Accuracy of tympanometric middle ear pressure determination: the role of direction and rate of pressure change with a fast, modern tympanometer.
OBJECTIVE
Modern tympanometers run at higher rates of pressure change than older tympanometers, which increases the inaccuracy of determining the middle ear pressure.


BACKGROUND
Tympanometric middle ear pressure may be susceptible to both the direction as well as the rate of pressure change, which is reflected by two different pressure peaks in a bidirectional recording. The resulting peak pressure difference results in an inaccuracy, which can amount to 25 daPa in older instruments with slower rates of pressure change. However, modern instruments often apply much faster rates, which may increase the peak pressure difference and thus the inaccuracy of middle ear pressure.


METHODS
Middle ear pressure was measured for a negative and positive direction of pressure change at four different rates (50, 100, 200, and 400 daPa/s) in 38 normal adults. The peak pressure difference was calculated by the middle ear pressure determined in positive minus negative direction.


RESULTS
The mean peak pressure differences ranged between 10 and 12 daPa (standard deviation = 8-11) in the four groups and were independent of the rate of pressure change (p = 0.321).


CONCLUSIONS
The peak pressure differences found by the current tympanometer were consistently small for all rates of pressure change and were thus independent of the rate. This means that high rates can be used without decreasing accuracy, and the mean error is only 5 to 6 daPa, corresponding to the intrinsic hysteresis of the middle ear system.
Therkildsen
Anette G
AG
Department of Otolaryngology, Head and Neck Surgery, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark.
Gaihede
Michael
M
D000158:Acoustic Impedance Tests / Q000295:instrumentation*; D000328:Adult; D000399:Air Pressure; D004432:Ear, Middle / Q000503:physiopathology*; D004548:Elasticity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010034:Otitis Media with Effusion / Q000175:diagnosis / Q000503:physiopathology; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D014160:Transducers, Pressure; D014783:Viscosity