Blood Flow Measurement via RF Phase Shift

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Solution Overview

Problem

Current methods for measuring cardiac output, such as the Fick method, thermodilution, and thoracic electrical bioimpedance, face challenges including invasive procedures, high costs, noise interference, and low signal-to-noise ratios, making them inefficient for accurate and continuous monitoring, especially in high-risk patients.

Innovation Solution

A system using radiofrequency signals to calculate blood flow by determining the phase shift between output and input signals, with a signal processing unit that reduces amplitude modulation and filters out noise, allowing for more accurate measurement of cardiac output and other blood flow parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If Fick method is used to measure cardiac output, then measurement can be performed, but invasive procedures and complex blood sampling are required

Engineering Contradiction:

Improvecardiac output measurement accuracyVSAvoidinvasiveness of procedure

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent replaces mechanical blood sampling and invasive catheterization with non-invasive electrical signal measurement. Instead of physically drawing blood for oxygen content analysis or using pulmonary artery catheters, the system uses electrical impedance measurements through the thorax to indirectly determine cardiac output, eliminating the need for invasive procedures while maintaining measurement capability

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces electrical impedance as an intermediary parameter to measure cardiac output. Rather than directly measuring blood flow or oxygen content through invasive means, the system measures changes in electrical impedance caused by blood volume changes, using this intermediary electrical signal to infer cardiac output without direct blood sampling

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If thoracic electrical bioimpedance is used to measure blood flow, then non-invasive measurement is achieved, but noise interference and low signal-to-noise ratio occur

Engineering Contradiction:

Improvenon-invasive measurementVSAvoidsignal-to-noise ratio

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent employs periodic action by using alternating current at specific frequencies to penetrate the thorax and detect blood flow. The system uses periodic electrical signals that can be distinguished from noise through their rhythmic nature, allowing the signal processing unit to filter out noise while retaining the periodic electrical impedance changes caused by pulsating blood flow

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the electrical parameters by using specific frequency ranges and amplitude modulation techniques. The system adjusts the frequency and amplitude of the electrical signals to optimize penetration through the thorax and to create signal characteristics that are easily distinguishable from background noise, thereby improving the signal-to-noise ratio while maintaining non-invasive measurement

Inventive Principle:

Principle #35Parameter changes

3Productivity

If continuous monitoring is implemented, then real-time blood flow data is obtained, but measurement accuracy is compromised by noise

Engineering Contradiction:

Improvecontinuous monitoring capabilityVSAvoidaccuracy of continuous measurement

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent ensures continuity of useful action by continuously measuring electrical impedance throughout the cardiac cycle and maintaining constant monitoring. The system continuously applies electrical signals and processes impedance changes in real-time, providing uninterrupted blood flow data without compromising accuracy, as the continuous measurement allows for consistent signal characterization and noise filtering

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent implements feedback through the signal processing unit that continuously analyzes the electrical impedance signals and adjusts measurement parameters accordingly. The system uses feedback from the measured impedance changes to refine the signal processing, filter noise, and maintain accurate continuous monitoring by adapting to varying signal conditions in real-time

Inventive Principle:

Principle #23Feedback

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 provides a more accurate and continuous measurement of cardiac output with improved signal-to-noise ratios, reducing the need for invasive procedures and lowering costs, while enhancing the reliability and efficiency of blood flow monitoring.

Implementation Method 1

determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals and using the phase shift to calculate the blood flow in the organ

Methodology Applied

Scientific EffectPhase shift:

Data Source

PatentUS8388545B2System, method and apparatus for measuring blood flow and blood volume

Publication Date: 2013.03.05 BAXTER INT INC

AI summary

A method of calculating blood flow in an organ of a subject using output radiofrequency signals transmitted to the organ and input radiofrequency signals received from the organ, the method comprises determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals and using the phase shift to calculate the blood flow in the organ.