What should you do if someone nearby suddenly collapses and you don’t know how to administer cardiopulmonary resuscitation (CPR)? Immediately call for emergency medical assistance and begin 100 chest compressions per minute—pushing hard and fast in the middle of the person’s chest until more advanced care arrives. The American Heart Association says this hands-only CPR method improves the survival odds but shouldn’t be used on infants and children or adults whose cardiac arrest is from respiratory causes, such as drug overdose or near drowning. It doesn’t replace conventional CPR—combined chest compressions and mouth-to-mouth breathing—but can be used in an emergency if you’re an untrained bystander. Each year, about 166,000 adults in the United States die from sudden cardiac arrest outside a hospital or emergency room setting. Learn conventional CPR—it takes only a couple of hours and you never know when you may need it.