pizzaman,

Polak187 explained the technicalities very well and the correct logic of performing the "Thump." I am happy to see that they use common sense in NYC. When a patient is electronically monitored, it is fairly easy to learn cause and affect of different treatment techniques.

Determining fibrillation in a patient manually can be very difficult. Just getting a pulse on weak, elderly, and / or over weight patients can be a real challenge. As Polak187 stated, witnessing an arrest is the best time to perform the "Thump."

Remember that once a patient's heart has been interrupted for a short time, their electrolytes become unbalanced and they will need replenishment before normall pulses can again be stimulated. So never give up doing CPR until the Paramedics arrive or you transport the patient to an equipped medical facility.