Blood Oxygen Calculation Using Cross-Signal PPG Peak Alignment
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Solution Overview
Problem
Ear-hook oximeters face challenges in accurately measuring blood oxygen saturation due to poor fitting on the user's ear structure and inconsistent signal contact, leading to poor quality PPG signals and misjudged physiological measurements.
Innovation Solution
A method for calculating blood oxygen saturation by defining the extreme value point of a non-red light signal as the extreme value point of a red light signal, filtering the red light signal to eliminate outliers, and using the AC and DC values of red and infrared light signals to calculate blood oxygen saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ear-hook oximeter is used to measure blood oxygen saturation, then the measurement can be obtained, but the accuracy deteriorates due to poor fitting and inconsistent signal contact
Solution Approach 1:
The patent applies preliminary action by pre-aligning the wave crests and wave troughs of the red light signal with those of the non-red light signal before calculating blood oxygen saturation. This preliminary waveform alignment ensures that the extreme value points correspond accurately between different light wavelengths, compensating for potential misalignment caused by poor fitting or inconsistent contact, thereby improving measurement accuracy and signal reliability
Solution Approach 2:
The patent changes the parameter approach by using the extreme value points (wave crests and troughs) of the aligned waveforms rather than direct amplitude comparisons. By transforming the measurement basis to extreme value point correspondence after alignment, the system can achieve more reliable measurements even when the oximeter does not fit perfectly or contact is inconsistent
2Measurement precision
If the red light signal is used directly for calculation, then the calculation process is simple, but the accuracy deteriorates due to noise and outliers in the signal
Solution Approach 1:
The patent extracts and removes noise and outliers from the red light signal through a filtering process that identifies and eliminates abnormal data points. By separating the useful signal components from the noise and outliers, the system maintains calculation simplicity while significantly improving measurement precision through cleaner signal data
Solution Approach 2:
The patent applies preliminary signal filtering before the actual blood oxygen saturation calculation. By pre-processing the red light signal to remove noise and outliers in advance, the subsequent calculation becomes more accurate without adding complex processing steps during the main calculation phase
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
Improves the accuracy of blood oxygen saturation calculations by aligning waveforms and filtering out noise, resulting in higher accuracy rates up to 99% compared to conventional methods.
Implementation Method 1
use photoplethysmography (PPG) signals reflected by the skin of the ear to measure physiological information in the human body
Data Source
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AI summary
A method for calculating blood oxygen saturation includes defining the extreme value point of a non-red light signal as the extreme value point of a red light signal, and calculating the blood oxygen saturation according to the extreme value point of the red light signal. The method for calculating blood oxygen saturation of the present disclosure proposes to use other light source signals to assist in finding the period of the red light signal, so that the calculation result of the red light signal is more accurate.