The invention is an apparatus for increasing intrathoracic pressure for resuscitating cardiac arrest patients. The apparatus comprises a flexible, substantially inelastic belt wrapped around the patient's chest and attached to a force converter. The force converter converts a downwardly directed force into a chestward resultant, which depresses the sternum, and two belt tightening resultants. The force converter comprises a pair of arm assemblies, each having a pair of spaced arms, which are pivotably mounted to a base. The base is positioned near the patient's sternum and the ends of the belt attach to one end of each arm assembly. The opposite, handle ends of the arm assemblies are depressed toward the chest causing tightening of the belt and compression of the chest cavity.