Novel methods of testing and calibration of oscillometric blood pressure monitors

Abstract

We present a robust method for testing and calibrating the performance of oscillometric non-invasive blood pressure (NIBP) monitors, using an industry standard NIBP simulator to determine the characteristic ratios used, and to explore differences between different devices. Assuming that classical auscultatory sphygmomanometry provides the best approximation to intra-arterial pressure, the results obtained from oscillometric measurements for a range of characteristic ratios are compared against a modified auscultatory method to determine an optimum characteristic ratio, Rs for systolic blood pressure (SBP), which was found to be 0.565. We demonstrate that whilst three Chinese manufactured NIBP monitors we tested used the conventional maximum amplitude algorithm (MAA) with characteristic ratios Rs = 0.4624±0.0303 (Mean±SD) and Rd = 0.6275±0.0222, another three devices manufactured in Germany and Japan either do not implement this standard protocol or used different characteristic ratios. Using a reference database of 304 records from 102 patients, containing both the Korotkoff sounds and the oscillometric waveforms, we showed that none of the devices tested used the optimal value of 0.565 for the characteristic ratio Rs, and as a result, three of the devices tested would underestimate systolic pressure by an average of 4.8mmHg, and three would overestimate the systolic pressure by an average of 6.2 mmHg.

Effects of a health education intervention on hypertension-related knowledge, prevention and self-care practices in Nigerian retirees: a quasi-experimental study

“…A lack of the necessary skills is another potential factor that may explain this finding. For instance, evidence suggests that effective HBPM requires the hearing acuity of the operator, the sensitivity of the stethoscope, positioning of the cuff bladder center is directly above the brachial artery, and validation of the automatic electronic BP monitors before use [74, 75]. Although, we provided demonstrations on self-BP measurements during the intervention, it is possible that some retirees did not acquire enough skills in the short-term.…”

The Effect of Expanded Measurement Uncertainty on the Outcome of Blood Pressure Measurement Validation Protocol Based on the ISO81060-2:2018 Guideline - A Monte Carlo Simulation Approach

“…In the next section of the study, the systolic BP values measured by a reference sphygmomanometer and by a device under test (n=304) from a shared database [13] were modeled by Monte Carlo simulation and were resampled (m=1000) with and without expanding the sampled values with the measurement uncertainty under 95% coverage probability.…”

Automated ‘oscillometric’ blood pressure measuring devices: how they work and what they measure

“…• For the oscillometric method, systolic and diastolic BPs are estimated typically by characteristic ratios of an envelope fitted to the 'oscillations' with systolic BP at about 50% (range 45-73%) of maximal amplitude on the rising phase of the waveform envelope and with diastolic BP at about 70% (range 69-83%) of maximal amplitude on the falling phase of the waveform envelope [45,50] • Mean arterial pressure is estimated on the oscillometric waveform envelope at the point of maximal amplitude • Digital readouts are provided for systolic and diastolic BPs and occasionally for mean arterial pressure should be regularly inspected for any damage, breaks or tears to the device cuff and tubing, as their integrity is essential to device accuracy. There is now a large global marketplace for automated BPMDs (worth USD 1.5 billion in 2020, projected to reach USD 3.2 billion by 2028) [24] with hundreds of companies manufacturing more than 3500 different models of automated BPMDs, many of which are without evidence of having passed validation testing [25][26][27][28][29].…”

“…• Algorithms for device functionality and those used to estimate mean arterial pressure, systolic and diastolic BP are closely guarded trade secrets that are not shared publicly nor independently scrutinised [45] a Descriptions provided are generally applicable to automated BPMDs but differences exist between manufacturers and devices.…”