Physiological Signal Qualification Using Sorted Difference Signals
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Solution Overview
Problem
Existing physiological monitoring systems face challenges in accurately determining pulse rate from photoplethysmographic signals due to noise components, subject movement, and variations in pulse shape, particularly in subjects with low perfusion or dicrotic notches, which can lead to incorrect rate determination.
Innovation Solution
The system employs a processing module that uses multiple operating modes, band-pass filtering, and qualification techniques to filter out noise, adjust algorithm settings based on signal analysis, and qualify calculated values to ensure accurate pulse rate determination, including the use of correlation calculations and signal conditioning to mitigate noise and artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If band-pass filtering is applied to reject noise, then noise rejection is improved, but the system may be initially tuned to noise and deviate from the correct physiological rate
Solution Approach 1:
The system uses qualification techniques that analyze the filtered signal to determine whether the band-pass filter is correctly tuned to the physiological rate. If the filter is tuned to noise, the qualification fails and the system adjusts the filter settings, creating a feedback loop that ensures the filter remains properly tuned to the actual physiological rate rather than noise
Solution Approach 2:
The system performs preliminary qualification analysis before final rate determination to ensure the band-pass filter is correctly tuned. This preliminary check prevents the system from committing to an incorrect rate determination based on noise, allowing the system to adjust filter settings in advance of final measurement
2Measurement precision
If strict criteria are used to determine physiological parameter, then measurement precision is improved, but the system may require more data processing and time
Solution Approach 1:
The determination process is divided into multiple independent qualification stages, each applying specific criteria to different aspects of the signal. This segmentation allows the system to efficiently evaluate multiple criteria without requiring exhaustive analysis of all data points, reducing processing time while maintaining precision
Solution Approach 2:
The system applies qualification criteria selectively to the most critical aspects of the signal that determine measurement accuracy. Rather than applying all possible criteria equally, the system focuses computational resources on the most discriminating parameters, achieving high precision with reduced processing overhead
3Reliability
If multiple operating modes and qualification techniques are implemented, then reliability of physiological parameter determination is improved, but device complexity increases
Solution Approach 1:
The system implements multiple operating modes that can be dynamically selected based on the characteristics of the input signal. The qualification techniques automatically adjust the stringency and type of criteria applied according to signal quality, allowing the system to maintain high reliability while adapting complexity to the specific measurement conditions rather than always using maximum complexity
Data Source
AI summary
A physiological monitoring system may determine physiological information, such as physiological rate information, from a physiological signal. The system may receive a calculated value indicative of a period associated with a physiological rate. The system may generated a first sorted difference signal based on a segment of the physiological signal having a size corresponding to the period. The system may generate second and third sorted difference signals based on segments of the physiological signal having sizes corresponding to a fraction of the period and a multiple of the period. The system may analyze the first, second, and third sorted difference signals, and qualify or disqualify the calculated value based on the analysis.