title: Opening pressures and atelectrauma in acute respiratory distress syndrome.
abstract: Open lung strategy during ARDS aims to decrease the ventilator-induced lung injury by minimizing the atelectrauma and stress/strain maldistribution. We aim to assess how much of the lung is opened and kept open within the limits of mechanical ventilation considered safe (i.e., plateau pressure 30 cmH2O, PEEP 15 cmH2O).
  
  
  
  Prospective study from two university hospitals. Thirty-three ARDS patients (5 mild, 10 moderate, 9 severe without extracorporeal support, ECMO, and 9 severe with it) underwent two low-dose end-expiratory CT scans at PEEP 5 and 15 cmH2O and four end-inspiratory CT scans (from 19 to 40 cmH2O). Recruitment was defined as the fraction of lung tissue which regained inflation. The atelectrauma was estimated as the difference between the intratidal tissue collapse at 5 and 15 cmH2O PEEP. Lung ventilation inhomogeneities were estimated as the ratio of inflation between neighboring lung units.
  
  
  
  The lung tissue which is opened between 30 and 45 cmH2O (i.e., always closed at plateau 30 cmH2O) was 10 ± 29, 54 ± 86, 162 ± 92, and 185 ± 134 g in mild, moderate, and severe ARDS without and with ECMO, respectively (p < 0.05 mild versus severe without or with ECMO). The intratidal collapses were similar at PEEP 5 and 15 cmH2O (63 ± 26 vs 39 ± 32 g in mild ARDS, p = 0.23; 92 ± 53 vs 78 ± 142 g in moderate ARDS, p = 0.76; 110 ± 91 vs 89 ± 93, p = 0.57 in severe ARDS without ECMO; 135 ± 100 vs 104 ± 80, p = 0.32 in severe ARDS with ECMO). Increasing the applied airway pressure up to 45 cmH2O decreased the lung inhomogeneity slightly (but significantly) in mild and moderate ARDS, but not in severe ARDS.
  
  
  
  Data show that the prerequisites of the open lung strategy are not satisfied using PEEP up to 15 cmH2O and plateau pressure up to 30 cmH2O. For an effective open lung strategy, higher pressures are required. Therefore, risks of atelectrauma must be weighted versus risks of volutrauma.
  
  
  
  Clinicaltrials.gov identifier: NCT01670747 ( www.clinicaltrials.gov ).
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Cressoni
authors.affiliation: Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milan, Italy.|Struttura Complessa Anestesia e Rianimazione ASST Santi Paolo e Carlo, Milan, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Chiumello
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Algieri
authors.affiliation: Struttura Complessa Anestesia e Rianimazione ASST Santi Paolo e Carlo, Milan, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Brioni
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Chiurazzi
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Colombo
authors.affiliation: Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Colombo
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Crimella
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Mariateresa
authors.initials: M
authors.lastname: Guanziroli
authors.affiliation: Department of Intensive Care Medicine, Rebro Hospital, University of Zagreb, Zagreb, Croatia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Tomic
authors.affiliation: Department of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Tonetti
authors.affiliation: Struttura Complessa Anestesia e Rianimazione ASST Santi Paolo e Carlo, Milan, Italy.
authors.forename: Giordano
authors.initials: G
authors.lastname: Luca Vergani
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Carlesso
authors.affiliation: Department of Intensive Care Medicine, Rebro Hospital, University of Zagreb, Zagreb, Croatia.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Gasparovic
authors.affiliation: Department of Anesthesiology, Emergency and Intensive Care Medicine, University of Göttingen, Robert-Koch-Straße 40, 37075, Göttingen, Germany. gattinoniluciano@gmail.com.
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008170:Lung Compliance; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy*; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed; D055397:Ventilator-Induced Lung Injury / Q000517:prevention & control*
keywords: ARDS; Atelectrauma; Lung recruitment; Opening pressure; Volutrauma