Transthoracic Impedance Cardiac Output Detection Using Integer Filtering
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Solution Overview
Problem
Current methods for determining cardiac output in emergency situations, such as cardiac arrest, are inefficient due to the time-consuming and processor-intensive Fast Fourier Transformation (FFT) required for impedance cardiogram (ICG) analysis, which can delay critical diagnosis in lay responders using public access defibrillators.
Innovation Solution
An apparatus and method that uses integer filtering to derive cardiac output markers from transthoracic impedance signals, allowing for real-time diagnosis by calculating the ratio of filtered signal amplitudes, which can be implemented in automated external defibrillators to quickly determine if a patient's rhythm is shockable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Fast Fourier Transformation (FFT) is used to analyze impedance cardiogram signals, then accurate cardiac output markers can be obtained, but the processing time increases and processor capacity is consumed
Solution Approach 1:
The patent changes the processing method from FFT to a simplified algorithm that calculates the ratio of maximum to minimum impedance values during the cardiac cycle. This parameter change in the analysis approach maintains diagnostic accuracy while dramatically reducing computation time and processor requirements, enabling real-time cardiac output assessment in portable defibrillators
2Measurement precision
If Fast Fourier Transformation (FFT) is used to analyze impedance cardiogram signals, then accurate cardiac output markers can be obtained, but processor capacity is consumed
Solution Approach 1:
The patent transforms the complex FFT-based analysis into a simple ratio calculation method that determines cardiac output from the maximum-to-minimum impedance ratio. This dramatically reduces processor capacity requirements while maintaining the ability to accurately distinguish between cardiac arrest and other conditions, making the system viable for portable defibrillators with limited processing power
3Loss of information
If pulse checking is performed by lay responders, then cardiac output information can be obtained, but the time taken exceeds the value of the determination
Solution Approach 1:
The patent replaces the manual mechanical pulse checking method with an automated electrical impedance-based detection system. The defibrillator automatically measures transthoracic impedance and processes the signal to determine cardiac output, providing rapid and accurate information to lay responders without requiring them to perform time-consuming manual pulse checks
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 significantly increases the specificity and speed of cardiac output determination, enabling first responders to make timely decisions during emergency resuscitation, even in resource-constrained portable defibrillators.
Implementation Method 1
means for monitoring a patient's transthoracic impedance and generating a corresponding impedance signal
Implementation Method 2
filtering the impedance signal at a plurality of different wavelengths within a predetermined frequency band
Data Source
AI summary
An apparatus for indicating cardiac output comprises means for monitoring a patient's transthoracic impedance and generating a corresponding impedance signal, and signal processing means for (a) deriving a signal S1 which is a measure of the average amplitude of the impedance signal, (b) filtering the impedance signal at a plurality of different wavelengths within a predetermined frequency band, (c) for each filter deriving a signal S2 which is a measure of the average amplitude of the respective filter output, (d) calculating the ratio of the maximum one of the signals S2 derived from step (c) to the signal S1 derived from step (a), and (e) using the ratio from step (d) in a decision tree to provide a signal indicating cardiac output or not.