Measurements
The data collected only pertained to the first course of dexamethasone for any given neonate, including demographic and historical data: birth-weight (BW), gestational age (GA), sex, antenatal corticosteroids, surfactant (number of doses), mode of delivery, maternal infection, oligohydramnios, patent ductus arteriosus (PDA), anaemia and previous episodes of sepsis, and air leaks.
Data were also collected on the neonate’s circumstances at the time of commencing systemic steroids: date commenced and starting dose of dexamethasone (mg/kg/day), ventilation mode (conventional vs high frequency ventilation (HFOV)), average fraction of inspired oxygen (FiO2) in preceding 24 hours, days on mechanical ventilation, previous extubation attempts, corrected GA, postnatal age, chest x-ray appearance, weight, parenteral nutrition (PN) use, whether receiving enteral feeds, type of enteral feed, total fluid volumes (mL/kg/day), partial pressure of carbon dioxide on blood gas (pCO2), mean airway pressure (MAP), oxygen saturations (SpO2) over preceding 24 hours, date extubated, and whether antibiotics were being used.
Data collected after dexamethasone commencement included the primary outcome of interest: was neonate successfully extubated within 14 days? Successfully extubated was defined as extubated within 14 days of starting dexamethasone and remaining extubated for at least seven days.
The last chest x-ray prior to the commencement of dexamethasone was graded by an independent neonatologist using the system of Kim15 based on interstitial lung changes associated with BPD: grade 1 – no abnormality; grade 2 – granular infiltration; grade 3 – diffuse streaky interstitial infiltration; grade 4 – diffuse course reticular infiltration.