[Correlation between tympanogram and middle ear pressure--some considerations from experimental results].

We investigated whether the peak position (mmH2O) of tympanogram (TG) always corresponds to the actual middle ear pressure (MEP). Using especially designed plastic models (Endo et al., 1983) to simulate the human middle ear, the experimental results outlined in paragraph (1) and (2) led to the conclusions found in pragraph (3). (1) The position (mmH2O) of TG peak was almost equivalent to the pressure behind the model's membrane, when the membrane was in the neutral position. (2) When the model's membrane was retracted or adhesive to, promontory equivalent-site of the model, the TG peak markedly deviated to negative pressure such as -150mmH2O, although actual pressure behind the membrane was at atmospheric pressure. Tentative experiments indicated that either/all the volume displacement of the membrane, the pressure required to remove the adhesive membrane or the rheological properties of the membrane affected the position of the TG peak. (3) From these experimental results it is suggested that the position of TG peak may not always indicate the actual MEP when the ear drum is extremly retracted or adhesive, although it is almost equivalent to the actual MEP when the ear drum is normal.