Flexible CPR Device Frequency Analysis DC Offset Elimination
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Solution Overview
Problem
Existing devices for assisting in performing chest compressions during CPR often cause discomfort to patients and strain on rescuers due to their rigid design, and they introduce errors in calculating the depth of compressions due to the double integration of acceleration signals, which superimposes a DC offset.
Innovation Solution
A device with a flexible compression pad and processing means that analyzes acceleration signals in the frequency domain to estimate the mean depth of chest compressions, eliminating the need for double integration and providing feedback on the frequency and depth of compressions without a DC component, thus offering a simpler and more accurate solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid housing is used for the accelerometer device, then the device structure is simple and stable, but it causes harm to the patient and strain on the assistant's hands during compressions
Solution Approach 1:
The device is divided into two functional parts: a rigid housing containing the accelerometer and electronics, and a separate flexible compression pad with padding. The rigid housing provides structural stability for accurate measurement, while the flexible padded portion provides patient comfort and reduces hand strain during compressions.
Solution Approach 2:
Different parts of the device have different mechanical properties optimized for their specific functions. The housing is rigid for stability, while the compression pad is flexible and padded for comfort. This local differentiation of material properties resolves the contradiction between structural strength and patient comfort.
2Device complexity
If double integration of acceleration signal is used to calculate chest compression depth, then the calculation method is simple, but it superimposes a DC offset over the depth signal introducing error
Solution Approach 1:
The system uses feedback from the accelerometer data to detect compression events and applies boundary conditions to eliminate the DC offset. By monitoring the acceleration signal characteristics and applying appropriate mathematical corrections based on detected compression start and end points, the system maintains measurement accuracy while using a relatively simple calculation approach.
Solution Approach 2:
The system performs preliminary detection of compression events (start and end points) before calculating the final depth values. This preliminary action allows the system to apply appropriate boundary conditions and eliminate DC offset before the final depth calculation, improving accuracy without significantly increasing overall system complexity.
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
The device provides precise feedback on chest compression depth and frequency without causing discomfort to patients or straining rescuers, improving the accuracy of CPR performance by eliminating errors associated with double integration and DC offset, and allowing for more comfortable and effective CPR assistance.
Implementation Method 1
a compression pad comprising an acceleration sensor unit producing acceleration signals which indicate the movement of the chest of the patient or manikin during chest compressions
Data Source
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AI summary
Device and method to assist in performing chest compressions on a patient or manikin (2) during cardiopulmonary resuscitation (CPR), in which a signal representative of the movement of the chest (3) of the patient or manikin (2) is analyzed in the frequency domain in short-time windows, and the mean depth of chest compressions in each window is estimated from the mean frequency and the amplitudes and phases of the first harmonics of said signal of each window.