The effectiveness of cardiopulmonary resuscitation (CPR) is dependent on the technique of the rescuers and the time after arrest that CPR is initiated to the victim. Incomplete chest wall recoil during the decompression phase of CPR increases intra-thoracic pressure and decreases coronary and cerebral perfusion. The Inspiratory Impedance Valve (ITD) prevents unnecessary air from entering the lungs during the decompression phase.