Radiofrequency Impedance Cardiography for Non-Invasive Exercise Capacity Estimation
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Solution Overview
Problem
Current methods for estimating exercise capacity in patients with congestive heart failure are invasive, costly, and carry risks, with direct measurement of cardiac output being cumbersome and non-invasive techniques lacking accuracy.
Innovation Solution
A method and system using radiofrequency signals to estimate exercise capacity by determining the phase shift of input signals relative to output signals, calculating cardiac output, and combining it with cardiopulmonary exercise testing measures to assess exercise capacity, featuring a dynamically variable filter to adapt to physiological changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement of cardiac output by thermodilution is used, then measurement accuracy is improved, but device complexity and invasiveness increase
Solution Approach 1:
The patent replaces the mechanical/physical thermodilution method with an electrical impedance-based measurement system. The system uses radiofrequency signals to detect changes in electrical impedance of the thorax, which correlate with blood volume changes and cardiac output, thereby eliminating the need for invasive catheter-based thermodilution while maintaining measurement capability
Solution Approach 2:
The patent introduces electrical impedance as an intermediary parameter to indirectly measure cardiac output. Instead of directly measuring blood flow or temperature changes, the system measures changes in electrical impedance caused by blood volume changes in the thorax, providing a non-invasive pathway to cardiac output measurement
2Ease of operation
If non-invasive techniques for cardiac output measurement are used, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent employs dynamic signal processing techniques including real-time filtering, phase shift analysis, and adaptive algorithms to extract accurate cardiac output information from non-invasive impedance measurements. The system dynamically adjusts to varying physiological conditions during exercise, maintaining measurement precision despite the non-invasive approach
Solution Approach 2:
The system incorporates feedback mechanisms where the measured impedance signals are continuously processed and compared against reference values or physiological models. This feedback loop enables real-time correction and refinement of cardiac output calculations, enhancing measurement accuracy from non-invasive data
3Measurement precision
If cardiopulmonary exercise testing with gas analysis is used, then exercise capacity assessment is improved, but device complexity and cost increase
Solution Approach 1:
The patent combines cardiac output measurement via impedance cardiography with exercise capacity assessment into a single integrated system. By merging these two functions, the system eliminates the need for separate complex gas analysis equipment while providing comprehensive exercise capacity evaluation through the relationship between cardiac output and oxygen consumption
Solution Approach 2:
The patent creates a multi-functional system that uses the same impedance measurement apparatus for both cardiac output monitoring and exercise capacity assessment. The system universally applies electrical impedance principles to derive multiple physiological parameters, reducing overall device complexity and cost compared to specialized equipment for each measurement
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 non-invasive, cost-effective means to estimate exercise capacity, correlating cardiac output with oxygen uptake and ventilation efficiency, offering a reliable assessment of exercise capacity and condition worsening in CHF patients.
Implementation Method 1
determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals
Implementation Method 2
using output radiofrequency signals transmitted to the subject during exercise and input radiofrequency signals received from the subject during exercise
Data Source
AI summary
A method of estimating exercise capacity of a subject is disclosed. The method uses output radiofrequency signals transmitted to the subject during exercise and input radiofrequency signals received from the subject during exercise. The method comprises: determining a phase shift of the input radiofrequency signals relative to the output radiofrequency signals; calculating cardiac output based on the phase shift; and using the cardiac output for estimating the exercise capacity of the subject.