It just shows how inadequate most chest compressions are done, plus the machine is more consistent. After only a minute or so of doing chest compressions I'd bet the
quality of compressions done manually decrease dramatically. We run with 3 - 4 guys on a truck. On a code we rotate on compressions as it can get pretty physical.
That machine is a lifesaver, pun intended. The first time we witnessed it in action was last summer on a call to a machine shop. We were doing compressions for a minute
or more before the paramedics arrived. They got the device attached and were off and running. We later found out that the patient lived.

John