Effect of Bias Gas Flow on Tracheal Cytokine Concentrations in Ventilated Extremely Preterm Infants: A Randomized Controlled Trial

BACKGROUND: The objective of this study was to determine whether ventilator bias gas flow affects tracheal aspirate (TA) cytokine concentrations in ventilated extremely preterm infants. METHODS: This is a randomized controlled trial in a tertiary neonatal unit in New Zealand. Preterm infants (<28 weeks' gestation/<1,000 g) requiring intubation in the first 7 days after birth were randomized to bias gas flows of 4 or 10 L/min. Cytokine concentrations in TA and plasma were measured at 24, 72, and 120 h after the onset of ventilation. The primary outcome measure was concentration of interleukin (IL)-8 in TA 24 h after the onset of mechanical ventilation. RESULTS: Baseline demographics were similar in babies randomized to 4 (n = 50) and 10 (n = 45) L/min bias gas flow. TA IL-8 concentrations were not different between groups. Plasma IL-8 concentrations decreased over time (p < 0.05). Respiratory support and incidence of bronchopulmonary dysplasia at 36 weeks' corrected gestational age were similar between groups. Fewer babies ventilated at 4 L/min developed necrotizing enterocolitis (NEC) ≥ stage 2 (n = 0 vs. n = 5; p = 0.02) and fewer died (n = 1 vs. n = 5, p = 0.06). CONCLUSIONS: Lower bias gas flow in ventilated extremely preterm infants did not alter TA cytokine concentrations but the lower incidence of NEC and mortality warrants further investigation.