Haemodynamic Data Estimation Using Waveform Form Factors
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Solution Overview
Problem
Current methods are inadequate for non-invasively estimating haemodynamic data, particularly mean pressure, mean pressure drop, and hydraulic resistance in vascular systems, especially in cases of stenoses and occlusions, due to the dynamic nature of vascular beds and the complexity of collateral circulation, which makes it difficult to assess disease magnitude and resistance accurately.
Innovation Solution
A system and method that uses non-invasive measurements of blood velocity and pressure to calculate the ratio of upstream and downstream resistances, allowing for the estimation of local absolute mean blood pressure, maximal vasodilation, and absolute resistance of specific lesions, using form factor measures derived from waveforms, enabling the mapping of haemodynamic data and the calculation of unit length resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If non-invasive methods are used to measure blood flow and pressure, then patient safety and comfort are improved, but the ability to obtain accurate local haemodynamic data is worsened
Solution Approach 1:
The patent uses form factor measures as an intermediary parameter that can be obtained non-invasively from velocity and pressure waveforms. These form factors serve as mediators that indirectly provide information about local haemodynamic conditions without requiring direct invasive measurement, thus resolving the contradiction between non-invasive measurement and data accuracy
Solution Approach 2:
The patent replaces direct mechanical/invasive pressure measurement systems with waveform analysis methods. By analyzing the shape characteristics (form factors) of velocity and pressure waveforms obtained through non-invasive Doppler and pressure cuff measurements, the system derives haemodynamic information without mechanical intrusion into the vascular system
2Device complexity
If conventional formulas (Poiseuille or Bernoulli) are used to calculate resistance, then calculation simplicity is improved, but accuracy in predicting lesion resistance is worsened
Solution Approach 1:
The patent changes the parameters used for resistance calculation from those required by Poiseuille or Bernoulli equations to form factor measures derived from waveform shapes. This parameter transformation allows the use of simpler waveform analysis while achieving more accurate lesion resistance estimation that accounts for the non-linear, flow-dependent characteristics of stenotic lesions
Solution Approach 2:
The patent introduces dynamic waveform analysis that captures the time-varying characteristics of blood flow through lesions. By analyzing how velocity and pressure waveforms change over time and extracting form factors from these dynamic signals, the method accounts for the dynamic nature of stenotic resistance that static formulas cannot capture
3Adaptability or versatility
If vascular bed characteristics are allowed to change dynamically (vasodilation/vasoconstriction), then physiological adaptability is improved, but the ability to assess lesion resistance is worsened
Solution Approach 1:
The patent employs periodic oscillations in driving pressure and analyzes the resulting periodic variations in velocity and flow waveforms. By examining how the vascular bed responds to these periodic perturbations and how form factors change during these cycles, the method can distinguish between changes due to vascular bed adaptability and changes due to fixed lesion resistance
Solution Approach 2:
The patent utilizes the feedback relationship between driving pressure, flow, and vascular bed resistance. By measuring how changes in driving pressure produce changes in velocity and pressure waveforms, and analyzing the form factors of these responsive waveforms, the system can calculate lesion resistance while accounting for the dynamic feedback nature of the cardiovascular system
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
Enables precise estimation of disease magnitude and resistance, independent of vascular load state, allowing for the identification of lesions and their impact on blood flow, and the assessment of changes in resistance, facilitating the localization of stenoses and occlusions without invasive procedures.
Implementation Method 1
Ultrasound based Doppler shift spectral analysis and imaging techniques using Continuous Wave Doppler and Duplex scanning machines allow velocity and (in the latter case) flow rate data to be directly measured non-invasively
Implementation Method 2
techniques exist for calculating blood velocity and flow rates from Magnetic Resonant Imaging (MRI) data
Data Source
AI summary
Techniques exist for measuring local blood velocity of flow rate waveforms in, for example, mammalian vascular segments. A method and system for deriving information on disease in vascular segments, for example mean pressure, drop in mean pressure and/or hydraulic resistance, from such measured waveforms is described. The waveforms can, for example, be measured non-invasively using Doppler ultrasound or magnetic resonance techniques. Form factors (Vff, Pff) for the velocity waveform and the central arterial pressure are determined. Stenosis may be detected by detecting changes e.g in Vff/Pff.