[Newer pathophysiologic considerations and treatment of neonatal respiratory distress syndrome (RDS)]

RDS is the major cause of morbidity and mortality in preterm infants. Hochheim first noted the pathologic appearance of the lungs with RDS in 1903, which included alveolar collapse associated with dilatation of the alveolar ducts and terminal bronchioles. This important finding now can be best explained by the newer model of pulmonary micromechanics proposed by Weibel and Bachofen. In this model, alveoli are not individual structures, but subunits of the alveolar duct system. The alveolar stability requires particular properties of both the fibrous skeleton and the alveolar surfactant film. With increasing surface forces resulting from surfactant deficiency, the alveolar volumes and surface areas decrease, more septal segments are folded up between the adjacent ducts, thereby widening the duct system and terminal bronchioles. In this situation, the shear forces triggered by mechanical ventilation cause damage of the terminal airways with increased permeability of plasma proteins into the airspaces, which tends to aggravate alveolar instability further. Exogenous surfactant replacement produced excellent results which decreased the pulmonary complications of RDS significantly with no adverse effects. In the not too distant future this therapy will be regularly practiced in NICU.