PULMONARY EFFECTS AFTER SURFACTANT TREATMENT IN PREMATURE-INFANTS WITH SEVERE RESPIRATORY-DISTRESS SYNDROME

To understand the mechanisms behind the improved oxygenation after int ratracheal surfactant instillation, the immediate effects on lung volu me and pulmonary mechanics were analyzed. All infants studied were enr olled in multicenter trials in which surfactant therapy was instituted according to a rescue protocol. Infants received either synthetic sur factant (Exosurf) or modified porcine surfactant (Curosurf). Measureme nts of lung volume and pulmonary mechanics were successfully performed in 12 patients with a birth weight of 1.3 +/- (SD) 0.6 (range 0.7-2.7 ) kg, and a gestational age of 28.3 +/- (SD) 1.4 weeks. Functional res idual capacity (FRC) and pulmonary mechanics were measured during mech anical ventilation. The FRC increased significantly by 70% (median), f rom 7.10 +/- (SD) 2.8 ml/kg to 11.5 +/- 3.3 ml/kg after surfactant ins tillation. However, a concomitant decrease in specific compliance was also seen. These findings could suggest that this immediate increase i n FRC is initially nonuniform. However, since no significant correlati on between changes in FRC and improvement in arterial-to-alveolar oxyg en tension ratio is seen, other effects of surfactant must also be con sidered. These could include local and/or systemic changes in hemodyna mics, such as decreased shunting as well. as various effects on gas di ffusion.