Improper arm positions sometimes used during blood pressure screenings may lead to significantly overestimated readings, according to a Johns Hopkins University study published on October 7 in JAMA Internal Medicine. Even small variations can potentially result in a hypertension misdiagnosis.
Blood pressure (BP) screenings are part of nearly every routine medical visit for good reason. Nearly half of US adults deal with elevated BP. High blood pressure, or hypertension, may have minimal symptoms, if any at all. Despite this, untreated hypertension often leads to an increased risk of heart attack, stroke, and other potentially serious medical issues.
According to the American Heart Association, the best position to obtain an accurate BP reading is to have a patient seated with adequate back support with their feet flat on the floor and legs uncrossed. Medical practitioners then need to ensure the automated BP monitor’s cuff is properly sized around the patient’s arm, which is positioned at mid-heart level while supported by a desk or table. During a screening, a BP machine then averages the blood flow pumped out of the heart (systolic BP) and the pressure in arteries between heartbeats (diastolic BP). A healthy adult BP is generally accepted as at or near 120/80.
The Johns Hopkins team’s study details just how easy it is to receive misreadings. The researchers first sorted 133 adults ranging in age from 18-80 into six randomized groups, each with a different order of the three most common arm positions. Medical experts then compared the advised arm position (resting on a desk) against two of the most usual alternative positions—supported on a patient’s lap and an unsupported arm hanging at a patient’s side.
[Related: Treating high blood pressure can save 76 million lives in 30 years, WHO says.]
The spectrum of results was striking. According to the study results, an arm in the patient’s lap can raise the top number in a blood pressure reading, known as systolic pressure, by almost 4 mmHg. Meanwhile, an unsupported arm’s results can generate systolic pressure readings nearly 7 mmHg over a person’s actual measurements.
“If you are consistently measuring blood pressure with an unsupported arm, and that gives you an overestimated BP of 6.5 mmHg, that’s a potential difference between a systolic BP of 123 and 130, or 133 and 140—which is considered stage 2 hypertension,” Sherry Liu, a Johns Hopkins epidemiology research coordinator and study author, said in a statement.
While it’s a clinician’s primary responsibility to ensure a patient’s proper positioning, study senior author and vice chair for clinical research at John Hopkins University School of Medicine’s Department of Pediatrics Tammy Brady said she hopes both the study’s results and increased medical literacy will help patients “advocate for themselves” during medical examinations.
