Cuff-less Blood Pressure Measurement via Local Pulse Wave Velocity
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Solution Overview
Problem
Conventional cuff-less blood pressure measurement techniques require patient-specific and population-specific calibration, limiting their accuracy and widespread use, especially due to the need for ECG measurements and assumptions that do not hold true in arterial trees with branching and viscoelastic properties.
Innovation Solution
A system and method for cuff-less blood pressure measurement using a combination of sensors (ultrasound, pulse, and pressure sensors) to measure local pulse wave velocity and changes in arterial dimensions, eliminating the need for calibration by employing mathematical models based on established physics of arterial wall dynamics, allowing direct computation of systolic and diastolic pressures without specific calibration coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If PTT based techniques are used for cuff-less BP measurement, then device complexity and cost are reduced, but measurement accuracy deteriorates due to requirement of patient-specific calibration
Solution Approach 1:
The patent changes the measurement parameters from time-based (PTT) to velocity-based (PWV) and dimension-based (arterial distension) measurements. By measuring the actual physical parameters of pulse wave propagation velocity and arterial dimension changes, the system eliminates the need for calibration coefficients while maintaining measurement accuracy. This is achieved through direct measurement of local PWV using dual sensors and arterial dimension changes using ultrasound, rather than inferring pressure from time delays that require population-specific calibration.
2Measurement precision
If tonometry is used for accurate arterial pressure measurement, then measurement accuracy is improved, but ease of operation deteriorates due to requirement of operator skill and external pressure application
Solution Approach 1:
The patent replaces the mechanical tonometry system (requiring manual application of external pressure) with an automated optical/electronic measurement system. Dual optical sensors detect pulse waveforms without requiring manual compression, and ultrasound measures arterial dimensions automatically. The system processes signals electronically to compute local PWV and arterial compliance, eliminating the need for operator skill in applying and maintaining applanation pressure while maintaining measurement accuracy.
3Measurement precision
If ECG measurement is used to accurately measure PTT, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the ECG component from the measurement system by directly measuring pulse waveforms at two arterial locations using optical sensors. Instead of measuring PTT from ECG R-wave to peripheral pulse, the system directly measures the pulse wave propagation between two arterial sites, obtaining local PWV without requiring cardiac electrical activity measurement. This extraction of the ECG requirement simplifies the device while maintaining the ability to measure pulse wave velocity accurately.
4Ease of operation
If Moens-Korteweg equation is used for BP estimation, then measurement simplicity is improved, but measurement precision deteriorates due to invalid assumptions in arterial trees with branching and viscoelastic properties
Solution Approach 1:
The patent applies local quality by measuring parameters at a specific local site in the arterial tree where the assumptions of the Moens-Korteweg equation are more valid. By selecting a measurement location with minimal branching and wave reflections, and by measuring local PWV and local arterial dimension changes rather than global parameters, the system maintains computation simplicity while improving measurement precision. The local measurements reduce the impact of viscoelastic effects and wave reflections that violate the equation's assumptions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables quick, easy, and accurate cuff-less blood pressure measurement on superficial arteries like the carotid or femoral without requiring extensive expertise or calibration, reducing measurement errors by focusing on a small artery section and eliminating wave reflections and viscoelastic effects.
Implementation Method 1
an ultrasound transducer to measure a change in arterial dimensions over a cardiac cycle of the arterial wall
Data Source
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AI summary
Embodiments herein disclose a method and system for cuff-less blood pressure (BP) measurement of a subject. The method includes measuring, by one or more sensors, a local pulse wave velocity (PWV) and/or blood pulse waveforms of an arterial wall of the subject. Further, the method includes measuring, by an ultrasound transducer, a change in arterial dimensions over a cardiac cycle of the arterial wall of the subject. The arterial dimensions include an arterial distension and an end-diastolic diameter. Furthermore, the method includes measuring, by a controller unit, BP of the subject based on the local PWV and the change in arterial dimensions.