Examples of scintigraphy images integrating the 15 min following tracer instillation (t0-t15; left panels ) and the last 15 min of the experiment (t195-t210; right panels ). Regions of interest (ROIs) were drawn around initial focus of edema (ROIE), the apex of the same lung (ROIA), the contralateral lung (ROICL), and over the thorax (ROIT). At baseline (left panels), all animals were ventilated with a tidal volume of 8 mL/kg and a PEEP of 2 cmH2O and exhibited focalized localization of the tracer in the left lung. When the same ventilator settings were kept during the experiment (a), the tracer remained remarkably confined to the initial zone; there was no contralateral and slight homolateral dissemination. High-volume ventilation (Pplat = 30 cmH2O) with no PEEP (b) induced strong homo- and contralateral dispersion of the tracer and systemic leakage, as attested by the evident decrease in overall activity. High-volume ventilation with 6 cmH2O PEEP (c) induced systemic, but not contralateral, dissemination of the tracer. Used with permission. From de Prost et al. .