Blood Oxygen Saturation Measurement Using Flow Signal Correction
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Solution Overview
Problem
Conventional pulse oximetry devices suffer from limited accuracy and high false alarm rates, particularly in neonatal care settings, due to the assumption that different wavelengths probe the same vasculature, leading to inaccuracies in blood oxygen saturation measurements.
Innovation Solution
A system that combines coherent light sources emitting at multiple wavelengths with laser speckle imaging or laser Doppler techniques to correct PPG signals based on flow signals, providing a feedback signal to assess the reliability of the measurements and correct for differences in tissue layers probed at different wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pulse oximetry uses multiple wavelengths to measure blood oxygen saturation, then the measurement can be performed non-invasively, but the accuracy is limited to ±3 saturation percent due to different tissue layers being probed at different wavelengths
Solution Approach 1:
The patent introduces laser speckle imaging or laser Doppler techniques as an intermediary measurement method. These techniques measure flow signals that are independent of wavelength-dependent tissue penetration differences. The flow signals serve as a mediator to correct the PPG signals, compensating for the inaccuracies caused by different tissue layers being probed at different wavelengths.
Solution Approach 2:
The patent implements a feedback mechanism where flow signals measured by laser speckle imaging or laser Doppler techniques are used to correct PPG signals. The system continuously compares and adjusts the PPG measurements based on the flow signal information, creating a closed-loop correction system that improves measurement accuracy and reduces false alarms.
2Device complexity
If conventional pulse oximetry assumes different wavelengths probe the same vasculature, then the device complexity remains simple, but measurement accuracy deteriorates due to variations in tissue penetration depth
Solution Approach 1:
The patent merges conventional PPG measurement with laser speckle imaging or laser Doppler flow measurement into a single integrated system. By combining these measurement techniques and their respective signal processing methods, the system achieves improved accuracy without requiring completely separate devices, thus maintaining reasonable device complexity while solving the accuracy problem.
Solution Approach 2:
The patent changes the measurement parameters by introducing flow signal measurements alongside traditional absorption-based PPG signals. By measuring and utilizing additional parameters (flow signals) that are independent of wavelength-dependent tissue penetration, the system corrects for accuracy errors without fundamentally changing the core PPG measurement approach.
3Reliability
If alarm thresholds are set at 89% and 95% for neonatal care, then the monitoring sensitivity is adequate, but false alarm rate increases due to limited measurement accuracy of ±3 saturation percent
Solution Approach 1:
The patent uses feedback from flow signal measurements to correct PPG signals before determining blood oxygen saturation values. This correction feedback mechanism reduces measurement variability and false alarms, allowing the alarm system to maintain high reliability with appropriate threshold settings without suffering from the ±3% accuracy limitation of conventional systems.
Solution Approach 2:
The patent replaces the purely absorption-based measurement mechanism with a hybrid approach that incorporates flow-based measurement (laser speckle imaging or laser Doppler). This substitution introduces a new measurement dimension that is less susceptible to the errors affecting traditional PPG, thereby improving alarm reliability and reducing false alarms in neonatal care.
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 measurements by correcting for variations in tissue penetration depth and vasculature, reducing false alarms and enhancing reliability in both contact and non-contact pulse oximetry systems.
Implementation Method 1
a coherent light source arranged to emit coherent light at a first wavelength and at a second wavelength towards a tissue region of the subject
Implementation Method 2
a PPG unit for deriving, from said first detection data, a first PPG signal indicative of an absorption of light within the tissue region at the first wavelength
Implementation Method 3
a flow unit for deriving, from said second detection data, a first flow signal indicative of a flow of light scattering particles probed at the first wavelength
Implementation Method 4
a first flow signal indicative of a flow of light scattering particles probed at the first wavelength within the tissue region
Data Source
Figure 1~2
Figure 3~5B
Figure 6A~7C
AI summary
The present invention relates to a device (10), system (1) and method (200) for use in blood oxygen saturation measurement of a subject. To enable blood oxygen saturation measurements with improved reliability, a processing device (10) is presented comprising an input (11) for receiving first and second detection data of a tissue region of the subject, said first detection data being data acquired over time by detecting radiation at a first wavelength (λ1) and at a second wavelength (λ2) received from said tissue region; said second detection data being data acquired over time by detecting radiation at the first wavelength and at the second wavelength received from said tissue region in response to coherent light at the first wavelength and coherent light at the second wavelength being emitted towards the tissue region; a PPG unit (12) for deriving, from said first detection data, a first PPG signal indicative of an absorption of light within the tissue region at the first wavelength, and a second PPG signal indicative of an absorption of light within the tissue region at the second wavelength; a flow unit (13) for deriving, from said second detection data, a first flow signal indicative of a flow of light scattering particles within the tissue region probed at the first wavelength, and a second flow signal indicative of a flow of light scattering particles within the tissue region probed at the second wavelength; and a processing unit (14) for correcting said PPG signals based on said flow signals and/or for providing a feedback signal based on a comparison of the first and second flow signals.