External compression without adjuncts.

Over the past decade many exciting and promising new approaches of delivering CPR have been studied. Considerable data have accumulated suggesting that forward flow during CPR is generated, at least in part, by the development of elevated intrathoracic pressure with an extrathoracic arteriovenous pressure difference. This mechanism, known as the "thoracic pump," has been documented during "cough-CPR" and has led to numerous attempts at optimizing the outcome by increasing intrathoracic pressure in CPR. Studies have demonstrated improved flows with simultaneous ventilation and sternal compression, with static or interposed abdominal compression, with longer duration compression, and with various combinations of these maneuvers. Other recent studies have suggested that the cardiac compression mechanism may indeed be operative, at least under certain circumstances, and that CPR may be optimized by increasing the force and rate of compression. Still others have advocated a simple change in the sequence of initiating ventilation and compression. Which, if any, of these newly advocated methods improve the outcome when applied to man remains to be established. If any of these techniques is shown to be more advantageous, its widespead use will depend on its applicability without adjuncts and its teachability to the lay public.