Ventilation Gas Estimation From Sidestream Sensing
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Solution Overview
Problem
Conventional methods for determining gas concentration in ventilation systems, such as mainstream and sidestream measurements, face inaccuracies and patient discomfort, particularly when ventilating newborns or infants, due to the size and weight of gas sensors required for accurate readings.
Innovation Solution
A method that estimates gas concentration in the main line by measuring it in a branch line using a gas sensor, combined with a signal processing device that generates an estimated gas concentration signal based on a mathematical model and known volumetric flow rates, allowing for accurate estimation without the need for a gas sensor in the main line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gas sensor is positioned in the main flow of the breathing gas for direct measurement, then measurement accuracy is improved, but the gas sensor volume increases leading to rebreathing of carbon dioxide and patient discomfort
Solution Approach 1:
The gas sensor is extracted from the main breathing flow path and positioned in a separate sampling line. A sampling pump draws a portion of the breathing gas through the sensor located in the sampling line, allowing accurate measurement without the sensor being in the main flow path, thus avoiding rebreathing issues while maintaining measurement accuracy
Solution Approach 2:
A sampling line acts as an intermediary medium between the main breathing flow and the gas sensor. The sampling line transports a representative sample of the breathing gas to the sensor, enabling indirect measurement that achieves the same measurement accuracy as direct mainstream measurement without requiring the sensor to be in the patient's airway
2Measurement precision
If a gas sensor with sufficient volume is used for accurate readings, then measurement precision is improved, but device complexity and patient discomfort increase
Solution Approach 1:
The ventilation system is segmented into separate functional components: the main breathing flow path and the sampling measurement path. This segmentation allows the gas sensor to be positioned in the sampling line away from the patient interface, reducing the complexity at the patient end while maintaining accurate measurement capabilities in the sampling line
Solution Approach 2:
The sampling line serves as an intermediary that decouples the measurement function from the patient interface. This allows the use of a properly sized sensor for accurate measurements without increasing the complexity or size of components that contact the patient, as the sensor is located remotely in the sampling line
3Measurement precision
If a gas sensor is placed in the main line for accurate measurement, then measurement precision is improved, but the main line volume increases causing rebreathing
Solution Approach 1:
The measurement function is extracted from the main breathing flow path by positioning the gas sensor in a separate sampling line. The sampling pump extracts a portion of the breathing gas for measurement, allowing the main line to remain small and preventing rebreathing while maintaining accurate gas concentration measurements through the sampling measurement system
Solution Approach 2:
The sampling line acts as an intermediary measurement path that prevents the main breathing line from needing to accommodate a large sensor. By measuring gas concentration in the sampling line rather than the main line, the system avoids increasing main line volume and the associated rebreathing problem while still achieving accurate measurements
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
Achieves accurate gas concentration determination similar to mainstream measurement while reducing the volume and weight of the main line, minimizing rebreathing of exhaled gas and improving patient comfort, especially for newborns or infants.
Implementation Method 1
a gas sensor for measuring a gas concentration at at least one first location in the branch line
Data Source
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Figure 2
AI summary
A method for determining a gas concentration in a ventilation system (1) comprises: receiving a first signal (19) indicating a gas concentration measured by a gas sensor (15) at at least one first location (17) in a side line (9) in a signal processing device (21); generating a second signal (23) indicating an estimated gas concentration at at least one second location (25) in a main line (7) from the first signal (19) by the signal processing device (21), wherein the main line (7) connects a port (5a) of a ventilator (3) for supplying a breathing gas to a patient interface (11) and the side line (9) branches off from the main line (7) so that the breathing gas can flow at least partially through the side line (9).