Systems and methods relating to implantable medical devices

Abstract

A method includes obtaining a measurement representative of an electrical impedance within a fluidic channel of an implantable medical device and processing the measurement to determine whether the implantable medical device is primed for implantation in a recipient. The implantable medical device can include an implantable drug reservoir having a charging port for receiving a drug solution, a drug delivery lumen having at least one release port and that is configured to be implanted within a recipient, and an intermediate drug lumen extending from the implantable drug reservoir to the drug delivery lumen to form a fluidic pathway between the charging port and the at least one release port. The implantable medical device is configured to be primed with drug before implantation in a recipient. The fluidic pathway is electrically discontinuous in the absence of a conductive solution.

Description

Systems And Methods Relating to Implantable Medical DevicesCROSS REFERENCE TO RELATED APPLICATION

[0001] This patent application claims priority to U.S. provisional patent application 63 / 534,216, filed August 23, 2023, which is incorporated by reference herein in its entirety.TECHN ICAL FIELD

[0002] The present disclosure relates to systems and methods for implantable medical devices for delivering drugs to recipients.BACKGROUN D

[0003] Medical devices have provided a wide range of therapeutic benefits to recipients over recent decades. Medical devices can include internal or implantable components / devices, external or wearable components / devices, or combinations thereof (e.g., a device having an external component communicating with an implantable component). Medical devices, such as traditional hearing aids, partially or fully-implantable hearing prostheses (e.g., bone conduction devices, mechanical stimulators, cochlear implants, etc.), pacemakers, defibrillators, functional electrical stimulation devices, and other medical devices, have been successful in performing lifesaving and / or lifestyle enhancement functions and / or recipient monitoring for a number of years.

[0004] The types of medical devices and the ranges of functions performed thereby have increased over the years. For example, many medical devices, sometimes referred to as "implantable medical devices," now often include one or more instruments, apparatus, sensors, processors, controllers or other functional mechanical or electrical components that are permanently or temporarily implanted in a recipient. These functional devices are typically used to diagnose, prevent, monitor, treat, or manage a disease / injury or symptom thereof, or to investigate, replace or modify the anatomy or a physiological process. Many of these functional devices utilize power and / or data received from external devices that are part of, or operate in conjunction with, implantable components.BRIEF SU MMARY

[0005] According to a first embodiment, a method comprises obtaining a measurement representative of an electrical impedance within a fluidic channel of an implantable medical device, and processing the measurement to determine whether the implantable medical device is primed for implantation in a recipient.

[0006] According to a second embodiment, a method comprises measuring an electrical impedance through a drug solution contained in fluidic lumen of an implantable medical device, wherein the fluidic lumen extends between a charging port and at least one release port in the implantable medical device, and determining from the electrical impedance when the fluidic lumen is primed with the drug solution.

[0007] According to a third embodiment, a non-transitory computer readable storage medium comprises computer readable instructions stored thereon for causing a computing system to determine an electrical impedance of drug solution in a medical device based on a measurement taken from the medical device, and determine if an obstruction is impeding diffusion of a therapeutic substance within the drug solution in the medical device based on the electrical impedance of the drug solution.

[0008] According to a fourth embodiment, an implantable drug delivery device comprises an implantable drug reservoir, wherein the implantable drug reservoir has a charging port for receiving a drug solution; a drug delivery lumen, wherein the drug delivery lumen has at least one release port and is configured to be implanted within an inner ear of a recipient; and an intermediate drug lumen, wherein the intermediate drug lumen extends from the implantable drug reservoir to the drug delivery lumen to form a fluidic pathway between the charging port and the at least one release port, and wherein the implantable drug delivery device is configured to be primed with drug before implantation in a recipient, and the fluidic pathway is electrically discontinuous in the absence of a conductive solution.

[0009] According to a fifth embodiment, an implantable medical device comprises a lead with at least one stimulating electrode located toward a distal end of the lead, an insulated fluid lumen having a closed proximal end and an open distal end, and a proximal electrode within the insulated fluid lumen and located toward the closed proximal end, wherein at least a distal section of the insulated fluid lumen is encapsulated within the lead.BRIEF DESCRI PTION OF DRAWINGS

[0010] Figure 1A depicts a schematic diagram of an exemplary cochlear implant that can be configured to implement aspects of the techniques presented herein, according to some exemplary embodiments.

[0011] Figure IB depicts a functional block diagram of the cochlear implant of Figure 1A.

[0012] Figure 2 is a diagram that illustrates an example of an implantable drug delivery device, according to an embodiment.

[0013] Figure 3 is a diagram that illustrates an example of a syringe positioned to fill the implantable drug delivery device of Figure 2 with a drug solution, according to an embodiment.

[0014] Figures 4A-4C are diagrams that illustrate examples of the implantable drug delivery device of Figure 2 implanted within a cochlea of an inner ear of a recipient.

[0015] Figure 5A is a diagram that illustrates an example of a drug delivery device that is attached to an implantable component of a cochlear implant.

[0016] Figure 5B is a diagram that illustrates an example of a drug delivery device that is separate from an implantable component of a cochlear implant.

[0017] Figures 6A-6C are diagrams that depict examples of a device that can be used to measure the electrical impedance or conductance of drug solution within a drug delivery device prior to implantation of the drug delivery device in a recipient to determine if any obstruction is impeding the diffusion of a drug within the drug delivery device.

[0018] Figure 7 illustrates an example of a computing system within which one or more of the disclosed embodiments can be implemented

[0019] Figure 8 is a diagram that depicts an example of an implantable drug delivery device having a drug lumen that is integrated in an extra-cochlear lead of a cochlear implant.DETAILED DESCRIPTION

[0020] Merely for ease of description, the techniques presented herein are primarily described herein with reference to illustrative medical devices, including cochlear implant systems. However, it is to be appreciated that the techniques presented herein may also be used with a variety of other devices that provide a wide range of benefits to recipients, patients, or other users of the devices. As other examples, the techniques presented herein may be used in or with medical devices such as other hearing prostheses, including bone conduction devices, hearing aids, middle ear auditory prostheses, direct acousticstimulators, other electrically stimulating auditory prostheses (e.g., auditory brain stimulators), etc. The techniques presented herein may also be used in or with medical devices that provide other types of sensory stimulation, such as vestibular devices (e.g., vestibular implants), and visual devices (i.e., bionic eyes). In at least some embodiments, the techniques presented herein may be applied in or with other forms of implantable devices, such as implantable sensors, pacemakers, drug delivery systems, defibrillators, functional electrical stimulation devices, seizure devices (e.g., devices for monitoring and / or treating epileptic events) etc. The techniques presented herein may also be applied in or with local drug delivery systems for treating pain, auto-immune diseases, and other innate and adaptive immune system related diseases.

[0021] The teachings detailed herein can be implemented in or with sensory prostheses, such as hearing implants. Other types of sensory prostheses can include retinal implants. Accordingly, any teaching herein with respect to a sensory prosthesis corresponds to a disclosure of utilizing those teachings in / with a hearing implant and in / with a retinal implant, unless otherwise specified, providing the art enables such. Moreover, with respect to any teachings herein, such corresponds to a disclosure of utilizing those teachings with a cochlear implant, a bone conduction device (active and passive transcutaneous bone conduction devices, and percutaneous bone conduction devices) and a middle ear implant, providing that the art enables such, unless otherwise noted. To be clear, any teaching herein with respect to a specific sensory prosthesis corresponds to a disclosure of utilizing those teachings in / with any of the aforementioned hearing prostheses, and visa-versa. Corollary to this is at least some teachings detailed herein can be implemented in somatosensory implants and / or chemosensory implants. Accordingly, any teaching herein with respect to a sensory prosthesis corresponds to a disclosure of utilizing those teachings with / in a somatosensory implant and / or a chemosensory implant.

[0022] While the teachings detailed herein are described for the most part with respect to hearing prostheses, in keeping with the above, it is noted that any disclosure herein with respect to a hearing prosthesis corresponds to a disclosure of another embodiment of utilizing the associated teachings with respect to any of the other devices or prostheses noted herein, whether a species of a hearing prosthesis, or a species of a sensory prosthesis, such as a retinal prosthesis. In this regard, any disclosure herein with respect to evoking a hearing percept corresponds to a disclosure of evoking other types of neural percepts in other embodiments, such as a visual / sight percept, a tactile percept, a smell precept or a taste percept, unless otherwise indicated and / or unless the art does not enable such. Anydisclosure herein of a device, system and / or method that is used to or results in ultimate stimulation of the auditory nerve corresponds to a disclosure of an analogous stimulation of the optic nerve utilizing analogous components, methods, and / or systems.

[0023] Figure (FIG.) 1A is a schematic diagram of an exemplary conventional cochlear implant (COCI) 100 configured to implement some aspects of the techniques presented herein. FIG. IB is a block diagram of the conventional cochlear implant 100 of FIG. 1A. For ease of illustration, FIGS. 1A and IB will be described together. The cochlear implant 100 comprises an external component 102 and an internal / implantable component 104. The external component 102 is directly or indirectly attached to the body of the recipient and typically comprises an external coil 106 and, generally, a magnet (not shown in FIGS. 1A-1B) fixed relative to the external coil 106. The external component 102 also comprises one or more input elements / devices 113 for receiving input signals at a sound processing unit 112. In this example, the one or more input devices 113 include sound input devices 108 (e.g., microphones positioned by auricle 110 of the recipient, telecoils, etc.) configured to capture / receive input signals, one or more auxiliary input devices 109 (e.g., audio ports, such as a Direct Audio Input (DAI), data ports, such as a Universal Serial Bus (USB) port, cable port, etc.), and a wireless transmitter / receiver (transceiver) 111, each located in, on, or near the sound processing unit 112.

[0024] The sound processing unit 112 also includes, for example, at least one power source 107, a radio-frequency (RF) transceiver 121, and a processing module 125. The processing module 125 comprises a number of elements, including an environmental classifier 131, a sound processor 133, and an individualized own voice detector 134. Each of the environmental classifier 131, the sound processor 133, and the individualized own voice detector 134 may be formed by one or more processors (e.g., one or more Digital Signal Processors (DSPs), one or more processing cores, etc.), firmware, software, etc. arranged to perform operations described herein. That is, the environmental classifier 131, the sound processor 133, and the individualized own voice detector 134 may each be implemented as firmware elements, partially or fully implemented with digital logic gates in one or more application-specific integrated circuits (ASICs), partially or fully in software, etc.

[0025] In the examples of FIGS. 1A and IB, the sound processing unit 112 is a behind-the- ear (BTE) sound processing unit configured to be attached to, and worn adjacent to, the recipient's ear. However, it is to be appreciated that sound processing unit 112 may have other arrangements, such as an off the ear (OTE) processing unit (e.g., a component having a generally cylindrical shape and which is configured to be magnetically coupled to therecipient's head), etc., a mini or micro-BTE unit, an in-the-canal unit that is configured to be located in the recipient's ear canal, a body-worn sound processing unit, etc.

[0026] In the exemplary embodiment of FIGS. 1A and IB, the implantable component 104 comprises an implant body (main module) 114, a lead region 116, and an intra-cochlear stimulating assembly 118, all configured to be implanted under the skin / tissue (tissue) 105 of the recipient. The implant body 114 generally comprises a hermetically-sealed housing 115 in which RF interface circuitry 124 and a stimulator unit 120 are disposed. The implant body 114 also includes an internal / implantable coil 122 that is generally external to the housing 115, but which is connected to the RF interface circuitry 124 via a hermetic feedthrough (not shown in FIG. IB).

[0027] As noted, stimulating assembly 118 is configured to be at least partially implanted in the recipient's cochlea 137. Stimulating assembly 118 includes a plurality of longitudinally spaced intra-cochlear electrical stimulating contacts (electrodes) 126 that collectively form a contact or electrode array 128 for delivery of electrical stimulation (current) to the recipient's cochlea. Stimulating assembly 118 extends through an opening in the recipient's cochlea (e.g., cochleostomy, the round window, etc.) and has a proximal end connected to stimulator unit 120 via lead region 116 and a hermetic feedthrough (not shown in FIG. IB). Lead region 116 includes a plurality of conductors (wires) that electrically couple the electrodes 126 to the stimulator unit 120.

[0028] As noted, the cochlear implant 100 includes the external coil 106 and the implantable coil 122. The coils 106 and 122 are typically wire antenna coils each comprised of multiple turns of electrically insulated single-strand or multi-strand wire. Generally, a magnet is fixed in position relative to each of the external coil 106 and the implantable coil 122, but the magnet may rotate or change orientation. In some embodiments, the external component 102 and / or the implantable component 104 can include magnet assemblies that each have more than one magnet component. The magnets fixed relative to the external coil 106 and the implantable coil 122 facilitate the operational alignment of the external coil with the implantable coil. This operational alignment of the coils 106 and 122 enables the external component 102 to transmit data, as well as possibly power, to the implantable component 104 via a closely-coupled wireless link formed between the external coil 106 with the implantable coil 122. In certain examples, the closely-coupled wireless link is a radio frequency (RF) link. However, various other types of energy transfer, such as infrared (IR), electromagnetic, capacitive and inductive transfer, may be used to transfer the powerand / or data from an external component to an implantable component and, as such, FIG. IB illustrates only one exemplary arrangement.

[0029] As noted above, sound processing unit 112 includes the processing module 125. The processing module 125 is configured to convert input audio signals into stimulation control signals 136 for use in stimulating a first ear of a recipient (i.e., the processing module 125 is configured to perform sound processing on input audio signals received at the sound processing unit 112). Stated differently, the sound processor 133 (e.g., one or more processing elements implementing firmware, software, etc.) is configured to convert the captured input audio signals into stimulation control signals 136 that represent electrical stimulation for delivery to the recipient. The input audio signals that are processed and converted into stimulation control signals may be audio signals received via the sound input devices 108, signals received via the auxiliary input devices 109, and / or signals received via the wireless transceiver 111.

[0030] In the embodiment of FIG. IB, the stimulation control signals 136 are provided to the RF transceiver 121, which transcutaneously transfers the stimulation control signals 136 (e.g., in an encoded manner) to the implantable component 104 via external coil 106 and implantable coil 122. That is, the stimulation control signals 136 are received at the RF interface circuitry 124 via implantable coil 122 and provided to the stimulator unit 120. The stimulator unit 120 is configured to utilize the stimulation control signals 136 to generate electrical stimulation signals (e.g., current signals) for delivery to the recipient's cochlea 137 via one or more stimulating contacts 126. In this way, cochlear implant 100 electrically stimulates the recipient's auditory nerve cells, bypassing absent or defective hair cells that normally transduce acoustic vibrations into neural activity, in a manner that causes the recipient to perceive one or more components of the input audio signals.

[0031] According to an embodiment disclosed herein, a method is provided for obtaining a measurement that is representative of an electrical impedance within a fluidic channel of an implantable medical device, such as the implantable component 104 of cochlear implant 100, and then processing the measurement to determine whether the implantable medical device is primed for implantation in a recipient. According to another embodiment disclosed herein, a method is provided for measuring an electrical impedance through a drug solution contained in a fluidic lumen of an implantable medical device. The fluidic lumen extends between a charging port and at least one release port in the implantable medical device. The method also includes determining from the electrical impedance measurement when the fluidic lumen is sufficiently primed with the drug solution. Theimplantable medical device can, for example, include a drug delivery device that includes the fluidic channel or fluidic lumen for delivering a drug to the recipient. The drug delivery device can be used with another medical device such as, for example, the cochlear implant of FIGS. 1A-1B, or another type of cochlear implant.

[0032] According to yet another embodiment disclosed herein, an implantable drug delivery device has an implantable drug reservoir that has a charging port for receiving a drug solution. The implantable drug delivery device also has a drug delivery lumen that has at least one release port and is configured to be implanted within an inner ear of a recipient. The implantable drug delivery device also has an intermediate drug lumen that extends from the drug reservoir to the drug delivery lumen to form a fluidic pathway between the charging port and the at least one release port. The implantable drug delivery device is configured to be primed with drug before implantation in a recipient, and the fluidic pathway is electrically discontinuous in the absence of a conductive solution. The drug delivery device can be used with a medical device such as, for example, the cochlear implant of FIGS. 1A-1B, or another type of cochlear implant.

[0033] The term "drug" generally refers to a bioactive substance or a combination of bioactive substances, including, but not limited to, pharmaceuticals, biologies, and other therapeutic substances and / or other chemical compounds that are intended to provide a therapeutic effect. Such drugs may include, for example, anti-inflammatory drugs, anti- fibrotic drugs, anti-apoptotic drugs, drugs that suppress or modify the body's immune response, and neurotrophins. Drugs that can be included in a drug solution include steroids, BDNF, and antibiotics. The term "primed" can refer to a device being charged, filled, and / or refilled with a liquid or solution, including, for example, a reservoir or lumen of the device. In at least some examples, a device is "primed" when there is an uninterrupted fluid path that extends between an inlet port and an outlet port.

[0034] Figure 2 is a diagram that illustrates an example of a drug delivery device 200, according to an embodiment. The drug delivery device 200 is an implantable drug delivery device that can deliver a drug to a recipient. A portion of (or all of) the drug delivery device 200 can be implanted in a recipient to deliver a drug to an organ (e.g., the inner ear) of the recipient.

[0035] The drug delivery device 200 shown in FIG. 2 includes a housing 201 (e.g., a titanium housing), a filter 204, a cannula 205, and a drug releasing outlet 206. The housing 201 houses a septum 202 (e.g., a self-healing silicon rubber septum) that covers a reservoir 203 within the housing 201. The housing 201 is designed to hold a drug solution within thereservoir 203 under the septum 202. The filter 204 is coupled between the reservoir 203 and the cannula 205. The cannula 205 is a cylindrical tube enclosing a lumen (i.e., a fluidic lumen or fluidic channel). The cannula, or at least the walls of the cannula that form the lumen, are electrically insulated. For example, the cannula can be formed from or lined with a biocompatible silicone. The cannula 205 shown in FIG. 2 has distinct proximal 205A and distal 205B sections. The diameter of the lumen within the proximal section 205A is larger than the diameter of the lumen within distal section 205B in the example of FIG. 2. In alternative embodiments, cannula 205 can be replaced with a cannula having a constant diameter across the length of the cannula or a cannula with a decreasing diameter across the length of the cannula moving away from housing 201.

[0036] The filter 204 allows drug solution to pass from the reservoir 203 to the lumens of the cannula 205, while filtering out impurities such as bacteria. The lumens of the proximal section 205A and the distal section 205B of cannula 205 are connected together to allow drug solution to pass between the lumens of the proximal and distal sections 205A and 205B. The drug releasing outlet 206 is attached to the distal end of cannula 205, as shown in FIG. 2. The outlet 206 includes a lumen that allows drug solution to pass from the cannula 205 through outlet 206. The lumen of outlet 206 has a release port located at the distal end of outlet 206. The outlet 206 is configured to be implanted within an inner ear, or another organ, of a recipient. In some embodiments, the housing 201 including reservoir 203 and the cannula 205 can also be implanted in a recipient.

[0037] The embodiment of the drug delivery device 200 illustrated in FIG. 2 and other figures herein is provided as an illustrative example and is not intended to be limiting. According to various examples, a drug can be delivered at multiple points, and / or continuously, along the cannula 205 and / or at the outlet 206 to a recipient. For example, in some embodiments, the drug delivery device can have multiple discrete release ports distributed along a section of the cannula, such as the intra-cochlea section of an inner ear drug delivery device. In other embodiments, the drug delivery device can have a single elongate release port that extends along a section of the cannula. In both embodiments, the drug outlet of the cannula is configured to deliver drug to the anatomy next to the release port or ports.

[0038] According to various embodiments, the drug releasing outlet 206 can include a filter that has any shape, such as flat, elliptical, rectangular, cylindrical, etc. As an example that is not intended to be limiting, the drug releasing outlet 206 can include a bacterial cylindrical filter inside a polydimethylsiloxane (PDMS) tube that is made of porous titanium. As a morespecific example that is not intended to be limiting, the dimensions of the drug releasing outlet 206 can be 0.15 x 0.5 millimeters (mm) (outer diameter x length), with a maximum pore size of less than 0.2 micrometers for the filter. According to various embodiments, the cannula 205 and the drug releasing outlet 206 can be made of any material. As an example that is not intended to be limiting, cannula 205 can be a tube made of PDMS. As other examples that are not intended to be limiting, cannula 205 can be a tube made of titanium with an electrically insulating biocompatible liner applied to the internal walls that define the fluidic lumen. According to another example that is not intended to be limiting, filter 204 and the filter in outlet 206 can each have a maximum pore size of 0.25 micrometers.

[0039] Figure 3 is a diagram that illustrates an example of a syringe 301 positioned to fill the drug delivery device 200 of Figure 2 with a drug solution, according to an embodiment. The syringe 301 of Figure 3 includes a plunger 302, a reservoir 303, and a needle 304. The reservoir 303 is initially filled with a drug solution (e.g., a saline solution). A drug is dissolved within the drug solution. The plunger 302 is in contact with the drug solution in reservoir 303.

[0040] The drug delivery device 200 is configured to be primed with drug solution before implantation in a recipient. The drug delivery device 200 can, for example, be placed in a package (not shown) that facilities priming the drug delivery device 200 with drug solution. Initially, the reservoir 203 is empty or filled with a sterile solution (e.g. purified water). In order to prime the drug delivery device 200 with drug solution, a user of the syringe 301 loads the drug solution into the housing 201 by first piercing the needle 304 through the septum 202 of the drug delivery device 200 and into the reservoir 203. The user can then depress the plunger 302 to force the drug solution from the reservoir 303 through the needle 304 and into the reservoir 203. The reservoir 203 has an opening in which a portion of the filter 204 is inserted. This opening in reservoir 203 functions as a charging port for receiving the drug solution and providing the drug solution to the filter 204. In other embodiments, the plunger 302 can be replaced with a pump, a syringe driver, or another mechanism that is used to force the drug solution from the reservoir 303 through the needle 304 and into the reservoir 203.

[0041] The user can continue to depress the plunger 302 to force the drug solution from the reservoir 203 through the filter 204, through the lumens of cannula 205, and through the lumen of outlet 206, until the drug solution forms a droplet 307 at the release port of the lumen of outlet 206. As shown in FIG. 3, a drug 305 is dissolved within the drug solution in the reservoir 203, the lumens of cannula 205, and the droplet 307. After the drug deliverydevice 200 has been successfully primed with the drug solution, the drug delivery device 200 can then be implanted in a recipient. The outlet 206 can, for example, be implanted into a target organ (e.g., a cochlea) of a recipient. When the outlet 206 is implanted in the target organ of the recipient, the release port of the lumen of outlet 206 can release the drug 305 into the target organ.

[0042] Figures 4A-4C are diagrams that illustrate various examples of the drug delivery device 200 of Figure 2 after being filled with drug solution. In FIGS. 4A-4C, the drug releasing outlet 206 has been implanted within a cochlea 137 of an inner ear 400 of a recipient. In the example of Figure 4A, the drug releasing outlet 206 of the drug delivery device 200 is implanted within the cochlea 137 of the recipient after the drug delivery device 200 has been primed with drug solution as described above with respect to FIG. 3. In the example of FIG. 4A, the drug 305 diffuses in the drug solution from the drug delivery device 200 into fluid within the cochlea 137 of the recipient, rather than being pumped into the recipient, in order to avoid increasing pressure within the cochlea 137. Figure 4A depicts diffusion of drug 305 in the drug solution from the drug delivery device 200 into the cochlea 137 of the recipient. The drug 305 diffuses from the drug solution in the reservoir 203 through the drug solution in filter 204, through the drug solution in the lumens of cannula 205, and through the drug solution in the lumen of outlet 206 into the fluid within the cochlea 137 of the recipient.

[0043] After priming, there is a drug concentration gradient between the reservoir 203 and the cochlea 137 that causes the drug molecules of drug 305 to move from a higher drug concentration in the reservoir 203 towards a lower drug concentration in the cochlea. The concentration of drug 305 decreases as drug 305 diffuses through the filter 204, the cannula 205, and the outlet 206 into the fluid in the cochlea 137. The concentration of the drug 305 in the cochlea 137 remains relatively low as the drug is not accumulating in the cochlea. Instead, the drug 305 diffuses into the rest of the body of the recipient and is eventually metabolized or eliminated from the body. Thus, the concentration of drug 305 in cochlea 137 remain less than the concentration of drug 305 in each of the reservoir 203, the cannula 205, and the outlet 206, as shown by graph 402 in FIG. 4A, until all drug molecules of drug 305 have left the device 200 and equilibrium is achieved.

[0044] The drug solution in a drug delivery device, such as drug delivery device 200, can include entrained gas that may or may not impede the diffusion of the drug in the drug solution. As an example, entrained gas may reduce the volume of the reservoir 203 available for storing the drug solution. If entrained gas reduces the volume of reservoir 203available for drug solution, the concentration of the drug in the reservoir 203 decreases faster, and the release rate of the drug at the outlet 206 is lower than expected, but the diffusion of drug molecules from the reservoir to the outlet 206 is not impeded.

[0045] In some instances, one or more large air bubbles can become trapped within the drug delivery device that can block or impede the diffusion of the drug in the drug solution, to the recipient. For example, an air bubble can become trapped in one of the lumens of cannula 205 of the drug delivery device 200. An air bubble in one of the lumens of the cannula 205 can potentially block or restrict diffusion of drug 305 from the reservoir 203 into the cochlea 137, preventing drug 305 from being fully delivered to the recipient.

[0046] Figure 4B depicts an example of an air bubble 410 that is trapped within the lumen of the proximal section 205A of cannula 205. Air bubble 410 completely blocks the lumen of proximal section 205A, preventing drug 305 from being delivered to the cochlea 137 of the recipient. Figure 4C depicts an example of an air bubble 411 that is trapped within the reservoir 203 at the charging port to the filter 204. Air bubble 411 completely blocks the charging port of the reservoir 203. The air bubble 411 may separate the cannula 205 from the reservoir 203, which slows down the release of drug 305, and eventually stops the delivery of drug 305 to the cochlea 137, after the cannula 205 is depleted of drug molecules.

[0047] In some exemplary embodiments, an implantable drug delivery device, such as drug delivery device 200, can be used in conjunction with an implantable medical device, such as a cochlear implant. The implantable drug delivery device can be integrated with the implantable medical device, or alternatively, separate from the implantable medical device. Figure 5A is a diagram that illustrates an example of a drug delivery device 500 that is attached to an implantable component 501 of a cochlear implant. The drug delivery device 500 includes one or more cannulas 502 that are connected to a port of the implantable component 501. Drug delivery device 500 can be used to deliver a drug to a recipient through the cannula 502 and the implantable component 501.

[0048] Figure 5B is a diagram that illustrates an example of a drug delivery device 510 that is separate from an implantable component 511 of a cochlear implant. In the example of FIG. 5B, the drug delivery device 510 can deliver a drug directly to the cochlea of a recipient, as described above with respect to FIGS. 4A-4C. Drug delivery device 510 can be, for example, drug delivery device 200 of FIG. 2.

[0049] Prior to implantation of a drug delivery device (such as drug delivery devices 200,500, and 510) in a recipient, it is typically desirable to determine if an air bubble (or other obstruction) is impeding the diffusion of a drug within the drug delivery device. Figures 6A-6C are diagrams that depict examples of a measurement device that can be used to measure the electrical impedance or conductance of drug solution within a drug delivery device prior to implantation of the drug delivery device in a recipient to determine if any obstruction is impeding the diffusion of a drug within the drug delivery device. A measurement of the electrical impedance or conductance of the drug solution can be processed (e.g., by a computing system) to determine whether the drug delivery device is primed for implantation in a recipient. The measurement device is shown in FIGS. 6A-6C as measuring the electrical impedance or conductance of a drug solution within the drug delivery device 200 of FIG. 2 as examples. The use of the term electrical conductance herein refers to the reciprocal of the electrical impedance. Thus, a measurement of the electrical conductance is also representative of the electrical impedance.

[0050] Figure 6A is a diagram that depicts an example of a measurement device 606 that is configured to measure the electrical impedance or conductance of drug solution in drug delivery device 200 using two electrodes 603-604. In the example of FIG. 6A, the measurement device 606 is electrically coupled to two electrical conductors 601 and 602. Electrical conductor 601 is electrically coupled to a first electrode 603, and electrical conductor 602 is electrically coupled to a second electrode 604. Electrode 603 is electrically coupled through electrical conductor 601 to a first terminal of measurement device 606. Electrode 604 is electrically coupled through electrical conductor 602 to a second terminal of measurement device 606. The electrical conductors 601-602 can be, for example, common electrical leads that couple electrodes 603-604 to the appropriate terminals of measurement device 606.

[0051] In order to measure the electrical impedance or conductance of drug solution in drug delivery device 200, the electrode 603 is brought into electrical contact with the drug solution to be tested in reservoir 203 (by piercing septum 202), and the electrode 604 is brought into electrical contact with the drug solution to be tested in droplet 307 at the distal end of drug releasing outlet 206. Thus, FIG. 6A shows the measurement device 606 coupled to measure the electrical impedance or conductance of drug solution in drug delivery device 200 between the reservoir 203 and droplet 307.

[0052] The measurement device 606 can measure the electrical impedance and / or conductance of drug solution in drug delivery device 200 between electrodes 603 and 604 using any electrical impedance or conductance measurement techniques. As an example, the measurement device 606 can apply a known voltage V to electrodes 603-604 through conductors 601-602, measure the resulting direct current I in conductors 601-602, and thencalculate the electrical resistance R in the drug solution in drug delivery device 200, according to Ohm's law (i.e., R = V / 1). Another example is to apply a known current I, measure the voltage V between electrodes 603-604, and then calculate the electrical resistance R in the drug solution in drug delivery device 200, according to Ohm's law (i.e., R = V / 1).

[0053] As another example, the measurement device 606 can use electrical impedance spectroscopy (EIS) to calculate the complex electrical impedance Z over a frequency range through the drug solution in drug delivery device 200 using electrodes 603-604. For electrical impedance spectroscopy, the measurement device 606 can apply a known, sinusoidal voltage signal V of a known frequency f to electrodes 603-604 through conductors 601-602 and measure the resulting sinusoidal current signal I and phase shift phi <p between the voltage and current signals V and I in conductors 601-602 to determine the complex electrical impedance Z of the circuit made of conductors 601-602, electrodes 603-604, and the drug solution in drug delivery device 200. The calculated electrical resistance R, the total complex impedance Z, or the components thereof including phase shift phi cp, resistance R (real) or reactance X (imaginary), in these examples is used to determine the impedance of the drug solution in drug delivery device 200. As used herein, a measurement of electrical impedance also includes a calculation of electrical impedance based on one or more measured values such as voltage, current, and / or phase shift; a measurement of electrical conductance; a calculation of electrical conductance based on one or more measured values such as voltage, phase shift, and / or and current; a measurement of any component of electrical impedance or conductance including phase shift phi cp, resistance R, or reactance X; and a calculation of any component of electrical impedance or conductance including phase shift phi cp, resistance R, or reactance X that is based on a measured value.

[0054] The phase shift phi <p of a complex impedance at a particular frequency allows the calculation of the capacitive and resistive portions of the total impedance Z. For example, if air is present in a drug delivery device, a capacitive portion of the total impedance can increase. In a drug delivery device completely filled with drug solution, the capacitive portion of the total impedance is limited to the metal-to-liquid interface of the drug delivery device, which is typically a known value. The fluid filled lumens (e.g., of cannula 205) typically only add resistive impedance. A bubble is likely to add a new capacitive portion to the total impedance that may be indicative of air being present in the drug delivery device.

[0055] Alternatively, the inverse of the calculated electrical resistance R, the inverse of the total complex impedance Z, or the inverse of components of the complex impedance Zincluding phase shift phi <p, resistance R or reactance X can be used as a measurement of the conductance of the drug solution in drug delivery device 200. As other examples, measurement device 606 can measure any one or more of the resistance, the capacitance, and / or the inductance between electrodes 603-604 at any frequency, or over any range of frequencies, of a current or voltage signal applied to electrodes 603-604 to generate a measurement of the impedance or conductance of the drug solution.

[0056] As examples, the measurement device 606 can be a stand-alone instrument, a device that is integrated with (or used with) a computer or computing system that generates a user interface 605, or part of a medical device. As a more specific example, measurement device 606 can be part of a cochlear implant system that is used with the implantable component, such as implantable component 501 of FIG. 5A.

[0057] In some embodiments, a cochlear implant can implement at least some of the functions of the measurement device 606. The measurement device 606 can be, for example, part of the implant body 114 of the cochlear implant 100 of FIGS. 1A-1B. The electronics inside the hermetic housing 115 of cochlear implant 100 can measure electrical impedance between electrodes 603-604. In some embodiments, the cochlear implant has dedicated measurement electrodes 603-604 integrated with the implantable component 104. For example, the drug reservoir housing 201 and / or outlet 206 can be configured to function as measurement electrodes 603-604. In at least some embodiments, the reservoir 201 and / or outlet 206 are fabricated from electrically conductive materials (such as biocompatible metals) and / or comprise electrically conductive sections that are exposed to the fluid path within the drug delivery device (e.g. one or more intentionally exposed electrically conductive internal surfaces within the reservoir and / or outlet). In other embodiments, existing cochlear implant electrodes (e.g., intra-cochlea electrodes 126 and / or extra-cochlea electrodes) can be electrically coupled to measurement electrodes 603-604 that are not part of the implantable component 104. For example, the sterile packaging in which the implantable component 104 is supplied can be configured to electrically bridge one or more intra-cochlea electrodes 126 and / or extra-cochlea electrodes to the charging port and / or release port of the drug delivery device during preimplantation priming so that the cochlear implant system can measure the impedance within the fluid pathway and confirm that the implantable component 104 is ready for implantation. In some embodiments, the sterile packaging can be configured to hold the extra-cochlea ball electrode (connected to the flying lead of the cochlear implant 100 shown in FIG. 1A) in close proximity to the drug outlet so that the ball electrode is brought in direct contact withthe droplet 307 that forms at the outlet 206. In other embodiments, an indirect electrical bridge, such as an electrical conductor embedded in the packaging, is used to connect an intra-cochlea electrode 126 and / or extra-cochlea electrode to the charging port and / or release port. The electrical connection to the fluid in the reservoir 203 can be made by connecting to the reservoir housing 201, to the needle 304 either directly or indirectly through a conductive fluid bridge, or to a solid conductor in the packaging of the cochlear implant. The electrode 604 can, for example, be brought into contact with the droplet 307 by having a sterile package of the cochlear implant shaped so that the outlet 206 and the electrode 604 are in the same well within the package. Also, in this example, an electrical connection between electrode 603 and the drug solution can be created using, for example, a conductive sticker with a conductive wire clamped to the needle of the priming syringe (e.g., syringe 301).

[0058] Alternatively, one or both of electrodes 603-604 can be electrical probes. As other examples, the measurement device 606 can use the housing 201 (e.g., that can be made of metal or other conductive material), the inner lining or wall of the reservoir 203 filled with the drug solution, or the filter 204 as an electrode for measuring the electrical impedance or conductance in the drug solution, in place of using electrode 603. In these examples, conductor 601 can be in electrical contact with the housing 201, reservoir 203, or the filter 204. In some embodiments, electrode 604 can, for example, be integrated into a package that houses the drug delivery device 200 to facilitate connection with conductor 602 and droplet 307.

[0059] The measurement device 606 can be used to measure the electrical impedance or conductance of drug solution within drug delivery device 200 to determine if any obstruction is preventing or impeding the diffusion of drug 305 within drug delivery device 200 during the priming of drug delivery device 200. The measurement device 606 can, for example, measure the electrical impedance and / or conductance of drug solution in drug delivery device 200 continuously or at intervals (e.g. every 10 milliseconds) to identify the presence of any obstruction in the drug solution.

[0060] The measurement device 606 can transmit one or more measurements of the electrical impedance or conductance (e.g., using a phase shift between current and voltage) of the drug solution in drug delivery device 200 to a computing system. The computing system can, for example, determine the probability that entrained gas will impede or prevent the diffusion of drug 305 within drug delivery device 200 based on the measurements of the electrical impedance or conductance of the drug solution in drugdelivery device 200 received from measurement device 606. The electrical impedance or conductance of the drug solution may fluctuate as the drug delivery device is primed with the drug solution. The computing system can include software that monitors the stability of the electrical impedance or conductance measurements obtained from the drug solution before determining if the electrical impedance or conductance is indicative of the drug delivery device having been primed successfully. The software can, for example, detect a relative drop in impedance as indicative of successful priming, instead of comparing the impedance to a predefined threshold (i.e., which can increase the need to calibrate the measurement device 606).

[0061] In addition or as an alternative to measuring the electrical impedance or conductance of drug solution in drug delivery device 200 that is caused by a bubble affecting diffusion of the drug, the measurement device 606 can also or alternatively measure the electrical impedance or conductance of the drug solution in drug delivery device 200 that is caused by residual gas trapped elsewhere in the drug delivery device 200. A bubble can move within the drug delivery device to become residual air that can potentially impede diffusion of the drug at a later time.

[0062] The computing system can provide the measurements of the electrical impedance or conductance of the drug solution in drug delivery device 200 to a user using the user interface 605. The user interface 605 can, for example, be generated by software running on the computing system that receives the measurements of the electrical impedance or conductance of the drug solution from measurement device 606. The user interface 605 can provide the measurements of the electrical impedance or conductance of the drug solution to the user, for example, visually though a display screen or through a speaker using audio.

[0063] As another example, the user interface 605 can include a light emitting diode (LED) that is red in response to a measurement of the electrical impedance of the drug solution in drug delivery device 200 being at or greater than a predefined set threshold indicative of the drug delivery device 200 not yet having been successfully primed. In this example, the LED turns from red to green in response to a measurement of the electrical impedance of the drug solution in drug delivery device 200 being less than (or equal to) a predefined set threshold (e.g., in the range of 100 ohms to 100 kiloohms) indicative of a successfully primed (e.g., completely filled) drug delivery device without a large air bubble. The primed drug delivery device 200 is then ready to be implanted and used to provide the drug 305 to a recipient.

[0064] Figures 6B-6C are diagrams that depict an example of a configuration of the measurement device 606 being coupled to measure the electrical impedance or conductance of drug solution in drug delivery device 200 using electrode 604 and syringe 301. In the example of FIGS. 6B-6C, electrical conductor 601 is electrically coupled to needle 304 of syringe 301, and electrical conductor 602 is electrically coupled to electrode 604. The needle 304 is electrically coupled through electrical conductor 601 to the first terminal of measurement device 606, and electrode 604 is electrically coupled through electrical conductor 602 to the second terminal of measurement device 606.

[0065] In the example of FIGS. 6B-6C, the needle 304 that is used to prime drug delivery device 200 with drug solution is also used as an electrode (i.e., instead of electrode 603) by the measurement device 606 to measure the electrical impedance or conductance of the drug solution. As discussed above with respect to FIG. 3, the needle 304 is brought into contact with the drug solution in reservoir 203 by piercing the septum 202. Electrode 604 can be, for example, a common impedance probe that is brought into contact with the droplet 307 of drug solution that forms at the outlet 206 of drug delivery device 200 during priming, as with previous examples.

[0066] In the example of FIGS. 6B-6C, measurement device 606 can measure the electrical impedance or conductance of drug solution in drug delivery device 200 between needle 304 and electrode 604 using any impedance or conductance measurement techniques, including the impedance and conductance measurement techniques described above with respect to FIG. 6A. Measurement device 606 can measure the electrical impedance or conductance of drug solution in drug delivery device 200 to determine if any obstruction is impeding the diffusion of drug 305 within drug delivery device 200, as discussed above with respect to FIG. 6A. For example, the measurement device 606 can generate a measurement or calculation of impedance or conductance that is indicative of a bubble 620 in the drug solution in the lumen of the proximal section 205A of cannula 205, as shown in FIG. 6C, or in any other portion of the drug delivery device 200.

[0067] The measurement device 606 can, for example, measure the electrical impedance and / or conductance of drug solution in drug delivery device 200 continuously or at intervals (e.g. every 10 milliseconds) during priming of the drug solution with syringe 301. Initially, the impedance of the drug solution between the needle 304 and electrode 604 is high (e.g., in the range of megaohms) during priming, until a droplet 307 forms and wets electrode 604, causing a rapid decrease in the impedance. Without an air bubble in the drug solution between needle 304 and electrode 604, the impedance of the drug solution may be, as anexample, in the range of 100 Ohms to 100 kiloohms, depending on the conductivity of the drug solution, the distance between needle 304 and electrode 604, the cross sectional area of the drug solution volume between needle 304 and electrode 604, the surface area and material of needle 304 and electrode 604, and the temperature of the drug solution. Measurement device 606 can, for example, be calibrated prior to use to compensate for these factors. Measurement device 606 can provide measurements of the electrical impedance or conductance of the drug solution in drug delivery device 200 to a computing system for comparison to one or more predefined thresholds and / or for display to a user using the user interface 605, as discussed above with respect to FIG. 6A.

[0068] According to other embodiments, a measurement device, such as measurement device 606, can be used to measure the electrical impedance or conductance of drug solution in a drug delivery device to determine if any obstruction (e.g., a bubble) is present in the drug solution, while the drug delivery device is being refilled with the drug solution (e.g., into the reservoir 203 of device 200). As an example, if drug delivery device 200 is implanted under the skin of a recipient, device 200 can be refilled with drug solution by piercing two needles through the skin of the recipient into the reservoir 203 of device 200. One of the needles functions as the inlet for the new drug solution being introduced into the drug delivery device, and the other needle functions as the outlet for the solution being removed from the drug delivery device. The inlet needle is coupled to the first terminal of the measurement device 606, and the outlet needle is coupled to the second terminal of the measurement device 606. The measurement device 606 can then measure the impedance or conductance within the reservoir during refilling to monitor for the introduction of gas, detect the presence of any bubble formed in the reservoir 203 as a result of the refilling process, and / or to confirm when the reservoir 203 is completely filled with the new drug solution.

[0069] According to another embodiment, the measurement device 606 is also used to measure the electrical impedance or conductance of drug solution in a drug delivery device to determine if any obstruction is present in the drug lumen, while the drug delivery device is being refilled with a drug solution, using an inlet needle and a conductive patch. In this embodiment, the inlet needle is coupled to the first terminal of the measurement device 606, and the conductive patch (e.g., an electrode patch) is placed on the skin of the recipient and coupled to the second terminal of the measurement device 606. Also, in this embodiment, the inlet needle can be electrically insulated from the skin / tissue of the recipient that the inlet needle pierces through. In order to electrically insulate the inletneedle, the shaft of the inlet needle is coated with an electrical insulator (e.g., parylene, silicone, silicon carbide, etc.), and only the outlet of the inlet needle that comes into contact with the drug solution inside the reservoir of the drug delivery device is bare metal for making the electrical connection with the drug solution. This configuration avoids a low impedance parallel current path through tissue of the recipient to the return electrode (e.g., the conductive patch on the skin). The electrical current is forced to pass through the drug delivery device, out through the outlet of the drug delivery device, and back to the conductive patch. The electrical circuit is closed through the inlet needle, the drug solution inside the electrically insulated lumen of the drug delivery device, the body fluids / tissue of the recipient, the skin of the recipient, the conductive patch on the skin, and a cable coupled to the conductive patch and the second terminal of the measurement device 606.Alternatively, instead of a skin patch electrode, a second needle can be pierced through the skin of the recipient to bring the second needle in contact with the body fluid of the recipient for measuring the impedance or conductance of the drug solution in the drug delivery device. These configurations allow testing for bubbles in the fluid path of the drug delivery device by measuring the electrical impedance or conductance of the drug solution in the drug delivery device.

[0070] As yet another example, the measurement device 606 can be integrated with the implantable component of a cochlear implant to enable impedance checks to be performed when the device is refilled in vivo. For example, electronics within the hermetic housing 115 of implantable component 104 can be configured to measure the impedance between a reservoir electrode (e.g., an electrically conductive internal surface of the reservoir housing 201) and a drug outlet electrode (e.g., an electrically conductive surface at the release port of the drug lumen). In some embodiments, an electrically conductive biocompatible bacterial filter is used at the outlet of the drug delivery device (i.e., the distal end of the fluid lumen). In these embodiments, the bacterial filter can be electrically connected to the measurement device 606 and configured to function as an outlet electrode. Similarly, the reservoir housing can be configured to function as a reservoir electrode.

[0071] Figure 7 illustrates an example of a computing system 700 within which one or more of the disclosed embodiments can be implemented. For example, computing system 700 can generate or include the user interface 605 of FIGS. 6A-6C. Computing systems, environments, or configurations that can be suitable for use with examples described herein include, but are not limited to, personal computers, server computers, hand-held devices, laptop devices, multiprocessor systems, microprocessor-based systems, programmableconsumer electronics (e.g., smart phones), network computers, minicomputers, mainframe computers, tablets, distributed computing environments that include any of the above systems or devices, and the like. The computing system 700 can be a single virtual or physical device operating in a networked environment over communication links to one or more remote devices. The remote device can be an auditory prosthesis (e.g., the cochlear implant of FIGS. 1A-1B), a personal computer, a server, a router, a network personal computer, a peer device or other common network node.

[0072] Computing system 700 includes at least one processing unit 702 and memory 704. The processing unit 702 includes one or more hardware or software processors (e.g., Central Processing Units) that can obtain and execute instructions. The processing unit 702 can communicate with and control the performance of other components of the computing system 700. The memory 704 is one or more software-based or hardware-based computer- readable storage media operable to store information accessible by the processing unit 702.

[0073] The memory 704 can store instructions executable by the processing unit 702 to implement applications or cause performance of operations described herein, as well as store other data. The memory 704 can be volatile memory (e.g., random access memory or RAM), non-volatile memory (e.g., read-only memory or ROM), or combinations thereof. The memory 704 can include transitory memory or non-transitory memory. The memory 704 can also include one or more removable or non-removable storage devices. In examples, the memory 704 can include non-transitory computer readable storage media, such as RAM, ROM, EEPROM (Electronically-Erasable Programmable Read-Only Memory), flash memory, optical disc storage, magnetic storage, solid state storage, or any other memory media usable to store information for later access. In examples, the memory 704 encompasses a modulated data signal (e.g., a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal), such as a carrier wave or other transport mechanism and includes any information delivery media. By way of example, and not limitation, the memory 704 can include wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio-frequency, infrared and other wireless media or combinations thereof.

[0074] In the illustrated example, the system 700 further includes a network adapter 706, one or more input devices 708, and one or more output devices 710. The system 700 can include other components, such as a system bus, component interfaces, a graphics system, a power source (e.g., a battery), among other components.

[0075] The network adapter 706 is a component of the computing system 700 that provides network access to network 712. The network adapter 706 can provide wired or wireless network access and can support one or more of a variety of communication technologies and protocols, such as ETHERNET, cellular, BLUETOOTH, near-field communication, and RF (Radiofrequency), among others. The network adapter 706 can include one or more antennas and associated components configured for wireless communication according to one or more wireless communication technologies and protocols.

[0076] The one or more input devices 708 are devices over which the computing system 700 receives input from a user. The one or more input devices 708 can include physical ly- actuatable user-interface elements (e.g., buttons, switches, or dials), touch screens, keyboards, mice, pens, and voice input devices, among others input devices.

[0077] The one or more output devices 710 are devices by which the computing system 700 is able to provide output to a user. The output devices 710 can include, displays, speakers, and printers, among other output devices, and can be part of, or used with, user interface 605.

[0078] Figure 8 is a diagram that depicts an example of a drug delivery device 800 having a drug delivery lumen 801 that is integrated in an extra-cochlear lead of a cochlear implant. In the example of Figure 8, the drug delivery lumen 801 of drug delivery device 800 is integrated in the extra-cochlear lead 116 of the cochlear implant 100 of FIGS. 1A-1B. The drug delivery device 800 also includes a drug delivery lumen 802 that is integrated in the intra-cochlear electrode array 128 of the cochlear implant 100. Drug delivery device 800 is configured to provide a drug in a drug solution to the cochlea of the recipient through the drug delivery lumens 801-802. Drug delivery device 800 can, for example, have the same structure as, or a similar structure to, the drug delivery device 200 of FIG. 2.

[0079] Any embodiment or any feature disclosed herein can be combined with any one or more other embodiments and / or other features disclosed herein, unless explicitly indicated otherwise. Any embodiment or any feature disclosed herein can be explicitly excluded from use with any one or more other embodiments and / or other features disclosed herein, unless explicitly indicated otherwise. It is noted that any method detailed herein also corresponds to a disclosure of a device and / or system configured to execute one or more or all of the method actions associated with the device and / or system as detailed herein. It is further noted that any disclosure of a device and / or system detailed herein corresponds to amethod of making and / or using that device and / or system, including a method of using that device according to the functionality detailed herein.

[0080] The foregoing description of the exemplary embodiments of the present invention has been presented for the purpose of illustration. The foregoing description is not intended to be exhaustive or to limit the present invention to the examples disclosed herein. In some instances, features of the present invention can be employed without a corresponding use of other features as set forth. Many modifications, substitutions, and variations are possible in light of the above teachings, without departing from the scope of the present invention.

Claims

Claims1. A method comprising: obtaining a measurement representative of an electrical impedance within a fluidic channel of an implantable medical device; and processing the measurement to determine whether the implantable medical device is primed for implantation in a recipient.

2. The method of claim 1, wherein the implantable medical device is configured to deliver a therapeutic substance to the recipient, and the method further comprises processing the measurement to determine that a solution containing the therapeutic substance fills the fluidic channel.

3. The method of claim 1, wherein the implantable medical device is configured to deliver a therapeutic substance to the recipient, and the method further comprises processing the measurement to determine that a solution containing the therapeutic substance extends continuously along a length of the fluidic channel that extends from a charging port to a release port.

4. The method of any one of claims 1-3 further comprising: obtaining a series of measurements representative of the electrical impedance in the fluidic channel of the implantable medical device over a period of time when the implantable medical device is being filled with a solution containing a therapeutic substance, and determining from the series of the measurements when the implantable medical device is ready for implantation.

5. The method of any one of claims 1-4 further comprising measuring the electrical impedance along a length of the fluidic channel that extends from a proximal charging port to a distal most release port.

6. The method of any one of claims 1-5 further comprising: executing instructions that cause the implantable medical device to obtain the measurement with two or more implantable electrodes of the implantable medical device, and communicating the measurement to an external device for processing.

7. The method of any one of claims 1-6, wherein obtaining the measurement representative of the electrical impedance further comprises obtaining the measurement representative of the electrical impedance within the fluidic channel using a needle of a syringe as an electrode.

8. The method of any one of claims 1-7, wherein obtaining the measurement representative of the electrical impedance further comprises obtaining the measurement representative of the electrical impedance within the fluidic channel between a reservoir of a solution in the implantable medical device and a droplet at a releasing outlet of the implantable medical device.

9. The method of any one of claims 1-8, wherein the method further comprises obtaining an additional measurement representative of the electrical impedance within the fluidic channel of the implantable medical device while the fluidic channel is being refilled with solution, and processing the additional measurement to determine if the fluidic channel is primed the solution.

10. A method comprising: measuring an electrical impedance through a drug solution contained in a fluidic lumen of an implantable medical device, wherein the fluidic lumen extends between a charging port and at least one release port in the implantable medical device, and determining from the electrical impedance when the fluidic lumen is primed with the drug solution.

11. The method of claim 10, wherein measuring the electrical impedance further comprises measuring the electrical impedance with at least two implantable electrodes of the implantable medical device.

12. The method of any one of claims 10-11, wherein measuring the electrical impedance further comprises measuring the electrical impedance through the drug solution in at least one cannula comprising the fluidic lumen.

13. The method of any one of claims 10-12, wherein measuring the electrical impedance further comprises measuring the electrical impedance during refilling of the fluidic lumen with the drug solution.

14. The method of any one of claims 10-13, wherein measuring the electrical impedance further comprises calculating the electrical impedance using a measurement taken from the implantable medical device.

15. A non-transitory computer readable storage medium comprising computer readable instructions stored thereon for causing a computing system to: determine an electrical impedance of drug solution in a medical device based on a measurement taken from the medical device; anddetermine if an obstruction is impeding diffusion of a therapeutic substance within the drug solution in the medical device based on the electrical impedance of the drug solution.

16. The non-transitory computer readable storage medium of claim 15, wherein the computer readable instructions further cause the computing system to determine if the medical device is primed for implantation in a recipient based on the electrical impedance of the drug solution.

17. The non-transitory computer readable storage medium of any one of claims 15-16, wherein the computer readable instructions further cause the computing system to provide a representation of the electrical impedance of the drug solution to a user using a user interface.

18. The non-transitory computer readable storage medium of any one of claims 15-17, wherein the computer readable instructions further cause the computing system to determine the electrical impedance of the drug solution in the medical device using electrical impedance spectroscopy.

19. The non-transitory computer readable storage medium of any one of claims 15-18, wherein the computer readable instructions further cause the computing system to determine the electrical impedance of the drug solution during refilling of the drug solution into a lumen of the medical device.

20. An implantable drug delivery device comprising: an implantable drug reservoir, wherein the implantable drug reservoir has a charging port for receiving a drug solution; a drug delivery lumen, wherein the drug delivery lumen has at least one release port and is configured to be implanted within an inner ear of a recipient; and an intermediate drug lumen, wherein the intermediate drug lumen extends from the implantable drug reservoir to the drug delivery lumen to form a fluidic pathway between the charging port and the at least one release port, and wherein the implantable drug delivery device is configured to be primed with drug before implantation in a recipient, and the fluidic pathway is electrically discontinuous in the absence of a conductive solution.

21. The implantable drug delivery device of claim 20, wherein the drug delivery lumen has an average inner diameter that is smaller than an average inner diameter of the intermediate drug lumen.

22. The implantable drug delivery device of any one of claims 20-21, wherein the intermediate drug lumen is integrated in an extra-cochlear lead of a cochlear implant, and wherein the drug delivery lumen is integrated in an intra-cochlear electrode array of the cochlear implant.

23. The implantable drug delivery device of any one of claims 20-22, wherein the implantable drug delivery device comprises at least one filter within the fluid pathway, and wherein the at least one filter has a maximum pore size of 0.25 micrometers.

24. The implantable drug delivery device of any one of claims 20-22, wherein the at least one release port of the drug delivery lumen comprises a filter with a maximum pore size of 0.25 micrometers.

25. The implantable drug delivery device of any one of claims 20-24, wherein the charging port of the implantable drug reservoir comprises a self-healing septum.

26. The implantable drug delivery device of any one of claims 20-25, wherein the implantable drug delivery device comprises at least two electrodes, and wherein the implantable drug delivery device is configured to measure an electrical impedance across the fluidic pathway between the charging port and the at least one release port using the at least two electrodes.

27. An implantable medical device comprising a lead with at least one stimulating electrode located toward a distal end of the lead, an insulated fluid lumen having a closed proximal end and an open distal end, and a proximal electrode within the insulated fluid lumen and located toward the closed proximal end, wherein at least a distal section of the insulated fluid lumen is encapsulated within the lead.

28. The implantable medical device of claim 27, wherein the closed proximal end of the insulated fluid lumen is closed by a septum.

29. The implantable medical device of claim 27, wherein the closed proximal end of the insulated fluid lumen comprises a drug reservoir.

30. The implantable medical device of claim 27, wherein the implantable medical device further comprises a distal electrode disposed within the distal section of the insulated fluid lumen toward the open distal end.

31. The implantable medical device of claim 30, wherein the implantable medical device further comprises electronic circuitry configured to measure an impedance between the proximal electrode and the distal electrode.

32. The implantable medical device of claim 30, wherein the distal electrode is part of a bacterial filter, and the bacterial filter is disposed at the open distal end of the insulated fluid lumen.

33. The implantable medical device of claim 27, wherein the open distal end of the insulated fluid lumen is located adjacent to the distal end of the lead.

34. The implantable medical device of claim 27, wherein the open distal end of the insulated fluid lumen is located distal to the distal end of the lead.

Images