Inverse Transfer Function for Cuff Pulse Wave Distortion
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Solution Overview
Problem
Cuff volumetric pulse waves obtained through existing methods are distorted due to propagation through compliant materials like air in cuffs or rubber tubes, leading to inaccurate evaluation and diagnosis of circulatory organs, especially when skin and subcutaneous tissue are involved.
Innovation Solution
An apparatus using an inverse transfer function to determine a no-delay cuff volumetric pulse wave, eliminating transmission delays and distortions by storing and applying an inverse transfer function corresponding to the transfer function between pressure pulsation and detected pressure oscillation, allowing for accurate pulse wave analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cuff volumetric pulse wave is obtained by extracting oscillatory component from pressure detected by pressure sensor connected to cuff via rubber tube, then the pulse wave can be obtained non-invasively, but the waveform is distorted due to propagation through air in cuff or rubber tube with great compliance
Solution Approach 1:
The patent introduces a transfer function as an intermediary mathematical model that characterizes the relationship between the original pulse wave and the distorted detected signal. This transfer function acts as a mediator that allows accurate reconstruction of the original pulse wave by compensating for the distortion introduced by the compliant transmission path (air in cuff, rubber tube). The transfer function is determined in advance through calibration and stored in memory, enabling real-time accurate pulse wave determination without modifying the physical measurement setup.
2Device complexity
If the pulse wave propagates through air in the cuff or rubber tube with great compliance, then the measurement system remains simple and non-invasive, but the waveform distortion increases leading to inaccurate circulatory organ evaluation
Solution Approach 1:
The patent applies preliminary action by determining and storing the transfer function in advance through a calibration process before actual pulse wave measurements are taken. This pre-determined transfer function is saved in memory and subsequently used to accurately determine pulse waves during normal operation. By performing the calibration and transfer function determination beforehand, the system maintains simplicity during actual measurements while ensuring high accuracy through the pre-computed compensation model.
3Ease of manufacture
If band-pass filter is used to extract pulse wave from pressure signal, then the oscillatory component can be separated, but the extracted pulse wave may not be sufficiently accurate due to waveform distortion
Solution Approach 1:
The patent implements a feedback mechanism where the determined transfer function is used to feed back into the pulse wave determination process. Instead of simply filtering the detected signal, the system uses the transfer function to actively compensate for distortion by solving the relationship equation. This feedback approach continuously corrects the pulse wave determination based on the characterized distortion, significantly improving accuracy over simple filtering while maintaining reasonable processing complexity.
Data Source
AI summary
A subject evaluation value measuring apparatus 10, functioning as a cuff volumetric pulse wave obtaining apparatus, includes a pulse wave determining device (i.e., a cuff volumetric pulse wave determining device) 52 that determines, using an inverse transfer function 1H(f), stored in a ROM (i.e., an inverse transfer function memory) 42, that corresponds to a pre-determined transfer function H(f) between input, i.e., pressure pulsation produced in a cuff 20, and output, i.e., pressure pulsation detected by a pressure sensor 24, a no-delay cuff volumetric pulse wave PK(t) having substantially no delay of transmission, based on an actual cuff pulse wave signal SM outputted by the pressure sensor 24. The thus determined cuff volumetric pulse wave PK(t) is free of waveform distortion and accordingly enjoys high accuracy.