Bad arm position can greatly skew blood pressure readings

Common arm positions for blood pressure (BP) measurements that deviate from guidelines (arm on lap or hanging at the side) led to significant overestimation of high blood pressure, a study has found. . JAMA Internal Medicine.

Blood pressure measurement guidelines recommend supporting your arm on a desk with the midcuff at heart level.. Overestimating blood pressure can lead to unnecessary patient follow-up and overtreatment. High blood pressure affects approximately 86 million U.S. adults and older 1 billion people worldwide.

Dr. Donald Dippett, who was not involved in the study but was asked to comment on the findings, said the study said it would have far-reaching implications. Dippett is a Distinguished Professor of Health Sciences at the Columbia School of Medicine at the University of South Carolina in Columbia.

massive overestimation

In a crossover randomized trial of 133 adults, Hairong Liu, MHS, Department of Epidemiology, Johns Hopkins University Bloomberg School of Public Health in Baltimore, and colleagues found that supporting your arm on your lap lowers your systolic blood pressure (SBP). was found to be rated as high as 3.9mmHg. Diastolic blood pressure (DBP) decreased by 4.0 mm Hg. With the arm hanging at the side, measurements overestimated SBP by 6.5 mm Hg and DBP by 4.4 mm Hg, with consistent results across subgroups.

Participants were randomly assigned to perform a series of blood pressure measurements with their arms positioned in three ways: Can be supported on a desk. Support your hands on your knees. And the arms are not supported at the sides. Because blood pressure readings are variable in nature, everyone took a fourth blood pressure measurement with their arms propped up on a desk.

The average age of participants was 57 years. Forty-eight participants (36%) had SBP ≥130 mmHg. Fifty-five participants (41%) had a BMI of 30 or higher.

Two members of the research team performed all measurements. They underwent standardized training and completed a blood pressure measurement certification test administered by the study authors. Measurements were taken from 9:00 a.m. to 6:00 p.m. using a validated oscillometric blood pressure device (ProBP 2000 Digital Blood Pressure Device, Welch Allyn). Only the right arm was used unless certain conditions existed, such as an open wound.

Research design sets it apart from others

The authors write that the study design makes this study stand out. “Early studies have shown that lack of support or the arm being positioned below heart level can overestimate SBP by 4 to 23 mm Hg and DBP by 3 to 12 mm Hg.” researchers point out. However, the study's strength was its randomized crossover design, the researchers wrote. “This is in contrast to the majority of published studies, where the order of arm positions before blood pressure measurement in a sitting position was not randomized or clearly described.”

“I've dedicated my career to understanding high blood pressure,” said Dippett, who also praised the design.

Dippett said it was important to initially randomize which position patients were assigned because the first reading was often higher than subsequent readings.

“It's natural as people adapt to their environment,” he explained. He noted that blood pressure can vary within the same measurement.

Inaccurate measurements due to various reasons

Given the number of settings and the number of healthcare professionals and patients who measure blood pressure, even with training, method certification, and educational materials, incorrect measurements are common.

“I recommend measuring blood pressure in every setting possible because it's so important,” he says. “Most of the time it's done in a busy primary care setting. There's pressure. Most of the time it's just one reading. That's the healthcare environment today.”

He noted that although the study found an overestimation, different arm positions, which are not recommended in the guidelines, could lead to an underestimation of hypertension.

“I liken blood pressure measurement to a clinical test that has a clear impact on treatment. Blood pressure measurement requires precision as exacting as a blood test or radiology machine,” he said.

Dippett said more education is needed for patients as well as health care workers, as patients may be measuring their own blood pressure at home. Patients also need to know that they can request repeat measurements, the correct arm position recommended by the guidelines, and the consequences of incorrect readings, he said.

This research was supported by Resolve to Save Lives, a project funded by Gates Philanthropies Partners with support from Bloomberg Philanthropies, the Bill and Melinda Gates Foundation, and the Chan Zuckerberg Foundation.

Mr. Liu reported that he received a grant from Resolve to Save Lives outside of the submitted work. Co-author Kunihiro Matsushita, MD, PhD, reports grants from the National Institutes of Health and personal fees from Kowa Co., Ltd., RhythmX AI, and Fukuda Denshi outside the submitted work. Mr. Dippet declared that he had no relevant financial relationships. He was part of the leadership team that developed the World Health Organization guidelines on hypertension.

Marcia Frelick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune, Science News, Northwestern Magazine, and Nurse.com, and was an editor at the Chicago Sun-Times, Cincinnati Enquirer, and St. Cloud Times. Follow her on X @MLfrelick.