Filter Scaling for PPG Signal Artifacts in Physiological Monitoring
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Solution Overview
Problem
Photoplethysmography (PPG) systems face filter artifacts due to simultaneous adjustments in light intensity and gain settings, which negatively affect the determination of physiological parameters like heart rate and oxygen saturation.
Innovation Solution
A physiological monitoring system that scales filter history and filter coefficients based on adjustments to light source power and gain settings to eliminate or attenuate these artifacts, using a processor to calculate a scaling factor and apply it to filter histories and coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If light intensity and gain settings are adjusted frequently to save power and improve signal-to-noise ratio, then energy efficiency and measurement quality are improved, but filter artifacts are introduced that degrade physiological parameter determination accuracy
Solution Approach 1:
The system performs preliminary scaling of filter coefficients and filter history data before signal filtering operations when gain or light intensity changes are detected. This preliminary action ensures that the filtering process operates on consistently scaled data, preventing the introduction of filter artifacts while maintaining the ability to frequently adjust gain and light intensity for power savings and signal quality.
2Measurement precision
If filter history and coefficients are scaled based on gain and light intensity adjustments, then filter artifacts are eliminated improving measurement accuracy, but computational complexity increases
Solution Approach 1:
The system applies scaling operations locally only to the filter history data and filter coefficients that are directly affected by gain or light intensity changes, rather than processing the entire signal stream. This localized approach eliminates filter artifacts while minimizing the additional computational burden, as only specific portions of the data require scaling adjustments.
3Use of energy by moving object
If dynamic adjustments to light emitters are made within a cardiac cycle to save power, then energy consumption is reduced, but filter artifacts are introduced that affect signal integrity
Solution Approach 1:
The system dynamically changes the scaling parameter based on the detected gain level and light intensity settings. When power-saving adjustments are made to light emitters within a cardiac cycle, the scaling parameter is updated accordingly, allowing the filter to adapt to the changed conditions and eliminate artifacts while maintaining the energy-efficient dynamic operation.
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 improves the accuracy of physiological parameter determination by reducing filter artifacts, leading to more reliable measurements of heart rate, oxygen saturation, and other parameters.
Implementation Method 1
a sensor configured to detect light attenuated by a subject and generate a photoplethysmography (PPG) signal
Data Source
AI summary
Systems and methods are provided for operating a physiological monitoring system for determining a physiological parameter of a subject. The physiological system may comprise a pulse oximetry sensor for generating a photoplethysmography (PPG) signal and a gain controller for setting a light detection level. The system may also comprise a filter for filtering the PPG signal. The filter may comprise at least one of filter history and filter coefficients. The system may comprise a processor for determining the power level of light sources of the pulse oximetry sensor and the light detection gain level, and calculating a scaling factor based on the determined power level and the light detection gain level. The processor may also be used for scaling one or more of the filter history and filter coefficients based on the scaling factor, and determining at least one physiological parameter based on the filtered PPG signal.