Pulse Wave Analysis for Respiratory Variation
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Solution Overview
Problem
Non-invasive methods for obtaining respiratory-induced variation of arterial pressure often suffer from noise interference, making it difficult to accurately calculate this vital circulatory index.
Innovation Solution
A pulse wave analyzing apparatus that non-invasively measures cuff pressure and pulse waves, performs signal processing to isolate unit pulse waves, calculates amplitude ratios, and applies frequency analysis to determine an index value for respiratory-induced variation, while assessing reliability through power spectrum analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-invasive blood pressure measurement using a blood pressure cuff is used, then the burden on the subject is reduced, but noise is easily included in the measured pressure waveform making it difficult to accurately obtain respiratory-induced variation
Solution Approach 1:
The invention extracts the pulse wave signal from the blood pressure waveform by detecting the timing of maximum pressure points. By isolating only the relevant pulse wave components and excluding the noisy blood pressure waveform data, the system achieves accurate respiratory-induced variation measurement without the burden of invasive catheterization.
Solution Approach 2:
The invention introduces an intermediary processing step that uses the relationship between pulse wave amplitude and respiratory-induced variation. By measuring pulse wave amplitude at different blood pressure levels and calculating the rate of change, the system indirectly obtains respiratory-induced variation while avoiding direct measurement of the noisy blood pressure waveform.
2Measurement precision
If invasive catheter insertion is used, then accurate respiratory-induced variation can be obtained, but excessive burden is imposed on the subject and measurement time is prolonged
Solution Approach 1:
The invention creates a computational model that copies the physiological relationship between pulse wave amplitude and respiratory-induced variation. By establishing the mathematical relationship dA/dP = k·PPV through non-invasive measurements, the system replicates the accuracy of invasive methods without requiring actual catheter insertion into blood vessels.
3Measurement precision
If blood pressure waveform measurement is used, then respiratory-induced variation can be obtained, but noise from body movement or external contact makes accurate calculation difficult
Solution Approach 1:
The invention extracts only the pulse wave amplitude information from the blood pressure waveform by detecting maximum pressure points. This extraction process removes the noise components present in the full blood pressure waveform while retaining the essential pulse wave data needed for calculating respiratory-induced variation.
Solution Approach 2:
The invention uses pulse wave amplitude as an intermediary parameter that is less susceptible to noise from body movement or external contact. By measuring amplitude changes rather than direct blood pressure variations, the system achieves more reliable respiratory-induced variation calculation in the presence of external disturbances.
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
This approach allows for accurate and reliable determination of respiratory-induced variation, comparable to invasive methods, by filtering out noise and isolating relevant frequency components, thus reducing subject burden and measurement time.
Implementation Method 1
a frequency analyzing unit that frequency-analyzes the variation rate of the amplitude of the pulse wave
Implementation Method 2
a pulse wave sensor or another sensor for acquiring a pressure waveform
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A pulse wave analyzing apparatus comprises an acquiring section (11) which acquires a pulse wave that is non-invasively measured, and an analyzer (12) which calculates data on the frequency axis by using the pulse wave, and which obtains the index value of the respiratory-induced variation based on the calculated data on the frequency axis.