New guidelines from the American Heart Association (AHA) state that hands-only cardiopulmonary resuscitation (CPR) can be done in an emergency situation, even by people who have no training in the technique. AHA experts say this does not rule out mouth-to-mouth breathing as part of CPR, but it does suggest that passers-by can save lives with chest compression alone. This finding means that if you see someone collapse in a public place or at home and you think it might be a heart attack, you...