Multi-Wavelength Optical Sensor for Physiological Monitoring
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Solution Overview
Problem
Current pulse oximetry systems are limited in their ability to noninvasively measure multiple physiological parameters beyond oxygen saturation and pulse rate, such as total hemoglobin, carboxyhemoglobin, and methemoglobin, and struggle to accurately measure parameters like fractional oxygen saturation and bilirubin.
Innovation Solution
A physiological sensor with an emitter array emitting light across multiple wavelengths, combined with a detector system using Si and InGaAs photodiodes, is designed to provide uniform tissue illumination through a light scattering medium, allowing for the measurement of various blood constituents and parameters by processing sensor signals to derive physiological parameters like total hemoglobin, carboxyhemoglobin, and methemoglobin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional pulse oximetry systems use single or dual wavelength LEDs, then the device complexity is low, but the measurement precision for multiple physiological parameters is insufficient
Solution Approach 1:
The emitter is divided into multiple independent LED elements, each emitting at a specific wavelength. This segmentation allows the system to target different hemoglobin components and tissue chromophores at specific wavelengths, enabling precise measurement of multiple physiological parameters including oxygen saturation, carboxyhemoglobin, methemoglobin, and total hemoglobin simultaneously
Solution Approach 2:
The multi-wavelength emitter and detector combination creates a universal sensor capable of measuring multiple physiological parameters (oxygen saturation, pulse rate, carboxyhemoglobin, methemoglobin, total hemoglobin) through a single device, eliminating the need for separate measurement systems for each parameter
2Illumination intensity
If the emitter is placed directly against tissue, then the coupling efficiency is high, but the illumination uniformity across multiple wavelengths is poor
Solution Approach 1:
An optical coupling medium with refractive index matching properties is introduced between the LED emitter and the tissue. This intermediary material optimizes light transmission by reducing reflection losses at the interface and ensures uniform illumination across all LED wavelengths, improving both illumination uniformity and measurement reliability
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
Enables the accurate and robust measurement of multiple physiological parameters, including oxygen saturation, pulse rate, total hemoglobin, carboxyhemoglobin, and methemoglobin, with enhanced accuracy and clinical relevance compared to conventional pulse oximetry systems.
Implementation Method 1
The emitters respond to the drive signals to transmit light into the tissue site. The detector generates a signal responsive to the emitted light after attenuation by pulsatile blood flow within the tissue site.
Implementation Method 2
A light scattering medium is disposed in a optical path between the emitter and tissue. The spacer and the light scattering medium provide at least a substantially uniform illumination of tissue by the emitted light for each of the wavelengths.
Implementation Method 3
A photodiode detector. The detector generates a signal responsive to the emitted light after attenuation by pulsatile blood flow within the tissue site.
Data Source
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AI summary
The present invention relates to a physiological sensor comprising an emitter array having multiple light emitting sources, the multiple light emitting sources being configured to generate light having multiple wavelengths, a detector that generates an output signal responsive to the emitted light after absorption by tissue an attachment assembly that removably positions the emitter and the detector with respect to the tissue to form an optical path from said emitter through said tissue to said detector, and an encapsulate disposed in said optical path between a first subset of the plurality of light emitting sources and tissue that provides notch or band-pass filter characteristics according to emitted wavelengths so as to substantially attenuate secondary emissions from one or more of the multiple light emitting sources.