Pulse Oximetry Signal Processing for Weak Perfusion Accuracy
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Solution Overview
Problem
Existing pulse oximetry technologies face challenges in accurately calculating blood oxygen saturation and pulse rate under weak perfusion and movement conditions due to interference, leading to inaccurate results and high computational complexity.
Innovation Solution
A method combining time and frequency domain technologies, involving time-to-frequency domain transformation, selection of rational frequency spectrum peaks, construction of stability coefficients, and compensation coefficients to improve the accuracy of physiological parameter calculation, specifically using venous oxygen compensation and power spectrum array methods to mitigate interference effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If time domain technology is used for blood oxygen measurement, then response speed is fast and phase information is clear, but anti-movement performance is poor due to inability to filter noise within physiological bandwidth
Solution Approach 1:
The patent replaces time domain signal processing with frequency domain signal processing. By transforming the signal to frequency domain, the system can selectively filter noise within physiological bandwidth while preserving useful signal components, thereby improving anti-movement performance while maintaining response speed through efficient frequency domain algorithms.
Solution Approach 2:
The patent changes the domain parameter from time to frequency. This parameter change enables the system to distinguish between useful physiological signals and noise based on their frequency characteristics, allowing for selective filtering and improving reliability under movement conditions while maintaining fast response through direct frequency domain calculation methods.
2Reliability
If frequency domain technology is used for blood oxygen measurement, then noise and useful signals can be separated in frequency bands, but accurate identification of fundamental frequency peak and energy ratios is difficult under interference conditions
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors frequency spectrum characteristics and adjusts its signal processing parameters accordingly. By using the identified fundamental frequency and energy ratios as feedback, the system can iteratively refine its measurements and compensate for interference, improving both identification accuracy and measurement precision under challenging conditions.
Solution Approach 2:
The patent performs preliminary identification of fundamental frequency peaks and energy ratios before final blood oxygen calculation. This preliminary action allows the system to establish reference values and filtering parameters in advance, making the subsequent measurement process more robust against interference and improving overall measurement precision.
3Measurement precision
If Masimo's R coefficient method is used to calculate arterial blood oxygen saturation, then accurate measurement under movement and weak perfusion is achieved, but computational complexity and hardware cost are high
Solution Approach 1:
The patent extracts and utilizes only the essential frequency domain characteristics (fundamental frequency peak and energy ratios) needed for blood oxygen calculation, rather than implementing the full Masimo R coefficient methodology. This extraction approach maintains measurement precision by focusing on the most critical signal features while significantly reducing computational complexity and hardware requirements.
Solution Approach 2:
The patent applies partial action by implementing a simplified version of the R coefficient method that focuses on key frequency domain parameters. Rather than computing all possible R coefficients and performing exhaustive searches, the system calculates only the necessary frequency spectrum peaks and energy ratios, achieving adequate measurement precision with reduced computational burden suitable for resource-constrained medical devices.
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 significantly enhances the accuracy of blood oxygen and pulse rate calculations under weak perfusion and movement conditions, providing clinical excellence and reducing computational demands.
Implementation Method 1
based on Lambert - Bear's law, the oxyhemoglobin (HbO2) and deoxyhemoglobin (HB) have different absorption characteristics in different light bands
Implementation Method 2
based on Lambert - Bear's law, the oxyhemoglobin (HbO2) and deoxyhemoglobin (HB) have different absorption characteristics in different light bands
Data Source
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AI summary
A method for calculating physiological parameters, comprising: selecting a section of time domain signal corresponding to at least one signal of red light and infrared light obtained by sampling, and performing a conversion from time domain to frequency domain to obtain a corresponding frequency domain signal; selecting all rational frequency spectrum peak information, calculating energy information of selected reasonable frequency spectrum peaks, and forming a frequency spectrum peak energy ratio sequence; constructing a stability coefficient according to the frequency spectrum peak energy ratio sequence, and if the stability coefficient is low, constructing a compensation coefficient by using the frequency spectrum peak energy ratio sequence; and compensating for at least one of the time domain signal and the frequency domain signal by using the compensation coefficient, and calculating based on at least one of the compensated time domain signal and the frequency domain signal to obtain the physiological parameters.