Research Shows Inaccuracy of Home BP Monitors

Seventy percent of readings from home blood pressure (BP) monitors are not accurate to within 5 mm Hg, which could cause serious health implications, according to a new study.

Researchers at the University of Alberta (Edmonton, Canada) and Mazankowski Albert Heart Institute (MAZ; Edmonton, Canada) conducted a study in 85 consecutive adults (mean 66 years of age, 58% female, 78% with hypertension) in order to examine the accuracy of their home oscillometric blood pressure (BP) devices. All patients had BP levels between 80–220 mm Hg systolic BP and 50–120 mm Hg diastolic BP, and arm circumferences between 25 and 43 cm. Pregnancy and atrial fibrillation (AF) were exclusion criteria.

Device measurements from each subject’s BP device were compared to simultaneous two-observer auscultations using a mercury sphygmomanometer, which served as reference BP measurements. The results showed that the proportion of devices with systolic or diastolic BP differences from auscultation of 5, 10, and 15 mm Hg was 69%, 29%, and 7%, respectively. Increasing arm circumference was a statistically significant predictor of higher BP. The study was published on April 17, 2017, in the American Journal of Hypertension.

“High blood pressure is the number one cause of death and disability in the world; monitoring for and treating hypertension can decrease the consequences of this disease. We need to make sure that home blood pressure readings are accurate,” said lead author Jennifer Ringrose, MD, of the University of Alberta. “What's really important is to do several blood pressure measurements and base treatment decisions on multiple readings. Taking home readings empowers patients and is helpful for clinicians to have a bigger picture, rather than just one snapshot in time.”

“Arm shape, arm size, the stiffness and age of blood vessels, and the type of blood pressure cuff are not always taken into account when a blood pressure machine is designed and validated,” added senior author professor Raj Padwal, MD, of the University of Alberta and MAZ. “No one should have drugs started or changed based on one or two measurements taken at a single point in time unless the measurements are clearly elevated.”

Oscillometric measurement devices use an electronic pressure sensor and a cuff inflated and released by an electrically operated pump and valve. Initially the cuff is inflated in excess of systolic arterial pressure, and then reduced to below diastolic pressure. Pressure variations are calculated using an algorithm that extrapolates values from the cyclic expansion and contraction of the brachial artery. While automated cuffs yield valid estimates of mean pressure, estimates of systolic and diastolic pressures are uncertain, as existing algorithms are sensitive to differences in pulse pressure and artery stiffness.

Related Links:
University of Alberta
Mazankowski Albert Heart Institute