title: Optimizing PEEP by Electrical Impedance Tomography in a Porcine Animal Model of ARDS.
abstract: BACKGROUND
  Mechanical ventilation is necessary in diverse clinical circumstances. Especially in the context of ARDS, so-called protective ventilation strategies must be followed. It is already known that PEEP might enhance oxygenation in ARDS. However, determining the optimal PEEP settings in clinical routines is challenging. Electrical impedance tomography (EIT) is a promising technique with which to adjust ventilator settings. We investigated whether the combination of different EIT parameters, namely the global inhomogeneity and hyperdistension indices, may lead to a feasible and safe PEEP setting.
  
  
  METHODS
  ARDS was induced by a double-hit approach in 18 pigs weighing, on average, 34.8 ± 3.97 kg. First, a surfactant washout was conducted; second, the tidal volume was increased to 20 mL/kg body weight, triggering a ventilator-induced lung injury. Subsequently, pigs were randomized to either the EIT or control groups, followed by an observation time of 24 h. In the control group, PEEP was set according to the ARDS network table. In the EIT group, a PEEP trial was conducted to determine an appropriate PEEP. At defined time points, hemodynamic measures, ventilation parameters, and EIT recordings, as well as blood samples, were taken. After euthanization, lungs were removed for subsequent histopathological and cytological examination.
  
  
  RESULTS
  The combination of PEEP and FIO2differed between groups, although respiratory compliance, gas exchange, and histopathological examinations, as well as hemodynamics, did not show any statistical differences between the EIT and control groups. However, in the control group, the PEEP/FIO2settings followed the given coupling; in the EIT group, divergent individual combinations of PEEP and FIO2ranges occurred.
  
  
  CONCLUSIONS
  PEEP setting by EIT facilitates a more individual ventilation therapy. However, in our relatively short ARDS observation period of 24 h, no significant differences appeared in common clinical parameters compared with a control group.
authors.affiliation: Department of Anesthesiology.|Medical Information Technology, RWTH Aachen University, Aachen, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Hochhausen
authors.affiliation: Department of Anesthesiology.
authors.forename: Ingeborg
authors.initials: I
authors.lastname: Biener
authors.affiliation: Department of Anesthesiology.|Department of Intensive Care.
authors.forename: Rolf
authors.initials: R
authors.lastname: Rossaint
authors.affiliation: Department of Anesthesiology.
authors.forename: Andreas
authors.initials: A
authors.lastname: Follmann
authors.affiliation: Department of Anesthesiology.
authors.forename: Christian
authors.initials: C
authors.lastname: Bleilevens
authors.affiliation: Institute of Pathology, University Hospital RWTH Aachen, Aachen, Germany.
authors.forename: Till
authors.initials: T
authors.lastname: Braunschweig
authors.affiliation: Medical Information Technology, RWTH Aachen University, Aachen, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Leonhardt
authors.affiliation: Department of Anesthesiology mczaplik@ukaachen.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Czaplik
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D017097:Electric Impedance / Q000627:therapeutic use*; D011175:Positive-Pressure Respiration / Q000379:methods*; D011663:Pulmonary Surfactants; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000628:therapy*; D013552:Swine; D014054:Tomography / Q000379:methods*; D016896:Treatment Outcome; D055397:Ventilator-Induced Lung Injury / Q000150:complications
chemical_list: D011663:Pulmonary Surfactants
keywords: ARDS; double-hit animal model of ARDS; electrical impedance tomography; global inhomogeneity index; hyperdistension index; individualized mechanical ventilation