The effect of a peptide-containing synthetic lung surfactant on gas exchange and lung mechanics in a rabbit model of surfactant depletion

.Methods: Twelve adult New Zealand white rabbits receiving conventional mechanical ventilation underwent repeated BAL to create acute lung injury and surfactant-deficient lung disease. Synthetic surfactants were then administered and their effects assessed at specified time points over 5 hours. The variables assessed before and after lavage and surfactant treatment included alveolar and physiological dead space, dead space/tidal volume ratio, arterial end-tidal carbon dioxide tension (PCO 2 ) difference (mainstream capnography), arterial blood gas analysis, calculated shunt, and oxygen ratios. Results: BAL led to acute lung injury characterized by an increasing arterial PCO 2 and a simultaneous increase of alveolar and physiological dead space/tidal volume ratio with no intergroup differences. Arterial end-tidal PCO 2 and dead space/tidal volume ratio correlated in the Synsurf, generic Exosurf and generic Exosurf containing Ca 2+ groups. A significant and sustained improvement in systemic oxygenation occurred from time point 180 minutes onward in animals treated with Synsurf compared to the other two groups (P , 0.001). A statistically significant decrease in pulmonary shunt ( P , 0.001) was found for the Synsurf-treated group of animals, as well as radiographic improvement in three out of four animals in that group. Conclusion: In general, surfactant-replacement therapy in the animals did not fully restore the lung to its prelavage condition. However, our data show that the formulated surfactant Synsurf improves oxygenation by lowering pulmonary shunt.