During Cardiopulmonary Resuscitation (CPR), Methods That Enhance the Usefulness of Chest

During cardiopulmonary resuscitation (CPR) , methods that enhance the usefulness of chest compressions include one of the following. Which is an effective technique?

A) Using a mechanical piston device to substitute for manual chest compression by health care providers
B) Alternating chest compressions with abdominal compressions
C) Performing chest compressions shallowly and slowly, to make certain they are coordinated with rescue breathing
D) Timing chest compressions to make certain they match the rate of cardiac depolarizations seen on the heart monitor to which the patient is attached