Tympanometry before and during nitrous oxide anesthesia with middle ear effusion.

During nitrous oxide anesthesia the nitrous oxide passes from blood to the normal middle ear space. Middle ear pressures before and during anesthesia in ears of pediatric patients with secretory otitis media have been measured with tympanometry. The subjects were divided into groups depending on the primary middle ear pressure and the pressure change during anesthesia. The reason for the different tympanometric findings in patients with secretory otitis media might be differences in the states of the mucous membrane of the middle ear. The usefulness of measuring middle ear pressures during nitrous oxide anesthesia is discussed.