Wrong size blood pressure cuffs produce ‘strikingly inaccurate’ readings

Many people with high blood pressure own an automated device to keep track of their numbers. The only problem with that, a new study finds, is those numbers could be “strikingly inaccurate.”

Just as you need the right dosage of medicine for the best results, you need the right size blood pressure cuff to get the right numbers.

Using a “regular,” or one-size-fits-all, arm cuff led to “inaccurate BP readings regardless of arm size, but especially in individuals with larger arms,” Tammy M. Brady, MD, PhD, of Johns Hopkins University School of Medicine in Baltimore, and co-authors reported in JAMA Internal Medicine.

For people with smaller arms, the researchers found, the wrong size cuff resulted in a 3.6-mm Hg lower systolic reading.

Systolic pressure — the top number of a reading — is the maximum pressure the heart exerts while beating. Diastolic pressure — the bottom number — is the amount of pressure in the arteries between beats.

For individuals who needed a larger cuff, using a regular size one registered a 4.8-mm Hg and 19.5-mm Hg higher systolic reading.

Diastolic results were also off, the researchers found.

“The discrepancies also consistently appeared in readings of diastolic BP for adults who had cuffs that were one size too large, one size too small, and two sizes too small, with differences of -1.3, 1.8, and 7.4 mm Hg, respectively,” MedPage Today wrote.

The randomized crossover study of 195 adults with “a wide range of mid-arm circumferences” took place March 16 through October 25, 2021, in Baltimore.

Each participants had four sets of triplicate blood pressure measurements taken. The first three sets used an appropriate, too-small or too-large cuff in random order; the fourth set was always completed with an appropriate BP cuff.

“In this randomized crossover trial, miscuffing resulted in strikingly inaccurate BP measurements,” the researchers wrote. “This is particularly concerning for settings where 1 regular BP cuff size is routinely used in all individuals, regardless of arm size. A renewed emphasis on individualized BP cuff selection is warranted.”