Breath Alcohol Sensor Using CO2 Dilution Correction
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Solution Overview
Problem
Current methods for measuring blood alcohol concentration, such as direct blood sampling and breath testing, face challenges including cost, reliability, and the risk of false readings due to dilution, especially in individuals with lung diseases, and lack a practical, contactless, and efficient solution for large-scale applications.
Innovation Solution
A method and apparatus that measure both carbon dioxide and alcohol concentrations in exhaled air, using a sensor arrangement positioned at a distance from the subject, which calculates the alveolar alcohol concentration by accounting for dilution factors through the ratio of carbon dioxide and alcohol signals, allowing for accurate determination of blood alcohol levels without direct sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct blood sampling is used to measure alcohol concentration, then measurement precision and reliability are improved, but device complexity, cost, and ease of operation deteriorate
Solution Approach 1:
The patent uses exhaled breath as an intermediary medium to indirectly measure blood alcohol concentration. Alcohol diffuses from blood to breath through the lung alveoli, allowing non-invasive measurement while maintaining correlation with blood concentration. This mediator approach eliminates the need for direct blood sampling while preserving measurement accuracy.
Solution Approach 2:
The patent replaces the mechanical/invasive blood sampling system with a gas-phase detection system. Instead of physically drawing blood and analyzing it chemically, the system captures and analyzes alcohol vapor in exhaled breath using gas sensors, thereby simplifying the overall measurement system.
2Ease of operation
If breath sampling is used to measure alcohol concentration, then ease of operation and productivity are improved, but measurement precision deteriorates due to dilution effects
Solution Approach 1:
The patent employs feedback mechanisms to monitor and compensate for breath dilution. By detecting the concentration of alcohol in the breath sample and comparing it against expected values, the system can identify dilution effects and apply correction factors to maintain accurate blood alcohol concentration calculations.
Solution Approach 2:
The patent changes the measurement parameter from direct alcohol concentration to a ratio or corrected value that accounts for dilution. By monitoring additional parameters such as breath flow rate, temperature, and humidity, the system adjusts the alcohol concentration reading to compensate for dilution effects, thereby maintaining precision despite the non-invasive sampling method.
3Ease of operation
If breath sampling is performed with individuals having lung diseases, then ease of operation is maintained, but measurement precision deteriorates due to impaired gas exchange
Solution Approach 1:
The patent collects multiple breath samples or extends the sampling duration to overcome impaired gas exchange in lung disease patients. By accumulating sufficient alcohol vapor through repeated or prolonged sampling, the system compensates for reduced diffusion efficiency in diseased lungs, thereby maintaining measurement accuracy.
Solution Approach 2:
The patent incorporates correction algorithms that anticipate and compensate for lung disease effects before they significantly impact measurement accuracy. By pre-programming compensation factors based on known lung disease characteristics, the system cushions against potential measurement errors and maintains precision even when gas exchange is impaired.
4Measurement precision
If dispersive devices such as mass spectroscopy or gas chromatography are used, then measurement precision and generality are improved, but device complexity and cost deteriorate
Solution Approach 1:
The patent employs inexpensive, simple gas sensors instead of complex and expensive analytical instruments like mass spectrometers or gas chromatographs. While individual sensors have limited sophistication, their low cost allows for simple, portable, and scalable alcohol testing systems that maintain sufficient accuracy for breath alcohol measurement applications.
Solution Approach 2:
The patent extracts and measures only the specific parameter of interest (alcohol concentration in breath) using targeted simple sensors, rather than employing complex dispersive devices that analyze all gas constituents. This selective approach removes unnecessary complexity while maintaining measurement precision for the specific application.
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
This approach provides a reliable, efficient, and contactless method for determining blood alcohol concentration, minimizing the risk of false readings and accommodating individuals with lung diseases, while being suitable for large-scale applications with high accuracy and reduced costs.
Implementation Method 1
a sensor arrangement for measuring the concentration of a first gas, carbon dioxide (CO2), and a second gas, alcohol (EtOH), in the exhaled air
Implementation Method 2
the measured concentrations of CO2 and EtOH in the exhaled air are used to calculate a dilution factor
Data Source
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AI summary
A method of assessing the blood concentration level in a human or animal subject, of a volatile blood constituent (preferably alcohol) is disclosed. The method comprises steps of positioning a sensor (21 ,22) within the expiratory gas flow of the subject, wherein the sensor (21 ,22) is configured to detect the presence of the constituent and provide a first output signal representative of the concentration of said constituent in air, and also to detect a presence of carbon dioxide and to provide a second output signal representative of the concentration of carbon dioxide in air. The flow of expiratory gases from the subject is sampled to provide a first signal and second signal in respect of the expiratory gases substantially simultaneously. The method also comprises the step of inputting said first and second signals obtained by the sampling step into an algorithm configured to compare the variation of the first signal over time with the variation of the second signal over time and, depending on the result of the comparison, to make said second signal representative of the degree of dilution of said expiratory airflow.