Cuffless Blood Pressure Measurement via PPG Signal Analysis

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current automatic noninvasive blood pressure measurement methods, such as oscillometry, lack accuracy and reliability for long-term monitoring, and cuff-based methods are inconvenient for frequent use, limiting their application in clinical settings like 24 h ambulatory monitoring and telemedicine.

Innovation Solution

A cuffless method using photoplethysmographic (PPG) signals from two sensors, one distal to the cuff and another more proximal, to measure systolic blood pressure (SBP) by analyzing amplitude-to-baseline ratio (AM/BL) and pulse transit time (PTT) parameters, with initial calibration by an accurate cuff-based method to enhance accuracy and convenience.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If oscillometry is used for automatic NIBP measurement, then the measurement process is automated and convenient, but the accuracy is low with mean difference exceeding 5 mmHg and standard deviation exceeding 8 mmHg

Engineering Contradiction:

Improveautomatic measurement convenienceVSAvoidblood pressure measurement accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical oscillometry system with an optical PPG-based system. Instead of using a pressure sensor to detect oscillations in the arterial wall, the invention uses photodetectors to measure light absorption changes in the blood, substituting mechanical detection with optical detection to achieve both automation and improved accuracy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the measurement parameter from mechanical oscillation amplitude to optical absorbance changes. By measuring the changes in light absorption (PPG signal) rather than mechanical vibrations, the system achieves higher measurement precision while maintaining automatic operation

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If cuff-based PPG method is used for calibration, then measurement accuracy improves to standard deviation of 4-5 mmHg, but the process requires cuff inflation and deflation which is inconvenient for frequent use

Engineering Contradiction:

Improveblood pressure measurement accuracyVSAvoidmeasurement convenience

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent extracts the essential measurement function from the cuff-based system. Instead of requiring cuff inflation and deflation, the invention uses a cuffless PPG sensor that continuously measures blood pressure through optical detection, separating the measurement function from the constraining cuff

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent enables continuous blood pressure monitoring by removing the intermittent cuff inflation/deflation cycle. The PPG sensor continuously measures optical parameters without requiring cuff application, allowing uninterrupted measurement during 24-hour ambulatory monitoring and telemedicine

Inventive Principle:

Principle #20Continuity of useful action

3Ease of operation

If cuffless PPG monitoring is implemented, then convenience is improved by eliminating cuff inflation, but initial calibration requires accurate cuff-based measurement which limits continuous monitoring capability

Engineering Contradiction:

Improvecuffless measurement convenienceVSAvoidcontinuous monitoring reliability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent performs preliminary calibration using a cuff-based method to establish baseline PPG parameters, then uses these calibrated parameters for continuous cuffless monitoring. This preliminary action enables the system to transition from accurate but inconvenient cuff-based measurement to convenient continuous monitoring

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by continuously monitoring PPG parameters and comparing them against calibrated reference values. The system uses the calibrated baseline to provide ongoing feedback on blood pressure changes, ensuring continuous monitoring reliability while maintaining cuffless convenience

Inventive Principle:

Principle #23Feedback

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

The method provides improved accuracy in SBP measurement with a mean root mean square error (RMSE) of 9.5 mmHg, closer to the standards required for automatic cuff-based meters, and reduces the inconvenience of cuff inflation and deflation, making it suitable for continuous monitoring.

Implementation Method 1

photoplethysmographic (PPG) sensor distal to a pressure cuff, which is inflated to above SBP value and then slowly deflated. The PPG signal disappears for cuff pressure above SBP value and reappears when the cuff pressure decreases to below SBP value

Methodology Applied

Scientific EffectPhotoplethysmography: Photoelectric Effect

Data Source

PatentUS7544168B2Measuring systolic blood pressure by photoplethysmography

Publication Date: 2009.06.09 JERUSALEM COLLEGE OF TECHNOLOGY

AI summary

The present invention relates to cuff-based method for the measurement of systolic blood pressure (SBP) by measuring photoplethysmographic (PPG) signals in peripheral blood vessels distal to the cuff and to a method for cuffless measurement of SBP by analyzing PPG signals in peripheral blood vessels, after suitable calibration by the cuff-based PPG method for the measurement of SBP.