A decremental PEEP trial identifies the PEEP level that maintains oxygenation after lung recruitment

Abstract

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.