In this observational study, very low birth weight preterm infants with RDS who require mechanical ventilation in first 24 hour of life will be recruited. A size appropriate nasogastric tube with multiple array of electrodes (Edi catheter) will be inserted in each eligible infant. The average EdI (Edi_avg) will be measured during mechanical ventilation just before extubation. All infants will be extubated to non-invasive positive pressure ventilation (NIPPV or CPAP) delivered through nasal cannula