Aim: Dry, cold gas is used for neonatal resuscitation, contributing to low admission temperatures and exacerbation of lung injury. Recently, a method of heating and humidifying neonatal resuscitation gases has become available. We aimed to determine the optimal flow rate, humidifier chamber and water volume needed to reach 36. °C, and near 100% humidity at the patient T-piece in the shortest possible time. Method: A T-piece resuscitator was connected via a heated patient circuit to a humidifier chamber. Trials were performed using different gas flow rates (6, 8 and 10. L/min), humidification chambers (MR290, MR225) and water volumes (30. g, 108. g). Temperature was recorded at the humidifier chamber (T1), distal temperature probe (T2) and the T-piece (T3) over a 20. min period at 30. s intervals. A test lung was added during one trial. Results: No significant difference existed between flow rates 8. L/min and 10. L/min (p= 0.091, p= 0.631). T3 reached 36. °C and remained stable at 360. s (8. L/min, MR225, 30. mL); near 100% RH was reached at 107. s (10. L/min, MR225, 30. mL). T3 and humidity reached and remained stable at 480. s (10. L/min, MR290, 30. mL). Target temperature and humidity was not reached with the test lung. Conclusions: It is possible to deliver heated, humidified gases in neonatal resuscitation in a clinically acceptable timeframe. We suggest the set-up to achieve optimal temperature and humidity for resuscitation purposes is 10. L/min of gas flow, a MR290 humidification chamber, and 30. mL of water
