DESCRIPTION

DEVICES AND METHODS FOR TESTING TYMPANOSTOMY TUBES

Background of the Invention

Otitis media, or middle ear infection, is a common ailment of children, affecting approximately 70% of all children by two years of age. This condition occurs when the Eustachian tube becomes inflamed and causes fluid to accumulate in the middle ear or the tympanic cavity. The build-up of fluid behind the tympanic membrane or eardrum leads to an increase in pressure in the middle ear and causes severe ear pain and conductive hearing loss.

For patients suffering multiple cases of otitis media or a prolonged period of fluid build-up, the most common and effective treatment is insertion of a tympanostomy tube into the tympanic membrane in a procedure called a myringotomy. Insertion of the tympanostomy tube can serve to relieve the pressure and reduce hearing loss by allowing trapped fluid to drain from behind the tympanic membrane. During the procedure a small incision is made in the anterior part of the tympanic membrane, fluid is suctioned out, and a tube is inserted.

A tympanostomy tube is usually manufactured of metal or plastic. To reduce plugging or blocking of the tube, which can occur in up to 30% of cases, special surface coatings or treatments may be utilized that inhibit adhesion of fluids or other materials, for example bacteria, blood, ear wax, etc. A tympanostomy tube typically stays in the tympanic membrane from 8 months to about 18 months, depending on the tube design, and eventually extrudes itself in over 90% of cases. However, in some situations, for example cleft palate patients or patients with chronic Eustachian tube dysfunction, it may be necessary for tubes to remain in place for longer periods of time. Conversely, for other types of patients, it may only be necessary for tubes to remain in place for a few months.

While tympanostomy tubes are a widely accepted treatment for otitis media and conductive hearing loss, there are a few complications associated with their use. The most common problem is occlusion or blockage of the tubes by mucus, blood, bacteria, etc. that can form a plug in and around the tube. In order to combat this problem, tympanostomy

tubes are manufactured with various coatings or other materials that reduce the adherence of materials to the tubes. Ear drops can also be recommended in order to clear the occlusion, but in about 1/3 of cases, the tympanostomy tube must be removed or replaced. The methods for inserting or removing tympanostomy tubes usually require general anesthesia.

The design of a tympanostomy tube, and coating or materials thereon, can determine how long a particular tube design will remain in place in a tympanic membrane. Currently research on tympanostomy tube occlusions and coatings is performed only in vivo on young children and can take months to years to complete. There is a need for an in vitro testing device that can reduce the research time and eliminate the need for multiple patients and clinical in vivo tests.

Brief Summary of the Invention

The subject invention provides devices and methods capable of simulating the outer and middle inner ear environments, particularly of children. The devices can be utilized in many situations where a natural or living ear environment may not be practical. In one embodiment, the devices of the subject invention facilitates in vitro testing of tympanostomy tubes and their rates and susceptibility to occlusion. It also allows for the isolation and testing of individual tympanostomy tube variables such as length, diameter, composition and coating materials that could not be achieved in previous in vivo studies.

The devices of the subject invention can be used to test the effectiveness of a large variety of tympanostomy tubes without the need for clinical in vivo tests. Advantageously, the devices of the subject invention can also reduce research time to only a few hours, instead of the many months usually required for in vivo testing. This reduces or eliminates the need for multiple surgical procedures, contributing to decreased health care costs.

The rates of occlusion encountered during testing with the devices of the subject invention provide insight into how long a particular tympanostomy tube may be expected to function in a natural ear environment. For example, the first tests performed with a device of the subject invention measured the effect that length has on the occlusion time of tubes. The initial results showed that length can be a significant factor in the times required to form and unplug an occlusion. Specifically, the results showed that a 12 mm tube required 23 minutes in a subject device before an occlusion formed in the opening of the tube, whereas a 4.8 mm tube required only 13.5 minutes in the subject device before an occlusion formed. The device

of the subject invention illustrated that, under certain conditions, a longer tube was more likely to resist occlusion for a greater period of time.

Thus, the subject invention provides a means for predicting and anticipating the effectiveness of various tympanostomy tubes.

Brief Summary of the Figures

Figures IA, IB, and 1C illustrate an embodiment of an artificial membrane that can be utilized with the subject invention. Figure IA illustrates the artificial membrane in a relaxed state. Figure IB illustrates the artificial membrane with the opening therein in a stretched state. Figure 1C illustrates the artificial membrane wherein the opening is conforming around a representative tympanostomy tube inserted therein.

Figure 2 is an exploded view of an embodiment of an artificial ear chamber utilized with the subject invention.

Figure 3A is a cross-sectional view showing the direction of air and fluid flow in an embodiment of an artificial ear chamber utilized with the subject invention.

Figure 3B is a cross-section view showing the direction of air and fluid flow in an alternative embodiment of an artificial ear chamber utilized with the subject invention.

Figure 4 illustrates an embodiment of a fluid delivery syringe assembly and scaffolding utilized with the subject invention.

Figure 5 is an enlarged view of an embodiment of a compression cup assembly utilized with an embodiment of the fluid delivery syringe assembly shown in Figure 4.

Figure 6 illustrates an embodiment of the air delivery syringe assembly and scaffolding utilized with the subject invention.

Figure 7 is a photograph showing an embodiment of an artificial ear chamber simultaneously connected to the fluid delivery syringe assembly and the air delivery syringe assembly that can be utilized with the subject invention.

Figure 8 is a photograph showing the details of an embodiment of the compression cup assembly.

Figure 9 is a photograph showing the details of an embodiment of the fluid delivery syringe assembly.

Figure 10 is a photograph showing the details of an embodiment of the air delivery syringe assembly.

Figure 11 is a photograph showing the details of an embodiment of the artificial ear chamber with an air delivery syringe and a fluid delivery syringe connected thereto.

Figure 12 is a graph that illustrates the results of a tympanostomy tube test indicating that there is a difference in the time required for an occlusion to form and be expelled between the 12 mm and 4.8 mm long tubes.

Detailed Description

The subject invention provides devices for simulating the outer and middle inner ear environments, particularly of children. In accordance with the subject invention, fluid (liquid or gas) is introduced into the devices, under varying or continuous pressure, to simulate the natural environmental conditions in a child's outer and middle ear. The devices of the subject invention facilitates in vitro testing of tympanostomy tubes and their rates and susceptibility to occlusion. It also allows for the isolation and testing of individual tympanostomy tube variables such as length, diameter, composition and coating materials that could not be readily evaluated in previous in vivo studies. Research time for individual tympanostomy tubes can be reduced from months of in vivo studied to a few hours of in vitro testing.

In general, the devices of the subject invention utilize an artificial membrane secured between a front compression plate and a rear compression plate. With reference to the attached figures, which show certain embodiments of the subject invention, it can be seen that the assembly creates an artificial ear chamber 40. The membrane has an opening similar to one that would be created during a myringotomy procedure. A tympanostomy tube 16 can be inserted into this opening prior to, or after assembly of, the artificial ear chamber 40, preferably prior to assembly. The compression plates further comprise openings to mimic natural outer and middle ear chambers on either side of the latex membrane.

The compression plates additionally comprise means for regulated and measurable delivery of fluid and/or air into the simulated ear chambers. This allows a researcher to simulate natural ear fluid flow and Eustachian tube air flow as would exist in a normal ear.

The delivery of liquid and/or air into the artificial ear chamber 40 can be accomplished using a delivery syringe and, in one embodiment, scaffolding systems that use, for example, stepper or gear head motors and plungers to compress air or liquid through openings in the rear compression plate and into a cavity within the compression plate that

simulates the middle ear cavity. Combined fluid and/or air pressure can be applied to this chamber that is in integral contact with the artificial membrane having the tympanostomy tube therein. The amount of pressure applied to the chamber and, hence, to the artificial membrane and tympanostomy tube can be measured and recorded utilizing techniques and devices known in the art. Changes in pressure can indicate the amount of occlusion occurring within or around a tympanostomy tube.

The artificial membrane 12 may comprise a variety of materials capable of simulating a natural tympanic membrane. Preferably, the membrane material is flexible and able to conform around the circumference of a tympanostomy tube 16 inserted and positioned within the artificial membrane (Figures IA and IB). The circumferential shape of the membrane 12 can vary including, for example, circular, square, oval, triangular, or any polygonal shape. Preferably, the membrane is capable of adequately simulating a tympanic membrane and being properly secured in the device of the subject invention, as discussed below.

An opening 14, similar to a myringotomy, can be provided in the membrane 12 prior to assembly of the device, or it can be created after assembly, hi a preferred embodiment, the opening 14 is provided and the tympanostomy tube 16 inserted and secured prior to assembly of the device of the subject invention (Figures IA, IB, and 1C). Materials that may be suitable for the membrane could include various elastomeric products, including, but not limited to, latex, rubber, plastics, gel compositions, natural fibers or products, or combinations thereof, etc. Alternatively, less elastomeric materials can be utilized, wherein a tympanostomy tube is secured by means other than conformation of the membrane around the circumference of the tympanostomy tube. For example, less elastomeric materials may require securing a tympanostomy tube in the membrane with various adhesives or tape products, stitching or securing means, or other means for reducing or closing the opening around the circumference of the tympanostomy tube. Certain materials may require additional support in order to maintain rigidity of the material or to assist in maintaining proper placement in the artificial ear chamber 40. For example, rings, bands, flanges, or other structures can be utilized to lend rigidity to various elastomeric materials in order for them to more accurately simulate a tympanic membrane. If necessary, the elastomeric, or other appropriate, material could also be temporarily or more permanently secured to the support structure in a variety of ways, including any mechanical means, adhesives, heat sealing, friction, etc.

In a preferred embodiment, the artificial membrane 12 comprises a thin elastic latex material stretched over a thin stainless steel metal washer 15. In a preferred embodiment, the latex material is stretched across the thin metal ring so that the latex material is rigid, yet still able to conform and able to hold a typmanostomy tube in position. Further, the metal ring is able to maintain its shape so as to provide support to the latex material while it is stretched and conforming. The stainless steel washer can be, for example, about 0.03 inch to about 0.1 inch thick with a diameter of approximately 0.5 inch to about 1 inch. In the most preferred embodiment, the washer is approximately 0.06 inch thick and approximately 0.6 inch in diameter. In a still further preferred embodiment, the latex material is adhered to the metal washer with an appropriate adhesive, for example cyanoacrylate or similar product. Li a still further preferred embodiment, an opening 14 is created in the stretched and secured membrane prior to assembly of the device of the subject invention. In yet a further preferred embodiment, a tympanostomy tube 16 to be tested is inserted and secured into the opening in the artificial membrane prior to assembly of the device, for example as shown in Figure 1C.

Once an artificial membrane 12 is prepared with a tympanostomy tube 16 (Figure 1C), it is secured between a front compression plate 18 and a rear compression plate 22 (Figure 2). The plates may be any of a variety of shapes, including, for example, round, square, oval, triangular, or other polygonal shape. Further, the plates may be formed of any of a variety of materials, but are preferably rigid and of sufficient strength to withstand the compression that will be exerted on the plates in order to form a secure seal around the artificial membrane 12, and when they are used during testing of various tympanostomy tubes. Materials that are appropriate for the plates include, for example, steel, iron, aluminum, or other metals, tempered or other glass materials, various plastics, ceramics, and rubber. Li a preferred embodiment, the compression plates comprise Lexan™ plastic.

The front compression plate 18 further comprises one or more exit channels 20 to simulate an outer ear canal. The circumferential shape of the one or more exit channels can vary, including, but not limited to, circular, oval, square, triangular or any other polygonal shape. Li a preferred embodiment, the front compression plate comprises a single exit channel 20. In a further preferred embodiment, the circumference of the exit channel is substantially circular. The exit channel 20 is designed to simulate a natural outer ear canal in that mucus and air exiting the artificial membrane 12 via the tympanostomy tube 16 can accumulate in the exit channel and/or in and around the tympanostomy tube forming an

occlusion. It is this rate of total occlusion of the tympanostomy tube 16 that provides insight into its effectiveness in a real world environment.

In one embodiment, the rear compression plate 22 further comprises one or more liquid input channels 24 and one or more air input channels 26. The one or more liquid input channels 24 allow for the introduction of one or more fluids of varying or continuous pressure against the back of the artificial membrane, opposite the exit channel 20 (Figure 2). The circumferential shape of the one or more liquid input channels 24 can vary, including, but not limited to, circular, oval, square, triangular or any other polygonal shape. In a preferred embodiment, the rear compression plate 22 comprises a single input channel 24. In a further preferred embodiment, the circumference of the input channel 24 is substantially circular, for example as shown in Figure 2. In still a further preferred embodiment, the fluid input channel is approximately 0.05 inch to about 0.15 inch in diameter. In a most preferred embodiment, the diameter is approximately 0.1 inch. Further, the length of the liquid input channel can be approximately between 0.15 inch and about 0.35 inch. In a preferred embodiment the liquid input channel is approximately 0.25 inch in length.

During testing, mucus or other fluids with similar characteristics, for example egg yolk, is injected into the liquid input channel 24 at continuous pressure utilizing a liquid delivery syringe assembly 60, which will be discussed below. In a preferred embodiment, approximately 0.05 ml to about 0.3 ml per hour of fluid is injected into the fluid input channel. In a most preferred embodiment, approximately 0.1 ml per hour of fluid is injected at a continuous pressure into the liquid input channel 24.

The one or more air input channels 26 in the rear compression plate 22 are designed to simulate Eustachian tube function. The Eustachian tube connects the middle ear with the back of the nose, in order to maintain compliance between pressures in the middle ear with pressure outside the ear. To achieve this compliance, the Eustachian tube allows the movement of air into or out of the middle ear chamber, behind the tympanic membrane, to equalize the pressure on both sides of the tympanic membrane. Thus, the one or more air input channels 26 are contiguous with the liquid input channel 24 so that air can be introduced with the fluid behind the artificial membrane 12. Figure 3 shows how the air input channel 26 is continuous with the liquid input channel 24, as well as the direction of flow within in each channel and through a representative tympanostomy tube. The circumferential shape of the one or more air input channels 26 can vary, including, but not

limited to, circular, oval, square, triangular or any other polygonal shape. In a preferred embodiment, the rear compression plate 22 comprises a single air input channel 26. In a further preferred embodiment, the circumference of the exit channel is substantially circular. Further, the diameter of the air input channel is between approximately 0.05 inch to approximately 0.15 inch. In a most preferred embodiment, the diameter is approximately 0.1 inch. Further, the length of the air input channel can be approximately between 0.15 inch and approximately 0.35 inch. In a preferred embodiment the air input channel is approximately 0.25 inch in length.

In an alternative embodiment, the positions of the one or more air input channels and the one or more liquid input channels in the rear compression plate can be reversed, for example as shown in Figure 3B. In this alternative embodiment, a continuous supply of air is injected into the rear compression plate 22 behind the artificial membrane 12 via the continuous air input channel 23. Compressed air or a pumped air supply can be utilized, as long as it is capable of providing a continuous, uninterrupted pressure. Further, the liquid drip input chamber 21, can enter within the center of the continuous air input channel 23, for example as shown in Figure 3B. hi this alternative embodiment, the liquid drip input chamber 21 can be connected to a mucus-filled graduated syringe 62. hi a further embodiment, a pressure transducer 25 is attached to the continuous air input channel 23 to measure the pressure and changes thereof within the air input chamber 23. hi this alternative embodiment, mucus or other fluids are delivered periodically into the fluid input channel 21 while air is being injected at a constant rate or pressure through the air input channel 23. The air pressure within the channels pushes or forces the fluid or mucus through the tympanostomy tube 16 installed within the artificial membrane 12. As described above, as the fluid passes through the tympanostomy tube 16 it can reduce, temporarily block, or eventually stop through build-up, the air flow through the tympanostomy tube 16, which will cause changes in the air pressure within the continuous air input channel 23 that are registered and/or recorded by the pressure transducer 25 affixed to the continuous air input channel 23.

Certain embodiments utilize a continuous supply of mucus flowing through the liquid input chamber 24, with periodic injections of air. This alternative embodiment instead utilizes continuous air pressure within the continuous air input channel 23 with the periodic

input of fluid or mucus, such that the continuous air pressure within the channel causes the mucus to exit through the tympanostomy tube 16 within the artificial membrane 12.

In a preferred alternative embodiment, the pressure within the continuous air input channel 23 is maintained at approximately 10 psi. However, this can be adjusted as necessary for the type of fluid or mucus being utilized, the type of membrane, tympanostomy tube being tested, etc. In a still further preferred embodiment, the fluid is introduced into the continuous air input channel 23 via the liquid drip input channel 21 at a rate of approximately 0.03ml being inserted approximately every 5 minutes.

The front compression plate 18 and the rear compression plate 22 are assembled prior to a test. A sealing material or device, such as, for example, a gasket 28 can be utilized between the plates to facilitate proper sealing of the artificial membrane 12 between the plates and to ensure proper sealing between the compression plates, for example as shown in Figure 2. In a preferred embodiment, a foam seal 28 is positioned between the compression plates.

In a further preferred embodiment, the foam seal further comprises an opening therein that circumscribes the exit channel 20 to provide the tympanostomy tube 16 access to said exit channel. In a further preferred embodiment, the foam seal 28 is positioned between the front compression plate 18 and the artificial membrane 12, for example as shown in Figure 2.

The plates can be assembled using a variety of techniques known in the art that provide a reliable, even pressure seal around the circumference of the artificial membrane. In one embodiment, the front compression plate 18 and the rear compression plate 22 are held together, with the foam seal 28 between them, utilizing at least two nut and bolt assemblies

27, for example, as shown in Figure 2. In a preferred embodiment, at least four nut and bolt assemblies 27 are used to join and seal together the front compression plate 18, a foam seal

28, and the rear compression plate 22, with an artificial membrane 12 there between, for example as illustrated in Figure 2. This assembly, an example of which is illustrated in Figures 2 and 3, is referred to as the artificial ear chamber 40.

In a still further embodiment, the front compression plate 18 and/or the rear compression plate 22 have countersunk depressions 32 to accommodate the artificial membrane 12 when the compression plates 18 and 22 are assembled. In a preferred embodiment, the rear compression plate 22 provides a countersunk depression 32 of sufficient depth and shape to accommodate the artificial membrane 12, maintain its position

between the compression plates 18 and 22, and allow substantially natural movement of the membrane 12 during testing. As mentioned above, liquid and air are introduced into the artificial ear chamber in order to simulate natural inner and middle ear environments. To accomplish this, the artificial ear chamber 40 can be connected to a fluid delivery syringe assembly 60 and an air delivery syringe assembly 80. Figure 4 illustrates an embodiment of a syringe delivery assembly 60 of the subject invention. Figure 6 illustrates an embodiment of an air delivery syringe assembly 80 that can be used with the subject invention. Figure 7 is a photograph of an embodiment of the assembled artificial ear chamber 40, the liquid delivery syringe assembly 60 and the air delivery syringe assembly 80.

In a specific embodiment, the delivery syringe assembly 60, comprisesan immovable graduated syringe 62 connected at the distal end 200 with the liquid input channel. The liquid delivery syringe 62 is connected to a linear actuator system wherein the pressure applied to the syringe can be measured and controlled. Specifically, in one embodiment, the subject device utilizes a syringe 62 with a plunger 64 therein for applying pressure to eject the contents, e.g., mucus, egg yolk, etc., of the syringe 62. The plunger 64 is connected to, or at least in contact with, a compression cup assembly 70. An embodiment of a compression cup assembly 70 is illustrated in Figures 5 and 8. In a preferred embodiment, the compression cup assembly 70 comprises a base component 66 and a compression component 68. A hydraulic actuator 67, comprising fluid-filled pliable container or bag, is positioned between the base component 66 and the compression component 68, as can be seen in Figure 7. The hydraulic actuator 67 is further connected to a device capable of measuring pressure and differences therein, calibrated to measure the amount of pressure being applied to the fluid-filled bag 68. Thus, when the base component 66 and the compression component 68 are pressed or squeezed together, they constrict the fluid-filled bag between them causing a change in pressure of the fluid within the bag, which can be measured by a pressure transducer, or other pressure measuring device, known in the art. In a preferred embodiment, a pressure transducer is utilized with a DAQ board and Labview computer program, all well- known to those with skill in the art, to measure and record pressure, and differences in pressure, during testing.

The compression component 68 may be pressed towards the base component 66 utilizing a variety of devices and techniques known in the art. In one embodiment, the compression component is fixedly attached to a linear actuator device capable of providing a

constant controllable pressure on the compression component 66. A constant controllable pressure applied to the compression component 68 translates through the fluid-filled bag 68 to the base component 66 of the compression cup assembly 70, causing the entire compression cup assembly, with the hydraulic actuator 67 therein, to move towards the plunger 64, that is fixedly attached to the distal end 200 of the base component, as illustrated in Figures 4, 7, 8 and 9. This connection to the base component 66 causes the plunger 64 to be pressed into the syringe 62, ejecting the fluid within the syringe into the liquid input channel 24 in the artificial ear chamber 40.

A person with skill in the art will recognize a variety of devices and methods could be utilized to accomplish the effect of applying pressure to the compression cup assembly 70, as described above. Numerous types of linear actuator devices can be utilized along with a variety of control mechanisms. It is important, however, that the devices or methods utilized provide a constant, measureable pressure and, preferably, in small gradient amounts. In a preferred embodiment of the subject invention, a stepper motor 78 is utilized with a threaded rod 76. However, while the pressure exerted by the threaded rod 76 is desirable, the circular rotation of the threaded rod 76 should not be translated to the compression component 68. Therefore, in a further preferred embodiment, the pressure from the threaded rod 76 is translated to the compression component 68 utilizing a fixed key 74 that cannot rotate, but is capable of sliding linearly along the same path as the threaded rod 76. In a further embodiment, the fixed key 74 is connected to, or in contact with, a translation device 72 that is fixedly attached to distal side 400 of the compression component, opposite the base component, as shown for example in Figures 4 and 7. hi operation, the distal end 200 of the threaded rod 76 pushes against the slidable key 74, which in turn pushes against the translation device 72 causing the compression component 68 to achieve the effect described above.

Measurement of the pressure exerted on the hydraulic actuator 67 by the compression cup assembly 70 provides a means for measuring the amount of resistance encountered as a tympanostomy tube being tested becomes occluded. A correlation can be drawn between an increase in pressure and occlusion of a tympanostomy tube. Therefore, it is desirable to ensure that the pressing or squeezing together of the base component 66 and the compression component 68 is stable and consistent between tests. This can be accomplished by numerous methods and devices known in the art.

In one embodiment of the subject invention, the compression component further comprises one or more flanges 63 fixedly connected to the distal end 200 of the compression component. In a preferred embodiment, there are two flanges 63 on each side of, and contiguous with, the compression component 68, which ensures a consistent position. In a further preferred embodiment, the base component 66 comprises flange guides 65 that ensure that the flanges 63 maintain a consistent position, without undesirable twisting, turning or any other movements that distort the pressure readings by the pressure transducer or pressure measuring device.

The entire liquid delivery syringe assembly can be manufactured so that each part of the assembly is supported and/or held secure by the surrounding connected components. However, in a preferred embodiment, a fluid delivery syringe scaffold 79 is utilized to provide support for the components of the fluid delivery syringe assembly 60. The scaffolding can comprise a variety of support mechanisms and materials. Figures 4 and 7 provide an example of a preferred scaffolding assembly 79 utilized with the fluid delivery syringe assembly of subject invention.

In order to effectively simulate an outer and a middle ear chamber, a means for introducing air similar to the function of a Eustachian tube is required. A number of well- known methods and devices can be used for delivery of air into the device of the subject invention. In one embodiment, the subject invention utilizes an air delivery syringe assembly 80 that can simulate the effect of ear "popping" caused when air quickly enters the middle ear to achieve compliance between the middle ear chamber and the outside air pressure.

An embodiment of an air delivery syringe assembly 80 that can be utilized with the subject invention is shown in Figures 6, 7, and 10. The syringe assembly comprises essentially an air filled graduated syringe 82 and plunger 84 device, wherein the movement of the plunger 84 is controlled by a linear actuator device. The linear actuator device may be any such device well-known in the art. In a preferred embodiment, a gear-head motor 86 is utilized with a threaded rod 88. In operation, the gear-head motor 86 periodically turns the threaded rod a defined distance. As the threaded rod 88 is turned, it can, either directly or indirectly, press the plunger 84 pushing it into the syringe 82, which correlates to a specific amount of air being ejected from the syringe 82 and into the air input channel 26 of the artificial ear chamber 40. In one embodiment of the subject invention, the turning of the threaded rod 88 causes a pressing key 89 to move towards the plunger 84 causing it to move

into the syringe 82. The advantage of this embodiment is that the linear movement of the threaded rod 88 is translated in a measureable fashion to the plunger 84, but the circular rotation of the threaded rod is not translated to the plunger, which eliminates undesirable spinning, turning or rotation of the plunger as it is pressed. However, a person with skill in the art would recognize that there are numerous methods and devices useful for providing a controlled and measureable introduction of air into the artificial ear chamber 40.

In a preferred embodiment, a volume of approximately 0.02 ml to approximately 0.07 ml of air is injected periodically into the air input channel 26. In a more preferred embodiment, a volume of approximately 0.05 ml of air is injected into the air input channel 26. The rate of injection can vary depending upon testing parameters. However, in a preferred embodiment, air is injected approximately every 10 to approximately every 20 minutes. In a most preferred embodiment, air is injected approximately every 15 minutes.

Maintaining an effective seal between the air delivery syringe 82 and the air input channel 26 can be important in order to quantify the amount of air utilized in a given test. Therefore, a means for holding the proper and effective positioning of the syringe 82 and plunger 84 is helpful. In a preferred embodiment, an air delivery syringe scaffolding assembly 85, for example as shown in Figures 6 and 10, is utilized with the subject invention. The air delivery syringe scaffolding assembly provides a means, for example a clamping mechanism 83, for securely holding the position of the syringe 82 once it is properly sealed to the air input channel 26. The air delivery syringe scaffolding also supports the linear actuator system 86 and 88 and, further, provides a means for carefully pressing the plunger at a regulated rate. The air delivery syringe scaffolding 85 may comprise a variety of materials, but in a preferred embodiment it comprises an aluminum frame to which are fixedly mounted the various aluminum components for supporting and assisting the air delivery syringe assembly.

An alternative embodiment is described above, wherein the air input channel 26 and the liquid input channel 24 are reversed to be a liquid drip input channel 21 and a continuous air input channel 23, respectively. In this alternative embodiment, the position of the fluid- filled syringe is reversed with the position of the original air-filled syringe. Further, the air delivery syringe apparatus is replaced with appropriate apparatus for delivery of a constant air flow into the continuous air input channel 23. Thus, in this reversed embodiment, the compression cup assembly can be eliminated and a pressure transducer 25 utilized instead to

measure the constant air pressure rate within the continuous air input channel 23. Li this embodiment, the pressure transducer 25 can be connected at some point along an air supply line 11 prior to attachment to the continuous air input channel 23. In one embodiment, a "T" valve 29 can be used to direct a portion of the air flow to the input of the pressure transducer 25, as known in the art. Further, a linear actuator device, comprising in a preferred embodiment, a gear-head motor 86 utilized with a threaded rod 88, can be utilized to control the fluid drip rate for the fluid-filled syringe.

Thus, in operation, as the mucus moves through the continuous air input channel 23 and through the tympanostomy tube 16, it will briefly block the tympanostomy tube 16. As a result, the pressure within the continuous air input channel will increase until the mucus has passed through the tube. However, a small amount of the fluid can remain along the surface of the tympanostomy tube 16 causing a build-up similar to that observed in vivo. Eventually, the diameter of the tympanostomy tube 16 decreases, which will increase the overall pressure within the continuous air input channel 23. Over time, the tympanostomy tube 16 becomes fully blocked so the mucus can no longer pass through the tube, and the pressure reaches a maximum value.

Example 1:

The device of the subject invention was utilized to test the effectiveness of two untreated tympanostomy Richards T-tubes (Gyrus, Silicone, 1.14mm LD.) of different length (12 mm and 4.8 mm). Throughout the testing of the tympanostomy tubes, egg yolk was used as a mucus analog due to a limited human mucus supply. Previous literature suggested that length plays a role in the formation of occlusions with shorter tubes performing more effectively.

Figure 12 shows that there is a difference in the time required for an occlusion to form and be expelled between the 12 mm and 4.8 mm long tubes. An ANOVA test was conducted using the MINITAB statistical analysis program. The results indicate that, for identical tube diameters, there is a statistically significant difference in the formation and clearance time for the 12mm (23 minutes) and 4.8mm (13.5 minutes) tubes. The p-value was 0.021 (P-value < 0.05 is considered significant).

The results show that the time for an occlusion to form is statistically greater in a longer than in a shorter tympanostomy tube. This increase in occlusion time also corresponds to a much larger pressure build-up in the longer tube which could be potentially damaging to the ear. The data confirm published clinical results suggesting that shorter tubes perform more efficiently than longer ones. Furthermore, the data were obtained over several days as opposed to months for clinical experiments.

AU patents, patent applications, provisional applications, and publications referred to or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.

It should also be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application.