Peripheral Pulse Waveform Segmentation for Central Blood Pressure Estimation
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Solution Overview
Problem
Existing methods for estimating central systolic blood pressure (cSBP) from peripheral measurements are inaccurate due to amplification issues and require complex, invasive procedures or calibration methods prone to errors, especially when using oscillometric cuff waveforms.
Innovation Solution
A method involving filtering peripheral pulse waveforms with high-pass filters to separate systolic and diastolic phases, followed by time division multiplexing and amplification to reconstruct an estimated intra-arterial waveform, allowing for calibration using oscillometric measurements of mean arterial pressure (MAP) and diastolic blood pressure (DBP).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If applanation tonometry is used to measure peripheral blood pressure waveform, then central systolic blood pressure can be estimated, but the procedure requires trained observers, takes several minutes to perform, requires relatively expensive equipment, and requires calibration from oscillometric measurements
Solution Approach 1:
The patent segments the peripheral pulse waveform into distinct phases (systolic and diastolic) using high-pass filters with different cut-off frequencies. The systolic phase is extracted using a first high-pass filter (e.g., 3-20 Hz) and the diastolic phase using a second high-pass filter (e.g., 1.5-20 Hz). This segmentation allows each phase to be processed separately through time-division multiplexing, simplifying the overall measurement procedure while maintaining accuracy in central blood pressure estimation.
Solution Approach 2:
The patent replaces the mechanical applanation tonometry procedure with an automated signal processing system. Instead of requiring manual compression of the radial artery by a trained observer, the system uses oscillometric cuff waveforms combined with digital filtering and time-division multiplexing to extract central blood pressure information automatically, eliminating the need for trained observers and reducing procedure time.
2Measurement precision
If general transfer function is applied to peripheral cuff pressure waveform, then central waveform can be transformed, but the transformation accuracy is limited and requires calibration from oscillometric measurements
Solution Approach 1:
The patent applies segmentation by dividing the peripheral pulse waveform into systolic and diastolic phases using high-pass filters. Each phase is then transformed separately through time-division multiplexing, which improves the accuracy of waveform transformation compared to applying a general transfer function to the entire waveform at once. This segmented approach reduces the need for external calibration while maintaining or improving transformation accuracy.
Solution Approach 2:
The patent performs preliminary filtering of the peripheral pulse waveform into distinct phases before applying the transfer function. By pre-separating the waveform into systolic and diastolic components using high-pass filters, the system prepares the data in a format that is more suitable for accurate transformation, reducing the need for subsequent calibration steps.
3Ease of operation
If oscillometric cuff measurement is used, then blood pressure can be measured non-invasively, but the systolic blood pressure is amplified above central values due to reflected pressure waves
Solution Approach 1:
The patent segments the oscillometric cuff waveform into systolic and diastolic phases using high-pass filters with different cut-off frequencies. This segmentation allows the system to process each phase separately through time-division multiplexing, which helps in accurately estimating central blood pressure by removing the amplification effect of reflected pressure waves while maintaining the non-invasive measurement approach.
Solution Approach 2:
The patent extracts the central blood pressure information from the peripheral oscillometric waveform by separating the systolic and diastolic phases and applying time-division multiplexing. This extraction process removes the amplification artifact caused by reflected pressure waves, allowing accurate estimation of central systolic blood pressure while maintaining the simplicity of non-invasive oscillometric measurement.
4Measurement precision
If applanation tonometry is used, then central blood pressure can be measured, but the equipment is relatively expensive and requires trained observers
Solution Approach 1:
The patent uses a copy of the oscillometric cuff waveform as input to the signal processing system. Instead of requiring expensive applanation tonometry equipment, the system processes a replicated version of the waveform data through digital filtering and time-division multiplexing to produce central blood pressure estimates. This copying approach maintains measurement precision while using inexpensive, readily available oscillometric equipment.
Solution Approach 2:
The patent replaces the mechanical applanation tonometry system with a digital signal processing system that uses oscillometric cuff waveforms. By substituting the mechanical compression method with automated digital filtering and time-division multiplexing, the system eliminates the need for trained observers and expensive equipment while maintaining the ability to measure central blood pressure accurately.
Data Source
AI summary
Embodiments of the present invention provide an improved transformation method whereby the peripheral pulse waveform is filtered to separate different phases which make up the waveform. The separate phases are transformed before being re-combined to provide an estimated intra-arterial transfer function. For example, in one embodiment the peripheral pulse waveform is filtered by a first high pass filter, and a copy of the peripheral pulse waveform filtered by a second high pass filter, having a different cut-off frequency. The two filtered waveforms may then be further processed, for example by being added back to original wave-form, and are then multiplexed together in a time division manner to provide a final waveform. For example, the part of the first filtered waveform corresponding to the systolic phase may be combined with the part of the second filtered waveform corresponding to the diastolic phase to produce the final waveform, and the respective filter cut-off frequencies may be chosen to extract characteristics of the respective phases of the heart.