Method of Estimating the Actual ECG of a Patient During CPR

Abstract

A method of processing a raw acceleration signal, measured by an accelerometer-based compression monitor, to produce an accurate and precise estimated actual depth of chest compressions. The raw acceleration signal is filtered during integration and then a moving average of past starting points estimates the actual current starting point. An estimated actual peak of the compression is then determined in a similar fashion. The estimated actual starting point is subtracted from the estimated actual peak to calculate the estimated actual depth of chest compressions. In addition, one or more reference sensors (such as an ECG noise sensor) may be used to help establish the starting points of compressions. The reference sensors may be used, either alone or in combination with other signal processing techniques, to enhance the accuracy and precision of the estimated actual depth of compressions.

1 . A system for estimating an actual ECG signal of a patient while performing chest compressions with an automatic chest compressions device, said system comprising:
 an ECG sensor capable of measuring an ECG signal of the patient, said ECG sensor producing a measured ECG signal having an actual ECG component and a noise component;   an automatic chest compression device adapted to repeatedly compress the chest of the patient disposed to provide chest compressions to the patient, said chest compression device having a load sensor capable of determining the presence of a chest compression when the load sensed by the load sensor exceeds a predetermined value, said load sensor producing a compression signal corresponding the presence a chest compression;   a signal processing system operable to receive the measured ECG signal and the compression signal, said signal processing system programmed to estimate the noise component of the measured ECG signal with a system identifier by processing the measured ECG signal and the compression signal using one or more filters selected from the group consisting of autoregressive moving average with truncated derivative filter, Kalman filter, recursive least squares filter, recursive instrumental variable filter, recursive prediction error filter, recursive pseudolinear regression filter, recursive Kalman filter for time-varying systems filter, recursive Kalman filter with parametric variation filter, combine the measured ECG signal and the estimated noise component of the measured ECG signal, and calculate the estimated actual ECG.   
   
   
       2 . A system for estimating an actual ECG signal of a patient while performing chest compressions with an automatic chest compressions device, said system comprising:
 an ECG sensor capable of measuring an ECG signal of the patient, said ECG sensor producing a measured ECG signal having an actual ECG component and a noise component;   an automatic chest compression device adapted to repeatedly compress the chest of the patient disposed to provide chest compressions to the patient, said chest compression device having an encoder capable of determining the presence of a chest compression, said encoder producing a compression signal corresponding the presence a chest compression;   a signal processing system operable to receive the measured ECG signal and the compression signal, said signal processing system programmed to estimate the noise component of the measured ECG signal with a system identifier by processing the measured ECG signal and the compression signal using one or more filters selected from the group consisting of autoregressive moving average with truncated derivative filter, Kalman filter, recursive least squares filter, recursive instrumental variable filter, recursive prediction error filter, recursive pseudolinear regression filter, recursive Kalman filter for time-varying systems filter, recursive Kalman filter with parametric variation filter, combine the measured ECG signal and the estimated noise component of the measured ECG signal, combine the measured ECG signal and the estimated noise component of the measured ECG signal, and calculate the estimated actual ECG.   
   
   
       3 . A system for estimating an actual ECG signal of a patient while performing chest compressions with an automatic chest compressions device, said system comprising:
 an ECG sensor capable of measuring an ECG signal of the patient, said ECG sensor producing a measured ECG signal having an actual ECG component and a noise component;   an automatic chest compression device adapted to repeatedly compress the chest of the patient disposed to provide chest compressions to the patient, said chest compression device having an accelerometer capable of determining the presence of a chest compression, said accelerometer producing a compression signal corresponding the presence a chest compression;   a signal processing system operable to receive the measured ECG signal and the compression signal, said signal processing system programmed to estimate the noise component of the measured ECG signal with a system identifier by processing the measured ECG signal and the compression signal using one or more filters selected from the group consisting of autoregressive moving average with truncated derivative filter, Kalman filter, recursive least squares filter, recursive instrumental variable filter, recursive prediction error filter, recursive pseudolinear regression filter, recursive Kalman filter for time-varying systems filter, recursive Kalman filter with parametric variation filter, combine the measured ECG signal and the estimated noise component of the measured ECG signal, combine the measured ECG signal and the estimated noise component of the measured ECG signal, and calculate the estimated actual ECG.