The introduction of closed chest massage in 1960 initiated a widespread interest in cardiopulmonary resuscitation. Until that time, open chest cardiac massage was the standard for CPR. Initial explanations for blood flow during closed chest CPR were based upon direct compression of the heart. This explanation has given way to demonstrations that blood flows during CPR because of changes in intrathoracic pressure. Changes in intrathoracic pressure that create blood flow have been created by simple maneuvers such as coughing. More involved methods of affecting intrathoracic pressure, in an attempt to improve upon standard closed chest massage, have included applying positive pressure to the airway, binding of the abdomen, and the use of MAST. Cardiac output with closed chest massage is approximately one fourth of normal, and cerebral perfusion is approximately one tenth of normal. Cardiac output with open chest massage is approximately double that obtained by closed chest massage. Cerebral blood flow during open chest massage approaches physiologic values. The use of drugs possessing alpha adrenergic activity and maneuvers that augment intrathoracic pressure improve vital organ perfusion.