Equivalent ear canal volumes in children pre- and post-tympanostomy tube insertion.

Pre- and postoperative equivalent ear canal volume measures were obtained from a group of 334 children ranging in age from 6 weeks to 6.7 years. The purpose of the study was to develop volumetric guidelines for the determination of tympanostomy tube patency. For children 4 years and older, almost no ambiguity existed in making this determination accurately. For younger children, the pre- and postoperative distributions overlap. A criterion value of greater than or equal to 1.0 cm3 as an indicator of a tympanic membrane perforation appears to yield the lowest possible error rate. When both pre- and postoperative measures are available, a difference of greater than or equal to 0.4 cm3 can be used in conjunction with the absolute value to identify a patent tympanostomy tube.