LAUSR

Background: The aim of this study is to assess the safety and efficacy of two protocols of automatic lung recruitment maneuver through stepwise increasing PEEP method, in a neonatal Acute Respiratory Distress Syndrome (ARDS) model. These protocols were designed with lower maximum opening pressures than traditional ones and differ each one in the duration of the opening phases (Fast vs Slow). We described hemodynamic changes through invasive monitoring and we analyzed if the behaviour of the variables depends on the duration of the opening phase of the LRM.Methods: We designed a prospective, experimental study with 10 Landrace x Large White pigs with less than 48 hours old. Under general anesthesia, tracheal intubation, invasive hemodynamic monitoring with a pediatric arterial thermodilution catheter, was performed. ARDS model was developed with bronco-alveolar lavages. Two types of lung recruitment maneuver (LRM) performed in each piglet, with maximum peak inspiratory pressure (PIP) of 30cm H2O and PEEP 15cm H2O applied during: 8.5 seconds in the Fast LRM-type1 and 17 seconds in the Slow LRM-type 2. A comparative analysis by virtue of the Wilcoxon signed-rank test and a regression analysis using generalized estimation equation was performed.Results: Both lung recruitment maneuver types have shown to be effective when it comes to oxygenation and respiratory mechanics. Shortening the duration of the opening branch and lowering the maximum opening pressures to PIP 30 and PEEP 15 cm H2O overpass the critical opening pressure to reverse alveoli collapse in our neonatal ARDS model. Although during both types of LRMs we observed hemodynamic variations, these were well tolerated.Conclusions: Our LRM protocols overpass the critical opening pressure to reverse alveoli collapse in our neonatal ARDS model. This range of pressures might involve less hemodynamic disturbance. Duration of the maximum opening pressure step is a determining factor for hemodynamic alterations.