Intrathoracic Pressure Regulator Performance in the Setting of Hemorrhage and Acute Lung Injury

Introduction The intrathoracic pressure regulator ITPR is a device designed to enhance venous return to the heart and subsequently cardiac preload by inducing negative end expiratory pressure in mechanically ventilated patients. Previous preclinical studies have shown increased mean arterial pressure MAP and decreased intracranial pressure ICP with use of the device. The aim of this study was to evaluate the hemodynamic and respiratory effects of ITPR in a porcine polytrauma model of hemorrhagic shock and acute lung injury ALI. Methods Swine were anesthetized and underwent a combination of sham, hemorrhage, andor lung injury. Our experimental groups included no injury with and without ITPR ITPR, Sham, hemorrhage with and without ITPR ITPRHem, Hem, and hemorrhage and acute lung injury with and without ITPR ITPRHemALI, HemALI. The ITPR device was started at a setting of -3 cmH2O and incrementally decreased by 3 cmH2O after 30 minutes on each setting with 15 minutes allowed for recovery between settings to a nadir of - 12 cmH2O. Vital signs and ventilator settings were recorded at baseline, following each injury, at the end of each respective ITPR setting, and at the end of each recovery period.Arterial blood gas measurements were obtained at baseline, following each injury, and at the end of recovery period. Of note, due to gasping at pressures below -6 cmH2O with the ITPR device, all animals were chemically paralyzed.