PPG Signal Normalization for CNIBP Recalibration Stability
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Solution Overview
Problem
Continuous non-invasive blood pressure monitoring systems often experience unnecessary recalibrations due to changes in light intensity or other sensor settings, leading to false recalibration triggers and instability in blood pressure measurements.
Innovation Solution
A system that normalizes photoplethysmograph (PPG) signals using a processor to compare signal metrics before and after changes, determining if a recalibration is necessary by checking if the normalized signal corresponds to the original signal within a threshold, thereby avoiding unnecessary recalibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the system adjusts light intensity to optimize sensor performance, then the monitoring accuracy is improved, but false recalibrations are triggered due to signal metric changes
Solution Approach 1:
The patent introduces a normalization process as an intermediary step between the raw PPG signal and the blood pressure calculation. The normalization function acts as a mediator that compensates for light intensity changes and other sensor parameter variations, allowing the system to distinguish between genuine blood pressure changes and artifact-induced signal variations. This intermediary normalization layer prevents false recalibrations while maintaining measurement accuracy.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the normalization parameters based on detected signal characteristics. When light intensity or other sensor parameters change, the system modifies the normalization factors to compensate for these changes. This dynamic parameter adjustment allows the system to maintain stable blood pressure measurements despite variations in operating conditions, preventing spurious recalibration events.
2Reliability
If the system performs frequent recalibrations to maintain accuracy, then measurement reliability is improved, but system stability deteriorates due to unnecessary recalibration events
Solution Approach 1:
The normalization function serves as a protective intermediary that filters out false recalibration triggers. By normalizing the PPG signal before analyzing it for recalibration conditions, the system can reliably distinguish between genuine physiological changes requiring recalibration and artifact-induced variations that do not require recalibration. This intermediary layer maintains measurement reliability while preventing unnecessary system instability.
Solution Approach 2:
The system implements a feedback mechanism where the normalized signal characteristics are continuously monitored to determine whether recalibration is actually needed. The feedback loop compares normalized signal metrics against threshold criteria to intelligently trigger recalibration only when necessary, rather than based on raw signal changes alone. This feedback approach maintains reliability while preserving stability by avoiding premature or false recalibration events.
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 stabilizes blood pressure measurements by reducing false recalibration events and maintaining accurate readings despite changes in light intensity or sensor settings, ensuring continuous and reliable monitoring.
Implementation Method 1
A pulse oximeter typically includes a light sensor that is placed at a site on a patient, typically a fingertip, toe, forehead or earlobe, or in the case of a neonate, across a foot. The oximeter may pass light using a light source through blood perfused tissue and photoelectrically sense the absorption of light in the tissue.
Data Source
AI summary
The present disclosure relates to systems and methods for analyzing and normalizing signals, such as PPG signals, for use in patent monitoring. The PPG signal may be detected using a continuous non-invasive blood pressure monitoring system and the normalized signals may be used to determine whether a recalibration of the system should be performed.