Research Summaries: Surfactant mitigation of Lung Injury

Surfactant mitigation of Lung Injury and Regional Lung Mechanics in a sheep model of ALI/ARDS

Introduction: Administration of exogenous surfactant to lavage injured sheep has been demonstrated to improve oxygenation and increase compliance. We used CT imaging to measure regional volume recruitment with PEEP pre- and post saline lavage and after surfactant treatment. 5 anesthetized, mechanically ventilated prone sheep were studied; lung injury was induced by 3 lavages with 40 ml/kg NS to lower PaO2 to <100mmHg. Contiguous end-expiratory 2.5 mm CT scans covering the entire lung from apex to base were obtained, randomly changing PEEP from 5-20 cm H2O. 100 mg/kg rSPC surfactant (Venticute, Byk-Gulden) was instilled and the imaging protocol repeated. Images were analyzed to determine lung air and “tissue” density, and longitudinal and vertical distributions of air content. Results: Lavage injury dramatically increased lung tissue density, with steep vertical gradients in regional air content which became uniform at higher PEEP. Surfactant treated lungs demonstrated little if any difference in gradient or tissue density when compared to injured lungs. Conclusions: Lavage injury produces a diffuse, recruitable lung injury in sheep. Surfactant treatment results in improvements in PaO2 without increased aeration. Such improvement may be at the alveolar level with micro-recruitment of alveoli and improved gas exchange. Future studies, with longer observation periods may show greater changes in aeration and tissue density to correlate with improved PaO2 over time.