PPG Signal Consistency Analysis for Respiration Rate
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Solution Overview
Problem
Signal processing systems, particularly pulse oximetry, face challenges in accurately determining consistent portions of signals to extract reliable physiological parameters due to noise and variability, which affects the precision of measurements such as respiration rate.
Innovation Solution
The method involves analyzing signal extrema, specifically local maxima and minima, to identify consistent portions of signals like photoplethysmograph (PPG) signals by setting amplitude thresholds and evaluating interpeak distances, thereby isolating reliable segments for parameter determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal processing is performed on raw PPG signals to extract physiological parameters, then parameter identification can be achieved, but noise and variability in the signal reduce measurement precision
Solution Approach 1:
The patent divides the PPG signal into multiple segments based on detected peaks and troughs. Each segment is then individually evaluated for consistency using criteria such as peak amplitude thresholds, inter-peak distance ranges, and signal morphology analysis. Only consistent segments are selected for physiological parameter extraction, thereby filtering out noise and variability while maintaining measurement precision.
Solution Approach 2:
The patent applies local quality analysis by evaluating specific characteristics (amplitude, inter-peak distance, morphology) of individual signal segments rather than treating the entire signal uniformly. This allows identification and selection of locally consistent portions of the signal that meet predefined criteria, while excluding inconsistent portions affected by noise or artifacts.
2Measurement precision
If consistency analysis is performed by identifying and evaluating signal peaks and segments, then measurement precision improves, but processing time increases
Solution Approach 1:
The patent performs preliminary actions by first detecting peaks and troughs in the PPG signal, then pre-evaluating each segment against consistency criteria before final parameter extraction. This staged approach allows the system to quickly identify and discard inconsistent segments early in the process, reducing overall processing time while maintaining high measurement precision through thorough consistency checking.
Data Source
AI summary
According to embodiments, techniques for selecting a consistent part of a signal, including a photoplethysmograph (PPG) signal, are disclosed. A pulse oximetry system including a sensor or probe may be used to obtain a PPG signal from a subject. Signal peaks may be identified in the PPG signal. Characteristics of the signal peaks, including the amplitude levels of the signal peaks and/or the time-distance between the signal peaks may be used to determine if the PPG signal is consistent. In an embodiment, signal peaks are processed based on a consistency metric, and the processed signal peaks are compared to the consistency metric to determine if the PPG signal is consistent. If the PPG signal is determined to be consistent, the PPG signal may be further analyzed to determine an underlying signal parameter, including, for example, a patient respiration rate. If the PPG signal is determined to be inconsistent, the inconsistent portion of the signal may be removed from the overall signal or otherwise transformed.