Low-cost oscillometric non-invasive blood pressure monitors: device repeatability and device differences.

Automated non-invasive blood pressure measuring devices based on the oscillometric technique are used widely for self-measurement and are often used in clinics in place of the manual, auscultatory method. Oscillometry was originally developed for monitoring purposes and there are questions over its suitability for making diagnostic measurements. This study measured the differences between automated devices, in the absence of physiological variability. We studied 19 low-cost, automated, non-invasive blood pressure devices, using a repeatable artificial arm simulator, and measured the within-device repeatability and between-device differences. We found that the devices were repeatable (mean within-device difference 1 mmHg), but between-device differences were 4.4 mmHg (systolic pressure) and 3.6 mmHg (diastolic pressure), for normal and high-normal blood pressures. Individual devices are sufficiently repeatable for clinical trend use, but differences between devices are sufficiently large that they may be misinterpreted as clinically significant.