Abstract: A device for delivering chest compressions for performing cardiopulmonary resuscitation includes a compression assembly and chest contact pad that can be positioned over the thorax of a patient experiencing a cardiac arrest. The compression assembly is supported by a frame and one or more positioning mechanisms for moving the compression assembly relative to the patient's left ventricle. A controller causes the compression assembly to deliver a plurality of chest compressions to the patient. A blood flow monitor, such as a Doppler ultrasound monitor, is coupled with the patient's femoral or carotid artery to monitor the flow of arterial blood when chest compressions are delivered and to communicate blood flow parameter information to the controller. The controller causes the positioning mechanism to move the location where the compressions are delivered to optimize the blood flow parameters.