Defibrillator CPR Rate Determination via Impedance
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Solution Overview
Problem
Current methods for determining cardiopulmonary resuscitation (CPR) compression rates using accelerometers and pressure-sensitive pads are prone to inaccuracies due to noise and complexity, while impedance-based methods face challenges from varying subject conditions and signal morphology changes.
Innovation Solution
A defibrillator system that utilizes electrodes to measure impedance and electrocardiogram signals, processing these signals to obtain frequency spectra and peak features, applying criteria to select the CPR compression rate, and providing feedback to users without the need for additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If accelerometers are used to measure chest motion for CPR compression rate determination, then the compression rate can be measured, but the measurement accuracy deteriorates due to double integration uncertainties and noise from subject motion
Solution Approach 1:
The patent replaces the mechanical accelerometer-based measurement system with an electrical impedance-based measurement system. Instead of using accelerometers to directly measure chest motion, the system uses electrodes to measure impedance changes caused by CPR compressions, thereby avoiding the double integration uncertainties and noise problems associated with mechanical acceleration measurement.
Solution Approach 2:
The patent introduces impedance changes as an intermediary parameter to indirectly measure CPR compression rate. Rather than directly measuring chest motion, the system measures the impedance changes that occur during compressions and uses these changes to determine the compression rate, providing a more reliable measurement pathway.
2Measurement precision
If additional sensors such as accelerometers or pressure-sensitive pads are added to the defibrillator, then CPR compression rate determination is enabled, but the device complexity increases
Solution Approach 1:
The patent makes the existing electrodes in the defibrillator multi-functional by enabling them to serve both their original purpose (electrical therapy delivery and ECG monitoring) and a new purpose (CPR compression rate measurement through impedance changes). This eliminates the need for additional dedicated sensors and reduces device complexity.
Solution Approach 2:
The defibrillator's existing electrode system serves itself by utilizing the same components for multiple functions. The electrodes already present in the device are repurposed to measure impedance changes during CPR, allowing the system to monitor compression rate without requiring external or additional sensing equipment.
3Device complexity
If impedance signal processing is used to determine CPR compression rate, then additional sensors are eliminated, but the signal morphology changes over time due to varying subject conditions
Solution Approach 1:
The patent implements dynamic signal processing that adapts to changing impedance signal morphology. The system continuously adjusts its analysis parameters and processing methods based on the varying characteristics of the impedance signal, allowing it to maintain measurement accuracy despite changes in subject conditions, chest shape, and compression techniques over time.
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 robust and accurate determination of CPR compression rates, improving the effectiveness of CPR by reducing noise-related inaccuracies and eliminating the need for extra sensors, thus enhancing user feedback and CPR quality.
Implementation Method 1
Chest compressions performed during CPR produce changes to transthoracic impedance of the subject. The subject's chest acts as a resistor to an applied electrical current and when the volume of the chest changes due to CPR compressions, the transthoracic impedance will change.
Implementation Method 2
an electrocardiogram signal measurement system connected to the electrodes and configured to measure at least one electrocardiogram signal of the subject
Data Source
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AI summary
A defibrillator (1) for determining a cardiopulmonary resuscitation (CPR) compression rate, comprising electrodes (3) adapted to be attached to the subject, an impedance signal measurement system (5) connected to the electrodes and configured to measure at least one impedance signal of the subject, an electrocardiogram signal measurement system (7) connected to the electrodes and configured to measure at least one electrocardiogram signal of the subject, an impedance signal processing system (9) connected to the impedance signal measurement system and configured to process the impedance signal of the subject to obtain a plurality of impedance signal compression rate estimates and a plurality of impedance signal features, an electrocardiogram signal processing system (11) connected to the electrocardiogram signal measurement system and configured to process the electrocardiogram signal of the subject to obtain a plurality of electrocardiogram signal features, a compression rate estimate processing system (13) connected to the impedance signal measurement system and the electrocardiogram signal measurement system and configured to apply a plurality of criteria to the impedance signal features and the electrocardiogram signal features and use compliance with one or more of the criteria to select one of the plurality of impedance signal compression rate estimates as the cardiopulmonary resuscitation compression rate, and an output unit (15) connected to the compression rate estimate processing system and configured to output feedback based on the cardiopulmonary resuscitation compression rate to a user of the defibrillator.