Positive end-expiratory pressure delays the progression of lung injury during ventilator strategies involving high airway pressure and lung overdistention

Franco Valenza, Massimiliano Guglielmi, Manuela Irace, Giuliana Anna Porro, Silvio Sibilla, Luciano Gattinoni

Research output: Contribution to journalArticle


Objective: Many studies have investigated the protective role of positive end-expiratory pressure (PEEP) on ventilator-induced lung injury. Most assessed lung injury in protocols involving different ventilation strategies applied for the same length of time. This study, however, set out to investigate the protective role of PEEP with respect to the time needed to reach similar levels of lung injury. Design: Prospective, randomized laboratory animal investigation. Setting: The University Laboratory of Ospedale Maggiore, Milano, IRCCS. Subjects: Anesthetized, paralyzed, and mechanically ventilated Sprague-Dawley rats. Interventions: Three groups of five Sprague-Dawley rats were ventilated using zero end-expiratory pressure ZEEP (PEEP of 0 cm H2O) and PEEP of 3 and 6 cm H2O and a similar index of lung overdistension (Pawp/P100 ≅ 1.1; where Pawp is peak airway pressure and P100 is the pressure corresponding to total lung capacity). To obtain this, tidal volume was reduced depending on the PEEP. To reach similar levels of lung injury, we measured respiratory system elastance while ventilating the animals and killed them when respiratory system elastance was 150% of baseline. Once target respiratory system elastance was reached, the lung wet-to-dry ratio was obtained. Results: Rats were ventilated with comparable high airway pressure (Pawp of 42.8 ± 3.1, 43.5 ± 2.6, and 46.2 ± 4.4, respectively, for PEEP 0, 3, and 6) obtaining similar overdistension (Pawp/P100 - index of overdistension: 1.17 ± 0.2, 1.06 ± 0.1, and 1.19 ± 0.2). The respiratory system elastance target was reached and wet-to-dry ratio was not different in the three groups, suggesting a similar degree of lung damage. The time taken to achieve the target respiratory system elastance was three times longer with PEEP 3 and 6 (55 ± 14 mins and 60 ± 17) as compared with zero end-expiratory pressure (18 ± 3 mins, p <.001). Conclusion: These findings confirm that PEEP is protective against ventilator-induced lung injury and may enable the clinician to "buy time" in the progression of lung injury.

Original languageEnglish
Pages (from-to)1993-1998
Number of pages6
JournalCritical Care Medicine
Issue number7
Publication statusPublished - Jul 1 2003



  • Mechanical ventilatory support
  • Positive end-expiratory pressure
  • Respiratory mechanics
  • Time
  • Ventilator-induced lung injury

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine

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