Separate Drive and Sense Electrodes for Low-Noise CPR Impedance Measurement
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Solution Overview
Problem
Conventional CPR assist technologies face inaccuracies in determining chest compression depth and cause rescuer pain due to electrode disturbances during CPR, especially when patients are on compressible surfaces, leading to distorted impedance measurements.
Innovation Solution
Utilizing separate sets of drive and sense electrodes on the patient, where the drive electrodes receive current and sense electrodes measure voltage, reducing noise and providing accurate impedance measurements even during chest compressions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional impedance measurement is performed during CPR, then voltage and energy compensation can be determined, but the measurement is distorted by noise from electrode disturbance
Solution Approach 1:
The electrode system is segmented into separate drive electrodes and sense electrodes. The drive electrodes are positioned to remain relatively stationary during CPR, while the sense electrodes are positioned to minimize disturbance. This segmentation allows the measurement function to be separated from the compression function, reducing noise in impedance measurements during chest compressions.
Solution Approach 2:
The patent introduces an intermediary measurement approach where impedance is measured through separate drive and sense electrodes rather than through the same electrodes experiencing mechanical disturbance. This intermediary measurement path avoids the direct noise source of electrode disturbance during CPR while still providing the necessary impedance data for compression depth monitoring.
2Measurement precision
If a puck is placed on the sternum for CPR assist, then compression depth can be monitored, but it causes hand pain for the rescuer
Solution Approach 1:
The patent replaces the mechanical puck system with an electrical impedance-based measurement system. Instead of using a physical puck that causes hand pain, the system uses electrical current and voltage measurements through electrodes to determine compression depth. This substitution eliminates the harmful mechanical contact while preserving the measurement capability.
3Ease of operation
If accelerometer-based CPR assist is used, then no puck is needed on the sternum, but compression depth is underestimated on compressible surfaces
Solution Approach 1:
The patent replaces accelerometer-based mechanical sensing with electrical impedance sensing. The impedance measurement system is not affected by the compressibility of the underlying surface because it measures electrical properties rather than mechanical acceleration. This substitution maintains measurement accuracy while preserving the ease of operation without requiring a sternum puck.
4Measurement precision
If force-based CPR assist is used, then compression force can be measured, but it requires 200-600 Newtons to compress the chest
Solution Approach 1:
The patent replaces force-based measurement with impedance-based measurement. Instead of directly measuring the mechanical force required for compression (which requires 200-600 Newtons), the system measures electrical impedance changes that occur during compression. This substitution provides indirect measurement of compression depth without requiring the rescuer to exert excessive force, as the impedance changes reflect the compression state.
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
Enables precise determination of chest compression depth and other complex impedance-based diagnoses by minimizing noise interference, improving CPR effectiveness and rescuer comfort.
Implementation Method 1
drive electrodes receive current
Implementation Method 2
sense electrodes measure voltage
Implementation Method 3
determine an impedance of the patient based on the sensed voltage and the applied current
Data Source
AI summary
A medical device for measuring an impedance of a patient or mammal when a current is applied by electrodes. The medical device includes an output transmits a drive signal to a set of drive electrodes coupled to a patient and an input receives a sense signal generated by a set of sensing electrodes coupled to the patient. A processor determines the impedance of the patient based on the drive signal transmitted to the set of drive electrodes and the sense signal received by the set of sensing electrodes. A user interface displays the determined impedance.