A blood pressure reading is one
of those indicators that can determine a whole course
of treatment. It's also perhaps the simplest and commonest
test performed in a physician's office. So you'd think
medical science would have the humble sphygmomanometer
pretty much figured out.
But the most common method of taking
blood pressure is likely to give consistently high readings,
according to a study by a group of nurses from the University
of Virginia Health System.
Their findings suggest that many
patients may be getting systolic blood pressure readings
as much as 14 points higher than they should be when
the test is conducted with the patient sitting in the
wrong position. The research was presented at the national
conference of the Preventive Cardiovascular Nurses Association
in Denver in late April.
The American Heart Association
recommends that patients be tested sitting in a chair,
with both feet on the floor, and that they are allowed
to sit quietly for five minutes before testing. But
the commonest method, say the nurses, is to test people
sitting on the examination table, with their feet dangling,
and no back support. And hardly anyone waits five minutes.
"It's a physiological response,"
says Melynda Zarzyski, the study project co-ordinator
and a nurse at University of Virginia Health System.
"If you're sitting on a chair, with your back and feet
supported, you're not doing as much work as you are
supporting yourself on the exam table. Also, for a lot
of elderly people, just climbing up onto the exam table
requires some physical exertion."
TAKE
IT HIGHER
One hundred patients were tested, having been randomized
to either chair-first or table-first examinations. Each
patient was then tested in the other position, and the
readings compared. "They served as their own controls,"
says Ms Zarzyski.
The exam table readings came in
14 points higher than those taken in chairs, a very
substantial difference that could lead to a lot of extra
diagnoses of hypertension.
In all cases, the patients rested
calmly for at least five minutes before each reading.
So even the exam table readings were taken under better
conditions than many real-world blood pressure tests.
All patients were also tested on
both arms, with the arms held at heart level. "This
is the part of the guidelines that people most often
forget," says Ms Zarzyski. "The elbows should be at
heart level, but you rarely see it done."
The researchers also sought to
study the "white coat effect," often claimed to raise
patients' blood pressure, but they found it had no significant
influence on readings. However, the authors note that
many of the patients knew the technicians taking the
readings, which could have attenuated that effect.
The nurses can't prove, of course,
that most people are failing to follow the correct procedure,
but they're pretty sure. "We're just basing it on experience.
And even some of the patients told us: 'My other doctor
always does it sitting on the exam table.'"
"It's easier to do when the patient
is higher up on the exam table," she adds. "And yet
the guidelines clearly state that the chair is the proper
way. That's why we did this study. It's one of those
things where what is recommended is very different to
what you see in practice. This gave us a good reason
to change our practice."
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