How Accurate Are Blood Pressure Machine Readings?
CBS Pittsburgh (con't)
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PITTSBURGH (KDKA) — We’ve all seen them; maybe you use them, those blood pressure machines in drugs stores or supermarkets. But how accurate are the readings they give you?
Well, wonder no more! KDKA’s David Highfield and Dr. Maria Simbra recently went to different machines across our area and put them to the test.
Together, they took a look at 10 different machines.
No one knew we were coming in advance, and we tried to make it as scientific as we could.
We started by making sure that David’s blood pressure was the same in both arms.
Here’s why that’s important; in our test, David put one arm in the machines, while Dr. Maria took his blood pressure at the exact same time on the other.
From Ross Township to North Fayette and West View to Downtown, we tested machines in Giant Eagle, Walmart, Kmart, CVS and Rite Aid – 10 different ones in all.
We wanted to know, what you do, when you sit down at a machine, can you trust the reading you get?
All of the machines were easy to use with simple instructions. All except for one, it squeezes your forearm rather than your upper arm, and repeatedly gave David no result at all.
Once he did get a reading, it was time to compare what the 10 machines found to what Dr. Maria recorded. Many of the results were actually pretty close.
“For the most part, the readings were very close,” said Dr. Maria. “I mean we were only off by a few points.”
However, two of them were off by more than 15 points.
The reading that was furthest off was 155 over 98 compared to Dr. Maria’s result of 132 over 90. It did, however, get better when we tried a second time.
Dr. Maria says one concern with these machines is that one size doesn’t fit all.
“Cuff size has to match appropriately,” she says. “In one in three people, the cuff size is actually too small.”
That is why some people don’t bother with them.
Another question is how often the machines are calibrated. Turns out, most machines aren’t owned by the stores they’re in, and in our area, it’s generally one of two companies that maintain them.
“We visit the units twice a year on a routine basis to do quality control and calibration,” says Doug Wilson is from Publicom.
In addition, he says they come out anytime a problem is reported.
And one more thing, there’s something you have to remember before you get your pressure taken.
“Ideally, to have your blood pressure, you should be sitting and calm for a least five minutes,” said Dr. Maria.
During our test, David didn’t do that. He and Dr. Maria kept moving in and out of stores, which may account for some of his higher than normal readings, from both the machines and Dr. Maria.
David: “You think I’m okay?”
Dr. Maria: “I think you’re okay.”
David: “Well, the other interesting thing is when we weren’t rushing and we didn’t have a photographer, your blood pressure came down and that was very reassuring.”
A spokesperson from American Heart association in Pittsburgh says the accuracy of these machines has improved over the years, but says they should never be used instead of a doctor.
There were warnings on the machines that said exactly that.
“We’re not here to replace a doctor,” said Wilson. “We’re not here to diagnose anybody. It’s just strictly awareness, that’s it.”
So, the bottom line, according to Dr. Maria: “I think they’re useful for this reason – they’re better than nothing. If you’re going to the drug store, and you actually check your blood pressure, you’re thinking about your blood pressure and that is a good, healthy behavior.”
She says it should not be your only blood pressure check, and that you really need a series of readings to know what’s going on.
She also says another option is an at-home blood pressure monitor. They make a variety to types. And what’s nice with these is for those of you who don’t have a Dr. Maria to go around with you; you can take them to your doctor’s office and compare them with your doctor’s readings.