an electronically controlled breast pump for generating cyclical suction includes a cumulative vacuum pump and a plurality of switches including at least an expression mode cycle time selection switch , a peak vacuum level selection switch , and a stimulation mode switch . a controller coupled to the cumulative vacuum pump controls the apparatus which optionally further includes a four - layer assembly of the various features , an adjustable safety valve , and / or a pump head with a groove traversing top dead center of the pump head .