In all the years I have been in EMS (since 1978), I have never had a CPR only save, many combined with meds and electricity, but not CPR alone with one exception. The exception and perhaps my most important save was my mother who coded at the dinner table. I was able to start CPR within 30 seconds and had her breathing and semi-conscious by the time the ambulance arrived.
With the exception of the medic on the scene (who knew me) no one, including the doctors at the ED could believe she really coded, since they had never received anyone from the field (non-hospital) who recovered from CPR alone. I knew her personal cardiologist, who also found it difficult to believe she had coded and was saved by CPR alone, since her EKG and cardiac enzymes showed no evidence of a cardiac event. That was until the next day when she coded in the hospital. Fortunately, the code team did their job and she was transferred down to Washington Hospital Center for a triple bypass. That was over eight years ago, today at 91 she has slowed down some, but still gets around. The next day, when I had the chance to talk to her cardiologist, he apologized for having doubted me, saying he had never had a patient who had successfully recovered from an arrest with CPR only. He knew that I was a paramedic and we discussed perhaps why, he surmised that even though I did not perform a cardiac thump, the initial chest compression performed so early in the arrest, likely acted as such.
Pete