Thoracic Impedance Respiratory Extraction Under Motion and Noise
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Solution Overview
Problem
Thoracic impedance measurements for respiratory parameter extraction are compromised by high levels of noise and artifacts due to motion, cardiac activity, and improper electrode contact, making it challenging to accurately determine respiration rate (RR) and tidal volume (TV), especially in conditions like shallow breathing, apnea, and oscillatory breathing.
Innovation Solution
A combination of time domain-based and autocorrelation-based methodologies is employed to assess signal quality and extract respiratory parameters from noisy thoracic impedance signals, utilizing accelerometer data and filtered noise to enhance accuracy, with heuristic rules to identify valid breaths and filter out artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If thoracic impedance measurements are used to extract respiratory parameters, then non-invasive monitoring is achieved, but measurement precision deteriorates due to high levels of noise and artifacts
Solution Approach 1:
The patent segments the thoracic impedance signal into multiple components using signal processing techniques, separating the respiratory signal from noise and artifacts. The signal is divided into respiratory-related components and artifact components, allowing selective analysis of the clean respiratory signal for parameter extraction.
Solution Approach 2:
The patent introduces accelerometer data as an intermediary to detect and characterize motion artifacts. The accelerometer signals serve as a mediator to identify artifact periods in the impedance signal, enabling the system to exclude or correct contaminated segments during respiratory parameter extraction.
2Device complexity
If traditional signal processing methods are used on noisy impedance signals, then processing complexity is reduced, but measurement precision deteriorates due to inability to filter artifacts effectively
Solution Approach 1:
The patent employs dynamic signal processing methods that adapt to varying signal conditions. The processing approach changes based on real-time signal quality assessment, switching between different filtering and analysis techniques to maintain precision across different noise levels and artifact conditions.
Solution Approach 2:
The patent changes processing parameters such as filtering thresholds, analysis windows, and detection sensitivity based on signal characteristics. By dynamically adjusting these parameters, the system maintains high measurement precision without requiring excessively complex fixed processing algorithms.
3Measurement precision
If multiple detection algorithms are used to improve respiratory parameter accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies multiple detection algorithms selectively rather than simultaneously to all signals. The system uses a primary detection method for most cases and activates alternative or supplementary algorithms only when signal quality metrics indicate their necessity, reducing overall computational complexity while maintaining precision.
Solution Approach 2:
The patent implements feedback mechanisms where signal quality metrics from initial processing inform the selection and configuration of subsequent detection algorithms. The system continuously monitors signal characteristics and adjusts algorithm selection accordingly, optimizing the balance between precision and complexity through adaptive feedback control.
Data Source
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AI summary
One embodiment is a method of extracting respiratory parameters from a short duration thoracic impedance ("TI") signal, the method comprising preprocessing the TI measurement signal to obtain a respiratory signal therefrom; assessing the respiratory signal for at least one of signal quality and signal integrity; executing at least one of an autocorrelation algorithm and a time-domain zero-crossing algorithm on the respiratory signal to extract at least one respiratory parameter therefrom, the at least one respiratory parameter comprising at least one of respiration rate ("RR") and tidal volume ("TV").