[The intratympanic pressure ratio modified by nitrous oxide and dependent upon retrotympanic volume]

We measured the middle ear pressure of patients with intact middle ear during general anaesthesia with Halothane and N2O. The Madsen-Impedance-Measuring-Instrument ZO 73 was used. The planimetric size of the mastoid bone cavity was determined on radiograms in Schüller projection. The pressure in the middle ear space was found dependent from the size of the mastoid bone. The height of the middle ear pressure during tympanoplasty is not without problems, this will be discussed, and the advantages of local-anesthesia will be pointed out as well.