Dynamic Band-Pass Filter for Accurate Pulse Rate Measurement
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Solution Overview
Problem
Determination of pulse rate from photoplethysmographic (PPG) signals is challenging due to noise components, subject movement, varying pulse shapes, and low perfusion, which can lead to inaccurate pulse rate measurements.
Innovation Solution
A physiological monitor employs a processing module that uses multiple operating modes, band-pass filtering, and algorithm settings to qualify calculated values, apply signal conditioning techniques, and manage status flags to mitigate noise and accurately determine pulse rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If band-pass filtering is applied to reject noise, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent implements dynamic adjustment of band-pass filter parameters based on detected pulse rate. The filter center frequency and bandwidth are automatically tuned to track the physiological signal characteristics, allowing the system to maintain optimal noise rejection while adapting to varying heart rates. This dynamic adaptation resolves the contradiction by making the filtering complexity conditional rather than static.
Solution Approach 2:
The system employs feedback mechanisms where the detected pulse rate information is fed back to adjust the band-pass filter settings. This closed-loop control ensures that the filter parameters are continuously optimized based on the actual physiological signal characteristics, improving measurement precision without requiring permanently complex processing for all conditions.
2Reliability
If multiple operating modes with strict criteria are used to qualify calculated values, then reliability is improved, but productivity decreases
Solution Approach 1:
The patent implements a hierarchical qualification approach where calculated pulse rates undergo progressive validation stages. Not all calculated values require the full suite of qualification tests - simpler checks are performed first, with more stringent criteria applied only when necessary. This partial application of qualification criteria maintains reliability for critical measurements while improving overall processing throughput.
Solution Approach 2:
The qualification process is segmented into multiple independent stages: initial detection, validation against physiological constraints, noise rejection testing, and final confirmation. Each stage can independently pass or fail a calculated value, allowing the system to efficiently reject obviously incorrect measurements without applying all qualification criteria to every single calculation, thus balancing reliability with productivity.
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
The solution reliably determines pulse rate by filtering noise and adjusting algorithm settings based on signal quality, ensuring accurate physiological parameter measurement even in noisy conditions.
Implementation Method 1
A physiological monitor may determine one or more physiological parameters such as, for example, a physiological rate based on signals received from one or more physiological sensors. The physiological monitor may analyze physiological signals (e.g., photoplethysmographic (PPG) signals)
Implementation Method 2
Another mode may implement a relatively narrow, adjustable band-pass filter on the physiological data (e.g., time series data), which is good at rejecting noise when it is tuned to the correct rate
Data Source
AI summary
A physiological monitoring system may determine physiological information, such as physiological rate information, from a physiological signal. The system may condition the physiological signal to assist in the determination of the physiological information. The system may generate a positive signal and a negative signal based on respective positive and negative values of the physiological signal. The system may filter the positive and negative signals, combine the filtered signals, and modify the physiological signal based on the combined signal. The physiological signal may be modified, for example, by subtracting the combined signal from the physiological signal.