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

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 cmH₂O and the PEEP levels were increased every 2 minutes: 25, 30, 35, 40 and 45 cmH₂O. Group 2: progressive levels of PC with a fixed PEEP level. The PEEP level was kept at 15 cmH₂O and the PC levels were increased every 2 minutes: 20, 25, 30, 35 and 40 cmH₂O. 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 cmH₂O and the PC levels were increased every 1 minute: 20, 25, 30, 35 and 40 cmH₂O. Immediately after, the PC was kept at 15 cmH₂O and the PEEP levels were increased every 1 minute: 25, 30, 35, 40 and 45 cmH₂O. The PaO₂/FiO₂ ratio, Cst, rs and PaCO₂ 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 PaO₂/FiO₂ ratio improved significantly in the three groups after the ARM. There are no statistical differences in Cst, rs and PaCO₂ after the ARM in the three groups. The initial PaO₂/FiO₂ ratio was: Group 1 (138.75), Group 2 (143.75) and Group 3 (131.12). When compared among the three groups, the PaO₂/FiO₂ 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 PaO₂/FiO₂ ratio, there are no differences between Group 1 and Group 2 (195.25 vs 194.75; P = 0.878).

Conclusion

ARM was effective in improving the PaO₂/FiO₂ ratio in the three groups. The three ARM were similar in improving the Cst, rs and PaCO₂. In our study, the ARM showed better results according to the PaO₂/FiO₂ ratio when performed initially with progressive levels of PC and later with progressive levels of PEEP in comparison with the other two approaches.