Pulse Oximeter Spectral Correction for Skin Pigmentation Error
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Solution Overview
Problem
Existing pulse oximeter measurements are prone to errors due to variations in tissue spectral characteristics, such as skin pigmentation, leading to inaccurate SpO2 readings.
Innovation Solution
A pulse oximeter system that includes emitters for two wavelengths of light (red and infrared) to estimate tissue scattering or absorption, using ratios of detected signals to calculate correction factors, and applies these factors to correct SpO2 measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulse oximetry uses standard light wavelengths to measure blood oxygenation, then the measurement process is simple and quick, but measurement precision deteriorates due to errors from tissue spectral characteristics like skin pigmentation
Solution Approach 1:
The system changes the wavelength parameters of light sources to include multiple wavelengths (e.g., red at 660nm and infrared at 940nm) beyond the standard two wavelengths, allowing measurement of tissue spectral characteristics and application of correction factors to improve SpO2 accuracy across different skin pigmentation levels
Solution Approach 2:
The system introduces correction factors as intermediary elements that mediate between the raw pulse oximetry measurements and the final SpO2 values. These correction factors, derived from tissue spectral characteristics, adjust the measurement to compensate for errors due to skin pigmentation and other tissue properties
2Measurement precision
If the system measures tissue spectral characteristics to correct for scattering and absorption errors, then measurement precision improves, but the measurement process becomes more complex and time-consuming
Solution Approach 1:
The system performs preliminary measurements of tissue spectral characteristics using the additional wavelength channels before calculating the final SpO2 value. These preliminary measurements allow the system to pre-compute correction factors that are then applied to the main pulse oximetry measurement, improving accuracy without significantly increasing total measurement time
Solution Approach 2:
The multi-wavelength light sources and detectors serve multiple functions: they provide the standard pulse oximetry measurements for SpO2 calculation while simultaneously enabling measurement of tissue spectral characteristics for correction factor derivation, thus obtaining multiple benefits from a single measurement system
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 SpO2 readings by accounting for tissue spectral characteristics, particularly skin pigmentation, through the use of correction factors based on signal ratios and normalization techniques.
Implementation Method 1
a first light source configured for light emission at a first wavelength through tissue and a second light source configured for light emission at a second wavelength through tissue
Implementation Method 2
A photodiode is used to capture the light after propagating through blood perfused tissue
Implementation Method 3
the spectrum of skin pigmentations can result in LED light for a pulse oximeter being scattered and absorbed differently
Implementation Method 4
skin pigmentation (or other characteristics of tissue causing light scattering or absorption (spectral characteristics of tissue)
Data Source
AI summary
The present disclosure provides systems and methods for correcting for errors dependent upon spectral characteristics of tissue for a medical device by estimating a spectral characteristic of tissue providing error due to scattering or absorption of emitted light based upon a ratio of measurements for a patient.