Oscillometric measurement of systolic and diastolic blood pressures validated in a physiologic mathematical model

Abstract

BackgroundThe oscillometric method of measuring blood pressure with an automated cuff yields valid estimates of mean pressure but questionable estimates of systolic and diastolic pressures. Existing algorithms are sensitive to differences in pulse pressure and artery stiffness. Some are closely guarded trade secrets. Accurate extraction of systolic and diastolic pressures from the envelope of cuff pressure oscillations remains an open problem in biomedical engineering.MethodsA new analysis of relevant anatomy, physiology and physics reveals the mechanisms underlying the production of cuff pressure oscillations as well as a way to extract systolic and diastolic pressures from the envelope of oscillations in any individual subject. Stiffness characteristics of the compressed artery segment can be extracted from the envelope shape to create an individualized mathematical model. The model is tested with a matrix of possible systolic and diastolic pressure values, and the minimum least squares difference between observed and predicted envelope functions indicates the best fit choices of systolic and diastolic pressure within the test matrix.ResultsThe model reproduces realistic cuff pressure oscillations. The regression procedure extracts systolic and diastolic pressures accurately in the face of varying pulse pressure and arterial stiffness. The root mean squared error in extracted systolic and diastolic pressures over a range of challenging test scenarios is 0.3 mmHg.ConclusionsA new algorithm based on physics and physiology allows accurate extraction of systolic and diastolic pressures from cuff pressure oscillations in a way that can be validated, criticized, and updated in the public domain.

The impact of blood pressure cuff location on the accuracy of noninvasive blood pressure measurements in obese patients: an observational study

“…Indeed, this remains an area of active research in the biomedical engineering community. 23 In addition to providing inaccurate BP readings, NIBP measurement systems are occasionally unable to provide any reading in obese patients. This results in prolonged time between measurements and can put patient safety at risk.…”

Haemodynamic Monitoring in the Intensive Care Unit

“…The exact point on the oscillometry envelope used to determine systolic and diastolic blood pressure remains controversial and commercially available oscillometric systems use proprietary algorithms that are not available for public scrutiny. Overall, mean arterial pressures measured by oscillometry closely approximate invasive mean arterial pressures [8].…”

Comparison of calf and brachial blood pressures in infants: Is there a difference between calf and brachial blood pressures?

“…14 Oscillometers measure BP by performing calculations from oscillations of the BP cuff. 15 The biomedical engineering department validated, inspected, and maintained the oscillometers used in this study. Chen et al 16 state that automated oscillometric devices are appropriate in measuring BPs, so long as the device is validated.…”