Relationship between ventilatory settings and barotrauma in the acute respiratory distress syndrome

Objective: High pressures or volumes may increase the risk of barotrauma in the acute respiratory distress syndrome (ARDS). Methods: The first part of the study analyzed data from a prospective trial of two ventilation strategies in 116 patients with ARDS retrospectively, and ventilatory pressures and volumes were compared in patients with or without pneumothorax. The second part consisted of a literature analysis of prospective trials (14 clinical studies, 2270 patients) describing incidence and risk factors for barotrauma in ARDS patients, and mean values of ventilatory parameters were plotted against incidence of barotrauma. Results: In our clinical trial comparing two tidal volumes, 15 patients (12.3%) developed pneumothorax. There was no significant difference in any pressure or volume between these patients and the rest of the population, including end-inspiratory plateau pressure (Pplat), driving pressure (Pplat-PEEP), respiratory rate and compliance. Multiple trauma was more frequent among patients with pneumothorax (27%) than in those without (7%). Duration of mechanical ventilation tended to be longer with pneumothorax. In the literature review, the incidence of barotrauma varied between 0% and 49%, and correlated strongly with Pplat, with a high incidence above 35 cmH2O, and with compliance, with a high incidence below 30 ml/cmH2O. Conclusion: Clinical studies maintaining Pplat lower than 35 cmH2O found no apparent relationship between ventilatory parameters and pneumothorax. Analysis of the literature suggests a correlation when patients receive mechanical ventilation with Pplat levels exceeding 35 cmH2O.