Artificial Respiration Leak Detection Using Thermal Conductivity

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Solution Overview

Problem

Existing methods for detecting leaks during artificial respiration are unreliable and prone to false alarms, particularly when the gas mixture composition is similar to ambient air, leading to inaccurate measurement of gas concentrations and potential harm to the patient.

Innovation Solution

A monitoring system that analyzes the thermal conductivity of a diverted gas sample using a sensor arrangement, determining the temporal change in thermal conductivity to detect leaks, supplemented by additional measurements of gas concentration and pressure, ensuring reliable leak detection without reliance on specific gas component concentrations or pressure changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If gas concentration measurement is used for leak detection, then leak detection can be performed, but false alarms occur when gas mixture composition is similar to ambient air

Engineering Contradiction:
Improveleak detection reliabilityVSAvoidgas concentration measurement accuracy
Core Design Contradiction:
ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the detection parameter from gas concentration to thermal conductivity. The sensor measures thermal conductivity of the gas sample, which differs between the breathing gas mixture and ambient air regardless of composition similarities. This parameter change resolves the false alarm issue while maintaining reliable leak detection.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces the chemical measurement approach (gas concentration analysis) with a physical measurement approach (thermal conductivity measurement). This substitution eliminates the problem of false alarms caused by similar gas compositions, as thermal conductivity provides a distinct physical property for differentiation.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If pressure changes are used for leak detection, then leak detection can be performed, but pressure changes may not occur or are insufficient for reliable detection

Engineering Contradiction:
Improveleak detection reliabilityVSAvoidpressure change detection
Core Design Contradiction:
ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent changes the detection parameter from pressure to thermal conductivity. This provides a more reliable and consistently measurable parameter for leak detection, as thermal conductivity changes are more pronounced and easier to detect than pressure changes in the breathing circuit.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent replaces pressure-based detection with thermal conductivity-based detection. This substitution provides more reliable measurement signals that are easier to detect and interpret, resolving the difficulty associated with pressure change detection.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If thermal conductivity analysis is used for leak detection, then reliable leak detection is achieved, but additional measurement equipment and processing are required

Engineering Contradiction:
Improveleak detection reliabilityVSAvoidmeasurement system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent integrates thermal conductivity measurement into the existing gas sampling system, allowing the same sensor to potentially serve multiple functions including leak detection and gas composition monitoring. This multi-functionality reduces overall system complexity despite the advanced detection capability.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements a feedback mechanism where the thermal conductivity measurement is continuously monitored and compared against reference values. The system automatically generates leak alerts when deviations are detected, providing intelligent automation that reduces operational complexity.

Inventive Principle:
Principle #23Feedback

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 system provides reliable and rapid detection of leaks, minimizing false alarms and ensuring accurate measurement of gas concentrations, thereby maintaining the integrity of artificial respiration.

Implementation Method 1

The sensor arrangement comprises a thermal conductivity sensor and a signal processing unit. The temporal progression of the thermal conductivity of the gas sample that has been drawn off and has reached the sensor arrangement is determined

Methodology Applied
Scientific EffectThermal conductivity: Conduction (thermal)

Implementation Method 2

At least temporarily, a negative pressure is created in the sensor fluid guide unit and/or the sensor arrangement relative to the surroundings of the measuring system. A gas sample is drawn from the patient fluid guide unit and guided through the sensor fluid guide unit to the sensor arrangement. The negative pressure contributes to this.

Methodology Applied
Scientific EffectNegative pressure: Pressure Gradient

Data Source

PatentEP4349388B1Apparatus and method for detecting a leak during artificial respiration
Publication Date: 2025.08.27 DRAGERWERK AG
  • EP4349388B1 patent drawingFigure 1
  • EP4349388B1 patent drawingFigure 2
  • EP4349388B1 patent drawingFigure 3

AI summary

The invention relates to a device and a method that are capable of automatically detecting a leak (L), in particular a sudden leak, during the artificial ventilation of a patient (P). A measuring system (100) with a sensor array (50) and a sensor fluid guide unit (52, 56) is monitored. A fluid connection between a patient-side coupling unit (21) and a medical device (1) is established by means of a patient fluid guide unit (32, 33). A gas sample (Gp) is diverted from the patient fluid guide unit and guided through the sensor fluid guide unit to the sensor array. Using measured values ​​from the sensor array, a thermal conductivity profile is determined, that is, a profile of the thermal conductivity of the gas sample as it reaches the sensor array.Depending on changes in the measured thermal conductivity over time, a decision is automatically made as to whether an indication of a leak (L) has occurred between the patient fluid guidance unit and the sensor assembly. This leak establishes a fluid connection between the sensor fluid guidance unit and/or the sensor assembly on the one hand, and the environment on the other.