CPR Depth Sensor Drift Compensation via Force Reference
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing CPR feedback systems face challenges in accurately determining real-time chest compression depth due to filter distortion and inadequate removal of sensor drift, which affects the precision of feedback provided to rescuers during cardiopulmonary resuscitation.
Innovation Solution
A system and method that utilize a combination of filtering and double integration of acceleration signals, along with a compensation signal derived from an adjusted reference signal, to accurately determine real-time chest compression depth by compensating for filter-induced distortions, ensuring precise and real-time feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-pass filter is used to remove drift in acceleration offset, then sensor drift removal is improved, but filter distortion increases
Solution Approach 1:
The patent introduces a reference signal (force signal or ECG) as an intermediary to represent the true compression depth. This reference signal is filtered using the same high-pass filter, and the filtered reference signal is subtracted from the double-integrated acceleration signal. This intermediary approach allows the filter distortion to be captured and removed, resolving the contradiction between drift removal and measurement precision.
Solution Approach 2:
The patent uses the filtered reference signal as feedback to compensate for filter distortion. By continuously comparing the filtered reference signal with the original reference signal and using the difference to correct the depth measurement, the system maintains accuracy while effectively removing drift through high-pass filtering.
2Loss of time
If double integration of acceleration signal is used to determine compression depth, then real-time depth measurement is achieved, but filter distortion accumulates
Solution Approach 1:
The reference signal serves as an intermediary that experiences the same filter distortion as the acceleration signal during double integration. By subtracting the filtered reference signal from the integrated acceleration signal, the distortion components cancel out, maintaining measurement precision while preserving real-time feedback capability.
Solution Approach 2:
The patent converts the harmful effect of filter distortion into a beneficial correction mechanism. The filter distortion that accumulates during double integration is captured in the filtered reference signal, and this same distortion is then used to correct the depth measurement by subtraction, turning the harm into a benefit.
3Reliability
If lower cut-off frequency is used in high-pass filter, then drift removal effectiveness is improved, but compression frequency distortion increases
Solution Approach 1:
The reference signal acts as an intermediary that captures the frequency-dependent distortion introduced by the high-pass filter. By filtering the reference signal with the same parameters and subtracting it from the acceleration-derived depth signal, the system compensates for frequency distortion while maintaining effective drift removal through lower cut-off frequencies.
Data Source
AI summary
Embodiments of the present invention are directed toward a system and method of determining real time chest compression depth of a CPR patient or manikin from acceleration and a reference signal, such as force. In one embodiment, an acceleration signal is filtered and integrated to determine a raw depth signal. A force signal is adjusted to having a similar amplitude, phase, and shape as the raw depth signal. The force signal is filtered. The adjusted force signal is subtracted from the filtered force signal to obtain a compensation signal. The chest compression depth is obtained by adding the raw depth signal to the compensation signal.