If a person suffering from a heart attack passes out, they may have had a cardiac arrest. Call for help (911) and an AED if not already done. Check for pulse and breathing. For those already trained in CPR, perform 30 chest compressions for every 2 mouth-to-mouth breaths. For the general public or bystanders, perform compression-only CPR by pushing hard (at least 5 cm but not exceeding 6 cm) and rapidly (about 100–120 times per minute) in the center of the chest ().