Correlation between Changes of Intrapulmonary Right to Left Shunt and Improvements in Oxygenation after Exogenous Surfactant Administration in Preterm Respiratory Distress Syndrome

ABSTRACT

PURPOSE: This study was aimed to investigate the relationship between changes in intrapulmonary right to left shunt(QSP/QT) and improvements in oxygenation during the 2-hr study period after Surfactant-TA(S-TA) administration. METHODS: Umbilical arterial blood gases and corresponding respiratory indexes of 27 preterm neonates with respiratory distress syndrome were studied. The neonates were separated into group A(n=20) and group B(n=7) according to whether their initial QSP/QT was above or below 30 %, respectively. And the patients were studied immediately before and after endotracheal single- dose S-TA administration within 6 hours after birth. RESULTS: In the case of P(a/A)O2, group A showed a significant increase throughout the study period(P<0.01, P<0.001), whereas group B showed an initial significant increase at 2 hr(P<0.05). Significant correlations between changes in QSP/QT and improvements in P(a/A)O2 were seen in both groups(P<0.001, P<0.05). Moreover in the case of PaO2/FIO2, group A showed a significant increase throughout the study period(P<0.01, P<0.001), whereas group B showed an initial significant increase at 30 min(P<0.05). Significant correlations between changes in QSP/QT and improvements in PaO2/FIO2 were also seen in both groups(P<0.01, P<0.05). And at 2 hr, VEI and VA showed a significant increase in both groups(P<0.05, P<0.01), whereas PaCO2 showed a significant decrease in both groups(P<0.001, P<0.05). CONCLUSION: Irrespective of initial QSP/QT, immediate improvements in oxygenation following surfactant replacement were accomplished by recruiting atelectatic alveoli and stablizing underventilated alveoli(namely by decreasing QSP/QT). Moreover, the patients with more severe respiratory failure had a more rapid and sustained improvement in oxygenation.