Regional lung opening and closing pressures in patients with acute lung injury

In acute lung injury (ALI), the application of positive end-expiratory pressure (PEEP) is known to prevent the alveoli from cyclic collapse and reopening and to homogenize ventilation. The setting of adequate PEEP could be optimized by the knowledge of regional lung opening and closing pressures at the bedside. The aim of our study was to determine regional opening and closing pressures in ventilated patients by electrical impedance tomography (EIT).Eight patients with healthy lungs and 18 patients with ALI were studied. A low-flow inflation and deflation maneuver with constant gas flow was performed. Regional opening and closing pressures were calculated for every pixel of the EIT scan. These pressures were defined as those values of global airway pressure at which the lung areas opened up or started to close.Injured lungs exhibited significantly higher regional opening pressures compared with healthy lungs (P.05). In ALI, significantly higher opening pressures were found in the dependent lung regions. Regional closing pressures did not significantly differ between healthy and injured lungs.Regional lung opening and closing pressures can be assessed by EIT. This information may facilitate the setting of adequate PEEP levels in patients in future.