A significant risk factor for the development of chronic lung disease in preterm newborns is invasive mechanical ventilation. Reduced ventilation effort and a decreased risk of ventilator-induced lung damage would result from a reduction in the dead space as a percentage of the total breathing volume. We compared the effectiveness of mechanical dead space washout via uncontrolled and controlled leakage flow in this experimental study to remove CO2 during conventional breathing in preterm newborns.