The apparatus is configured for applying chest compressions to a patient to apply CPR. The apparatus includes a housing configured to mount the apparatus to the patient, a unidirectional motor, and a plunger connected to the unidirectional motor, the plunger configured to apply the chest compressions to the patient when the motor is operated. The apparatus may include a device configured to control a compression distance of compressions, The apparatus is simpler, lighter and eliminates complicated motor control required in prior devices.