Warming and humidifying inspiratory gases to minimise lung injury during resuscitation of extremely preterm infants

The intervention is administration of warm humidified (WH) blended oxygen-air gas (approximately 37 degrees celcius and 100% relative humidity) during resuscitation. WH gas will be used for any of CPAP, mask or endotracheal ventilation administered via a standard T piece ventilator (Neopuff, Fisher and Paykel Health Care, Auckland New Zealand). WH gas will be administered to babies born vaginally or by caesarean section. All other clinical care during resuscitation is at the discretion of the neonatal clinical team guided by a senior neonatal clinician and informed by standardised in house protocols based on ILCOR resuscitation guidelines. The resuscitating team will personalise the extent of respiratory support required (CPAP, face mask or endotracheal ventilation, level of inspired oxygen) using clinical judgement based on the clinical condition of the baby. WH gas is administered from birth until admission to the Neonatal Unit. Following admission to the Neonatal Unit, all babies in intervention and control groups who require continuing respiratory support will receive WH gases as normal standard of care. The heated humidified circuits used for resuscitation with WH gases will use components standardly used in intensive care (MR850 baseplate, MR290 humidifier chamber, and 900RD110 heated circuit, all components made by Fisher and Paykel Health Care, Auckland, New Zealand). Default factory settings produce a gas temperature of 39 degrees celcius close to the end of the inspiratory tubing. A short length of extension tubing is a bridge between the heated tubing and the connection to a Neopuff T piece. The humidifier chamber is filled with 30mL of water. Heated humidified circuits will be set-up and available in the birthing suite and theatres, and will be turned on when a birth is imminent and for at least 10 minutes before birth. Blood samples (200 microlitres of whole blood) will be taken from the umbilical cord (artery), and from the baby at 12 hours, 24 hours and 48 hours after birth via an arterial line (preferred) or heel prick if there is no arterial line. Whole blood will be centrifuged immediately, plasma decanted and then frozen at -80 degrees celcius for batched analysis of biomarkers at the conclusion of the study using enzyme linked immunosorbent assays (R&D Bioscience). Trial fidelity will be assessed by the attendance of one of the trial investigators at each delivery who will not be involved in the resuscitation but with the role of recording and timing resuscitation interventions and trial adherence. Fidelity of sample processing will similarly be via attendance of a trial investigator with sole responsibility for the samples. All clinical and sample processing variables will be recorded.