PERSONALIZABLE SYSTEM AND METHOD FOR ANESTHETIZING TYMPANIC MEMBRANE

Abstract

Systems and methods are provided for anesthetizing a tympanic membrane of an ear. The systems are personalizable to ensure proper anesthetizing solution administration. The systems and methods may also be useful for administering a solution to the ear canal of a human patient and for maintaining the solution therein.

Claims

1. A method, comprising: engaging an ear plug with an ear canal of a subject such that a shaft extending through a passageway defined by the ear plug has a distal end disposed between the ear plug and a tympanic membrane of the subject, an outer surface of a portion of the shaft disposed within the passageway being spaced from an inner surface of the ear plug, the shaft defining a lumen extending from a proximal end of the shaft to the distal end of the shaft, the distal end of the shaft defining a plurality of spray holes in fluid communication with the lumen, and delivering a solution to a region of the ear canal between the ear plug and the tympanic membrane via the lumen of the shaft and the plurality of spray holes to fill the ear canal with the solution from a portion near the tympanic membrane out toward an outer ear portion.

2. The method of claim 1, further comprising: evacuating air from the region of the ear canal between the ear plug and the tympanic membrane.

3. The method of claim 1, wherein the plurality of spray holes face the tympanic membrane upon the ear plug being engaged with the ear canal of the subject.

4. The method of claim 1, further comprising: coupling a return electrode to a skin of the subject, the return electrode electrically coupled to a control unit; and applying a current to the solution delivered to the region of the ear canal via an iontophoresis electrode coupled to the solution, the iontophoresis electrode electrically coupled to the return electrode via the control unit.

5. The method of claim 1, wherein an electrode is at least partially disposed between the ear plug and the portion of the shaft disposed within the passageway.

6. The method of claim 1, wherein the portion of the shaft disposed within the passageway has a smaller outer diameter than a portion of the shaft disposed distal to the ear plug.

7. A system, comprising: an ear plug defining a passageway; and a shaft partially disposed within the passageway defined by the ear plug, the shaft having a distal end and a proximal end and defining a lumen extending from the proximal end to the distal end, the shaft including a tip portion at the distal end of the shaft, the tip portion defining a plurality of spray holes in fluid communication with the lumen, the tip portion disposed distal to the ear plug and having an outer diameter greater than an outer diameter of a portion of the shaft proximal of the tip portion.

8. The system of claim 7, further comprising an electrode at least partially disposed between the ear plug and the portion of the shaft disposed within the passageway, the ear plug including a vent system via which accumulated air from a portion of the ear canal distal to the electrode can be evacuated to a portion of the ear canal proximal to the electrode.

9. The system of claim 7, further comprising an electrode at least partially disposed between the ear plug and the portion of the shaft disposed within the passageway.

10. The system of claim 8, wherein the tip portion is disposed distal to the electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1A shows a frontal view of an outer ear.

[0036] FIG. 1B shows a partial cross-sectional view of an outer, middle and inner ear.

[0037] FIG. 2 shows a perspective view of a headset for iontophoretic substance delivery, according to one embodiment of the invention.

[0038] FIG. 3A shows a perspective view of a set of ear plug sizers according to one embodiment of the invention.

[0039] FIG. 3B shows a perspective view of a set of ear plugs for iontophoretic substance delivery according to one embodiment of the invention.

[0040] FIG. 3C shows a side view of an ear plug for iontophoretic substance delivery according to one embodiment of the invention.

[0041] FIG. 4 shows a perspective view of a return electrode patch for iontophoretic substance delivery according to one embodiment of the invention.

[0042] FIG. 5 shows a perspective view of a control unit for iontophoretic substance delivery according to one embodiment of the invention.

[0043] FIG. 6 shows a perspective view of the proper positioning of the headset on a patient's head.

[0044] FIG. 7A shows a perspective view of a manual fill nozzle according to one embodiment of the invention.

[0045] FIG. 7B shows a perspective view of the nozzle tip of the manual fill nozzle of FIG. 7A.

[0046] FIG. 7C shows a perspective view of the manual fill nozzle of FIG. 7A in combination with a speculum according to a further embodiment of the invention.

[0047] FIG. 8 is a flow diagram showing the method of the invention for anesthetizing the ear canal.

[0048] FIG. 9 is a perspective view of a headset for iontophoretic drug delivery according to the invention.

DETAILED DESCRIPTION

[0049] The embodiments of the invention are intended to provide systems that are useful for delivering and retaining a drug solution in a patient's ear canal that are individually and uniquely adapted to be used for a particular patient. In this way, variations in patient anatomy can be accommodated while maintaining patient comfort. Further, efficient filling of the ear canal can be accomplished under direct visualization with a microscope, limiting the amount of air bubbles in the ear canal, and facilitating the venting of excess air or fluid.

[0050] FIG. 1A shows a view of an outer ear 10. The outer ear 10 includes a major element known as the auricle 100. The outer ear serves as a funnel for directing sounds into the internal portions of the ear. The major physical features of the ear include the lobule, 102, concha 104, anthelix 106, helix 108, scapha 110, triangular fossa 112, tragus 114, antitragus 116 and ear canal 118.

[0051] FIG. 1B shows a cross-section of the inner and outer portions of the ear. The outer ear 10 is shown connected to the ear canal 118. The ear canal is shown as a relatively straight passage, but is often a more curved, tortuous passageway. The ear canal is connected to the middle ear 120, which includes the tympanic membrane 122. The middle ear 120 in turn is connected to the internal ear 124 which leads to the auditory tube 126 (also known as the Eustachian tube). The middle ear 120 normally has a pocket of air behind the tympanic membrane 122. When the middle ear 120 is infected, fluid swells behind the tympanic membrane 122. Fluid expansion causes extreme pain to an individual with a middle ear infection, as often occurs in young children.

[0052] As can be imagined from FIGS. 1A and 1, the anatomies of the ear canal 118 and the tympanic membrane 122 are quite variable across individuals of different ages, and even among those of the same age. The length and diameter of the ear canal 118 may vary, as well as its shape. Further, the size and position of the tympanic membrane 122 is not constant. Accordingly, it would be useful for treatment of middle ear infection, to be able to individualize the systems that are used to perform procedures in the ear.

[0053] FIG. 2 shows a headset 200 according to one embodiment of the invention. The headset 200 includes a headset frame 202, dual temporal pads 204a and 204b, temporal cushions 206a and 206b, locking arms 208a and 208b, electrodes 210a and 210b, locking arm elbows 212a and 212b, fill system valves 214a and 214b, fill system tips 224a and 224b, fill system tubing 226a and 226b, a return electrode connector 216, the electrode wiring 218 and the control unit connector 220.

[0054] The headset 200 is useful for administering an iontophoretic substance to the ear canal and retaining it in the ear canal for anesthetizing the ear canal and tympanic membrane prior to treatment. The frame 202 serves to connect the portions of the headset together. These portions extend from the right side to the left side of the head and extend to the temporal pads 204a and 204b on the right and left side, respectively. The frame 202 is thus configured to be placed around or over a patient's head. Further, the frame 202 secures the headset 200 on the patient's head. In this way, the frame 202 is sized appropriately for the patient such that when in position over the patient's ears, the frame supplies a compressive force to the patient's head. A sizing aid may be used to determine the appropriate headset size. In some embodiments, the frames come in 3 sizes, small, medium and large, and in other embodiments, they may come in 2, 4, 5, 6 or more sizes. Further, in another embodiment, the frame may be expandable such that a single size may be supplied that can be adjusted according to the size of the patient's head. In other embodiments, accessories may be attached to the frame base to entertain a patient during the iontophoresis procedure. These accessories include, but are not limited to be re-usable glasses that can stream movies, music, and/or video games, fun attachments such as horns, antler, antennas, elephant ears, etc. Bone conduction could also be included such that a sound vibration element may be incorporated into the headset to entertain and/or distract a patient.

[0055] In a further aspect, the headset 200 may be useful for administering a drug solution or other therapeutic solution to the ear canal and retaining the solution in the ear canal for treating the ear canal or the tympanic membrane or for anesthetizing the ear canal or tympanic membrane. The electrodes, return electrode connector, electrode wiring and control unit connector would not be present in such system. Such solutions include but are not limited to antifungal or antibacterial agents such as benzalkonium chloride, boric acid, acetic acid, and clotrimazole, anti-inflammatory agents such as beclamethazone and antibiotic and steroids such as betnesol, prednisolone sodium phosphate, gentamycin, neomycin, and quinolones, astringent agents such as aluminum acetate, ceruminolytics such as sodium chloride solution, hydrogen peroxide or sodium bicarbonate solution. The solutions may be administered to one ear or both ears (unilaterally or bilaterally) and the solutions may be administered sequentially or simultaneously.

[0056] In order to ensure that the ear canal is completely filled with the drug solution, the ear canal may be initially filled manually with the therapeutic solution. Such filling of the ear canal may be done through the use of the manual fill nozzle shown in FIGS. 7A and 7B and described further below. To ensure that the ear canal is completely filled and that there are no air pockets remaining, the patient's head may be tilted to one side, the ear canal filled using the manual fill nozzle, and then the ear canal is sealed using the appropriate headset 200 and ear plug 304 combination compatible with the size and shape of the patient's head and the size and shape of the patient's ear canal, as will be described further below.

[0057] Once the appropriate headset 200 has been chosen, the appropriate ear plugs may be chosen such that the plugs can be attached to the headset and can provide a seal to keep anesthetizing solution or other therapeutic solution in the ear canal 118. As shown in FIG. 3A, a set 300 of ear plug sizers 302a, 302b, 302c, 302d, 302e and 302f may be provided that will aid in determining which size will best fit the patient's anatomy. The ear plug sizers 302a-f are provided with lugs 303a-f and ear plugs 304a-f In the illustrative embodiment, there are 6 different ear plug sizes, but in other embodiments there may be 1, 2, 3, 4, 5, 7, 8 or even more than 8 ear plug sizes. The lugs 303a-f are constructed for example of a rigid plastic material for insertion past the concha 104 (see FIG. 1A) and into the ear canal (118) for initial selection of the size of the ear plugs 304a-f. The outer diameters of the lugs are equivalent to the sealing diameters of the ear plugs. The ear plugs 304a-f are further shown in FIG. 3B. Each ear plug 304a-f is made of a flexible material that can conform to the contours of the ear canal and may be made of silicone rubber or other similar materials such as polyurethane, styrene butadiene, butyl, and fluorosilicone rubbers. Each ear plug 304a-f is constructed of a rounded distal end 306 a-f for insertion into the ear canal 118 and orientation toward the tympanic membrane 122 (see FIG. 1B) and a tubular proximal end 308a-f for attachment to the ear plug sizer 302a-f (See FIG. 3A) or for attachment to the headset 200 over electrodes 210a and/or 210b. As shown in FIG. 3C an exemplary umbrella shaped ear plug 312 has a sealing diameter (SD) 314 that fits against the ear canal for sealing the iontophoresis solution into the ear canal and a maximum outer diameter (OD) 316 contains one to ten vent holes 318 with diameters between 0.001 and 0.050 inches that enable air and excess fluid to escape during iontophoresis solution delivery.

[0058] In one embodiment, the ear plugs sizers 302a-f are provided as a set of six (6) color-coded parts and correspond to six (6) color-coded ear plug 304a-f sizes. Size 0 (the smallest) is purple (SD=0.276″, OD=0.323″), Size 1 is orange (SD=0.315″, OD=0.364″), Size 2 is green (SD=0.354″, OD=0.408″), Size 3 is yellow (SD=0.394″, OD=0.452″), Size 4 is red (SD=0.433″, OD=0.497″) and Size 5 is green (SD=0.472″, OD=0.548″). The shafts 310a-f of the ear plug sizers 302a-f are color-coded, rigid and attached to the ear plugs 304a-f, so that a health care professional can hold one of the ear plug sizers 302a-f and insert it into the ear canal of the patient prior to treatment to determine the appropriate size useful for the particular anatomy of the patient. The ear plug sizer that is believed to best match the opening of the ear canal should be used, and the health care professional should try one size larger and one size smaller to confirm the appropriate size. Once the proper ear plug is determined, it is placed over the locking arm elbow of the headset 200. The lumen of the tubular portion of the selected ear plug is pushed over the fill system tip 224a or 224b of the headset arm 208a or 208b until it seats into place against the lips 222a and 222b of the locking arm elbows 212a and 212b. The fill system tips 224a and 224b of the headset have three spray holes in an atraumatic tip for easy filling of the ear canal 118 through the fluid delivery channels 226a or 226b attached to the fill system valves 214a and 214b. The spray holes and atraumatic tip portion of the fill system tips 224a and 224b are similar to the spray holes 806 and atraumatic tip 808 of the manual fill nozzle 800 described below with regard to FIGS. 7A and 7B. In addition, a design of the fill system tips 224a and 224b more similar in shape to the ear canal 118 may be useful. The most distal portion of the fill system tip 224a and 224b should be near the tympanic membrane such that the spray holes face the tympanic membrane. Accordingly, the fill system tips 224a and 224b may essentially span the distance from the locking elbows 212a and 212b to the tympanic membrane. The number of spray holes range from one to three or more and are evenly distributed one from the other (where there are three spray holes, they are spaced 120 degrees apart) to create turbulence in the ear canal 118. Further, the most distal portion of the fill system tip 224a or 224b is designed to face the tympanic membrane 122 such that during iontophoresis, the ear canal fills from the portions closest to the tympanic membrane out towards the outer ear 10 and air that has accumulated in the ear canal 118 will be evacuated as a result of low pressure escape of air through vent holes 318 in the ear plugs 312 as shown in FIG. 3C. In this way, air bubbles in the ear canal are minimized, leakage of therapeutic solution from the ear canal is minimized and pressure in the ear canal is maintained at below about 50 kilopascals and often below about 25 kilopascals.

[0059] The electrodes 210a and 210b consist of a solid silver electrode with a cylindrical shape attached to the electrode wiring 218 (see FIG. 2). Small openings in the fluid delivery channels 226a and 226b near the electrodes 210a and 210b ensure that the electrodes are submerged in and establish electrical connection with the anesthetizing solution and the system operates properly. During the iontophoresis procedure, the electrode conductivity changes due to electrochemical reactions between the electrode and the anesthetizing solution. This change may raise the voltage from the iontophoresis system. An electrode with greater surface area may be desirable. In one embodiment, the electrode may be made of a single wound coil and in another embodiment, it may be made of two concentric-oppositely wound coils of silver wire may be provided with a gap between the inner surface of the outer coil and the outer surface of the inner coil. The inner coil may have an open space on the inner diameter. The outer coil may be right hand wound and the inner coil may left hand wound, or alternatively, the outer coil may be left hand wound and the inner coil may be right hand wound. In another embodiment, the coil wire may be formed against the inside wall of the ear plug lumen and integrated into the ear plug to provide maximum surface area and maximum space between electrode elements. The anesthetizing solution flowing in around the lumen will encounter little interference and therefore will submerge the electrode efficiently, ensuring good contact with the electrode. The electrode material can be silver, gold, platinum, silver-silver chloride, stainless steel or any other materials that can achieve the electrochemical function of the electrode.

[0060] Once the appropriate ear plug 304 has been placed on the appropriate headset 200, return electrode patch 400 is attached to the headset at the return electrode connector 220 by connection at the mechanically conductive return electrode snap 402. The return electrode patch 400 is shown in FIG. 4 and may be adhered to the patient's skin at a clean, dry site, such as the arm or back, that is clear of lesions, bony protuberances, and excessive hair. A protective lining may be supplied on the base of the patch 400, such that when the lining is removed, an adhesive layer on the patch 400 may be adhered to the skin.

[0061] Following positioning of the headset 200 on the patient's head and the return electrode patch 400 on the patient's skin as will be described below, the control unit 500 shown in FIG. 5 may be connected to the control unit connector 220 on headset 200 as shown in FIG. 2 and the headset 200 will be clipped to the patient's or the parent's clothing.

[0062] The method according to the invention is carried out according to FIG. 8. The anesthetizing solution is prepared (in this case a solution of 1:12,000 epinephrine, 3.3% lidocaine and 0.7% sodium bicarbonate but may be any appropriate combination thereof such as lidocaine, lidocaine plus epinephrine, or lidocaine plus epinephrine and sodium bicarbonate or other anesthetizing solution known in the art) and warmed to body temperature. A syringe is filled with approximately 10 cc of anesthetizing solution. The headset 200 is prepared for placement on the patient as follows. As previously described above with regard to FIGS. 3A, 3B and 3C, an ear plug sizer is placed into a patient's ear canal to determine the appropriate ear plug size for personalization of the headset according to the size and shape of the patient's ear canal (610). The appropriate ear plug is positioned onto the headset (620). The spring loaded locking arms 208a and 208b are opened and locked by rotating them outwards until they click and until they hold a position pointing in the outward direction. While being held at the site of the temporal pads 204a and 204b, the headset 200 is carefully placed about the patient's head (630) such that the temporal cushions 206a and 206b are resting on the patient's temporal bone and the headset frame 202 is routed around the back of the patient's head (see FIG. 6). The return electrode patch 400 is connected to the headset 200 via the return electrode snap 402 on the electrode patch 400 and the return electrode connector 216 on the headset 200 and the adhered to the patient. The integrated fill system of the headset is primed with the anesthetizing solution by attaching the syringe to the fill system valves 214a and 214b and injecting until the solution exits the ear plug 312. The syringe is disconnected and reconnected to the other side if both ears are being treated. The syringe is then connected to the manual fill nozzle 800 (See FIGS. 7A and 7B).

[0063] Once the headset 200 is properly primed and positioned, the auricle 100 of the ear is gently pulled to straighten the ear canal 118. Using the syringe with the manual fill nozzle 800 attached at the luer connector 802, the ear canal 118 is manually filled with anesthetizing solution (640), taking care to eliminate air bubble formation during the fill (see FIGS. 7A and 7B). The manual fill nozzle 800 has a proximal end 812, a distal end 814 and a lumen 816 therebetween that may have a bend angle 804 of 130 degrees (or between about 120 degrees and 140 degrees, or it may have an angle of between 0 and 140 degrees to enable microscopic visualization of the ear canal while the solution is administered) and 3 spray holes 806 in an atraumatic tip 808 for easy filling of the ear canal 118 under direct visualization. A typical ear canal 118 will accommodate approximately 1-2 cc of fluid. The anesthetizing solution is administered via the manual fill nozzle 800 at a flow rate of approximately 0.5 cc/sec and is overfilled to ensure that all air has been evacuated. The three spray holes distributed 120 degrees apart on the tip provide for solution turbulence when filling the ear canal. There may be any number of spray holes between 3 and 12, for example 4, 5, 6 or more spray holes that are distributed about the atraumatic tip 808 of the manual fill nozzle 800. After the anesthetizing solution has been administered to the ear canal, while holding the auricle 100 with one hand, the other hand may be used to unlock the locking arms 212a and 212b of the headset 200 and insert the ear plug 312 into the ear canal so that the tip of the ear plug 312 points towards the tympanic membrane (650). In addition, the locking and unlocking of the locking arms 212a and 212b may be carried out at any time during the filling ear canal and iontophoretic delivery of the solution in order to visually observe the ear canal.

[0064] The headset control unit connector 220 is connected to the control unit 500 until it snaps in place. The battery tab located on the back of the control unit case is removed. Empty status bars should appear on screen once the device is powered on. To start the iontophoresis procedure, the control unit is activated (660) by pressing the yellow button 502 and/or the blue button 504 on the control unit 500 are holding for 2 seconds. Each button controls an independent channel, with button colors corresponding to the colors of the left and right sides of the headset. A short beep confirms when a button has been activated. The control unit 500 is clipped to the patient's or the parent's clothing. The status bars will fill up to indicate each channel's progress toward completion. A typical procedure takes approximately 10 minutes, with each status bar segment representing approximately 20% of procedure time. A flashing segment indicates that current is running; a solid segment indicates the portion already completed. To pause the procedure, the button for the appropriate channel is pressed and held for 2 seconds. The pause symbol and status bar segment will both flash and then turn solid when current delivery has stopped. To resume the procedure, the same button is pressed and held for 2 seconds. The control unit 500 will play a long beep when each channel (yellow or blue side) has completed delivering a full dose. The status bars will also turn completely solid to indicate that full charge has been delivered through each channel. Once the tympanic membrane is anesthetized, to deactivate the control unit, the button for the appropriate channel is pressed and held for 2 seconds (670). Alternatively, the control unit may stop after a preset period of time of between about 5 minutes and 60 minutes, often between about 5 minutes and 30 minutes or about 10 minutes.

[0065] The procedure described above may also be useful for administering a therapeutic solution to the ear canal without the use of iontophoresis. The headset may be placed on the head of the patient and the ear may be primed with the therapeutic solution as described above followed by placement of the ear plugs into the ears, or the ear plugs may be inserted into the ears and the therapeutic solution administered through the headset fill system valves 214a and 214b. One or both of the valves (in this case, one way valves) are connected to delivery devices such as syringes or delivery pumps and the therapeutic solution is administered to one or both ear canals (unilaterally or bilaterally) either sequentially or simultaneously. As noted above, vent holes 318 are incorporated in the ear plugs to ensure that the ear canal is not over filled and thereby cause pressure to build up in the ear canal. Other vent systems for ensuring proper venting to ensure that patient comfort is maintained include but are not limited to vent slits and vent screens.

[0066] Proper sizing of the headset and the ear plugs ensure proper filling of the ear canal and further aid in retaining the therapeutic solution in the ear canal for a predetermined period of time that coincides with the duration of therapy. Such period of time may be from about five to ten minutes to about one to two hours. The therapeutic solution may be removed from the ear canal following the therapy by positioning of the patient's head, suctioning of the ear canal, or other procedures including but not limited to tympanocentesis.

[0067] In an alternative aspect of the invention, the manual fill nozzle 800 shown in FIG. 7A and FIG. 7B may be incorporated into a rigid speculum 810 and fixedly attached thereto as shown in FIG. 7C for easy and accurate insertion of the nozzle 800 by the physician user allowing direct visualization of the outer ear and the tympanic membrane. Further, the manual fill nozzle may be used for purposes other than administration of iontophoresis solution. It may be used for anesthetizing the ear canal or tympanic membrane or for administering solutions for other therapeutic purposes. Such solutions include but are not limited to antifungal or antibacterial agents such as benzalkonium chloride, boric acid, acetic acid, and clotrimazole, anti-inflammatory agents such as beclamethazone and antibiotic and steroids such as betnesol, prednisolone sodium phosphate, gentamycin, neomycin, and quinolones, astringent agents such as aluminum acetate, ceruminolytics such as sodium chloride solution, hydrogen peroxide or sodium bicarbonate solution.

[0068] An alternative headset 700 is shown in FIG. 9. In this embodiment, a wire support frame 702 is provided to minimize hand to auricle contact by the healthcare professional, reduce the time to insert the ear plugs 704a and 704b into the ear canals, and provide support to the ear plug in the x, y and z axis. A wire frame 706a and 706b for around each ear is provided to support the ear plug in the x and y directions and a pad 708a and 708b for each ear, in this case of white foam Y20 cross-linked closed cell 2 pound density but may be other similar material, is provided to support the ear plug in the z direction. In this embodiment, and in the embodiments described above, the headset and fill systems are designed for maximum patient comfort and stability. The headsets are designed such that the pressure of the device is distributed about the patient's head and not solely in or on the ears. The fill system tubing is routed (and iontophoresis system wiring, if included) outside of the treatment area, such as behind the patient's head and may be secured behind the patient's neck with a system connector such as a tie, clip or other similar connector.

[0069] As noted above, according to the method of the invention, it is important to ensure that air bubbles in the anesthetizing solution or therapeutic solution are minimized Air bubbles may result from a variety of conditions including but not limited to orientation of the canal relative to gravity, surface tension of the liquid and surface conditions of the canal, such as a waxy ear canal wall. An alternative system is described for evacuating the external ear canal prior to filling such that minimal air bubbles are left behind in the anesthetizing solution. To enable reliable and tolerable filling of an ear canal in an awake patient, evacuation of entrapped air bubbles may be accomplished by providing a dual chamber instillation device. A first chamber of double or triple the volume of the liquid required to fill the canal is provided. This first chamber has a plunger or other means to forcibly expel liquid out and through an instillation port. A second chamber, vented to atmosphere, captures and stores excess liquid returning from the outlet port. Ear plugs with instillation and outlet ports are hydraulically balanced to enable filling of the ear canal with low pressure (supplied through the Instillation Chamber). Balancing is achieved by orifice diameter selection. The instillation port is constructed to create a turbulent flow at low exit pressure such that an irrigation effect is achieved, maximum surface wetting is obtained with minimum flow rate, and mobility of air bubbles is maximized. The slight positive pressure created within the ear canal mobilizes any air bubbles such that they will travel out of the outlet port. Low exit pressure is required to minimize the likelihood of pain due to high pressure jetting of liquid against sensitive tissue of the ear canal wall or tympanic membrane. Embodiments of the instillation port include tubing with a fine mesh screen to create separation and reduce fluid head, and alternatively, providing a tube with a coaxial, protracting structure to divert and separate flow.

[0070] In operation, the instillation chamber is filled with a volume greater than the volume of the ear canal. Ear plugs are inserted into the ear canal. The patient's ear canal is oriented vertically to reduce the likelihood of bubble entrapment. The plunger is driven to completely expel all liquid from the instillation chamber. The instillation device is disconnected from the plug and a fluid seal is maintained with bubbles evacuated.

[0071] Air in the fluid delivery channel and inside the electrode must be removed with low fluid pressure in order to minimize dead-space that would insulate the working electrode from the fluid and therefore increase system impedance. A method to manage air entrapment during application and use of anesthesia fluid is further described herein. Semi-porous material such as expanded polytetrafluoroethylene (EPTFE) or sintered solid EPTFE may be incorporated directly into the electrode housing or inside the ear canal interface of the device. The air in the fluid delivery channel and inside the electrode housing may be removed with low anesthetizing solution pressure since the required fluid pressure is inversely proportional to the porosity of the material used. To further remove entrapped air such as microbubbles in the system, a surfactant may be added to the anesthetizing solution to assist wetting and effectively decrease the surface tension of the incoming liquid to prevent formation of the bubble. Such surfactants may be any commonly used surfactant such as polyethylene glycol. During system filling, this would allow for dislodgement, coalescence and escape of microbubbles from the system through the semi-porous material. Other alternatives to remove entrapped air include a fluid-activated valve that would allow air to escape but would seal itself upon fluid entry, a one-way air valve incorporated in vent holes that would allow air and fluid to overflow but prevent any fluid from re-entering the system, an air reservoir in the system that would allow entrapped air to accumulate but strategically located not to disrupt anesthetizing solution delivery, or reducing surface tension by cleaning or etching the parts or enhancing their surface finishes such that microbubble formation is reduced.

[0072] Minimizing surface area on the inside of the ear plugs to prevent air bubbles from sticking to the inside surface of the ear ply and travelling into the elbow, blocking the conductance of the electrode is accomplished by providing 4 slots equally spaced at 90 degrees apart starting on the outside surface of the ear plug and travelling around to the inside diameter on the distal end of the ear plug. Flat surface are inside the ear plug creates tension between the air bubble and the earplug with allow the air bubbles to block electrode conductance. Slotted surface are minimized tension between air bubbles and the plug preventing such blockage.

[0073] Fluid leakage around the earplugs leads to air pockets in the ear canal that disrupt iontophoresis. With a constant pressure system, when fluid leaves the ear, it is immediately replaced, reducing air pocket development and further reducing user variability in delivering the fluid and the possibility of insufficient fluid in the ear canal. In an alternative embodiment of the invention, a compressed air canister is preloaded with a desired pressure. This air pressure is allowed to press against a piston, thereby delivering anesthetizing solution at a desired pressure. In an alternative embodiment, an expanding polymer such as polyacrylic acid can be used to created pressure, thereby propelling the anesthetizing solution once the polymer is wetted. Further embodiments would involve the use of a spring or rubber band to propel the anesthetizing solution or the use of a weight to press down on the anesthetizing solution with a constant gravitational force. Yet another embodiment would contemplate the acceleration of anesthetizing solution using an electrical charge to deliver precise pressure levels for delivery of the anesthetizing solution.

[0074] The invention has been described with reference to certain examples or embodiments of the invention, but various additions, deletions, alterations and modifications may be made to those examples and embodiments without departing from the intended spirit and scope of the invention. For example, any element or attribute of one embodiment or example may be incorporated into or used with another embodiment or example, unless otherwise specified or if to do so would render the embodiment or example unsuitable for its intended use. Also, where the steps of a method or process have been described or listed in a particular order, the order of such steps may be changed unless otherwise specified or unless doing so would render the method or process unworkable for its intended purpose. All reasonable additions, deletions, modifications and alterations are to be considered equivalents of the described examples and embodiments and are to be included within the scope of the following claims.