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 Current hypertension guidelines are based on blood pressure measured
with a brachial cuff, the kind typically used in doctor's offices,
and applied on the upper arm. But many devices used by patients at
home, including the increasingly available wearable monitors,
measure blood pressure at the wrist and other locations.
Dr. James E. Sharman of the University of Tasmania, in Hobart,
Australia, and his team measured blood pressure consecutively at the
upper arm and wrist in 180 middle aged and older individuals
undergoing coronary angiography.
Systolic blood pressure - the top number in a blood pressure reading
that reflects pressure within the arteries when the heart beats -
averaged 5.5 mmHg higher at the wrist than at the upper arm, the
researchers report in the journal Hypertension.
"We expected to see a lot of variation in how systolic blood
pressure changed from the upper arm to the wrist, but were
interested to see the amount of people (14 percent) with what may be
considered as very large differences; on average 20 mmHg (or more),"
Sharman said in an email. "So the magnitude of variation between
individuals was substantial."
Fewer than half of the patients had wrist systolic pressure readings
within 5 mmHg of their upper arm reading; for 46 percent the
readings differed by 5mmHg or more, including 27 percent whose
readings differed by 10mmHg or more.
One in nine participants (11 percent) had wrist systolic pressure
readings that were lower by 5 mmHg or more than their upper arm
reading.
On average, wrist systolic blood pressure was 12.9 mmHg higher than
systolic pressure measured in the aorta, the main artery delivering
blood from the heart to the rest of the body. More than half of this
difference was accounted for by the pressure difference between
aorta and upper arm measurements, and the rest was the difference
between upper arm and wrist measurements, researchers found.
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"If you do an online search, you will see there are hundreds of
devices available for sale, including many that measure blood
pressure with a cuff or a band at the wrist," Sharman said. "Our
research adds further weight to the evidence that the vast majority
of these wrist devices will not record blood pressure values that
are comparable with the clinical standard of upper arm cuff blood
pressure."
Sharman suggested that doctors and patients can use an "easy-to-use"
and comprehensive guide to measuring blood pressure at home,
published (here: https://bit.ly/2vbI0IV) in 2016 by the journal
Australian Family Physician. "The guide provides instructions on the
standardized method, as well as a diary to record blood pressure
values."
He added, "The study findings feed into a bigger story on the need
to improve the accuracy of blood pressure devices in general."
Blood pressure guidelines are based on external upper-arm cuff
measurements, noted Dr. Giacomo Pucci of the University of Perugia
and Terni University Hospital in Italy, who wasn't involved in the
study.
"Unfortunately," Pucci told Reuters Health, there is
distortion of pressure readings taken externally, compared to blood
pressure measured inside an artery. And, "we are not able, at
present, to predict the degree of such distortion in each individual
in a non-invasive way. Therefore, we should keep relying on
non-invasive brachial BP" as a surrogate for internal measurements.
"There is increasing availability on the market of devices proposing
the non-invasive assessment of central BP," he said. "Unfortunately,
many of these devices are lacking in scientific background. Further
research is needed in this field, and rigorous quality assessment of
novel devices is obviously mandatory."
SOURCE: https://bit.ly/2UImGds Hypertension, March 25, 2019.
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