title: PEEP titration guided by ventilation homogeneity: a feasibility study using electrical impedance tomography.
abstract: BACKGROUND
  Lung protective ventilation requires low tidal volume and suitable positive end-expiratory pressure (PEEP). To date, few methods have been accepted for clinical use to set the appropriate PEEP. The aim of this study was to test the feasibility of PEEP titration guided by ventilation homogeneity using the global inhomogeneity (GI) index based on electrical impedance tomography (EIT) images.
  
  
  METHODS
  In a retrospective study, 10 anesthetized patients with healthy lungs mechanically ventilated under volume-controlled mode were investigated. Ventilation distribution was monitored by EIT. A standardized incremental PEEP trial (PEEP from 0 to 28 mbar, 2 mbar per step) was conducted. During the PEEP trial, "optimal" PEEP level for each patient was determined when the air was most homogeneously distributed in the lung, indicated by the lowest GI index value. Two published methods for setting PEEP were included for comparison based on the maximum global dynamic compliance and the intra-tidal compliance-volume curve.
  
  
  RESULTS
  No significant differences in the results were observed between the GI index method (12.2 +/- 4.6 mbar) and the dynamic compliance method (11.4 +/- 2.3 mbar, P > 0.6), or between the GI index and the compliance-volume curve method (12.2 +/- 4.9 mbar, P > 0.6).
  
  
  CONCLUSIONS
  According to the results, it is feasible and reasonable to use the GI index to select the PEEP level with respect to ventilation homogeneity. The GI index may provide new insights into the relationship between lung mechanics and tidal volume distribution and may be used to guide ventilator settings.
authors.affiliation: Department of Biomedical Engineering, Furtwangen University, Jakob-Kienzle-Strasse 17, D-78054 Villingen-Schwenningen, Germany. zhanqi.zhao@hs-furtwangen.de
authors.forename: Zhanqi
authors.initials: Z
authors.lastname: Zhao
authors.forename: Daniel
authors.initials: D
authors.lastname: Steinmann
authors.forename: Inéz
authors.initials: I
authors.lastname: Frerichs
authors.forename: Josef
authors.initials: J
authors.lastname: Guttmann
authors.forename: Knut
authors.initials: K
authors.lastname: Möller
mesh_terms: D000328:Adult; D017097:Electric Impedance; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D012189:Retrospective Studies; D013990:Tidal Volume; D014054:Tomography / Q000379:methods*