The Effects of Patent Ductus Arteriosus on Pulmonary Function in Infants with Respiratory Distress Syndrome

ABSTRACT

PURPOSE: Patent ductus arteriosus (PDA) is a common problem in infants with respiratory distress syndrome (RDS). The reported effects of closure of ductus on pulmonary function are variable. The purpose of this study was to compare the respiratory indices between infants with RDS with and without PDA and in infants with PDA, between before and after closure of PDA. METHODS: The respiratory indices, settings of mechanical ventilation and arterial blood gas analysis were investigated in 31 infants who were admitted to Seoul National University Hospital NICU from June 1998 to May 1999 with a diagnosis of RDS. The respiratory parameters were compared between infants with and without PDA. In the infants with PDA, the parameters were compared before and after closure of PDA with administration of indomethacin. The diagnosis of a significant PDA was made by cardiovascular distress scoring of greater than 3 and echocardiographic confirmation of ductal shunt. RESULTS: Nineteen infants (61.3%) were diagnosed with PDA and 4 infants were excluded due to failure of closure. Infants with PDA showed lesser pre-surfactant PaCO2 (32.5+/-10.5 vs 43.5+/-8.5, P<0.05) and lesser total pulmonary compliance (0.65+/-0.20 vs 1.05+/-0.17, P<0.01), tidal volume (4.78+/-1.53 vs 7.19+/-2.02, P<0.05) and higher airway resistance (435+/-44 vs 301+/-49, P<0.01) at 12 hours after surfactant treatment than infants without PDA. In infants with PDA, oxygenation index (7.27+/-9.84 vs 3.29+/-6.21, P<0.05) and airway resistance(439+/-45 vs 291+/-93, P<0.05) were decreased and total pulmonary compliance (0.55+/-0.21 vs 1.35+/-0.48, P<0.05) were increased after closure of PDA. CONCLUSIONS: The pulmonary functions were poor in infants with PDA and closure of the ductus with indomethacin lead into a significant improvement in pulmonary function.