This is a Phase I, open-label, single center trial to evaluate the feasibility and safety of low concentration CO2 gas mixture (5% CO2 + 95% air) inhalation in asphyxiated, cooled, mechanically ventilated newborns at risk of hypocapnia with The hypothesis is that hypocapnia, which is driven by hyperventilation in the presence of metabolic acidosis, is deleterious to the injured brain and can be safely avoided with low concentration CO2 inhalation.