Respiratory Event Detection Using Expiratory Sub-Window Regression
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Solution Overview
Problem
Patients with obstructive sleep apnea using nasal masks during PAP therapy may experience mouth puff events, leading to discomfort and reduced therapy efficacy due to gas leaks, which existing methods struggle to accurately detect, especially when nasal congestion changes breathing patterns.
Innovation Solution
A respiratory event determination system that uses a sub-window of the expiratory window to calculate the linear regression slope, dynamically selecting boundaries based on zero-crossings of the first derivative of the flow waveform to improve the accuracy of mouth puff event detection, allowing for real-time adjustments in therapy parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the entire expiratory window is used to calculate the linear regression slope, then the measurement covers the full respiratory cycle, but steep transitions between inhalation and exhalation skew the slope value and reduce detection accuracy
Solution Approach 1:
The expiratory window is divided into a sub-window that excludes the steep transition regions at the beginning and end of exhalation. By segmenting the measurement period to only include the stable middle portion of the expiratory phase, the calculation avoids being skewed by rapid flow changes during transitions, thereby improving the reliability of the slope determination while maintaining detection accuracy.
2Ease of operation
If a nasal mask is used to seal around the nose, then the interface is less obstructive and more patient-friendly, but gas leaks through the mouth reduce therapy efficacy
Solution Approach 1:
The system continuously monitors the expiratory flow waveform and calculates the linear regression slope to detect mouth puff events. When mouth puff is detected (indicated by an abnormally flat expiratory slope), the system can provide feedback to alert the patient or automatically adjust therapy parameters, thereby maintaining therapy efficacy despite the use of a comfortable nasal mask interface.
3Measurement precision
If the linear regression slope is calculated using a sub-window of the expiratory window, then the certainty of mouth puff determination is improved, but the analysis period is reduced
Solution Approach 1:
Instead of analyzing the entire expiratory window with uniform importance, the method applies local quality by identifying and prioritizing the middle portion of the expiratory phase where the flow is most stable. This sub-window represents the region of highest diagnostic value for detecting mouth puff, allowing precise local measurement that compensates for the reduced overall analysis duration.
Data Source
AI summary
A respiratory event determination system can have a controller that determines the presence of a respiratory event. The respiratory event can be a mouth puff event. The controller determines the presence as a function of a sub-window of an expiratory window of the breath. The expiratory window extends between a first time t1 and a second time t2. The sub-window is limited to a portion of the expiratory window. The sub-window can extend between a third time t3 and a fourth time ta. The fourth time ta can be before the second time t2.