PPG Signal Motion Artifact Removal via Adaptive Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing wearable and mobile photoplethysmographic (PPG) biosensors face challenges in enhancing signal quality due to motion artifacts, which degrade the integrity of PPG signals and lead to inaccurate readings, increasing the workload and cost of care.
Innovation Solution
A multi-stage adaptive method that identifies, quantifies, and removes motion-induced errors in red and infrared PPG signals, efficiently separating arterial and venous pulsations, and using a synthetic noise reference to extract heart rate and oxygen saturation levels, thereby producing clean, artifact-free signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive noise cancellation using accelerometers is used to reduce motion artifact, then motion-induced noise is reduced, but device complexity and computational load increase
Solution Approach 1:
The patent extracts and removes motion artifact noise from PPG signals using adaptive filtering techniques. The system separates the desired physiological signal from motion-induced noise by identifying and eliminating the noise component, thereby improving signal quality without requiring additional hardware sensors beyond the basic PPG sensor.
Solution Approach 2:
The patent introduces an adaptive filter as an intermediary processing stage between the PPG sensor and the signal output. This filter acts as a mediator that processes the raw signal, removing motion artifacts while preserving the physiological information, thus improving reliability without directly adding complex hardware.
2Reliability
If reflectance PPG sensor is added as reference signal to reduce motion artifact, then motion artifact reduction is achieved, but device complexity increases
Solution Approach 1:
The patent makes the single PPG sensor perform multiple functions by using it both for physiological measurement and for generating the reference signal for noise cancellation. The same sensor data is utilized dually: for extracting physiological parameters and for creating the reference input for the adaptive filter, thereby avoiding the need for additional sensors.
Solution Approach 2:
The PPG sensor serves itself by generating its own reference signal for noise cancellation. The raw PPG signal, which contains both physiological information and motion artifacts, is fed into the adaptive filter to create a noise reference that is then used to cancel the motion artifacts, eliminating the need for separate reference sensors.
3Reliability
If Fast Fourier Transform and Singular Value Decomposition are used to generate reference noise signals, then motion artifact reduction is achieved, but computational intensity increases
Solution Approach 1:
The patent applies adaptive filtering with a moderate filter order that provides sufficient noise cancellation without over-processing the signal. By using a filter order that is adequate but not excessive, the system achieves acceptable signal quality while minimizing computational energy consumption, avoiding the heavy computational burden of more complex decomposition methods.
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 effectively enhances signal quality by removing tissue and venous blood noise during motion, allowing for accurate extraction of heart rate and oxygen saturation, even in the presence of motion artifacts, thereby improving the reliability of PPG signals.
Implementation Method 1
Photoplethysmography is a non-invasive measurement of the blood flow at the surface of the skin of a human by using two-wavelength lights, such as red (R) and infrared (IR) lights, to generate photoplethysmographic (PPG) signals
Implementation Method 2
The output of the adaptive filter is an estimate of the noise in the PPG signal. The estimate of the noise is subtracted from the PPG signal to reduce the effect of the noise and generate an enhanced PPG signal.
Data Source
AI summary
A system and method for signal processing to remove unwanted noise components including: (i) wavelength-independent motion artifacts such as tissue, bone and skin effects, and (ii) wavelength-dependent motion artifact/noise components such as venous blood pulsation and movement due to various sources including muscle pump, respiratory pump and physical perturbation. Disclosed are methods, analytics, and their uses for reliable perfusion monitoring, arterial oxygen saturation monitoring, heart rate monitoring during daily activities and in hospital settings and for extraction of physiological parameters such as respiration information, hemodynamic parameters, venous capacity, and fluid responsiveness. The system and methods disclosed are extendable to include monitoring platforms for perfusion, hypoxia, arrhythmia detection, airway obstruction detection and sleep disorders including apnea.