A method is provided for controlling an automatic external defibrillator
without stopping CPR (primarily chest compressions). While chest
compressions continue to be applied to the victim, the system
differentiates between (1) a perfusing rhythm that has the capability of
leading to a beating heart without a shock and (2) ventricular
fibrillation (VF) which sometimes occurs in the presence of ventricular
tachycardia (VT), in which there is no capability for leading to a
beating heart without a shock. Defibrillation shocks should be applied
only when needed and that is in the presence of VF and sometimes in the
presence of VT. Electrocardiographic (ECG or EKG) signals obtained from
electrodes applied to the patient's chest are analyzed so that the
presence of a QRS signal characteristic of a rhythm which has the
potential of supporting a beating heart, or the absence of a QRS signal
which indicates ventricular fibrillation, may be detected in the presence
of artifacts resulting from chest compressions.
