Prevention and treatment of plugged tympanostomy tubes

Ear, Nose & Throat Journal, Nov, 2007 by Ramzi T. Younis

The placement of tympanostomy tubes was pioneered by Politzer in the 19th century, but the procedure was soon abandoned because of a high rate of complications. (1) In 1954, Armstrong (1) "reinvented" the procedure, and it became widely accepted. Today, tympanostomy tube placement has become the most common procedure performed in children under general anesthesia. (2)

When Armstrong reintroduced tympanostomy tube placement, he wrote, "An ideal tube should not plug or extrude prematurely, should be inserted and removed easily and should have a low complication rate." (1) However, plugging of tympanostomy tubes remains a common complication, occurring in 7 to 10.5% of cases, which amounts to perhaps 100,000 cases per year. (3,4)

Consequences of plugged tubes

A plugged tube can cause symptomatic otitis media and lead to hearing loss secondary to a lack of ventilation in the middle ear. Tube obstruction may also lead to tube extrusion. (5,6)

On a larger scale, the ramifications of occluded tubes include higher costs to the healthcare system. Many clinicians may not recognize the direct healthcare expenditures and indirect nonmedical costs that are associated with plugged tubes. The direct costs include an increase in the number of office visits and the cost of drops or remedies used to unblock a tube; if conservative therapy fails, reoperation becomes necessary. Indirect nonmedical costs include transportation expenses, lost wages, and missed school time.

Etiology of plugged tubes

Among the possible causes of tympanostomy tube plugging are an accumulation of wax and/or keratin, perioperative bleeding, middle ear effusion, and the presence of biofilms. (7,8)

Reid et al studied blocked tubes by light microscopy. (7) They found that in 56% of the tubes, the luminal material was made up of eosinophilic coagulum that had been infiltrated by leukocytes. They also found that in 70% of extruded tubes, the base of the tube was covered with a cast of squamous epithelium that had been derived from middle ear effusion. Finally, they found a statistically significant association between tube blockage and the presence of thick middle ear fluid.

Westine et al studied the biochemical composition of tube plugs by high-performance liquid chromatography (HPLC). (8) They compared the HPLC profiles of three substances potentially responsible for tube plugs: blood, cerumen, and mucoid middle ear effusion. Their HPLC amino acid and monosaccharide analyses revealed that the likely cause was mucoid effusion. They concluded that tube plugs are not products of cerumen and blood. Cerumen is produced in the lateral auditory canal and is not likely to move against the direction of natural migration. (6) Although blood might become mixed in with mucoid middle ear effusion, it is more of a problem during the immediate postoperative period.

The type of material used to manufacture a tube might have an effect on plugging. (7,9-14) Theoretically, using a tube with a very smooth surface would reduce the risk of bacterial adherence and prevent occlusion. Tsao et al studied the association between tube composition and plugging in six types of tubes: stainless steel, titanium, silicone, ion-bombarded silicone, fluoroplastic, and phosphorylcholine-coated fluoroplastic (30 tubes of each material were studied). (9) As the surface of fluoroplastic tubes is smoother than the surface of silicone tubes, the irregular surface of the latter theoretically facilitates the development of bacterial adhesion and fouling. Also, stainless steel and titanium both have a theoretical advantage over both silicone and fluoroplastic in that they are associated with fewer manufacturing irregularities, and therefore they should be easier to unplug. However, neither of these theories was borne out by the findings of Tsao et al. (9) They found that with one exception, mucoid plugs cleared at approximately the same rate regardless of the type of material. The only significant difference was seen in the plug clearance rates of ion-bombarded silicone and untreated silicone; the former were cleared more quickly. Overall, Tsao et al concluded that tube composition does not significantly change the rate of mucoid plug dissolution ex vivo. (9)

Handler et al prospectively compared silicone tubes with gold-plated tubes and found that the gold tubes, which have a smoother surface, had a higher rate of extrusion; they also occluded more frequently. (12) In a separate study, these authors found no difference in extrusion rates and occlusion rates between titanium and silicone tubes. (13) Tami et al compared gold and polytetrafluoroethylene (Teflon) tubes and found a significantly higher rate of extrusion with the gold tubes; the rate of occlusion was also higher, but not significantly so. (14)

Biofilm was recently implicated in the formation of tympanostomy tube plugs. (15) The presence of biofilm may lead to the development of other dynamic factors in an in vivo situation that may play a role in tube plugging.