In vitro testing of tympanostomy tube occlusion

Tympanostomy tubes (TTs) are commonly rendered nonfunctional by mucus plug formation. The purpose of this study was to determine whether an in vitro model could be developed to assess TT plug formation with results consistent with human trials.

An ear chamber was designed to mimic middle ear air and mucus flow conditions in post-TT otorrhea. TT occlusion was tested and correlated to published in vivo results.

TTs that had previously been studied in vivo (Goode "T" and Reuter Bobbin collar buttons) were placed in the model chamber. Pooled, homogenized human middle ear mucus and an analog, egg white, were delivered at 80 muL per hour through the TTs. An air bolus was delivered every two minutes to simulate swallowing. Chamber pressure was monitored over 2.5 hours. Occlusion was determined by a pressure peak and visual confirmation.

Obstruction was found in 60 percent of the Reuter Bobbin and 40 percent of the Goode TTs using the mucus analog. These results are similar to those reported from previous in vivo studies. No plugging was reported for either TT using homogenized human ear mucus.

The in vitro TT chamber simulates the in vivo environment and yields results consistent with in vivo observations. This model system may allow for rapid prototyping and evaluation of new TTs that may be less vulnerable to occlusion.