A Decremental PEEP Trial Identifies the PEEP Level That Maintains Oxygenation After Lung Recruitment

OBJECTIVE: To assess the ability of a decremental trial of positive end-expiratory pressure (PEEP) to identify an optimal PEEP level that maintains oxygenation after a lung-recruitment maneuver.

DESIGN: Prospective clinical trial.

SETTING: Surgical intensive care unit of a university hospital.

PATIENTS: Twenty sedated patients with acute lung injury and/or acute respiratory distress syndrome, ventilated for 1.2 ± 0.4 d.

INTERVENTION: Each patient received up to 3 lung-recruitment maneuvers with continuous positive airway pressure of 40 cm H₂O sustained for 40 s to increase the ratio of P_aO2 to F_IO2 by > 20%. Following the lung-recruitment maneuver, PEEP was set at 20 cm H₂O and then the F_IO2 was decreased until the oxygen saturation (measured via pulse oximetry [S_pO2]) was 90–94%. PEEP was then decreased in 2-cm H₂O steps until the S_pO2 dropped below 90%. The step preceding the drop to below 90% was considered the optimal PEEP. The lung was then re-recruited and PEEP and F_IO2 were set at the identified levels. The patients were followed for 4 h after the PEEP trial and the setting of PEEP and F_IO2.

RESULTS: After the lung-recruitment maneuver, all the patients' P_aO2/F_IO2 increased > 50%. The mean ± SD P_aO2/F_IO2 on the optimal decremental trial PEEP was 211 ± 79 mm Hg, versus 135 ± 37 mm Hg at baseline (p < 0.001), and was sustained at that level for the 4-h study period (227 ± 81 mm Hg at 4 h). F_IO2 at baseline was 0.54 ± 0.12 versus 0.38 ± 0.12 (p < 0.001) at 4 h. PEEP was 11.9 ± 3.0 cm H₂O at baseline and 9.1 ± 4.7 cm H₂O (p = 0.011) at 4 h.

CONCLUSION: A decremental PEEP trial identifies a PEEP setting that sustains for 4 h the oxygenation benefit of a 40-cm H₂O, 40-s lung-recruitment maneuver.