Abstract
Objective
We sought to determine the efficacy of commonly used earplugs using an anatomically correct ear model.
Methods
The total volume and rate of water that leaked past the earplug and subsequent defect in the tympanic membrane over separately measured 30, 60, 120, and 180-second intervals were recorded. Scenarios tested included a control with no earplug, custom molded earplug (Precision Laboratories, Orlando, FL), Mack’s plug (Warren, MI), Doc’s plug (Santa Cruz, CA), and cotton balls coated with petroleum jelly.
Results
All plugs tested resulted in less leakage at all time points when compared with no plug ( P < .05). At 30 seconds, the custom molded, Mack’s and Doc’s plugs all showed significantly less leakage when compared with the cotton ball coated with petroleum jelly ( P < .05). At 60, 120, and 180 seconds, Mack’s, Doc’s, and the cotton plugs all showed significantly less leakage compared with the customized plug ( P < .05). At 120 and 180 seconds, Mack’s plugs had significant less leakage than the cotton plug ( P < .05). Among the types of plugs, the molded variety (Mack’s) showed the least volume and lowest leakage rate (f 4,45 = 94 [ P < .001]). In addition, Doc’s and cotton balls coated with petroleum jelly were more effective than the customized earplugs.
Conclusions
If the clinician feels that middle ear and external canal water exposure should be minimized, then use of earplugs, particularly the moldable variety, merits further consideration.
1
Introduction
Bilateral myringotomy with tympanostomy tube insertion is one of the most commonly performed surgical procedures in the United States. Despite its frequency, there is much controversy among clinicians over the necessity of using earplugs while tympanostomy tubes are in place to minimize water exposure to the middle ear. Accordingly, there is a debate on the utility of earplugs after tympanostomy tube placement. The middle ear cavity is exposed and vulnerable to waterborne pathogens in patients with surgical or traumatic defects in the tympanic membrane. Literature has shown that there may be a small but statistically significant increase in the rate of otorrhea in children who swim without the use of earplugs . In addition, water exposure is often avoided and plugs prescribed in patients with acute otitis externa. However, otolaryngologists and primary care physicians continue to routinely prescribe earplugs after tympanostomy tube placement without literature supporting the efficacy of commercially available earplugs.
There are several older studies in the literature, which have compared earplugs currently available to the clinician. However, these studies all had limitations, including but not limited to, inability to quantify the rate and volume of leakage; the older studies did not have access to currently available plugs and did not take into consideration the unique shape of the pinna and external auditory canal . One such study used an in vitro model using a small 0.8-cm diameter tube as a model of the external ear canal . Another group used dry green crystal violet dye as an indicator of water penetration in an in vivo study without controlling for confounders such as sweat and sebum, which are naturally found in the external auditory canal . Robinson used pH indicator paper covered with micropore tape as the test for water penetration past earplugs in swimmers. Results were grouped as dry, moist, or wet, which preclude statistical analysis and ability to quantify the water leakage . A more recent in vivo study placed neurosurgical patties in the external auditory canal. Pre– and post–water exposure neurosurgical pattie weights were compared to quantify the leakage, which is limited by the volume of water that the neurosurgical pattie can absorb .
There have been inconsistent recommendations on the use of commercially available earplugs. Some of the earliest studies demonstrated cotton with petroleum jelly as superior to other plugs in preventing leakage of water . Chisholm et al also concluded that the cotton wool plugs with petroleum jelly resulted in less water measured in the external auditory canal by weighing neurosurgical patties. Other studies have shown foam plugs to be more beneficial . We, therefore, sought to determine the leakage rate and volume leaked between commonly used earplugs in an anatomically correct ear model.
2
Methods
We used an anatomical outer ear model manufactured by GPI anatomicals (Lake Bluff, IL; Fig. 1 ). The model was anatomically accurate, consisting of a helix, antihelix, tragus, conchal bowl, and external auditory canal, all composed of soft rubber as well as a more rigid tympanic membrane. This tympanic membrane consisted of a silicone barrier that separated the external auditory canal and the middle ear space. A myringotomy was created using a small drill bit to establish a 1.14-mm inner diameter defect in the tympanic membrane to mimic the luminal diameter of the Armstrong grommet ventilation tube that we commonly use at our institution (Gyrus ACMI; Bartlett, TN). A water tight cylinder was placed around the pinna to allow 100 mL of water to be placed over the pinna. We recognize that this water exposure model may be a more robust testing situation than most patients encounter in common clinical situations. A graduated beaker collected the water that leaked past both the earplug and the tympanostomy tube, and this volume was recorded over preset time points of 30, 60, 120, and 180 seconds. Flow rate was calculated for each ear plug by dividing the volume leaked, by the time required for the leakage to occur at each preset time point.
The scenarios tested included a control with no earplug, custom molded plug (Precision Laboratories, Orlando, FL), Mack’s moldable earplugs (Warren, MI), Doc’s soft plastic earplugs (Santa Cruz, CA), and cotton balls coated with petroleum jelly ( Fig. 2 ).
