Prolonged recruitment manoeuvre improves lung function with less ultrastructural damage in experimental mild acute lung injury

The effects of prolonged recruitment manoeuvre (PRM) were compared with sustained inflation (SI) in paraquat-induced mild acute lung injury (ALI) in rats. Twenty-four hours after ALI induction, rats were anesthetized and mechanically ventilated with VT = 6 ml/kg and positive end-expiratory pressure (PEEP) = 5 cmH2O for 1 h. SI was performed with an instantaneous pressure increase of 40 cmH2O that was sustained for 40 s, while PRM was done by a step-wise increase in positive inspiratory pressure (PIP) of 15–20–25 cmH2O above a PEEP of 15 cm H2O (maximal PIP = 40 cmH2O), with interposed periods of PIP = 10 cmH2O above a PEEP = 15 cmH2O. Lung static elastance and the amount of alveolar collapse were more reduced with PRM than SI, yielding improved oxygenation. Additionally, tumour necrosis factor-α, interleukin-6, interferon-γ, and type III procollagen mRNA expressions in lung tissue and lung epithelial cell apoptosis decreased more in PRM. In conclusion, PRM improved lung function, with less damage to alveolar epithelium, resulting in reduced pulmonary injury.