Purpose of review: Heart-lung interaction is an important parameter in the understanding of blood-flow induction during cardiopulmonary resuscitation. The impedance threshold valve is a device which has been created to increase venous return by occluding the airway during the decompression phase of cardiopulmonary resuscitation. This review analyzes the available literature focusing on the rationale of this device.
Recent findings: Animal and human studies suggest that the impedance threshold valve increases cardiopulmonary circulation by taking advantage of the kinetic energy of the movement of the chest wall during standard cardiopulmonary resuscitation or active chest-wall decompression. When used in conjunction with active compression/decompression cardiopulmonary resuscitation during clinical evaluation, addition of the impedance valve resulted in sustained systolic and diastolic pressures as well as improvement of vital-organ blood flow. Recent studies have also found an increase in short-term survival rates.
Summary: It seems clear, from both animal and human data, that enhancement of preload by a decrease in the intrathoracic pressures in the decompression phase improves overall cardiopulmonary resuscitation efficacy. By this means, the impedance threshold valve may be beneficial in patients in asystole or shock-refractory ventricular fibrillation. The potential long-term benefits of this new valve remain under investigation.