A comparison of three alveolar recruitment maneuver approaches in acute lung injury and acute respiratory distress syndrome

Abstract

Objective: To evaluate three alveolar recruitment maneuvers (ARM) in patients with acute lung injury and acute respiratory distress syndrome. Methods: Twenty-four patients randomized in three similar groups were evaluated. Each group received one kind of ARM. Group 1: progressive levels of positive end-expiratory pressure (PEEP) with a fixed pressure control (PC). The PC was kept at 15 cmH 2 O and the PEEP levels were increased every 2 minutes: 25, 30, 35, 40 and 45 cmH 2 O. Group 2: progressive levels of PC with a fixed PEEP level. The PEEP level was kept at 15 cmH 2 O and the PC levels were increased every 2 minutes: 20, 25, 30, 35 and 40 cmH 2 O. Group 3: progressive levels of PC with a fixed PEEP level plus progressive levels of PEEP with a fixed PC level. Initially, the PEEP level was kept at 15 cmH 2 O and the PC levels were increased every 1 minute: 20, 25, 30, 35 and 40 cmH 2 O. Immediately after, the PC was kept at 15 cmH 2 O and the PEEP levels were increased every 1 minute: 25, 30, 35, 40 and 45 cmH 2 O. The PaO 2 /FiO 2 ratio, Cst, rs and PaCO 2 were evaluated before and after 1 hour of the ARM in each group alone and were later compared among the three groups by the Wilcoxon test. P <0.05 was considered significant. The ventilator used was the Bennet 840. Results: The PaO 2 /FiO 2 ratio improved significantly in the three groups after the ARM. There are no statistical differences in Cst, rs and PaCO 2 after the ARM in the three groups. The initial PaO 2 /FiO 2 ratio was: Group 1 (138.75), Group 2 (143.75) and Group 3 (131.12). When compared among the three groups, the PaO 2 /FiO 2 ratio in Group 3 presented a significant improvement in comparison with Group 1 and Group 2: 257.87 vs 195.25 (P <0.05) and 257.87 vs 194.75 (P = 0.02), respectively. According to the PaO 2 /FiO 2 ratio, there are no differences between Group 1 and Group 2 (195.25 vs 194.75; P = 0.878). Conclusions: ARM was effective in improving the PaO 2 /FiO 2 ratio in the three groups. The three ARM were similar in improving the Cst, rs and PaCO 2. In our study, the ARM showed better results according to the PaO 2 /FiO 2 ratio when performed initially with progressive levels of PC and later with progressive levels of PEEP in comparison with the other two approaches.