Respiratory Effort Measurement Using Differential Signal Smoothing
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Solution Overview
Problem
Current methods for assessing respiratory effort in subjects with chronic obstructive pulmonary disease (COPD) face challenges due to high variance and potential biases from lack of motivation or pain inhibition, especially in clinical applications, and the recruitment of unwanted muscles during maximum inspiratory maneuvers.
Innovation Solution
A system and method that involve smoothing relaxed and forced breathing signals using different averaging windows to accurately determine respiratory effort, with electrodes placed at the parasternal intercostal muscle to measure electrical activity, and a processor to calculate respiratory effort by comparing peak values and applying filtering techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sharp maximum inspiration maneuver is used to determine normalized respiratory effort, then the measurement can be obtained, but the measurement has large variance and may be biased due to lack of motivation or pain inhibition
Solution Approach 1:
The patent uses forced breathing maneuvers that require only partial activation (sharp sniff-like inspiration) rather than full maximum inspiration. This reduces the impact of motivation and pain inhibition while still providing sufficient signal to calculate respiratory effort through normalization with relaxed breathing signals
Solution Approach 2:
The patent introduces relaxed breathing signals as an intermediary reference to normalize the forced breathing signals. This intermediary measurement allows calculation of respiratory effort without requiring absolute maximum activation, thereby reducing bias from motivation and pain inhibition issues
2Measurement precision
If full activation is required during maximum inspiratory maneuver, then respiratory effort can be assessed, but it is difficult to achieve in clinical applications with pain-related inhibition and elderly subjects
Solution Approach 1:
The patent accepts partial activation during forced breathing maneuvers rather than requiring full activation. The sharp sniff-like inspiration requires minimal effort while still generating detectable EMG signals that can be normalized against relaxed breathing to assess respiratory effort
Solution Approach 2:
The patent changes the parameter from requiring maximum activation level to using ratio-based normalization between forced and relaxed breathing. This parameter transformation allows assessment of respiratory effort without demanding full muscle activation, making it feasible for subjects with pain inhibition or limited capacity
3Measurement precision
If maximum inspiratory maneuver is performed, then respiratory effort measurement is obtained, but other muscles such as postural muscles are recruited which act as disturbance and potentially elevate maximum RMS values
Solution Approach 1:
The patent extracts and isolates the respiratory muscle signal from contaminated maximum inspiratory maneuvers by using relaxed breathing as a reference. Through normalization, the harmful postural muscle artifacts are removed or minimized, leaving the pure respiratory effort component
Solution Approach 2:
The patent uses relaxed breathing signals as an intermediary to separate respiratory from postural muscle activity. The ratio between forced and relaxed breathing signals serves as a mediator that cancels out common postural muscle artifacts while preserving the respiratory effort information
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 effectively reduces noise and maintains information integrity, providing a reliable and unbiased measurement of respiratory effort, even in subjects with difficulty achieving full activation, by distinguishing between relaxed and forced breathing signals.
Implementation Method 1
the assessment of the parasternal muscle activity (measured from surface electromyography (EMG), e.g. with electrodes positioned at the 2nd intercostal space)
Data Source
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AI summary
The invention provides a system and method for determining a respiratory effort for a subject. The method comprises obtaining a relaxed signal representing a subject breathing in a relaxed manner and a forced signal representing a subject breathing in a forced manner. The relaxed signal is then smoothed over a first averaging window and the forced signal is smoothed over a second averaging window, wherein the first averaging window is longer than the second averaging window. Based on the smoothed relaxed signal and the smoothed forced signal, a respiratory effort can thus be determined.