Pulse Wave Extraction From Electrical Signals Using ECG Timing
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Solution Overview
Problem
Existing methods for monitoring heart rate and cardiovascular parameters, such as photoplethysmography (PPG) and bioelectrical impedance analysis (BIA), suffer from artifacts due to subject movement, discomfort, and inability to accurately quantify parameters like pulse transit time and blood pressure, necessitating an improved method and system for pulse wave signal extraction.
Innovation Solution
A method utilizing electrocardiographic (ECG) and electrical signals to determine a pulse wave signal by identifying specific points in the ECG signal and subtracting a cleaned electrical signal, allowing for continuous monitoring of cardiovascular parameters, particularly from major vessels in the trunk, using a measurement device that can be fixedly attached to the subject.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If photoplethysmography (PPG) is used to monitor cardiovascular parameters, then the method is easy to use and accessible for long term measurements, but artefacts arise in the pulse wave signal due to movements or varying position
Solution Approach 1:
The patent uses an intermediary approach by combining PPG signal processing with ECG-derived timing information. The system introduces a mediator (ECG R-wave detection) that provides reliable temporal markers to synchronize and clean the PPG pulse wave signal, thereby maintaining ease of use while improving signal accuracy and reducing artefacts from movement or position changes
2Ease of operation
If photoplethysmography (PPG) is used to monitor cardiovascular parameters, then the sensor is easily dislodged from the patient, but this increases the difficulty of continuous monitoring
Solution Approach 1:
The system implements feedback mechanisms to detect when the sensor is dislodged or signal quality deteriorates. By continuously monitoring the pulse wave signal characteristics and comparing them against expected patterns, the system can identify sensor displacement and trigger alerts or adjust measurement parameters, thereby maintaining continuous monitoring capability despite the sensor being easily dislodged
3Ease of operation
If photoplethysmography (PPG) is used to monitor cardiovascular parameters, then the sensor may increase discomfort, but this leads to pain and sleep problems
Solution Approach 1:
The patent extracts and utilizes only the essential information from the PPG signal (pulse wave morphology and timing) while discarding the need for continuous sensor contact during sleep. By deriving cardiovascular parameters from the pulse wave characteristics and ECG timing data, the system can provide monitoring during sleep without requiring the sensor to remain in contact with the patient, thereby eliminating discomfort and pain associated with prolonged sensor attachment
4Ease of operation
If photoplethysmography (PPG) is used to monitor cardiovascular parameters, then the pulse wave signal is not quantified, but this prevents accurate determination of parameters like pulse transit time
Solution Approach 1:
The system performs preliminary actions by pre-processing the PPG signal to identify and mark key features (dicrotic notch, peak, foot point) and pre-calculating timing parameters relative to ECG R-waves. This preliminary characterization of the pulse wave signal enables subsequent accurate quantification of parameters such as pulse transit time, pulse wave velocity, and other derived cardiovascular parameters, transforming the unquantified signal into a basis for precise measurements
5Adaptability or versatility
If bioelectrical impedance analysis (BIA) is used to measure cardiovascular parameters, then it is possible to measure cardiac output and stroke volume, but the measurements are confounded by high technical variability and spontaneous biological variability
Solution Approach 1:
The patent replaces the electrical impedance measurement approach with an optical-based PPG system that uses light absorption characteristics of blood. This substitution eliminates the confounding effects of technical variability and spontaneous biological variability inherent in BIA, while maintaining the capability to measure cardiovascular parameters such as cardiac output, stroke volume, and pulse wave characteristics. The optical method provides more reliable and reproducible measurements
6Measurement precision
If additional equipment is necessary to retrieve cardiovascular parameters based on measured electrical signal, then the device complexity increases, but this is required for accurate parameter extraction
Solution Approach 1:
The patent merges the PPG optical sensing system with ECG electrical signal processing into a unified monitoring platform. By combining these two complementary measurement techniques and processing them through integrated algorithms, the system achieves accurate extraction of multiple cardiovascular parameters (pulse wave velocity, arterial stiffness, cardiac output, stroke volume) without requiring separate dedicated equipment for each parameter, thereby reducing overall device complexity while maintaining measurement precision
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 and continuous monitoring of cardiovascular parameters, reducing artifacts and discomfort, while providing information on physiological changes and respiration phases, and allowing for the determination of parameters like blood pressure and pulse transit time.
Implementation Method 1
One method is photoplethysmography (PPG), in which a sensor is attached to a finger or an earlobe to obtain information indicative of volume changes in the arteries
Implementation Method 2
One way of monitoring some cardiovascular parameters is to use bioelectrical impedance analysis (BIA) in which a weak current is sent through tissue and the voltage is measured, thereby allowing the corresponding impedance, i.e. the bio impedance, to be calculated
Data Source
AI summary
The present disclosure relates to a method and a system for determining a pulse wave signal (PWS) of a subject. The method (M100) comprises: a step M101) of providing an electrocardiographic (ECG) signal (S2) of a subject (200); a step (M102) of providing an electrical signal (S3) of the subject (200); a step (M103) of determining a collection of points of interest (S2x) in the ECG signal (S2); a step (M104) of determining a collection of specific points (S3x1, S3x2) using the collection of points of interest (S2x); a step (M105) of determining a cleaned electrical signal (S4) based on the collection of specific points (S3x1, S3x2); a step (M106) of determining a pulse wave signal (PWS) by subtracting the cleaned electrical signal (S4) from the electrical signal (S3).