Accelerometer Signal Processing for Heart Rate Detection
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Solution Overview
Problem
Existing processing devices and systems for seismocardiogram (SCG) signal processing struggle to accurately detect heart-rate, especially in cases of irregular heart-rates or movement artifacts, which are common in patients with heart diseases or during patient movement.
Innovation Solution
A processing device and method that adjusts accelerometer signals by calculating an adjustment factor based on the estimated time interval between physiological events, such as aortic valve opening and closing, to enhance the detection of heart-related vital signs, while suppressing signals with low signal strength and preserving those with high signal strength, thereby improving accuracy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SCG signal processing methods are used, then the system is simple and easy to operate, but the measurement precision and reliability of heart-rate detection deteriorates in cases of irregular heart-rates or movement artifacts
Solution Approach 1:
The patent segments the SCG signal into distinct physiological events (aortic valve opening, aortic valve closing, mitral valve opening, mitral valve closing) and processes each event separately through envelope detection and peak identification. This segmentation allows accurate measurement of individual cardiac intervals even in the presence of arrhythmias or movement artifacts, resolving the contradiction between measurement precision and processing complexity.
Solution Approach 2:
The patent applies preliminary envelope detection and signal conditioning before peak detection and interval measurement. By pre-processing the signal to extract envelopes and identify potential event locations in advance, the system prepares the data structure needed for accurate heart-rate calculation, improving measurement precision without requiring overly complex real-time processing during the measurement phase.
2Reliability
If conventional processing methods are used, then the device complexity is low, but the reliability of vital sign detection worsens in the presence of movement artifacts and arrhythmias
Solution Approach 1:
The patent implements feedback mechanisms where detected peaks and intervals are used to validate and adjust subsequent detections. The system monitors the consistency of measured intervals and can identify and reject outliers caused by movement artifacts or arrhythmias, thereby maintaining high reliability of heart-rate detection even in challenging conditions without requiring excessively complex processing systems.
Solution Approach 2:
The patent employs dynamic thresholding and adaptive signal processing parameters that adjust based on the detected signal characteristics. The envelope detection thresholds and peak identification criteria are dynamically adjusted according to the signal strength and variability, allowing the system to maintain reliability across different physiological states and movement conditions without fixed complex processing rules.
3Measurement precision
If signal processing enhances detection accuracy, then measurement precision improves, but the computational time and processing duration increase
Solution Approach 1:
The patent applies local quality enhancement by focusing processing resources on specific regions of the signal where physiological events are expected to occur. By using envelope detection to identify local maxima and minima corresponding to valve events, the system achieves high measurement precision for critical intervals without requiring exhaustive processing of the entire signal, thus minimizing processing time while maintaining accuracy.
Solution Approach 2:
The patent implements partial action by detecting and measuring only the most critical cardiac intervals (such as aortic valve opening to closing) rather than analyzing every aspect of the cardiac cycle. This selective measurement approach provides sufficient precision for heart-rate monitoring while significantly reducing the computational time required compared to comprehensive cardiac analysis.
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 enables accurate and reliable detection of heart-related vital signs, even in the presence of movement artifacts or arrhythmias, by effectively distinguishing between different physiological events and maintaining signal morphology, thus improving the overall monitoring of heart-related parameters.
Implementation Method 1
vibrations of the heart or blood-transport can be measured directly on the skin of a person via an accelerometer. The SCG signals can be analyzed in order to detect respiratory and heart signals.
Data Source
Figure 1(A)~2
Figure 3(A)~3(F)
Figure 4
AI summary
The present invention relates to a processing device for processing accelerometer signals (17, 17a-c) for use in monitoring vital signs of a subject, comprising - a signal input unit (38) for inputting an accelerometer signal (17, 17a-c) of the subject in time, the accelerometer signal (17, 17a-c) being related to at least one physiological event being a cardiovascular or a respiratory event of the subject and measured for at least one spatial direction, an envelope determination unit (19, 40) for determining an envelope signal (21) of the input accelerometer signal (17, 17a-c), a calculation unit (44) for calculating an adjustment factor (43) based on an estimated time interval (45) between a first and a second physiological event of the subject, and a signal adjustment unit (42) for adjusting the determined envelope signal (21) by multiplying the envelope signal (21) with the calculated adjustment factor (43).