A new study from Johns Hopkins Medicine has found that the way your arm is positioned during a blood pressure check can seriously affect the results.
In fact, some common positions may give numbers that are too high, which could lead to a wrong diagnosis of high blood pressure.
The researchers tested three ways of positioning the arm: resting on a desk, resting on a lap, and hanging unsupported at the side. They discovered that when the arm was resting on the lap, the top number (systolic pressure) was almost 4 mmHg higher than it should be. When the arm was left hanging by the side, the top number was nearly 7 mmHg too high.
This may not sound like a big deal, but it is. According to the American Heart Association, a systolic reading of 130 is considered stage 2 hypertension. So, an incorrect reading due to poor arm positioning could mean someone is told they have high blood pressure when they actually don’t.
Blood pressure checks are a key part of preventing heart attacks and strokes. Since high blood pressure often has no symptoms, regular checks are important. Most people can manage it with lifestyle changes, like eating healthier and exercising, or by taking medicine.
The proper way to measure blood pressure, according to experts, is to have your back supported, your feet flat on the floor, and your arm resting on a desk or table at the same height as your heart.
But in many clinics, this isn’t how it’s done. Often, people sit on an exam table with no support, or they hold their arm in their lap. Sometimes, a nurse or doctor might hold the arm instead. These less-than-ideal positions can throw off the reading.
To study this issue, the Johns Hopkins team worked with 133 adults from different backgrounds. They tested blood pressure in all three arm positions during one visit.
Before each test, participants walked around for two minutes, like they would before a typical doctor’s appointment. Then they rested and had their blood pressure measured three times in a row using a digital device.
The results were clear. The desk-supported position gave the most accurate readings. The lap and hanging-arm positions gave readings that were 4 to 7 mmHg higher for the top number and about 4 mmHg higher for the bottom number. These differences are enough to mislabel people as having high blood pressure.
This shows that following the correct steps is very important when measuring blood pressure. The study used digital BP machines, so the results might not apply to other kinds of devices.
Still, the takeaway is important: healthcare workers must follow the guidelines, and patients should feel comfortable speaking up if their blood pressure is being taken the wrong way.
If you’re checking your blood pressure at home, make sure you’re doing it right—sit properly and support your arm at heart level. A small mistake in arm position could lead to a big mistake in your health records.
The study is published in Cerebral Circulation – Cognition and Behavior.
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