The eight minute response time standard for Category A (immediately life-threatening) calls is based on clinical evidence that shows that within the first 10 minutes of a sudden cardiac arrest, a patient's survival rate improves 10 per cent. for every minute that is saved by getting the defibrillator to the patient (Eisenberg, Horwood and Cummins 1990). Category B offers a fast response for those patients presenting conditions that are serious but not immediately life-threatening.
In 2006, The Department commissioned an evaluation on ambulance response time targets from the University of Sheffield titled ‘The costs and benefits of changing ambulance service response time performance standards’.