Scalogram Wedge Region Estimation for Pulse Oximetry Signal Processing
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Solution Overview
Problem
Pulse oximetry systems face challenges in accurately measuring patient parameters like oxygen saturation and respiration rate due to noise and motion artifacts in photoplethysmograph (PPG) signals, which degrade signal quality and reliability.
Innovation Solution
The system employs a continuous wavelet transform to process PPG signals, generating a scalogram where energy values in the wedge region are estimated using a grid-like structure and estimation parameters, allowing for determination of signal parameters like oxygen saturation and respiration rate, with confidence metrics ensuring reliability and noise filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional pulse oximetry systems process PPG signals using conventional methods, then the system is simple to implement, but measurement precision deteriorates due to noise and motion artifacts
Solution Approach 1:
The patent segments the PPG signal processing into multiple frequency bands using wavelet transform, separating signal components at different scales. This allows selective analysis of specific frequency ranges (e.g., pulse band, respiration band, noise band) to improve measurement precision while managing complexity through structured decomposition
Solution Approach 2:
The patent transforms the one-dimensional time-domain PPG signal into a two-dimensional time-frequency representation (scalogram) using continuous wavelet transform. This dimensional change enables simultaneous analysis of temporal and spectral characteristics, improving ability to distinguish signal from noise and motion artifacts
2Productivity
If the system processes all scalogram values directly, then measurement completeness is maintained, but processing time increases due to the wedge region requiring estimation
Solution Approach 1:
The patent performs preliminary processing of the scalogram by identifying and estimating values in the wedge region before final parameter extraction. This preliminary action completes the scalogram data structure in advance, allowing subsequent processing to proceed without waiting for estimation calculations during critical measurement phases
Solution Approach 2:
The patent introduces an intermediary estimation process that fills in the wedge region values based on resolved scalogram values and statistical relationships. This intermediary step creates a complete data representation without requiring direct measurement of all points, balancing information completeness with processing efficiency
Data Source
AI summary
According to embodiments, techniques for estimating scalogram energy values in a wedge region of a scalogram are disclosed. A pulse oximetry system including a sensor or probe may be used to receive a photoplethysmograph (PPG) signal from a patient or subject. A scalogram, corresponding to the obtained PPG signal, may be determined. In an arrangement, energy values in the wedge region of the scalogram may be estimated by calculating a set of estimation locations in the wedge region and estimating scalogram energy values at each location. In an arrangement, scalogram energy values may be estimated based on an estimation scheme and by combining scalogram values in a vicinity region. In an arrangement, the vicinity region may include energy values in a resolved region of the scalogram and previously estimated energy values in the wedge region of the scalogram. In an arrangement, one or more signal parameters may be determined based on the resolved and estimated values of the scalogram.