Depending on the cause of respiratory arrest, it is very effective. I think I mentioned this once before, but in infants and children, the number 1 cause of cardiac arrest is respiratory arrest. That why with infants and children, it is recommended to perform rescue breathing or CPR (which ever is indicated) for 1 minute prior to activating 911(this is if you are alone, never delay 911 if there are others around to start life saving procedures). This prevents any delay in the administration of those procedures shown to be most effective in infants and children. As noted in other posts, cardiac arrest in adults most often is attributed to some type of cardiac problem. Where early defibrillation and cardiac drugs are more likely to succeed than CPR alone. This why with adults (again only if you are alone) activation of 911 is recommended prior to the start of CPR. Pete