Pulse Oximeter Signal Processing for Noise Reduction
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Solution Overview
Problem
Current signal processing methods in pulse oximeters are inefficient in separating noise from body movement, leading to inaccurate measurement of oxygen saturation and pulse rate, especially when noise amplitude is significant compared to the pulse wave signal.
Innovation Solution
A method involving light emitters and receivers to generate pulse wave signals, separating these signals into amplitude signals associated with specific frequencies, calculating ratios between them, and selecting the appropriate signals to calculate oxygen saturation with reduced noise interference using FFT processing or digital filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency analysis methods are used to separate noise from pulse wave signals, then measurement accuracy is improved, but computational load increases significantly
Solution Approach 1:
The patent segments the pulse wave signal into multiple frequency bands using band-pass filters, then processes each frequency band separately to extract pulse wave components. This segmentation approach reduces computational complexity compared to processing the entire signal spectrum at once, while maintaining measurement accuracy by focusing on relevant frequency ranges where pulse wave information is concentrated.
2Measurement precision
If regression line calculation is performed using large amounts of sampling data, then oxygen saturation calculation accuracy is improved, but processing time increases
Solution Approach 1:
The patent performs preliminary signal processing by separating the pulse wave signal from noise components before regression line calculation. By pre-processing the signal to extract clean pulse wave data and remove noise, the subsequent regression calculation requires fewer data points and less computation time while maintaining or improving accuracy compared to using raw, unprocessed sampling data.
3Reliability
If signal processing is performed to remove body movement noise, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical or hardware-based noise rejection mechanisms with software-based signal processing algorithms. By using digital signal processing techniques including frequency analysis and regression calculation, the system achieves reliable measurements during body movement without requiring additional mechanical components or complex hardware modifications, thus improving reliability while controlling device complexity.
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 reduces computational load and enhances accuracy in measuring oxygen saturation and pulse rate even under conditions of significant noise from body movement, improving precision and processing speed.
Implementation Method 1
The principle of the pulse photometer is to determine the concentration of an object material from a pulse wave signal obtained by causing a living tissue to transmit or reflect light beams, which have a plurality of wavelengths respectively correspond to different absorbances of the object material
Implementation Method 2
a separator, operable to separate each of the pulse wave signals into a plurality of amplitude signals each of which is associated with one frequency
Data Source
AI summary
In an apparatus for measuring an oxygen saturation in blood, a plurality of light emitters irradiate a living tissue with a plurality of light beams having different wavelengths. A light receiver receives the light beams reflected from or transmitted through the living tissue to generate pulse wave signals in accordance with pulsations of the blood in the living tissue. A separator separates each of the pulse wave signals into a plurality of amplitude signals each of which is associated with one frequency, thereby generating pairs of amplitude signals each of which is associated with one of a plurality of frequencies. A first processor calculates a ratio between the amplitude signals in each of the pairs of the amplitude signals. A selector selects one of the pairs of the amplitude signals. A second processor calculates the oxygen saturation from the ratio of the selected pair of the amplitude signals.