External voiding sensor system Number:7,522,061 from the United States Patent and Trademark Office (PTO) owispatent

Title: External voiding sensor system

Abstract: The disclosure describes an external sensor attached to an undergarment worn by a patient that detects voiding information. The sensor stores the voiding information in a voiding log and transmits the voiding log to an external device. The external device includes a user interface that displays the voiding log to the patient for review. The patient may correct any incorrect voiding information that was logged in error or due to a non-voiding event. A user, such as a clinician or the patient, may use the voiding information to diagnose a condition of the patient. In addition, the voiding information of the voiding log may be used by the user to adjust a stimulation therapy or the external device to automatically adjust stimulation therapy. The undergarment may be disposable or washable after patient use.

Patent Number: 7,522,061 Issued on 04/21/2009 to Rondoni,   et al.

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Inventors:	Rondoni; John C. (Plymouth, MN), Gerber; Martin T. (Maple Grove, MN)
Assignee:	Medtronic, Inc. (Minneapolis, MN)
Appl. No.:	11/414,626
Filed:	April 28, 2006

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Current U.S. Class:	340/573.5 ; 340/571; 340/573.4; 340/573.6; 604/133; 604/361; 604/362; 607/41; 607/48
Current International Class:	G08B 23/00 (20060101)
Field of Search:	340/573.4,573.5,573.6,571-604 604/133,361,362 607/41-48 128/886

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References Cited [Referenced By]

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Primary Examiner: Hofsass; Jeffery
Assistant Examiner: Yacob; Sisay
Attorney, Agent or Firm: Shumaker & Sieffert, P.A.

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Claims

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The invention claimed is:

1. A method comprising: detecting urinary voiding information via a sensor disposed adjacent to a patient via an undergarment worn by the patient; storing the voiding information in a voiding log; delivering electrical stimulation therapy to the patient according to a set of stimulation parameters to alleviate urinary incontinence; and adjusting one or more of the stimulation parameters based on the voiding information in the voiding log.

2. The method of claim 1, wherein storing the voiding information in a voiding log includes locally storing the voiding information in a voiding log in memory associated with the sensor.

3. The method of claim 1, wherein storing the voiding information in a voiding log includes transmitting the voiding information to an external device for storage in a voiding log in memory associated with the external device.

4. The method of claim 1, further comprising displaying the voiding information in the voiding log to a user.

5. The method of claim 4, further comprising receiving user input correcting the voiding information.

6. The method of claim 1, wherein detecting voiding information comprises detecting voiding of urine from the patient.

7. The method of claim 6, further comprising identifying a characteristic of the urine, wherein the characteristic is at least one of an impedance, a temperature, a pH, a volume, and an electrolyte concentration.

8. The method of claim 1, wherein detecting voiding information comprises detecting deformation of at least a portion of the undergarment, wherein the deformation indicates that the patient has removed the undergarment to voluntarily void urine.

9. The method of claim 1, wherein adjusting one or more of the stimulation parameters includes adjusting one or more of the stimulation parameters in response to user input based on review of the voiding information in the voiding log.

10. The method of claim 1, wherein adjusting one or more of the stimulation parameters includes automatically adjusting one or more of the stimulation parameters based the voiding information in the voiding log.

11. The method of claim 1, further comprising transmitting the voiding information from the sensor to an external device via wireless telemetry.

12. A system comprising: an undergarment for a patient; a sensor carried by the undergarment and positioned to detect urinary voiding information; a memory that stores the voiding information in a voiding log; an implantable stimulator that delivers electrical stimulation therapy according to a set of stimulation parameters to the patient to alleviate urinary incontinence; and a processor that adjusts one or more stimulation parameters based on the voiding information in the voiding log.

13. The system of claim 12, wherein the memory storing the voiding log resides within the sensor.

14. The system of claim 12, further comprising an external device, wherein the memory storing the voiding log resides within the external device, and the sensor includes telemetry circuitry to transmit the voiding information to the external device.

15. The system of claim 12, further comprising an external device that receives the voiding information in the voiding log from the sensor and displays the voiding information in the voiding log to a user.

16. The system of claim 12, further comprising an external device that receives the voiding information in the voiding log from the sensor, wherein the external device receives user input correcting the voiding information.

17. The system of claim 12, wherein the sensor detects voiding of urine from the patient as at least part of the voiding information.

18. The system of claim 17, wherein the sensor identifies a characteristic of the urine, wherein the characteristic is at least one of an impedance, a temperature, a pH, a volume, and an electrolyte concentration.

19. The system of claim 12, wherein the sensor detects deformation of at least a portion of the undergarment as at least part of the voiding information, the deformation indicating that the patient has removed the undergarment to voluntarily void urine.

20. The system of claim 12, further comprising an external programmer that comprises the processor that adjusts the one or more of the stimulation parameters based on the voiding information in the voiding log.

21. The system of claim 12, wherein the processor adjusts the one or more of the stimulation parameters in response to user input based on review of the voiding information in the voiding log.

22. The system of claim 12, wherein the processor automatically adjusts the one or more of the stimulation parameters based the voiding information in the voiding log.

23. The system of claim 12, further comprising transmitting the voiding information from the sensor to an external device via wireless telemetry.

24. A system comprising: means for detecting urinary voiding information via a sensor disposed adjacent to a patient via an undergarment worn by the patient; means for storing the voiding information in a voiding log; means for delivering electrical stimulation therapy according to a set of stimulation parameters to the patient to alleviate urinary incontinence; and means for adjusting one or more of the stimulation parameters based on the voiding information in the voiding log.

25. The system of claim 24, further comprising means for locally storing the voiding information in a voiding log in memory associated with the sensor.

26. The system of claim 24, further comprising means for transmitting the voiding information to an external device for storage in a voiding log in memory associated with the external device.

27. The system of claim 24, wherein the means for detecting voiding information detects voiding of urine from the patient.

28. A system comprising: an implantable stimulator that delivers electrical stimulation therapy to a patient to alleviate urinary incontinence; an undergarment for the patient; a sensor carried by the undergarment and positioned to detect urinary voiding information; an external programmer that controls the implantable stimulator and receives the voiding information from the sensor, wherein the programmer stores the voiding information in a voiding log; and a processor that adjusts the electrical stimulation therapy based on the voiding information in the voiding log.

29. The system of claim 28, wherein the external programmer displays the voiding information in the voiding log to a user, and receives user input correcting the voiding information.

30. The system of claim 28, wherein the external programmer comprises the processor that adjusts the electrical stimulation therapy based on the voiding information in the voiding log.

31. The system of claim 28, wherein the processor adjusts the electrical stimulation therapy in response to user input based on review of the voiding information in the voiding log.

32. The system of claim 28, wherein the processor automatically adjusts the electrical stimulation therapy based the voiding information in the voiding log.

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Description

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TECHNICAL FIELD

The invention relates to implantable medical devices and, more particularly, external sensors.

BACKGROUND

Urinary incontinence, or an inability to control urinary function, is a common problem afflicting people of all ages, genders, and races. Various muscles, nerves, organs and conduits within the urinary tract cooperate to collect, store and release urine. A variety of disorders may compromise urinary tract performance and contribute to incontinence. Many of the disorders may be associated with aging, injury or illness.

In some cases, urinary incontinence can be attributed to improper sphincter function, either in the internal urinary sphincter or external urinary sphincter. For example, aging can often result in weakened sphincter muscles, which causes incontinence. Some patients also may suffer from nerve disorders that prevent proper triggering and operation of the bladder or sphincter muscles. Nerves running though the pelvic floor stimulate contractility in the sphincter. A breakdown in communication between the nervous system and the urinary sphincter can result in urinary incontinence.

Monitoring urinary incontinence aids a clinician in diagnosing the precise condition of the patient. Monitoring may include a diary maintained by the patient in which the patient logs voluntary voiding events, involuntary voiding events, i.e., leakage, or other related problems. The patient may keep the diary on paper or in an electronic device. The clinician may review the diary to view the frequency and number of voiding events experienced by the patient. In some cases, the clinician may tailor a stimulation therapy according to the diary.

Electrical stimulation of nerves in the pelvic floor may provide an effective therapy for a variety of disorders, including urinary incontinence. For example, an implantable electrical stimulator may be provided. The electrical stimulator may be a neurostimulator that delivers electrical stimulation to the sacral nerve to induce sphincter constriction and thereby close or maintain closure of the urethra at the bladder neck. In addition, electrical stimulation of the bladder wall may enhance pelvic floor muscle tone and assist fluid retention in the bladder or voiding fluid from the bladder. An appropriate course of neurostimulation therapy may be aided by the diary that monitors voiding events and tracks the therapy.

SUMMARY

The disclosure is directed to an external sensor attached to an undergarment worn by a patient that detects voiding information. The sensor stores the voiding information as a voiding log locally or in a separate device. The separate device may include a user interface that displays the voiding log to the patient for review. The patient may correct voiding information that was logged in error or relates to a non-voiding event. A user, such as a clinician or the patient, may use the voiding information to diagnose a condition of the patient, such as urinary incontinence.

Maintaining an accurate voiding diary is often difficult for a patient. The patient needs to spend time to manually enter a voiding event whenever it occurs. This manual diary also can be inaccurate because entries by the patient are subjective and may be influenced by embarrassment or other issues. An external sensor, as described herein, may be beneficial in providing the patient with an objective sensing system that automatically detects voiding information and stores it in a voiding log, without the need for significant patient interaction.

In some embodiments, the external sensor is located in an undergarment worn by the patient. However, other external sensors are possible either in addition or as an alternative to a sensor in an undergarment. If an undergarment is used, it may also be disposable or washable to reduce possible contamination problems from bodily fluids that come into contact with the undergarment, such as urine. In addition to keeping a voiding log, the voiding information may be used by the user to manually adjust electrical stimulation therapy to a nerve or muscle of the patient. In addition, or in the alternative, the external device may automatically adjust the stimulation therapy after processing the voiding log.

In one embodiment, the invention provides a method comprising detecting urinary voiding information via a sensor disposed adjacent to a patient via an undergarment worn by the patient, and storing the voiding information in a voiding log.

In another embodiment, the invention provides a system comprising an undergarment for a patient, a sensor carried by the undergarment and positioned to detect urinary voiding information, and a memory that stores the voiding information in a voiding log.

In an additional embodiment, the invention provides a system comprising an implantable stimulator that delivers electrical stimulation therapy to a patient to alleviate urinary incontinence, an undergarment for the patient, a sensor carried by the undergarment and positioned to detect urinary voiding information, an external programmer that controls the implantable stimulator and receives the voiding information from the sensor, wherein the programmer stores the voiding information in a voiding log.

In various embodiments, the invention may provide one or more advantages. For example, the patient may discreetly wear an undergarment that includes a sensor to automatically generate a voiding log based on detected voiding information. This may allow the patient to eliminate the need to keep a manual voiding diary. The undergarment may be disposable or washable to maintain a healthy detection environment. The system also allows the patient or clinician to review the voiding log and make changes to incorrect voiding information. The sensor may also be used as feedback for manual or automatic adjustment of electrical stimulation therapy delivered to the patient for urinary incontinence.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an implantable stimulation system, incorporating a sensor in an undergarment to detect voiding information.

FIG. 2 is a schematic diagram illustrating an absorbable pad of an undergarment with a sensor attached to an external surface of the pad.

FIG. 3 is a cross-section of a sensor disposed within an absorbable pad of an undergarment.

FIG. 4 is an enlarged schematic diagram illustrating a sensor sewn to an absorbent pad of an undergarment.

FIG. 5 is an enlarged, bottom view of the sensor of FIG. 4.

FIG. 6 is a schematic diagram illustrating a wearable undergarment, incorporating a deformation sensor to detect when the undergarment is removed.

FIG. 7 is an enlarged cross-sectional side view of the deformation sensor of FIG. 6.

FIG. 8 is a functional block diagram illustrating various components of an exemplary sensor.

FIG. 9 is a functional block diagram illustrating various components of an external device that communicates wirelessly with a sensor.

FIG. 10 is a flow chart illustrating a technique for detecting and storing voiding information, and transmitting a voiding log to an external device when connected to the sensor.

FIG. 11 is a flow chart illustrating a technique for detecting and storing voiding information, and transmitting a voiding log to an external device when requested by the device.

FIG. 12 is a flow chart illustrating a technique for reviewing and correcting voiding information in a voiding log.

FIG. 13 is a flow chart illustrating a technique for automatically adjusting stimulation therapy with the voiding information in the voiding log.

DETAILED DESCRIPTION

Urinary incontinence is a condition that affects the quality of life and health of many people. Tracking urinary voiding events may be important in quantifying the number of voluntary or involuntary events a patient has every day or qualifying the severity of the urinary incontinence condition. In accordance with this disclosure, a sensor is located outside of a patient to detect voiding information from the patient. The voiding information may be stored in a voiding log, and the voiding log may be reviewed by a clinician or the patient. The voiding log may eliminate the need for a patient to manually track voiding events, such as urine leakage or complete voluntary or involuntary voids.

Manually tracking voiding events, e.g. keeping a voiding diary, is often undesirable for the patient. Keeping the voiding diary takes time out of the patient's day and may be noticed by other people, causing embarrassment to the patient. In addition, manually tracking voiding events may result in voiding information errors. For example, the patient may inadvertently forget to record an event, fail to objectively describe the event, or even purposefully keep false voiding information in the diary. These problems with a voiding diary may undermine the ability of the clinician to properly assess patient condition and prescribe an effective therapy.

As described herein, the patient may wear an undergarment that includes an attached sensor that detects voiding information and saves the voiding information in a voiding log. The sensor may record and transmit a voiding log to an external device, e.g., an external programmer. Alternatively, the sensor may transmit voiding information to the external device, which then records and maintains the voiding log. In either case, the voiding log allows the clinician or the patient to review the voiding log and address the condition of the patient. The programmer may allow the patient or clinician to correct or remove voiding information that is incorrect. For example, the sensor may incorrectly indicate a voiding event based on detected wetness from a drink spilled on the patient's legs.

In addition, the voiding log may be used in conjunction with stimulation therapy. The patient or clinician may review the voiding information of the voiding log to manually adjust one or more stimulation parameters of the therapy. Alternatively, the external device, e.g., programmer, may process the voiding information and automatically adjust one or more stimulation parameters to increase the efficacy of the stimulation therapy. For example, if leakage frequency increases, the patient, clinician or programmer may increase the intensity of electrical stimulation to prevent or reduce involuntary voiding.

An external sensor described herein may also be used to correlate external voiding data with internal sensor data to indicate which internal data is indicative of a voiding event. In this manner, the internal sensor may be trained to recognize voiding events based upon the voiding information from the external sensor. This system may reduce or eliminate the need to receive input from the patient or a clinician to calibrate an implanted feedback system.

While the sensor described herein is attached to an undergarment worn by the patient, the sensor may be located on the outside of the patient in a different manner. For example, the sensor may be adhered to skin of the patient by an adhesive or tape, the sensor may be sutured to the skin of the patient, or the sensor may be strapped to the patient via a strap or cable. In other embodiments, the sensor may be sewn or adhered to another article of clothing worn by the patient or the sensor may be attached to a material which is placed between clothing and the skin of the patient.

FIG. 1 is a schematic diagram illustrating an implantable stimulation system 10, incorporating a sensor in an undergarment to detect voiding information. As shown in FIG. 1, system 10 includes stimulator 20, external programmer 16, and undergarment 18. Undergarment 18 includes absorbent pad 24 that holds sensor 26 near the opening of the patient's urethra (not shown). Sensor 26 transmits voiding information to external programmer 16 when the sensor detects moisture or when the external programmer requests the voiding information. The voiding information is stored in a voiding log, where the voiding log is stored in a memory of sensor 26, programmer 16, or both.

Patient 12 wears undergarment 18 between regular articles of clothing and the skin of the patient so that sensor 26 may detect voiding information. Voiding information may include complete voiding events, urinary leakage, or other wetness events from urine exiting bladder 14. Sensor 26 detects the presence of fluid which indicates that voiding has occurred. Sensor 26 may determine wetness by detecting a decrease in resistance between two electrodes of the sensor. In some cases, sensor 26 may be capable of also detecting fluid pH, impedance, electrolyte concentration, or other characteristics of the fluid to identify that the fluid is urine.

Sensor 26 may be located on an external surface of absorbent pad 24 or within the absorbent pad. Absorbent pad 24 may be constructed of cotton, cellulose, or a hydro-gel. As patient 12 voids urine, absorbent pad 24 holds the urine by allowing the urine to spread out in the pad. When the urine reaches sensor 26, the sensor detects the wetness as voiding information and stores the voiding information in a voiding log, either locally or in external programmer 16. Absorbent pad 24 may be capable of retaining an ounce of fluid or greater than 20 ounces of fluid, depending on the material used to construct the absorbent pad.

Sensor 26 may transmit voiding information to external programmer 16 as pre-determined by the factory or the clinician. In some embodiments, sensor 26 may transmit voiding information any time that the sensor detects voiding information and a connection with programmer 16 can be established. In other embodiments, if sensor 26 locally stores a voiding log, sensor 26 may transmit voiding information when the sensor can no longer store more voiding information in the voiding log. Alternatively, sensor 26 may transmit voiding information at any time the information is requested by external programmer 16. Patient 12 or the clinician may interact with external programmer 16 and cause the programmer to request the voiding log from sensor 26.

Patient 12 or the clinician may enter a review program of external programmer 16 to view each component of the voiding information contained in the voiding log. A component may be one voiding event detected by sensor 26. External programmer 16 may allow patient 12 or the clinician to modify a component of the voiding log to correct any incorrect voiding information. During normal operation, sensor 26 may detect voiding information that is not an actual voiding event, otherwise known as a false positive. False positives may be produced by activities or situations in which patient 12 participates during normal living. Exemplary false positives may include sweating during an aerobic activity, spilling a glass of liquid on the lap of patient 12, or any other time when urine is not the source of the voiding information detection.

In some embodiments, sensor 26 may detect other characteristics of the fluid to identify the fluid as urine in order to reduce any false positive detection. In addition, sensor 26 may be configured to sense an amount of fluid associated with a voiding event. Hence, the voiding information may include a variety of information including a voiding event indication, the date and time of the voiding event, an amount of fluid discharged in association with the voiding event, and/or physical characteristics of the fluid.

Although external programmer 16 is generally described as a programmer in contemplation its combined role in storing and presenting a voiding diary, and controlling an implantable stimulator 20, it may alternatively be configured only as a voiding diary recording device. For example, an external voiding diary logging device may be provided in addition to a separate external programmer for an implanted electrical stimulation device. Alternatively, an external voiding diary logging device may be used in combination with sensor 26 prior to implantation of stimulator 20, e.g., for study of the patient's condition to determine whether implantation is advisable.

Stimulator 16 at least partially prevents unwanted urinary voiding events by electrically stimulating a pelvic floor nerve, a pelvic floor muscle, or the urinary sphincter. Examples of a pelvic floor nerve include the pudendal nerve, the sacral nerve, or nerves of the sacral plexus. Stimulator 16 includes a pulse generator that generates electrical pulses and delivers the electrical pulses to a target tissue, e.g., the urinary sphincter, via lead 22 and one or more electrodes 23 located at the distal end of the lead. After reviewing the voiding log, the clinician or patient 12 may use the information to adjust one or more stimulation parameters that define the stimulation therapy provided by stimulation 20 via lead 22. The clinician interacts with external programmer 16 to adjust the stimulation therapy to reduce the frequency or number of voiding events identified in the voiding log.

In some embodiments, stimulator 20 uses multiple programs to deliver stimulation therapy, wherein one program includes a set of stimulation parameters. The clinician may change each of the programs, or only the programs used during the time when the voiding information was detected. Example stimulation parameters include an electrode configuration, a pulse rate, a pulse width, and voltage amplitude or current amplitude. Electrode configuration may refer to both a combination of selected electrodes and polarities of the electrodes, i.e., as cathode or anode.

In other embodiments, external programmer 16 may automatically analyze the voiding log, e.g., for leakage frequency or other characteristics, and automatically make adjustments to one or more stimulation parameters. External programmer 16 may include instructions that identify which parameters to adjust when a certain type of voiding information is detected. Alternatively, external programmer 16 may provide suggested adjustments to the clinician or patient 12, and the adjustments may not take effect until the clinician or the patient agrees with the suggestion.

Because undergarment 18 and, more specifically, absorbent pad 24 may come into contact with urine or other bodily fluids, the undergarment may be either disposable or washable. If undergarment 18 is disposable, patient 12 may discard the undergarment and everything attached as refuse. Patient 12 may use a new undergarment 18 if a voiding log is still to be stored. If undergarment 18 is washable, patient 12 may reuse the undergarment after the undergarment is cleaned to remove any urine or other bodily fluids. In either case, sensor 26 may stay with undergarment 18, but patient 12 may need to remember to transmit the voiding log from the sensor to external programmer 16 prior to disposal to prevent risk of loss of detected voiding information.

While stimulation 20 is described in FIG. 1, in conjunction with external programmer 16, other embodiments of system 10 do not include stimulation 20 or any other stimulation therapy device. In these embodiments, sensor 26 is used primarily as a diagnostic tool to provide objective patient 12 condition information for the clinician. The clinician may use the voiding log to determine an appropriate course of treatment, which may or may not include stimulation therapy. In this case, the voiding log is stored locally in memory associated with sensor 26, or stored in an external voiding diary logging device, as mentioned above.

In alternative embodiments of system 10, sensor 26 may not be included in undergarment 18. For example, sensor 26 may be included in a separate absorbent pad that fits in patient 12 underwear to maximize patient comfort. The pad may be gender specific, with sensor 26 located near the middle for female anatomy and near the anterior side for male anatomy. In addition, sensor 26 may also be located at the distal tip of a condom-like device that males may use to cover the penis. Other embodiments may also include sensor 26 taped to the skin of patient 12, trapped between clothing and the skin, attached to the inside of other clothing, sutured to the skin of the patient, or held to the skin of the patient via a strap.

FIG. 2 is a schematic diagram illustrating an absorbable pad of an undergarment with a sensor attached to an external surface of the pad. As shown in FIG. 2, an external surface of undergarment 18 that faces the skin of patient 12 includes absorbent pad 24 and sensor 26. Undergarment 18 also includes elastic bands 28A and 28B (collectively `elastic bands 28`) which help to retain any voided urine from leaking out from the sides of undergarment 18.

Absorbent pad 24 is shaped to catch and retain any urine that is voided from patient 12. Generally, the shape of absorbent pad 24 allows at least a portion of the absorbent pad to be placed adjacent to the opening of the urethra in either a male or female patient 12. Absorbent pad 24 allows the urine to spread throughout the pad, which distributes the fluid in the pad and attempts to reduce the amount of wetness against the skin of patient 12. In some embodiments, absorbent pad 24 may distribute fluid such that all sensors 26 come into contact with a portion of the fluid. As mentioned above, absorbent pad 24 may be constructed of cotton, cellulose, a hydro-gel, some other hydrophilic material that retains urine.

The absorbent nature of absorbent pad 24 also allows sensor 26 to be placed away from the exact location that urine exits patient 12. The urine will spread through absorbent pad 24 and reach a centrally located sensor 26, such that the sensor may detect the voiding information and create an accurate voiding log from the voiding information. In the example of FIG. 2, sensor 26 is positioned slightly to the anterior, or front, location of absorbent pad 24 which is indicated by the direction of arrow 29. In gender specific undergarments 18, sensor 26 may be moved in the anterior direction for males and the sensor may be moved in the posterior direction according to arrow 27 for females.

While sensor 26 is generally oval shaped in the example of FIG. 2, the sensor may be constructed in a number of different shapes. Sensor 26 may be constructed as a flexible flat rectangle, a rigid curved shell, a sphere, a rounded and flat triangle, or any other shape capable of housing the components of sensor 26. In alternative embodiments, undergarment 18 may contain a plurality of sensors 26 arranged throughout absorbent pad 24. The plurality of sensors may each transmit data to external programmer 16 or connect to each other and transmit data together as one larger sensor. In some embodiments, multiple sensors 26 may be connected by wires to enable communication between each sensor. It may be desirable to reduce the number of wires used to connect the sensors, such as only one wire.

FIG. 3 is a cross-section of a sensor 26 disposed within an absorbable pad of an undergarment. As shown in FIG. 3, sensor 26 is secured by absorbent pad 24. Sensor housing 30 of sensor 26 is embedded in absorbent pad 24, e.g., between layers of the pad. In the example of FIG. 3, sensor 26 includes circuit board 32, power source 34, and sensing element 36. Sensor housing 30 may be in the shape of a rounded capsule, as shown in FIG. 3, and includes a smooth surface. Sensing element 36 extends from housing 30. Sensing element 26 may detect a change in impedance, e.g., between two or more electrodes 37A, 37B. In this manner, sensing element 36 detects voiding information from a fluid present in absorbent pad 24. In other embodiments, sensing element 36 may include a strain gauge to detect pressure, which slightly protrudes from the housing to sense deformation changes in absorbent pad 24.

Sensor 26 rests in cavity 38 formed within absorbent pad 24. Cavity 38 may be formed between upper and lower layers of absorbent pad 24 or formed as a hollowed out region of a bed of fibers within the absorbent pad. In some embodiments, sensor 26 may have a capsule-like shape, and may have a length of approximately 2 to 10 mm, a width of approximately 2 to 5 mm, and a thickness of approximately 1 to 5 mm. The capsule-like shape may produce a circular or oval-like cross-section, in which case sensor 26 may have a diameter or major diameter of approximately 1 to 5 mm, rather than width and height dimensions. However, a capsule-like shape is merely described for purposes of example.

Sensing element 36 senses an impedance change in the space around sensor 26 from fluid within absorbent pad 24 as urine is voided from bladder 14. Sensing element 36 may detect electrical differentials, or other detectable parameters of the fluid. In some embodiments, fluid characteristics such as pH or electrolyte concentration may also be detected using pH or other chemical sensors. Processing electronics on circuit board 32 detect changes sensed by sensing element 36. Circuit board 32 communicates the voiding information to external programmer 16 by wireless telemetry. Circuit board 32 also controls the operation of sensor 26.

Embedding sensor 26 within absorbent pad 24 may be a simple method for securing the sensor 26. As bladder 14 voids urine, sensing element 36 detects a fluid within absorbent pad 24 and indicates that voiding has occurred. For example, a decrease in impedance of absorbent pad 24 may indicate that a fluid is present to more easily conduct the electrical current between two electrodes of sensing element 36. Although sensing element 36 may include electrodes, many other types of sensing components may be used to sense voiding, such as a strain gauge that measures deformation of absorbent pad 24, which indicates that the pad is swelling with urine.

Sensor 26 may have a biocompatible housing, which may be formed from titanium, stainless steel or other materials that resist corrosion. In some embodiments, sensor 26 may carry one or more expandable elements that help to anchor the sensor within absorbent pad 24. The expandable elements may be constructed from a hydrogel material. In the hydrated state, the expandable elements have a larger perimeter and may interact with the surround material of absorbent pad 24. Expansion of the expandable elements resists migration of the sensor 26 within absorbent pad 24. When allowed to dry, sensor 26 may be securely embedded within absorbent pad 24.

FIG. 4 is an enlarged schematic diagram illustrating a sensor sewn to an absorbent pad of an undergarment. Sensor 42 represents another exemplary embodiment of a sensor deployed within a patient's undergarment to detect voiding events. Sensor 42 is sutured, i.e., sewn, to absorbent pad 24, or in some cases, directly to undergarment 18 or another article of clothing. Sensor housing 44 is attached to absorbent pad 24 and includes circuit board 46, power source 48, and sensing element 50. Sutures 52 and 54 are used to attach bladder sensor 42 to absorbent pad 24. Although only two sets of sutures can be shown in FIG. 4, sensor 42 may include four or more sets, one at each corner of the rectangular shaped sensor.

Circuit board 46, power source 48 and sensing element 50 may all be similar to circuit board 32, power source 34 and sensing element 36 of FIG. 3. In addition, sensor housing 44 may be functionally similar to sensor housing 30 of FIG. 3. Differences between these components of each embodiment may relate to only the size or shape of each component. As in some embodiments of sensing element 36, sensing element 50 may include two or more electrodes 51A, 51B that detect a change in impedance of absorbent pad 24 as absorbent pad 24 swells with fluid. Sensing element 50 sends the voiding information to circuit board 46. Circuit board 46 wirelessly communicates the voiding information to external programmer 16. Circuit board 46 also may control the operation of sensor 42.

Once sensor 42 is placed on the external surface absorbent pad 24, the operator uses sutures to tie sensor 42 to absorbent pad 24, which is illustrated by sutures 52 and 54 in FIG. 4. The sutures may or may not penetrate through absorbent pad 24, and no urine will escape absorbent pad 24 in either case. In some embodiments, metal or plastic staples may be used to fix sensor 42 to absorbent pad 24 instead of nylon sutures. In some embodiments, multiple sensors 42 may be placed around absorbent pad 24 to generate an average expansion or contraction of the entire bladder.

Once attached to absorbent pad 24, sensing element 50 may be securely forced against absorbent pad 24. As absorbent pad 24 expands and contracts, sensing element 50 may sense the changed pressure by absorbent pad 24 and indicate a change in size of the pad. Similar to sensing element 36 of FIG. 3, many other types of sensing components may be used to detect voiding information of patient 12. However, electrodes that detect a change in impedance are described herein for purposes of illustration.

As an example of another fixation mechanism, sensor 42 may be provided with an adhesive backing on its underside 53 for permanent or removable attachment to absorbent pad 24 or undergarment 18. As a further alternative, the underside 53 may carry one half of a reciprocal hook-and-loop fastening device. The pad 24 or undergarment 18 may carry the other half of the hook-and-loop fastening device, which may be sewn or adhesively attached to the pad or undergarment. In this manner, sensor 42 may be removably attached to pad 24 or undergarment 18 via the hook-and-look attachment. A hook-and-loop fastener device, such as a Velcro.RTM. device, may be used. Other examples of removable attachment devices include snap-fit fasteners, press-fit fasteners or the like. Removable attachment devices may permit sensors 42 to be reused, e.g., by removing and reattaching the sensor to the different undergarments or pads, or to the same undergarment or pads between washing.

FIG. 5 is an enlarged, top view of the sensor of FIG. 4. Sensor 42 includes sensor housing 44 and sensing element 50. Fixation holes 56, 58, 60 and 62 are voids in housing 44 and allow suture to be passed through housing 44 in order for sensor 42 to be attached to absorbent pad 24. Sensing element 50 may occupy a majority of the surface area of bladder sensor 42 that faces patient 12. While sensing element 50 is rectangular in shape, the electrodes may be formed of any symmetric or asymmetrical shape, preferably circular in shape. Sensor 42 may have a length of approximately 2 to 15 mm, a width of approximately 2 to 10 mm, and a thickness of approximately 2 to 10 mm.

Fixation holes 56, 58, 60 and 62 each contain a pair of passages through housing 44. Each pair of passages is located near a corner of housing 44. An operator may pass a suture through these holes to attach housing 44 to absorbent pad 24 in a desired location of absorbent pad 24. While fixation holes 56, 58, 60 and 62 each contain two holes, other embodiments may include more or less holes in housing 44. For example, each corner of housing 44 may only contain one hole. Thread would then pass through the hole and around the outside of housing 44. As a further example, each corner may contain three holes for further securing housing 44 to absorbent pad 24.

Other fixation methods to secure bladder sensor 42 to absorbent pad 24 may include other structures different than sutures. For example, each corner of housing 44 may contain a barbed needle or helical screw that ejects from housing 44 into absorbent pad 24. The barbed needles may secure sensor 42 to absorbent pad 24 without lengthy attachment procedures. Also, as mentioned above, adhesives or hook-and-loop fasteners may be used as an alternative, or in addition to, mechanical fasteners such as staples, needles or screws. In alternative embodiments, sensor 42 is attached to the side of absorbent pad 24 facing away from patient 12. In this case, sensing element 50 would contact a surface of absorbent pad 24 to detect the voiding information.

FIG. 6 is a schematic diagram illustrating a wearable undergarment, incorporating a deformation sensor to detect when the undergarment is removed. As shown in FIG. 6, system 64 includes external programmer 16, undergarment 66, and deformation sensor 68. System 64 may be used in conjunction with system 10 to provide more complete voiding information. Sensor 68 is attached to elastic band 70, where the elastic band is disposed within waistline channel 72 of undergarment 66. Sensor 68 detects anytime that elastic band 70 is lengthened, which indicates that patient 12 is removing undergarment 66 to void bladder 14, e.g. voiding information.

Since sensor 26 of system 10 (FIG. 1) can only detect voiding information that is in the form of urine contacting undergarment 18, the voiding log may be incomplete. The voiding log of system 10 does not include voiding events that occurred when patient 12 used a toilet or other receptacle to voluntarily void urine from bladder 14. Sensor 68 may allow external programmer 16 to obtain a more complete voiding log by including all possible voiding events.

When patient 12 removes undergarment 66, the patient generally places one hand on each side of the undergarment, pulls the top of the undergarment slightly away from the skin of the patient, and lowers the undergarment from the pelvis. During this action, elastic band 70 stretches around the entire circumference of the band. Deformation sensor 68 is attached to one or both ends of elastic band 70 and transfers the force caused by stretching the elastic band into an electrical signal indicating that undergarment 66 is being removed.

The electrical signal detected by deformation sensor 68 may need to be greater than a pre-defined threshold to be considered indicative of undergarment 66 being removed. Patient 12 or the clinician may set the threshold based upon the signal from sensor 68 normally produced when the patient wears undergarment 66 and elastic band 70 encircles the patient's waist. In some cases, the threshold may be crossed for a certain period of time before sensor 68 indicates the event as a removal event. For example, a signal lasting for two seconds may be indicative of undergarment 66 being removed, in contrast to a signal lastin