Bi-directional Flow Meter for Respiration
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Solution Overview
Problem
Current techniques for measuring human respiration, such as hotwire anemometry, are temperature-dependent and inaccurate for exhalation measurements, and non-intrusive methods like nasal prongs fail to provide accurate flow rate measurements, limiting their clinical usefulness.
Innovation Solution
A bi-directional flow meter using total pressure probes to measure static and stagnation pressures independently, with a constriction and development length in the sampling tube to condition the fluid flow, allowing for temperature-independent and sensitive volumetric flow rate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hotwire anemometry is used to measure flow rate, then measurement sensitivity is improved, but temperature dependence causes measurement accuracy to deteriorate
Solution Approach 1:
The patent replaces the thermal measurement mechanism (hotwire anemometry) with a pressure-based measurement mechanism. Total pressure probes measure static and stagnation pressures to determine flow rate, eliminating temperature-dependent thermal effects while maintaining measurement sensitivity through pressure differential detection.
Solution Approach 2:
The patent changes the measurement parameter from temperature-based (hotwire resistance change) to pressure-based (static and stagnation pressure differential). This parameter transformation allows accurate flow rate measurement independent of temperature variations, particularly improving exhalation measurement reliability.
2Ease of operation
If nasal prongs are used for non-intrusive measurement, then patient comfort is improved, but flow rate measurement accuracy deteriorates
Solution Approach 1:
The patent employs pneumatic measurement principles using total pressure probes that measure static and stagnation pressures within the nasal passage. This pneumatic approach enables accurate flow rate determination through pressure differential measurements while maintaining the non-intrusive nasal prong configuration for patient comfort.
3Measurement precision
If complex hardware setups are used, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent creates a multi-functional nasal prong device that simultaneously performs non-intrusive positioning and accurate pressure-based flow rate measurement. The total pressure probes are integrated into the nasal prong structure, enabling both patient comfort and measurement accuracy without requiring separate complex hardware systems.
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
The solution provides a robust, reliable, and minimally invasive method for measuring air flow rates during human respiration, offering high sensitivity and accuracy for both inhalation and exhalation, suitable for medical diagnostics.
Implementation Method 1
measuring the difference between local static and stagnation pressures independently... The local temperature may also be sampled. The volumetric flow rate is then inferred from these signals
Implementation Method 2
a constriction and development length in the sampling tube to condition the fluid flow
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
A flow meter (1) comprising a sampling tube (3) through which fluid may flow and a sensor arrangement (9, 25, 27, 39, 41, 43, 44, 45, 46, 47), wherein the sampling tube (3) comprises a first hollow section (51, 53) having a first internal cross-sectional area (A1) and a second hollow section (55, 57) having a second internal cross-sectional area (A2) being less than the first internal cross-sectional area (A1); and the sensor arrangement (9, 25, 27, 39, 41, 43, 44, 45, 46, 47), is for measuring the difference between stagnation and static pressures (P01, P02, P1, P2) within the second hollow section (55, 57).