressure monitoring devices, or drugstore automated
pressure-testing setups.
Non-mercury measuring devices are common in clinics
and physician's offices -- they have round faces attached to a cuff, which
is inflated while the doctor listens to the pulse with a stethoscope.
These new devices are portable and simple to use, making them ideal in
certain situations, especially for home monitoring.
However, a crucial issue
with the newer instruments is their reliability.
In order to insure reliability, instruments must
be calibrated -- in the same way that a scale is "zeroed" before
you step on it to check your weight.
Unless the instrument
is properly calibrated, the reading it gives cannot be accurate.
The American Heart Association's Council for High
Blood Pressure Research, caution that the new electronic and non-mercury
blood pressure devices are seldom calibrated regularly
in hospital or office settings.
Most manufacturers of these instruments recommend
calibration against a mercury manometer every six months. However, few
hospitals and clinics have a regular program of evaluation and calibration.
Indeed, most of these devices must be returned to the manufacturer for
calibration.
Justification for replacement of the mercury manometers
has focused primarily on concerns over the safety of
the mercury used in the devices. Nevertheless, modern mercury
blood pressure measurement devices are available in models that prevent
accidental spillage of mercury, which essentially eliminates
the concern for this rare occurrence.
The researchers warn that decisions by hospitals
and clinics to replace the tried-and-true mercury-gravity based instruments
with the newer non-mercury or electronic monitors have been made without
proper consideration of the health risks involved in using less accurate
devices to measure blood pressure in these settings.
At present the world
primary standard for pressure measurement is a mercury manometer.
Hypertension: Journal
of the American Heart Association, February 16, 2001
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