According to the American Heart Association, almost 50 percent of Americans have hypertension, or high blood pressure. That's why many people measure their BP at home.

Online instructions with photos about how to take a reading are readily available, but the images connected with them often depict the wrong way to get an accurate blood pressure reading.

A recent study from researchers in Australia found that only one in seven photos online correctly depict how to take a BP reading. The photos could lead to more inaccurate BP readings being taken at home, and even in providers' offices and hospitals. Inaccurate BP readings both at home and in health care settings are a problem, according to Alta Schutte, lead author on the study.

Only one in seven online photos online correctly depicted how to take a BP reading.

The problem with an inaccurate BP reading that is either too high or too low is that it can lead to too aggressive or not aggressive enough treatment.

Photos showing the wrong way to take a blood pressure reading are especially misleading. “Because people tend to remember images better than words, a phenomenon known as the picture-superiority effect, inaccurate photos could have serious public health consequences,” Schutte said in a statement.

The researchers evaluated more than 1,000 images from 11 stock photo sites such as Flickr and iStock. Sixty-three percent of the photos depicted BP measurement in a provider's office, hospital or clinic and 37 percent showed BP measurement in a home setting. BP was measured by a provider in 73 percent of the photos, by patients in 24 percent and by someone else in three percent of the photos.

The American Heart Association offers these tips for accurate BP measurement at home, including:

  • Sit upright with your back supported.
  • Your forearm should rest on a flat surface or table at heart level.
  • Use an electronic or battery-operated device.
  • Keep your feet flat on the floor.
  • Don't talk.
  • Don't cross your legs.
  • Place the cuff over your bare arm.

Schutte, a professor of cardiovascular medicine at the University of New South Wales Sydney, and her team found the person's back was unsupported in 73 percent of the photos; in 55 percent of the photos, the patient's forearm was not resting on a flat surface or table; in 52 percent, a manual BP measuring device or sphygmomanometer was used rather than an electronic or battery-operated device.

In over a third of the photos, the patient's feet were not flat on the floor; in nearly 20 percent of them, the patient's mid-arm was not at heart level; and in 18 percent, the patient was talking or laughing. The patient's legs were crossed in 13 percent of the photos and in 12 percent, the blood pressure cuff had been placed over the patient's clothing. In five percent of the photos, the patient was not sitting.

People's backs were unsupported in 73 percent of the photos. In 55 percent of the photos, the patient's forearm was not resting on a flat surface or table at heart level.

Measurement techniques varied according to where the reading was taken and the person taking it. Thirty-five percent of the photos of BP measurement by a patient at home showed it being done correctly, compared to eight percent of photos of BP measurement by a provider in a clinic. Only 13 percent of the pictures showed blood pressure being taken correctly by other people.

It's worth noting that these are the findings are for photographic representations of blood pressure being taken. They may not accurately represent what actually happens in a home or clinic. The results do make clear that patients should not just mimic what they see in online photos and should be aware of the right way to get an accurate BP reading — whether they are taking it themselves or having it done in a healthcare setting.

The researchers even found photos on the websites of major universities and health care organizations that depicted the wrong way to measure BP. They encourage these universities, organizations, stock photo agencies and web developers to look again at their photos of blood pressure being taken to be sure they show the correct way to measure BP.

The study is published in Hypertension.