Adaptive CO2 Sensor Gas Flow Control for Medical Ventilation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining carbon dioxide concentration in ventilated patients suffer from inaccuracies due to cross-influences from gas parameters like temperature and humidity, and the volume flow generated by pumps disrupts the measurement signal, making it difficult to precisely differentiate between inspiratory and expiratory phases.
Innovation Solution
A method that controls the fluid delivery unit to maintain a constant volume flow and gas pressure during both inspiratory and expiratory phases by adapting to airway pressure, using a piezo pump and look-up table to ensure uniform gas flow to the sensor unit, and incorporates a heat conduction sensor for thermal conductivity measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a pump is used to generate volume flow in the branch line, then measurement gas can be delivered to the sensor unit, but the changing volume flow disrupts the measurement signal and creates measurement inaccuracies
Solution Approach 1:
The pump's operating point is dynamically adjusted during the breathing cycle by changing the occlusion ratio. During inspiration, the occlusion ratio is reduced to decrease pump-induced volume flow changes, while during expiration, the occlusion ratio is increased to maintain adequate gas delivery. This dynamic adaptation minimizes pump artifacts on the measurement signal while ensuring sufficient measurement gas supply.
Solution Approach 2:
The invention changes the pump's operational parameters (occlusion ratio, rotation speed) depending on the breathing phase. By modulating these parameters, the system optimizes the balance between delivering enough measurement gas to the sensor and minimizing volume flow variations that would otherwise distort the carbon dioxide concentration measurement.
2Reliability
If airway pressure changes during breathing phases, then physiological conditions are reflected, but the pressure difference across the branch line creates varying volume flow that generates measurement signal artifacts
Solution Approach 1:
The system uses feedback from airway pressure measurements to dynamically adjust pump operation. The control unit monitors airway pressure changes during inspiration and expiration and adapts the pump's occlusion ratio and rotation speed accordingly, compensating for pressure-induced volume flow variations and eliminating measurement artifacts.
Solution Approach 2:
The system takes preliminary action by preemptively adjusting pump parameters in response to detected airway pressure changes. Before pressure artifacts can significantly distort the measurement signal, the pump's occlusion ratio and speed are modified to counteract the expected volume flow variations caused by physiological pressure changes.
3Object-affected harmful factors
If hydrophobic barrier is used to prevent condensing moisture, then moisture protection is provided, but cross-influences from temperature and humidity lead to insufficient accuracy
Solution Approach 1:
The system introduces an intermediary approach by using a heated sample line and temperature control mechanism between the measurement gas source and the sensor. This intermediary heating system prevents condensation without relying solely on a hydrophobic barrier, and maintains stable temperature and humidity conditions that eliminate cross-influences on the measurement while still protecting against moisture damage.
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 approach provides precise and accurate determination of carbon dioxide concentration by minimizing the influence of airway pressure changes and maintaining consistent gas flow, leading to improved measurement accuracy and reduced measurement errors.
Implementation Method 1
the thermal conductivity of a measurement gas to determine a carbon dioxide concentration in the measurement gas
Implementation Method 2
convey the measurement gas from the main line through the branch line to the sensor unit by means of a fluid delivery unit
Data Source
Figure 1~2
Figure 3~4
Figure 5A~6
AI summary
The present invention relates to a method for determining a carbon dioxide concentration in measurement gas, said method comprising the steps of: branching off the measurement gas from a main line (15) of a medical apparatus (12) during an inspiratory phase of a person (13) connected to the medical apparatus (12) as an inspiratory gas and during an expiratory phase of the person (13) as an expiratory gas to a sensor unit (11) by means of a branch line (14), conveying the measurement gas from the main line (15) through the branch line (14) to the sensor unit (11) by means of a fluid-conveying unit (24), adaptively adjusting the fluid-conveying unit (24) taking into account an airway pressure in the main line (15) for generating a volume stream, which is uniform during the inspiratory phase and the expiratory phase, and/or gas pressure of the measurement gas in the branch line (14) to the sensor unit (11), and determining the carbon dioxide concentration in the measurement gas by means of the sensor unit (11). The invention also relates to a determination device (10), a medical apparatus (12), an adjustment unit (26), a computer program product (29) and a storage means (30) with a computer program product (29) stored thereon for carrying out the method according to the invention.