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.