Reducing electrocardiogram artifacts during and post CPR

A method for processing an ECG signal, comprising:

• a port of an external defibrillator receiving the ECG signal including ECG data that represents QRS complexes of a patient, the ECG signal having a forward direction and a reverse direction, the forward direction representing the ECG data in temporal order, the reverse direction representing the ECG data in reverse temporal order;
• a filter mechanism of the external defibrillator applying a filter to the ECG signal in the forward direction to create a forward-filtered ECG signal;
• the filter mechanism applying the filter to the ECG signal in the reverse direction to create a reverse-filtered ECG signal;
• and
• a processor of the external defibrillator combining a latter portion of the forward-filtered ECG signal with a temporally earlier portion of the reverse-filtered ECG signal to create a composite-filtered ECG signal, wherein the ECG signal further comprises impedance data that represents an impedance between at least two electrodes attached to the patient, and wherein the method further comprises:
• the filter mechanism applying the filter to the ECG signal to remove compression artifacts that result from mechanical chest compressions delivered to the patent at a periodic rate;
• the processor correlating the at least a portion of the impedance data with the ECG data;
• and
• the processor analyzing the correlated ECG and impedance data to determine if the patient has return of spontaneous circulation.