A pneumatically-powered external device designed for the application of rhythmic compression to the chest in the region of the heart to provide blood flow during treatment of cardiac arrest [cardiopulmonary resuscitation (CPR)]. It is typically powered from medical gas cylinders or a medical gas pipeline system and may consist of a solid base with an attached band that straps across the patient's chest to produce the compressions, or have other configurations. The device is typically used as an adjunct to or substitute for manual external cardiac compression, to prevent fatigue and to provide better consistency in the applied force and rate of compression.