The effect of a single bolus of exogenous surfactant on lung compliance persists until two weeks after treatment in a model of acid aspiration pneumonitis

Aspiration pneumonitis, a direct cause of acute lung injury, is associated to a severe deterioration of lung function due in part to endogenous surfactant system impairment. We evaluated the effects of selective exogenous surfactant administration in a murine model of acid-induced lung injury both at short and long term. Hydrochloric acid was instilled into the right bronchus of the mice (0.1 M, 1.5 ml/kg). Six hours from acid instillation, they received, in the injured lung, a 1 ml/kg bolus of porcine surfactant (Curosurf®) 40 or 80 mg phospholipids/ml (Surf40 or Surf80), or saline (0.9% NaCl, vehicle) Functional, biochemical, histological and inflammatory results were obtained 24 h after injury. In the Surf80 and vehicle group, lung mechanics and histology were assessed again after two weeks. Micro-Computed Tomography scans were performed at 24 h and two weeks. 24 h after injury in the Surf80 group respiratory system compliance and oxygenation were significantly improved compared to the vehicle, while neutrophilic fraction in bronchoalveolar lavage was significantly lower. Surfactant-treated mice maintained a better compliance and a significantly reduced inflammatory infiltrate also two weeks after treatment compared to vehicle. Micro-Computed Tomography scan suggested a more pronounced reduction of injury in surfactant-treated animals two weeks after injury (p = 0.09). We showed a beneficial effect on lung function of a single bolus of exogenous surfactant in unilateral acid-induced lung injury up to two weeks after treatment. Our results may suggest a role of surfactant replacement in modulating spontaneous evolution of injury.