title: Prone position and positive end-expiratory pressure in acute respiratory distress syndrome.
abstract: OBJECTIVE
  To determine whether positive end-expiratory pressure (PEEP) and prone position present a synergistic effect on oxygenation and if the effect of PEEP is related to computed tomography scan lung characteristic.
  
  
  METHODS
  Prospective randomized study.
  
  
  METHODS
  French medical intensive care unit.
  
  
  METHODS
  Twenty-five patients with acute respiratory distress syndrome.
  
  
  METHODS
  After a computed tomography scan was obtained, measurements were performed in all patients at four different PEEP levels (0, 5, 10, and 15 cm H2O) applied in random order in both supine and prone positions.
  
  
  RESULTS
  Analysis of variance showed that PEEP (p <.001) and prone position (p <.001) improved oxygenation, whereas the type of infiltrates did not influence oxygenation. PEEP and prone position presented an additive effect on oxygenation. Patients presenting diffuse infiltrates exhibited an increase of Pao2/Fio2 related to PEEP whatever the position, whereas patients presenting localized infiltrates did not have improved oxygenation status when PEEP was increased in both positions. Prone position (p <.001) and PEEP (p <.001) reduced the true pulmonary shunt. Analysis of variance showed that prone position (p <.001) and PEEP (p <.001) reduced the true pulmonary shunt. The decrease of the shunt related to PEEP was more pronounced in patients presenting diffuse infiltrates. A lower inflection point was identified in 22 patients (88%) in both supine and prone positions. There was no difference in mean lower inflection point value between the supine and the prone positions (8.8 +/- 2.7 cm H2O vs. 8.4 +/- 3.4 cm H2O, respectively).
  
  
  CONCLUSIONS
  PEEP and prone positioning present additive effects. The prone position, not PEEP, improves oxygenation in patients with acute respiratory distress syndrome with localized infiltrates.
authors.affiliation: Service de Réanimation Médicale, Hôpitax Sud, Marseille, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Gainnier
authors.forename: Pierre
authors.initials: P
authors.lastname: Michelet
authors.forename: Xavier
authors.initials: X
authors.lastname: Thirion
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Arnal
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Sainty
authors.forename: Laurent
authors.initials: L
authors.lastname: Papazian
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001784:Blood Gas Analysis; D003422:Critical Care / Q000379:methods; D005260:Female; D005602:France / Q000453:epidemiology; D006439:Hemodynamics; D006801:Humans; D016014:Linear Models; D008170:Lung Compliance; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D016684:Prone Position; D011446:Prospective Studies; D011652:Pulmonary Circulation; D011859:Radiography; D012128:Respiratory Distress Syndrome / Q000000981:diagnostic imaging / Q000378:metabolism / Q000401:mortality / Q000628:therapy*; D012720:Severity of Illness Index; D016683:Supine Position; D013990:Tidal Volume; D016896:Treatment Outcome