Deflation opening pressure of the eustachian tube.

Measurements derived from tests of the performance of the eustachian tube (ET) under a variety of normal and pathologic conditions are widely diffuse and overlap considerably. In this survey, the deflation opening pressure (DOP) of the ET was tested in 31 patients suffering either from recurrent otitis (these patients had ventilating tubes inserted) or from chronic otitis media. Oxygen was deflated from the external ear canal, through the middle ear to the pharyngeal end of the ET. The DOP was the pressure needed for the passing of the oxygen. This pressure was usually between 100 to 200 mm H2O. No difference was found in the DOP between infants and adults or between discharging ears and dry ones. A second measurement was obtained through measuring the deflation flow pressure (DFP) required for the continuous passage of oxygen through the ET. The DFP was less than the DOP by approximately 20 to 60 mm H2O, and again no difference was noted between age groups or between infected and noninfected ears. It was concluded that DOP and DFP measurements of the ET are similar in a variety of conditions and therefore cannot indicate whether the ET is normally or abnormally functioning. The existence of a linear connection between the health of the ET and its performance is not proven; hence the role of the ET in predicting the likely outcome of tympanoplasty should be assessed within a different context.