Quantitation of Pneumatic Otoscopy

Abstract

Pneumatic otoscopy has long been espoused as an easily and rapidly used, inexpensive method for routine evaluation of the tympanic membrane and middle ear. This widely used technique, however, has not been explored in a quantitative manner. Therefore, we measured the differential pressure and frequency of the pressure pulse used by a group of experienced otoscopists during routine pneumatic otoscopic examination. We found the pressure pulse varied from 170 to 520 mm H2O and the frequency varied from 2.2 to 4.9 pulses per second. We used a pneumatic pump to deliver a controlled pressure pulse—at a frequency of 4.0/sec—to the pneumatic otoscope. This device was used to measure the minimum pressure pulse necessary for the experienced otoscopist to merely detect tympanic membrane movement in normal ears. The threshold for visible movement ranged from 10 to 15 mm H2O. Thus, even the most gentle otoscopist used a pressure pulse an order of magnitude higher than the threshold for detection of visible movement in normal ears. The gap between the pressure pulse at threshold for visual detection of movement and that which is routinely used offers the possibility of increased sensitivity and specificity for this commonly used diagnostic tool. Preliminary data are presented from this study in which the pressure pulses required for visual detection of tympanic membrane movement in diseased ears were determined.