Integrated Gas Flow and Composition Sensor for Respiratory Analysis
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Solution Overview
Problem
Current methods for measuring molecular flow, particularly in respiratory applications, face challenges such as inaccurate oxygen consumption and carbon dioxide production measurements due to temporal misalignment of gas flow and concentration measurements, and are unsuitable for use in anaesthesia and critical care settings where inspired gas composition varies.
Innovation Solution
Integration of a gas flowmeter and gas composition analyzer in the same measurement space, with frequent measurements of gas concentrations and flow rates, using flow-sensing mesh screens and differential pressure sensors to ensure accurate and time-aligned data, correcting for variations in composition, viscosity, and density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If gas flow and concentration measurements are taken separately at different locations, then device complexity is reduced, but measurement precision deteriorates due to temporal misalignment
Solution Approach 1:
The patent combines the gas flow meter and gas composition analyzer into a single integrated measurement device. The flow meter measures gas flow through a measurement space while the analyzer simultaneously measures gas composition within the same space, eliminating temporal misalignment between measurements and enabling accurate calculation of molecular flow by directly multiplying concurrent flow and concentration values.
2Ease of operation
If remote positioning of analyser is used, then ease of operation is improved, but measurement precision deteriorates due to variable delay times and longitudinal mixing
Solution Approach 1:
The analyzer is positioned within the measurement space of the flow meter rather than remotely, ensuring that gas composition and flow measurements are taken simultaneously at the same location. This eliminates delay times and longitudinal mixing effects that occur in remote sampling configurations.
3Ease of operation
If fan chamber is used to homogenise gas, then ease of operation is improved, but measurement precision deteriorates due to poor temporal resolution
Solution Approach 1:
The integrated device measures gas composition and flow simultaneously within the same measurement space without using fan chambers for homogenisation. This allows direct calculation of molecular flow with high temporal resolution, enabling breath-by-breath measurements while maintaining measurement accuracy.
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 precise, breath-by-breath measurement of oxygen consumption and carbon dioxide production, improving accuracy and temporal resolution, and is suitable for various medical and industrial applications, including anaesthesia and critical care.
Implementation Method 1
using flow-sensing mesh screens and differential pressure sensors to ensure accurate and time-aligned data
Implementation Method 2
Integration of a gas flowmeter and gas composition analyzer in the same measurement space, with frequent measurements of gas concentrations and flow rates
Data Source
Figure 1
Figure 2(A)~2(B)
Figure 3
AI summary
A molecular flow sensor comprises a flowmeter integrated with an in airway laser gas analyser. The laser gas analyser spectroscopically analyses the concentrations of gases such as oxygen, carbon dioxide and water in a measurement space which is in the gas flow path between two Lilly-type flow-sensing mesh screens. The gas flow through the measurement space is measured by measuring the pressure drop across the flow-sensing mesh screens using a differential pressure sensor. Helical baffles are provided upstream and downstream of the measurement space to provide a low resistance gas flow path while blocking ambient light from entering the measurement space, and flow-conditioning elements of mesh or metal foam are provided between the helical baffles and the flow- sensing meshes. Pressure averaging is conducted circumferentially around the gas flow path by the use of circumferentially spaced gas sensing holes connected to a pressure averaging channel which communicates with the differential pressure sensor. The differential pressure sensor is composed of an array of individual pressure sensors to improve baseline stability and linearity. At least two independent pressure sensors may be provided, switchable out independently to allow regular calibration while the other is still measuring. The flow sensor is particularly useful for measuring respiratory gas exchange such as oxygen consumption or carbon dioxide production by a respiring subject.