Cuffless Blood Pressure Measurement Using Differential PPG Sensors
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Solution Overview
Problem
In non-clinical settings, existing devices struggle to provide accurate blood pressure measurements using Pulse Wave Velocity (PWV) due to the confounding effect of gravity, which is not easily neutralized by untrained users positioning the measurement points inconsistently relative to the heart.
Innovation Solution
A device with at least two PPG sensors and a microprocessor that performs Differential Pulse Wave Analysis (Differential PWA) to measure and compare pulse wave characteristics between two points on the same hand, factoring out the effects of gravity and allowing for accurate blood pressure calculation without the need for a cuff or ECG signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single PPG sensor is used to measure blood pressure at one point, then the device structure is simple, but the measurement accuracy is compromised due to gravity's effect on pulse wave velocity
Solution Approach 1:
The patent divides the measurement system into multiple PPG sensors positioned at different locations (first and second measurement points). By segmenting the measurement process across multiple points, the system can calculate pulse wave velocity and isolate gravity's effect, enabling accurate blood pressure measurement without requiring complex cuff apparatus while maintaining measurement precision.
2Ease of operation
If the measurement point is positioned below the heart level, then the device is easier to use in non-clinical settings, but gravity artificially increases pulse wave velocity and compromises measurement accuracy
Solution Approach 1:
The patent converts the harmful effect of gravity into a beneficial measurement parameter. By positioning sensors at different heights and measuring the time difference for pulse waves to travel between them, the system uses gravity's effect on pulse wave velocity to calculate blood pressure. The gravity effect that would normally compromise accuracy becomes the basis for the measurement calculation, allowing accurate readings even when the device is held in convenient non-clinical positions.
3Measurement precision
If a cuff-based blood pressure measurement system is used, then measurement accuracy is maintained, but the device complexity and ease of operation are reduced due to the need for trained administration
Solution Approach 1:
The patent replaces the mechanical cuff-based measurement system with an optical PPG sensor system. Instead of using a cuff that requires manual inflation and deflation by trained personnel, the system uses photoplethysmography sensors to optically detect pulse waves and calculate blood pressure electronically. This substitution eliminates the need for complex mechanical apparatus and trained administration while maintaining measurement accuracy through computational analysis of pulse wave characteristics.
4Measurement precision
If multiple PPG sensors are used to measure pulse waves at different points, then gravity's effect can be neutralized through differential measurement, but the device complexity increases
Solution Approach 1:
The patent combines multiple PPG sensors and their signals into a unified measurement system that processes pulse wave data from different locations simultaneously. By merging the signals from the first and second measurement points and analyzing their time differences, the system neutralizes gravity's effect and calculates accurate blood pressure. This merging approach maintains measurement precision while managing device complexity through integrated signal processing.
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 accurate blood pressure measurement by the lay user without the need for consistent positioning relative to the heart, effectively neutralizing the impact of gravity and eliminating the requirement for a cuff or trained administration.
Implementation Method 1
prior art exists describing the inclusion of a PPG (photoplethysmography) monitoring circuit in a device
Data Source
AI summary
A device and method to obtain accurate blood pressure measurement without a cuff, using a plurality of PPG sensors, in a non-clinical setting; that is, without the measurement being administered by a medically trained person. Unique and novel elements make this possible by eliminating the confounding effects of gravity in cases where the lay user is not careful to position the device at a specific or consistent elevation relative to that of the heart.