More than one thousand of the victims received some kind of medical assistance from witnesses. Seven hundred and twelve received CPR. Four hundred and thirty-nine received chest presses only. No mouth-to-mouth rescue breaths were given to them. The researchers say any kind of CPR improved chances of the patient's survival. But, they said those people treated with only chest presses suffered less brain damage. Twenty-two percent survived with good brain ability. Only ten percent of the victims treated with traditional CPR survived with good brain ability. The American Heart Association changed its guidelines for CPR chest presses in two thousand five. It said people should increase the number of chest presses from fifteen to thirty for every two breaths given.