[Clinical evaluation of a new hand-held impedance audiometer]

In order to evaluate the accuracy and clinical availability of MicroTymp (Welch Allyn) which was new, portable, cordless, and hand-held impedance audiometer, 64 normal subjects and 52 patients with otitis media with effusion were examined by use of MicroTymp and Amplaid 702 (Dana Japan). The types of tympanogram were agreed with each other in 87% of ears. Six cases of type C tympanograms in MicroTymp were shown to be type A by Amplaid 702, and the average of peak pressure of MicroTymp was more negative than Amplaid 702. The difference of peak pressure seemed to be influenced by the speed of ear canal pressure change, because the speed of MicroTymp was considerably higher than Amplaid 702; -200mmH2O/sec in MicroTymp, and -50mmH2O/sec in Amplaid 702. In the experimental study on 7 normal ears, negative shift of peak pressure was observed by increasing the rate of ear canal pressure change from -25mmH2O/sec to -50mmH2O/sec in Amplaid 702. These findings suggest that one should note in the judgment of type C tympanogram in MicroTymp having the peak pressure close to -100mmH2O.