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BackgroundAlthough antenatal steroids and early use nasal continuous positive airway pressure (NCPAP) have significantly improved outcomes of neonatal respiratory distress syndrome, intubation with ventilator support is still commonly required in extremely low birth weight (ELBW) infants. The optimal timing of extubation in ELBW infants remains unclear.MethodsWe retrospectively analyzed all ELBW preterm infants who were admitted to our neonatal intensive care unit (NICU) from January 2009 to December 2013. Demographic, ventilation, and arterial blood gas analysis results prior to and 2 hours after extubation were collected. Extubation failure was defined as reintubation due to deterioration of respiratory condition within 7 days after extubation. Risk factors for extubation failure were analyzed.ResultsIn total, 173 ELBW infants were born and admitted to our NICU during these 5 years. Among these 173 infants, 77 (44.5%) used NCPAP only during their hospitalization (20 diagnosed with chronic lung disease (CLD), 25.9%). Among the 95 patients that required intubation, 27 patients expired so extubation was not attempted. Sixteen of 68 (23.5%) survival cases required reintubation within 7 days after extubation. We found that gestational age, birth body weight, and sex ratio did not differ between the successful extubation group and the failed extubation group. Univariate analysis showed that the failed extubation group had a lower arterial pH right before and 2 hours after extubation, with a lower bicarbonate level after extubation. Further multivariate logistic regression analysis revealed an association between poor acid-base homeostasis 2 hours after extubation (pH

13 patients who received surfactant therapy devel-oped PH within 72 hours of surfactant therapy. Among thesepatients, half (7 /13: 53%) were diagnosed with coexistentPDA by echocardiography during PH. PDA was bidirectionalshunt in five patients. For the other five patients whodeveloped severe PH despite no surfactant use, the medianage for severe PH was 3.2 days (range, 2e7 days). Only onepatient was diagnosed with hemodynamically significant PDAduring the occurrence of severe PH. This patient was notdiagnosed with respiratory distress syndrome but he pre-sented with thrombocytopenia soon after birth. PH devel-oped at age 3 days and cardiac echography showed abidirectional flow with left atrium:aortic root ratio of 1.8.The patient received PDA ligation on the next day.Why was no heart murmur found prior to PH in these in-fants?Onepossibleexplanationisthatthepulmonarypressurewas still high in these very-low-birth-weight infants with res-piratory distress syndrome. After surfactant therapy, thepulmonary compliance improved and it caused dramaticallydecreased pulmonary pressure. If PDA coexists, the dramati-cally decreased pulmonary pressure will result in significantleft-to-right shunt and it may lead to PH due to volume over-load. This hemodynamic change may happen quickly evenprior to when hemodynamically significant PDA is found.As mentioned by Cole et al