Lung surfactant for replacement therapy.

In recent years, several attempts have been made to treat, or prevent, the neonatal respiratory distress syndrome (RDS) with exogenous surfactants. The most successful clinical trial so far reported concerned a series of artificially ventilated RDS-patients who were treated with a mixture of bovine natural surfactant and the synthetic phospholipids dipalmitoylphosphatidylcholine (DPPC) and unsaturated phosphatidylglycerol (PG). The rationale of this combination is that enrichment of natural surfactant with DPPC and PG strikingly modifies the lin vitro surface properties of the surfactant preparation, reducing surface tension to very low values already at moderate surface compression. In other similar clinical trials, promising results have been obtained with natural surfactant suspended with CaCl2, with human surfactant purified from amniotic fluid, and with protein-free natural surfactant from bovine lungs. Encouraging results have also been reported from a recent trial in which a dry, artificial surfactant, composed of DPPC and unsaturated PG, was administered prophylactically into the airways of premature babies shortly after birth. More studies, involving a combination of in vitro and in vivo experiments, are nevertheless needed to identify the optimal composition of an artificial surfactant and to evaluate the long-term effects of surfactant replacement on the premature lung.