Study highlights the dangers of incorrectly sized blood pressure cuffs

Research shows that blood pressure measuring cuffs must fit well to offer accurate readings. Cuffs that are too small can result in inaccurately high blood pressure readings, while cuffs that are too large can fail to detect high blood pressure.

High blood pressure, or hypertension, affects nearly half of U.S. adults, with many unaware of their condition. Blood pressure is considered high when the systolic number (the top reading) reaches 130 mm Hg or higher, or when the diastolic number (the bottom reading) is 80 mm Hg or higher. Uncontrolled high blood pressure significantly raises the risk of heart and kidney disease, stroke, vision problems and other related conditions, and it was a primary or contributing cause of over 500,000 deaths in the U.S. in 2019.

Accurate blood pressure readings are vital for managing heart health. However, they depend on “proper patient preparation, positioning, measurement technique and individualized selection of cuff size, which should be based on the measured mid-arm circumference,” according to Dr. Tammy M. Brady, who is the medical director of the Pediatric Hypertension Program at Johns Hopkins University in Baltimore.

Blood pressure measurement cuffs must evenly squeeze the brachial artery in the arm to get an accurate reading. However, the rigidly cylindrical shape of standard blood pressure cuffs keeps them from properly hugging human arms over a certain size, leading to uneven compression on the brachial artery.

Meanwhile, applying larger cuffs often requires two hands. That makes them impractical for home blood pressure monitoring — a practice the American Heart Association recommends for healthy blood pressure management.

While clinical practice guidelines already emphasize the importance of selecting the right cuff size, previous research primarily focused on manually inflated cuffs that rely on stethoscopes to measure pressure. However, a study Brady led and published in June 2022 examined the impact of cuff size on the accuracy of today's widely used automated blood pressure monitors.

Brady and a team of researchers examined blood pressure readings from 165 U.S. adults with an average age of 55. The scientists compared the averages of three blood pressure readings from each participant, which they obtained using a regular adult-sized cuff, with those obtained using a cuff tailored to the individual's size.

The study found that using a cuff that was too small led to higher blood pressure readings in 39% of participants, while a cuff that was too large failed to detect hypertension in 22% of people. More than 40% of the participants were classified as obese, and those requiring a large or extra-large cuff displayed significantly higher readings when a regular-sized cuff was used. Systolic readings were 4.8 mm Hg higher for individuals needing a large cuff and 19.7 mm Hg higher for those requiring an extra-large cuff.

"It's important for health care professionals and the public to recognize the importance of cuff size for the clinician's office, kiosk and home blood pressure measurement," says Brady. "For example, cuff size may be even more important in communities with high prevalence of obesity since large or extra-large cuff sizes may provide more accurate blood pressure readings."