A method, apparatus and computer program for defibrillation delivery decision comprising the steps of: a)Determining a shockable rhythm with a first algorithm, whereby said first algorithm is adapted to analyze an ECG signal in the presence of chest compression； b) Determining a shockable rhythm with a second algorithm, whereby said second algorithm is adapted to analyze an ECG in the absence of chest compression； c) Determining with a third algorithm if the patient is undergoing chest compression.
