Arterial Pulse Wave Velocity Determination via Parametric System Identification
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Solution Overview
Problem
Conventional methods for determining pulse wave velocity (PWV) are prone to errors due to waveform interference and artifact detection issues, leading to inaccurate measurements of arterial stiffness and blood pressure monitoring.
Innovation Solution
The application of parametric system identification to simultaneously measured proximal and distal arterial waveforms, using models such as tube-load and black-box models to determine pulse transit time (PTT) and PWV, effectively eliminating reflected wave interference and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the foot-to-foot detection method is used to determine pulse transit time, then the measurement process is simple and easy to implement, but the measurement precision deteriorates due to waveform interference and artifact detection issues
Solution Approach 1:
The patent extracts and eliminates the reflected wave component from the composite arterial waveform by modeling it as a separate entity. By identifying and removing the reflected wave interference, the method isolates the true forward wave foot, enabling accurate PTT measurement without being affected by waveform distortion or artifacts.
Solution Approach 2:
The patent introduces an intermediary mathematical model (transfer function) that relates the proximal and distal arterial waveforms. This model serves as a mediator to determine PTT by comparing the modeled distal waveform with the actual measured waveform, thereby avoiding direct foot-to-foot detection and its associated errors from waveform interference.
2Ease of operation
If the foot-to-foot detection method is used, then the measurement process is straightforward, but the reliability deteriorates when waveform artifacts are present or waveform feet are difficult to detect
Solution Approach 1:
The patent replaces the mechanical/visual foot-to-foot detection method with a mathematical system identification approach. By using parametric models and transfer functions to analyze the waveform relationships, the method eliminates reliance on visual identification of waveform feet, thereby achieving robustness against artifacts and difficult-to-detect waveform features.
Solution Approach 2:
The patent employs an iterative optimization process where the model parameters are adjusted to minimize the difference between the modeled and actual distal waveforms. This feedback mechanism ensures that the determined PTT accurately reflects the true physiological conditions even in the presence of noise or artifacts, improving measurement reliability.
3Device complexity
If conventional PWV measurement methods are used, then the measurement process is simple, but the measurement precision deteriorates leading to large errors in BP monitoring
Solution Approach 1:
The patent applies dynamic system identification techniques to model the arterial system as a time-varying system. By using dynamic models that can adapt to changing physiological conditions and by continuously updating the transfer function parameters, the method maintains high precision in PWV and BP monitoring despite variations in arterial compliance and wave reflection patterns.
Data Source
AI summary
Methods are presented for determining pulse transit time (PTT) and/or pulse wave velocity (PWV) of a subject by application of parametric system identification to proximal and distal arterial waveforms. The two waveforms are measured from the subject. A system is defined that relates the proximal arterial waveform to the distal arterial waveform (or vice versa) in terms of the unknown parameters of a parametric mathematical model. The model parameters are determined from the measured waveforms using system identification. PTT between the proximal and distal arterial sites is then determined from the system model. PWV may also be determined by dividing the distance between measurement sites (D) by PTT.