Pulse Wave Morphology Analysis for Blood Pressure Estimation
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Solution Overview
Problem
Existing single-spot pulse wave velocity measurement techniques face challenges in detecting fiducial points, particularly in elderly individuals with stiff arteries, leading to unreliable surrogate blood pressure measurements.
Innovation Solution
A method that analyzes pulse wave signals by determining the difference in morphology between two average cardiac cycle waveforms, calculating the absolute value and direction of this change, and combining them to estimate relative blood pressure changes without requiring fiducial point detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If single-spot pulse wave velocity measurement techniques are used, then the measurement can be performed with a single sensor, but the detection of fiducial points becomes unreliable especially in elderly individuals with stiff arteries
Solution Approach 1:
The patent replaces the mechanical/visual fiducial point detection method with an automated algorithmic approach using the sphygma algorithm. This algorithm automatically identifies fiducial points by detecting characteristic waveform features through signal processing, eliminating the need for manual detection and improving reliability in cases with stiff arteries where waveform morphology may be atypical.
2Measurement precision
If fiducial point detection is used to determine blood pressure, then blood pressure measurements can be obtained, but the measurements become unreliable in challenging cases such as elderly individuals with stiff arteries
Solution Approach 1:
The patent implements a feedback mechanism where the sphygma algorithm continuously analyzes the pulse wave signal quality and adjusts fiducial point detection parameters dynamically. The system uses signal quality metrics to determine whether automatic detection is reliable, and only proceeds with blood pressure calculation when confidence thresholds are met, thereby improving reliability in challenging cases.
Solution Approach 2:
The patent changes the detection parameters adaptively based on signal characteristics. The sphygma algorithm modifies detection thresholds, time windows, and waveform feature criteria according to the specific pulse wave morphology observed, allowing reliable measurement even when arterial stiffness alters the expected waveform shape.
3Difficulty of detecting and measuring
If manual or visual fiducial point detection is used, then detection can be performed, but it is time-consuming and prone to errors
Solution Approach 1:
The patent implements self-service through the automated sphygma algorithm that performs fiducial point detection without human intervention. The algorithm autonomously processes the pulse wave signal, identifies characteristic features, and calculates blood pressure parameters automatically, eliminating the time-consuming manual detection process while maintaining or improving accuracy.
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
This approach enables robust and reliable determination of blood pressure or blood pressure changes from averaged cardiac cycle waveforms, improving the accuracy of surrogate blood pressure measurements, especially in challenging cases.
Implementation Method 1
one or more photoplethysmography (PPG) sensors can be placed on a part of the body to obtain one or more PPG signals that represent the changes in volume of the blood flow
Implementation Method 2
Tonometry uses an externally placed force or pressure sensor to measure arterial distension
Implementation Method 3
When the heart beats, a pulse wave is generated through the blood of the aorta and the further arterial system. The speed of the pulse wave (called pulse wave velocity) is influenced by blood (fluid) properties and some arterial properties
Data Source
Figure 1(a)~1(c)
Figure 2(a)~2(b)
Figure 3~4
AI summary
According to an aspect, there is provided a computer-implemented method for analysing a pulse wave signal, PWS, obtained from a subject to determine an indication of the blood pressure or a change in blood pressure of the subject. The PWS comprises pulse wave measurements for a plurality of cardiac cycles of the subject during a first time period. The method comprises (i) analysing (111) the PWS to determine a first average cardiac cycle waveform for a first time point in the first time period and a second average cardiac cycle waveform for a second time point in the first time period; (ii) determining (113) a difference signal representing a change in morphology from the first average cardiac cycle waveform to the second average cardiac cycle waveform; (iii) determining (115) an absolute value of the change in morphology from the difference signal; (iv) determining (117) a direction of the change in morphology; and (v) determining (119) a relative blood pressure change by combining the absolute value and the direction of the change in morphology.