PPG Signal Venous Pulsatility Reduction via Weighted Averaging
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Solution Overview
Problem
Existing methods for determining physiological parameters using photoplethysmography (PPG) signals struggle to separate arterial and venous pulsatility components effectively, leading to inaccurate measurements due to the influence of venous pulsatility, which affects the estimation of blood pressure, blood oxygen saturation, and other cardiovascular parameters.
Innovation Solution
A method that involves using a PPG sensor to measure PPG signals, identifying venous-related features from pulse morphology parameters, assigning weighting factors based on these features, and computing a weighted-average PPG pulse to reduce the influence of venous pulsatility, allowing for accurate determination of physiological parameters using single-wavelength PPG signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If venous pulsatility is present in the PPG signal, then the PPG signal contains information from both arterial and venous systems, but the accuracy of physiological parameter determination deteriorates due to confounding factors
Solution Approach 1:
The patent segments the PPG signal into arterial and venous pulsatility components by analyzing waveform morphology parameters. By identifying characteristic features of each component type, the method separates the mixed signal into distinct parts that can be processed independently, resolving the contradiction between retaining full information content and achieving measurement precision.
Solution Approach 2:
The patent extracts and removes the venous pulsatility component from the PPG signal through waveform analysis and filtering techniques. By taking out the harmful venous component while preserving the arterial information, the method maintains the useful information content while eliminating the confounding factors that degrade measurement accuracy.
2Measurement precision
If source separation techniques are used to separate arterial and venous components, then component separation may be achieved, but the device complexity and computational requirements increase significantly
Solution Approach 1:
The patent employs computationally efficient waveform morphology analysis rather than complex source separation algorithms. By using relatively simple parameter extraction and filtering methods that can be implemented with minimal computational resources, the patent achieves effective component separation without requiring complex processing systems, thus resolving the contradiction between separation capability and device complexity.
3Measurement precision
If pressure is applied onto the PPG sensor device against the body, then arterial signal quality improves, but venous pulsatility increases and becomes significant
Solution Approach 1:
The patent converts the harmful effect of pressure-induced venous pulsatility into a beneficial outcome by using waveform morphology analysis to identify and remove the venous component. The pressure application still improves arterial signal quality, and the resulting venous pulsatility artifacts are systematically identified and eliminated through the separation methodology, thus resolving the contradiction between signal quality improvement and venous contamination.
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 the determination of physiological parameters with reduced venous pulsatility influence, improving the accuracy of measurements by isolating arterial pulsatility and minimizing the impact of venous contributions, applicable to various cardiovascular applications.
Implementation Method 1
The light interacts with the body mainly through scattering and absorption processes. The PPG signal corresponds to the amount of light that reaches the detector, i.e., the amount of light which is not absorbed or scattered away from the detector.
Implementation Method 2
The light interacts with the body mainly through scattering and absorption processes.
Data Source
AI summary
A method for determining a physiological parameter, including: providing a PPG sensor device configured to measure a PPG signal; measuring a PPG signal on the user, the PPG signal containing at least two cardiac cycles; identifying PPG pulses from the PPG signal, each corresponding to a cardiac cycle and having a non-modulated component and a time-modulated component; for each PPG pulse, determining at least one venous-related feature indicative of the contribution of venous pulsatility to the time-modulated component of the PPG pulse; assigning a weighting factor to each pulse including calculating the weighting factor by using a weighting function including a mathematical operator inputted with the set of at least one venous-related feature; computing a weighted-average PPG pulse by using the PPG pulses and their respective weighting factors; and determining the physiological parameter by using the weighted-average PPG pulse.