End-Tidal Gas Sampling for Accurate Exhaled Air Measurement
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Solution Overview
Problem
Existing gas measurement technologies in exhaled air, particularly for ventilators, struggle with high temporal resolution for gases like CO2 and O2, especially when using slower sensors, which are often more cost-effective and smaller, limiting their application in emergency ventilation.
Innovation Solution
A device and method that utilizes a respiratory phase sensor to determine the current phase and control a controllable valve or pump to isolate gas samples during specific phases, allowing slower sensors to measure gas content accurately by ensuring samples are taken during the end-tidal region of exhalation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If slower gas sensors are used for measurement, then device cost and size are reduced, but temporal resolution deteriorates
Solution Approach 1:
The system performs preliminary detection of the respiratory phase using a fast sensor (flow, pressure, or CO2 sensor) to identify when the end-tidal phase is reached. Based on this preliminary detection, the system then activates the slower gas sensor at the optimal moment, ensuring that the slower sensor only needs to measure during the relatively long end-tidal phase where gas composition is stable, thus achieving accurate measurement without requiring the slower sensor to respond quickly to rapid changes.
2Speed
If continuous high-resolution measurement is performed, then temporal resolution is improved, but energy consumption and device complexity increase
Solution Approach 1:
Instead of continuous measurement, the system uses periodic action by detecting the respiratory phase with a fast sensor and only activating the slower gas sensor during specific periods (end-tidal phase). This periodic activation based on respiratory cycle detection reduces energy consumption while maintaining measurement quality, as the slower sensor operates only when needed during the stable end-tidal phase rather than continuously throughout the respiratory cycle.
3Speed
If continuous high-resolution measurement is performed, then temporal resolution is improved, but device complexity and cost increase
Solution Approach 1:
The measurement system is segmented into two functional parts: a fast respiratory phase detection system (using flow, pressure, or CO2 sensors) and a slower gas composition measurement system. The fast sensor continuously monitors respiratory phase, while the slower sensor is activated only during the end-tidal phase. This segmentation allows the use of simpler, cheaper, slower sensors for the main gas measurement task while using a fast sensor only for phase detection, thereby reducing overall device complexity and cost.
4Ease of manufacture
If slower sensors are used, then device cost is reduced, but measurement precision for rapid changes deteriorates
Solution Approach 1:
The system extracts and isolates the end-tidal phase from the complete respiratory cycle using fast respiratory phase detection. By taking out only the end-tidal phase (where gas composition is stable and changes slowly) for measurement with the slower sensor, the system eliminates the need for the slower sensor to accurately capture rapid changes during inhalation and early exhalation phases, thus allowing cost-effective slower sensors to achieve 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
Enables accurate measurement of gas content with slower sensors by isolating samples during the end-tidal phase, improving temporal resolution and enabling cost-effective, efficient gas analysis in ventilators.
Implementation Method 1
determining the respiratory phase with the aid of a respiratory phase sensor
Implementation Method 2
by means of a pump device, a gas sample is transportable out of the respiratory air stream into the region of the gas sensor
Implementation Method 3
the controllable valve is actuable according to the respiratory phase determined with the aid of the respiratory phase sensor, so that the gas sample conveyed with the aid of the pump device is conductable through an opened valve path toward the gas sensor
Implementation Method 4
measuring the supplied gas sample with the aid of the at least one gas sensor
Data Source
AI summary
A method and a device for measuring the content of at least one gas in exhaled air and to a device for ventilation. Due to the combination of a rapid respiratory phase sensor with a valve controllable depending on the detected respiratory phase, the use is made possible of a slower gas sensor to measure the content of a specific gas in the exhaled air during a certain period in the respiratory cycle so that the use of more economical and/or smaller and/or more accurate gas sensors is possible.