Exhaled Air Gas Sensor Humidity Stabiliser Condensation Control
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Solution Overview
Problem
Current devices for measuring gas concentration in exhaled air are not suitable for performing measurements at multiple flows, especially at high flows, due to condensation issues in the pneumatic circuit, which affects the reliability of the measurements and prevents the establishment of a suitable relationship between NO concentration levels and exhalation flow.
Innovation Solution
The device includes a humidity stabiliser arranged downstream of the first air inlet and upstream of the flow meter, which protects all device elements from moisture condensation. Additionally, the air suction pump maintains a constant air flow rate through the sensor, and the device features a control unit that stores gas concentration values only when the exhalation flow is within predetermined values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If measurements are performed at multiple high exhalation flows, then the ability to establish relationship between NO concentration and flow is improved, but condensation occurs in the pneumatic circuit affecting measurement reliability
Solution Approach 1:
The pneumatic circuit is pre-heated to 37°C before measurements are performed. This preliminary heating action prevents condensation from forming during subsequent high-flow exhalation measurements, thereby maintaining measurement reliability across multiple flow rates without requiring the patient to repeat measurements
Solution Approach 2:
The temperature parameter of the pneumatic circuit is changed from ambient temperature to 37°C (body temperature). This parameter change prevents condensation by ensuring the circuit temperature remains above the dew point of exhaled breath, enabling reliable measurements at multiple high exhalation flows
2Reliability
If humidity stabiliser is placed upstream of the sensor, then humidity is stabilised for sensor operation, but all pneumatic circuit elements upstream remain unprotected from condensation
Solution Approach 1:
The pneumatic circuit is segmented into two zones: a heated zone (37°C) containing vulnerable components like the flow meter and pump, and a non-heated zone containing the humidity stabiliser and sensor. This segmentation allows each component to operate in its optimal temperature environment while protecting against condensation in the heated zone
Solution Approach 2:
Different temperature conditions are applied to different parts of the pneumatic circuit. The flow meter and pump are maintained at 37°C to prevent condensation, while the sensor area maintains ambient temperature for optimal sensor operation. The humidity stabiliser operates at ambient temperature to effectively stabilise humidity for the sensor
3Productivity
If exhalations are performed in short periods at high flows, then measurement efficiency is improved, but condensation problem worsens affecting operation
Solution Approach 1:
The system performs preliminary heating of the pneumatic circuit to 37°C before the measurement sequence begins. This preliminary action ensures that when multiple high-flow exhalations are performed in succession, condensation does not form in the heated components, allowing efficient repeated measurements without operational disruptions
Solution Approach 2:
The heated pneumatic circuit maintains continuous operation at 37°C throughout the measurement sequence, allowing multiple high-flow exhalations to be performed without interruption. The continuous heating prevents condensation formation, enabling uninterrupted efficient measurements at multiple flows
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 configuration allows for reliable gas concentration measurements at multiple exhalation flows, including high flows, without condensation issues, enabling the establishment of a suitable relationship between gas concentration levels and exhalation flow, and facilitating the application of different mathematical models of the respiratory system.
Implementation Method 1
it entails a condensation problem in the pneumatic elements of the device
Implementation Method 2
a sensor to measure gas concentration in the exhaled air
Data Source
Figure 1
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Figure 5~7
AI summary
The present invention relates to a device for measuring gas concentration in exhaled air comprising an inlet (1) for exhaled air, another inlet (3) for filtered ambient air, an air suction pump (5), a sensor (6) to measure concentration of a gas in the exhaled air, valves (8,9,10) to direct the air, a meter (11) to measure the flow of exhaled air, a humidity stabiliser (12) and an air exhaust (13), wherein the humidity stabiliser (12) is arranged downstream of the first air inlet (1) and upstream of the flow meter (11), such that all the elements of the device are protected against the humidity of the exhaled air, the device being suitable for performing several exhalations, especially repetitive and at high flows, in short periods of time.