Peter was born by normal vaginal delivery at 32 weeks gestational age weighing 2.49 kg. This was the first pregnancy for his 22-year-old mother who had no significant past medical history and had been well throughout pregnancy. Antenatal ultrasound at 20 weeks showed no fetal abnormality, a well grown fetus and mild polyhydramnios. The pregnancy was unremarkable until the onset of spontaneous labour at 32 weeks. Amniotic membranes remained intact until just before delivery. Cardiotocographic monitoring was within normal limits prior to delivery and there was no history of vaginal bleeding. Peter cried immediately following cephalic vaginal delivery; his heart rate was more than 100 beats/min and he did not require any resuscitation. By 10 min of age Peter was noted to be dusky and was grunting. He was given intermittent positive pressure ventilation (IPPV) and his colour improved. He was transferred from the delivery suite to the special care baby unit in facial oxygen and on arrival was saturating at 95% in 30% oxygen with a respiratory rate of 40 breaths/min and a temperature of 36.9°C.

On examination the admitting senior house officer (SHO) noted that despite being pink with an oxygen saturation of 95% Peter continued to grunt and had subcostal recession and nasal flaring while in 30% ambient oxygen. His systolic blood pressure (BP) was 60 mm Hg, capillary refill time (CRT) was <2 s and his heart sounds were normal with no murmur audible; abdominal examination was also normal. A capillary blood gas at 40 min of age showed: pH 7.099, pCO₂ 8.75 kPa, BE −9.5, HCO₃ 20.6 mmol/l. The SHO advised continuing oxygen and repeating the capillary blood gas in 1 h. Intravenous dextrose saline was commenced at 100 ml/kg/day and a full blood count (FBC), C reactive protein (CRP) and blood culture …