Nitrous oxide and middle ear pressure. A study of induction methods in children

The effects of different methods of induction of anaesthesia on middle ear pressure were investigated in healthy children. An increase in middle ear pressure associated with positive pressure ventilation with a bag and mask was demonstrated. When nitrous oxide was used, middle ear pressure increased by 39 mmH2O/minute in spontaneously breathing patients and 63 mmH2O/minute in those who were ventilated. Maximum pressures, with venting through the Eustachian tube, could be reached within 5 minutes in the latter group.