Impedance tympanometry and acoustic reflectometry at myringotomy.

A total of 220 ears undergoing myringotomy and pressure-equalizing tube placement were studied with impedance tympanometry and acoustic reflectometry in a direct comparison for detection of middle-ear effusion. Impedance tympanometry and acoustic reflectometry were equally accurate, detecting the presence or absence of middle-ear effusion in 73% and 72% of ears, respectively. The presence of effusion in ears with tympanographic patterns other than type A and type B was not consistently and reliably predicted. The higher sensitivity of impedance tympanometry (90%) compared with that for acoustic reflectometry (58%) contrasted with the opposite findings for specificities (54% vs 88%). It is concluded that impedance tympanometry and acoustic reflectometry measure different events at the tympanic membrane and their utility lies in the fact that they complement each other. These instruments can aid the experienced otoscopist in confirming a clinical impression and assist the less experienced clinician in validating or improving otoscopic skills.