Although approximately one million sudden cardiac deaths occur yearly in the US and Europe,cardiac arrest (CA)remains a clinical condition still characterized by a poor prognosis.In an effort to improve the cardio- pulmonary resuscitation(CPR)technique,the 2005 American Heart Association(AHA)Guidelines for CPR gave the impedance threshold device(ITD)a Class IIa recommendation.The AHA recommendation means that there is strong evidence to demonstrate that ITD enhances circulation,improves hemodynamics and increases the likelihood of resuscitation in patients in CA.During standard CPR,venous blood return to the heart relies on the natural elastic recoil of the chest which creates a transient decrease in intrathoracic pressure.The ITD further decreases intrathoracic pressure by preventing respiratory gases from entering the lungs during the decompression phase of CPR. Thus,although ITD is placed into the respiratory circuit it works as a circulatory enhancer device that provides its therapeutic benefit with each chest decompression. The ease of use of this device,its ability to be incor- porated into a mask and other airway devices,the absence of device-related adverse effects and few requirements in additional training,suggest that ITD may be a favorable new device for improving CPR efficiency.Since the literature is short of studies with clinically meaningful outcomes such as neurological outcome and long term survival,further evidence is still needed. The provisional arrest of cardiac arrest (CA) remains a clinical condition still characterized by a poor prognosis. In an effort to improve the cardio-pulmonary resuscitation (CPR) technique, the 2005 American Heart Association (AHA) Guidelines for CPR gave the impedance threshold device (ITD) a Class IIa recommendation. That there is strong evidence to demonstrate that ITD enhances circulation, improves hemodynamics and increases the likelihood of resuscitation in patients in CA.During standard CPR, venous blood return to the heart relies on the natural elastic recoil of the chest which creates a transient decrease in intrathoracic pressure. The ITD further reduces intrathoracic pressure by preventing respiratory gases from entering the lungs during the decompression phase of CPR. Thus, although ITD is placed into the respiratory circuit it works as a circulatory enhancer device that provides its therap eutic benefit with each chest decompression. The ease of use of this device, its ability to be incor- porated into a mask and other airway devices, the absence of device-related adverse effects and few requirements in additional training, suggest that ITD may be a favorable new device for improving CPR efficiency .ince the literature is short of studies with clinically meaningful outcomes such as neurological outcome and long term survival, further evidence is still needed.