title: Physiological Effects of the Open Lung Approach in Patients with Early, Mild, Diffuse Acute Respiratory Distress Syndrome: An Electrical Impedance Tomography Study.
abstract: BACKGROUND
  To test the hypothesis that in early, mild, acute respiratory distress syndrome (ARDS) patients with diffuse loss of aeration, the application of the open lung approach (OLA) would improve homogeneity in lung aeration and lung mechanics, without affecting hemodynamics.
  
  
  METHODS
  Patients were ventilated according to the ARDS Network protocol at baseline (pre-OLA). OLA consisted in a recruitment maneuver followed by a decremental positive end-expiratory pressure trial. Respiratory mechanics, gas exchange, electrical impedance tomography (EIT), cardiac index, and stroke volume variation were measured at baseline and 20 min after OLA implementation (post-OLA). Esophageal pressure was used for lung and chest wall elastance partitioning. The tomographic lung image obtained at the fifth intercostal space by EIT was divided in two ventral and two dorsal regions of interest (ROIventral and ROIDorsal).
  
  
  RESULTS
  Fifteen consecutive patients were studied. The OLA increased arterial oxygen partial pressure/inspired oxygen fraction from 216 ± 13 to 311 ± 19 mmHg (P < 0.001) and decreased elastance of the respiratory system from 29.4 ± 3 cm H2O/l to 23.6 ± 1.7 cm H2O/l (P < 0.01). The driving pressure (airway opening plateau pressure - total positive end-expiratory pressure) decreased from 17.9 ± 1.5 cm H2O pre-OLA to 15.4 ± 2.1 post-OLA (P < 0.05). The tidal volume fraction reaching the dorsal ROIs increased, and consequently the ROIVentral/Dorsal impedance tidal variation decreased from 2.01 ± 0.36 to 1.19 ± 0.1 (P < 0.01).
  
  
  CONCLUSIONS
  The OLA decreases the driving pressure and improves the oxygenation and lung mechanics in patients with early, mild, diffuse ARDS. EIT is useful to assess the impact of OLA on regional tidal volume distribution.
authors.affiliation: From the Department of Anaesthesia and Intensive Care, University of Foggia, Foggia, Italy (G.C., P.R., D.D., L.M., M.R., M.D.); and Department of Anaesthesia and Intensive Care, University of Bari, Bari, Italy (S.G.).
authors.forename: Gilda
authors.initials: G
authors.lastname: Cinnella
authors.forename: Salvatore
authors.initials: S
authors.lastname: Grasso
authors.forename: Pasquale
authors.initials: P
authors.lastname: Raimondo
authors.forename: Davide
authors.initials: D
authors.lastname: D'Antini
authors.forename: Lucia
authors.initials: L
authors.lastname: Mirabella
authors.forename: Michela
authors.initials: M
authors.lastname: Rauseo
authors.forename: Michele
authors.initials: M
authors.lastname: Dambrosio
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D042241:Early Diagnosis; D017097:Electric Impedance / Q000627:therapeutic use; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011175:Positive-Pressure Respiration / Q000379:methods*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012121:Respiration, Artificial / Q000379:methods; D012128:Respiratory Distress Syndrome / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy*; D015656:Respiratory Mechanics / Q000502:physiology; D014054:Tomography / Q000379:methods*