Latest AHA guidelines about adult CPR emphasize on high quality chest compression, currently at the rate of 100 to 120 per minute.
In a prospective observational study, Kilgannon JH et al demonstrated that chest compression rate of 121–140 compressions/min had the highest odds ratio of ROSC.
What they did
222 consecutive patients were enrolled in study, found a mean chest compression rate of 139 ± 15(Higher than recommended!). Overall 53% achieved ROSC(I am envy!).
They used chest compression rates measured by defibrillation electrodes, which recorded changes in thoracic impedance. (Hmmm)
Abstract may be seen here
I believe that a randomized controlled trial is needed to settle the matter. But this is a good beginning.