Implanted Medical Device Respiratory Cycle Artifact Detection
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Solution Overview
Problem
Existing methods for diagnosing respiratory sleep disorders using trans-thoracic impedance measurements are prone to false positives and false negatives due to artifacts not fully eliminated by current filtering techniques, particularly movement-related artifacts and cardiac influences, which can lead to erroneous diagnoses in implanted devices.
Innovation Solution
An implanted medical device with enhanced filtering capabilities to identify and manage artifacts, including static impedance jumps and singularities in respiratory cycles, by inhibiting diagnosis during artifact detection and updating averages, thereby reducing false positives and negatives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If trans-thoracic impedance measurement is used to detect respiratory cycles, then respiratory activity can be monitored continuously, but artifacts from patient movement and cardiac contractions cause false positives and false negatives
Solution Approach 1:
The patent introduces an intermediary artifact detection mechanism that mediates between the raw impedance signal and the final respiratory cycle detection. This intermediary layer identifies artifacts through specific criteria (amplitude thresholds, rate of change calculations, pattern recognition) and prevents them from triggering false respiratory event detections, thereby resolving the contradiction between continuous monitoring capability and diagnostic reliability
Solution Approach 2:
The system implements feedback by continuously monitoring impedance signal characteristics and adjusting artifact rejection decisions based on real-time signal analysis. The artifact detection algorithm provides feedback to the respiratory cycle detection process, dynamically filtering out artifacts while preserving genuine respiratory events, thus improving both measurement precision and diagnosis reliability
2Measurement precision
If filtering techniques are applied to eliminate cardiac components and static impedance, then respiratory signal quality improves, but some respiratory cycles with artifacts remain undetected
Solution Approach 1:
The patent applies local quality by implementing targeted artifact detection criteria that specifically address movement-related artifacts and cardiac interference without applying blanket filtering to all signals. The system selectively identifies and rejects only those cycles meeting artifact criteria (abnormal amplitude changes, inconsistent patterns) while preserving genuine respiratory cycles, thus improving signal quality without losing respiratory information
Solution Approach 2:
The system changes parameters by analyzing multiple characteristics of each respiratory cycle (amplitude, duration, rate of change, pattern consistency) rather than relying on a single threshold. This multi-parameter approach allows the system to distinguish between genuine respiratory variations and artifacts, maintaining measurement precision while preventing information loss
3Reliability
If artifact detection and inhibition mechanisms are implemented, then false positives and negatives are reduced, but device complexity increases
Solution Approach 1:
The patent segments the artifact detection process into distinct, modular components: impedance signal acquisition, respiratory cycle identification, artifact criteria evaluation, and detection inhibition. This segmentation allows each function to be implemented independently with clear logic, reducing overall device complexity while maintaining high diagnosis reliability through systematic artifact management
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 solution effectively reduces false positives and negatives in respiratory disorder diagnosis by automatically controlling for artifacts, ensuring more accurate detection of apnea and hypopnea events in implanted devices.
Implementation Method 1
The measurement of the minute-ventilation necessary for this detection of the apnea or of hypopnea is carried out by injecting of impulses of a constant current of a few hundred microamperes at a frequency of some Hertz between two electrodes laid out in the rib cage of the patient, or between the case of the implanted device and an electrode
Implementation Method 2
The trans-thoracic impedance varies according to the resistivity of tissue at the time current impulses are injected. As this resistivity depends primarily on the quantity of air in the lungs and the quantity of blood in the cardiac cavities
Data Source
AI summary
An active implantable medical device comprising circuits for measuring trans-thoracic impedance and delivering an impedance signal varying with respiratory activity of a patient. A signal representative of the respiratory activity of the patient is delivered starting from the impedance signal, and circuits for diagnosing respiratory disorder analyze variations of the respiratory signal on a plurality of successive cycles to detect there a profile of predetermined variation in relation to a given respiratory disorder. The device also includes circuits for automatically controlling respiratory cycles with artifacts, able to identify in the impedance signal a jump of static impedance, and/or to identify in a respiratory cycle or in a sequence of respiratory cycles a predetermined singularity representative of a cycle with artifact.