Optical Sensor for Capnography Using Fluorophore Coatings
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Solution Overview
Problem
Conventional devices for monitoring respiration, such as pulse-oximeters and capnography systems, are inadequate for measuring ventilation and respiration sufficiency, are large and power-intensive, and lack the ability to provide real-time, accurate measurements of oxygen and carbon dioxide levels within the airways due to size and power constraints, and require additional sensors for temperature correction.
Innovation Solution
An optical sensor system using a substrate with multiple thin film layers, including oxygen impermeable and permeable coatings with temperature-dependent fluorophores, integrated with an optical fiber for measuring oxygen levels and calculating carbon dioxide levels, which is compact, low-power, and temperature-corrected without electrical components, allowing for remote monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional gas sensors are used to measure carbon dioxide, then measurement capability is provided, but device size becomes too large to be placed in or near patient airway
Solution Approach 1:
The patent replaces conventional electrical gas sensors with an optical sensing system that uses fluorophores and optical fibers to detect carbon dioxide levels. This substitution eliminates the need for large electrical sensor components, enabling miniaturization to fit within patient airways while maintaining measurement capability through optical detection of gas composition changes.
Solution Approach 2:
The invention employs thin film coatings containing fluorophores deposited on optical fiber surfaces. These thin film structures provide the sensing functionality in a minimally invasive form factor that can be inserted into patient airways, replacing bulky conventional sensor housings and enabling placement near the measurement site without significant size constraints.
2Measurement precision
If side stream gas sampling is used in conventional capnography, then gas measurement is enabled, but temporal response is dampened and fine temporal patterns are lost
Solution Approach 1:
The patent extracts the sensing function from remote side stream sampling and places it directly at the measurement location within the patient airway. By positioning the optical sensor tip in direct contact with or near the gas of interest, the system eliminates the time delay inherent in pumping gas through external sampling lines, capturing fine temporal patterns in real-time.
Solution Approach 2:
The optical fiber acts as an intermediary that transmits both excitation light to and fluorescence signal from the sensing tip located within the airway. This intermediary enables direct measurement at the source without requiring physical gas transport, preserving temporal fidelity while maintaining measurement capability.
3Volume of moving object
If optical oxygen sensors are used, then smaller size and lower power requirements are achieved, but temperature correction requires additional electrical temperature sensors that negate electrical safety advantages
Solution Approach 1:
The patent merges the oxygen sensing and temperature correction functions into a single integrated optical sensor system. By incorporating temperature-dependent fluorophores that provide both oxygen measurement and temperature information through their fluorescence characteristics, the system eliminates the need for separate electrical temperature sensors, maintaining electrical safety while reducing device complexity.
Solution Approach 2:
The optical sensor system performs multiple functions simultaneously: it measures oxygen levels through oxygen-sensitive fluorophores and provides temperature correction through temperature-sensitive fluorophores. This multi-functional approach allows a single non-electrical device to accomplish what previously required separate sensors, maintaining miniaturization and electrical safety benefits.
4Measurement precision
If conventional capnography systems are used, then gas measurement capability is provided, but the systems are large, expensive and require high power levels making them impractical for field emergency care
Solution Approach 1:
The patent replaces power-intensive electrical sensors and pumping systems with low-power optical detection using fluorophores and optical fibers. The passive optical sensing mechanism requires minimal power for light source modulation and detection, enabling portable field deployment while maintaining ventilation and respiration measurement capabilities previously available only in large stationary systems.
Solution Approach 2:
The invention changes the detection parameter from electrical signals requiring high power amplification and processing to optical fluorescence signals that can be detected with minimal power consumption. By measuring fluorescence intensity and lifetime changes in response to gas composition and temperature, the system achieves accurate physiological monitoring with dramatically reduced power requirements suitable for battery-operated field 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
Enables accurate, real-time measurement of oxygen and carbon dioxide levels within the airways, improving ventilation assessment and reducing the risk of apnea in patients, while being compact and energy-efficient, thus suitable for emergency care.
Implementation Method 1
a first fluorophore having a fluorescence characteristic that is dependent upon temperature... a second fluorophore having a fluorescence characteristic dependent upon temperature and oxygen gas level
Data Source
AI summary
The present application describes an optical sensor for measuring oxygen gas levels in a medium. The optical sensor includes a substrate having a first and second surface. The optical sensor also includes a first coating applied on the first surface of the substrate. The first coating may include an oxygen impermeable matrix doped with a first fluorophore. The optical sensor may include a second coating applied on the substrate. The present application also describes a capnography system for measuring oxygen including an optical sensor and an algorithm to estimate the maxima of oxygen levels from instantaneous oxygen levels and calculating instantaneous carbon dioxide levels from the difference between average maximum oxygen gas level and instantaneous oxygen gas level.