Effective CPR provided immediately after a heart attack can double a victim's chance of survival, and help to maintain blood flow between the heart and brain which can prevent brain death. Brain death occurs four to six minutes after cardiac arrest without CPR intervention. There really is no single agency collecting statistics on how many people get CPR and are saved by it. CPR buys time until medical professionals with a defibrillator arrive on the scene. The biggest benefit is CPR plus defibrillation within 3-5 minutes of collapse for individuals. Since 88 percent of cardiac arrests occur at home, it would be beneficial to learn CPR. Unfortunately, less than eight percent of people who suffer cardiac arrest outside the hospital survive. The American Heart Association states that bystander CPR immediately provided after cardiac arrest can double or triple a person's chance of survival.