WO2004034929A2

WO2004034929A2 - Incontinence sensor

Info

Publication number: WO2004034929A2
Application number: PCT/US2003/033204
Authority: WO
Inventors: James E. Hubbard, Jr.; Michael D. Healy
Original assignee: Trustees Of Boston University
Priority date: 2002-10-18
Filing date: 2003-10-20
Publication date: 2004-04-29
Also published as: WO2004034929A3; AU2003285910A1; AU2003285910A8; WO2004034929B1

Abstract

A body fluid sensor (100) for remote volume reading of expelled fluid, e.g., urine, is disclosed. A bottom layer (15) has a conductor pattern (20) of separate electrodes (22, 24) extending a given length in closely spaced relationship. An apertured sheet (30) covers over the layer and the conductor pattern with plural apertures (32) aligned with the electrodes over the given sensing length at staggered intervals thereof. A fluid absorbent skin (40) covers the apertured sheet allowing fluids applied to the skin to migrate through one or more of the apertures forming an electrical bridge of a resistance characteristic of the fluid between the electrodes.

Description

INCONTINENCE SENSOR

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the priority of U.S. Provisional Application No. 60/419,581 filed October 18, 2002 entitled, INCONTINENCE SENSOR, the whole of which is hereby incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT N/A

BACKGROUND OF THE INVENTION

Urinary incontinence or enuresis can be an embarrassing and highly inconvenient problem for children and older adults. For children, bed-wetting beyond the age when most other children have achieved nocturnal bladder control is the most frequent manifestation. For older adults, the problem can range from minor leakage upon sneezing or coughing to complete incontinence for nursing home patients.

Children achieve bladder control at different ages. By the age of five years, most children no longer urinate in their sleep. However, more than five million children in the United States alone continue to wet the bed past the age of six. The exact cause of bed-wetting is not known. Many factors are involved. In some children, the cause may be genetic (bed-wetting tends to run in families) . In other children, nighttime bed-wetting may occur because more urine in produced during sleep. Another cause of bed-wetting may be a small bladder and its inability to hold urine for a long time. A less common cause of bed-wetting may be a problem with the bladder, the kidneys or the nervous system. Deep sleep is not thought to be a cause of bed-wetting. However, deep sleep may prevent a child from responding to the signal from the bladder of a need to urinate. For adults, enuresis is more likely to be caused by a loss of sphincter control, which may be minor or more serious. In this type of situation, the adult can be unaware of the leakage of urine.

As an aid for managing enuresis in both children and adults, moisture alarms or incontinence sensors can be very helpful. Many families have found that use of a nighttime moisture alarm enables parents to help a child wake up and void in the bathroom. Eventually, the child can learn to wake up on his or her own without the alarm or even to sleep through the night while remaining dry. Adults can use a moisture detector with a private alarm so that they can be aware of the leakage before more extensive wetting occurs. For those adults who are incontinent and rely on the help of others, the moisture alarm can be configured for remote notification of the caregiver.

Existing sensor devices come in a variety of sizes and configurations. For example, one type of device is gold plated and the size of a postage stamp. This device is designed to be worn within the clothing of the subject and is washable and long- lasting. It can be configured for wired or wireless notification of either the wearer or a remotely located caregiver. Other available devices are configured for use in a bed. One type is a foil embossed plastic mat that fits between the sheets and on top of the mattress. Another type of sensor is a three layer absorbent pad consisting of a soft absorbent top cover, an absorbent inner filling and a lower moisture barrier. In this device, the electrical sensor is a pair of conductive fabric strips sewn into the pad above the fill layer, and the presence of urine, which has a relatively high salt content, is detected by measuring the resistance between the conductive strips. This device, which does not detect plain water, is described as being machine washable or dry cleanable. However, there still exists a need for additional types of incontinence sensors that would provide broader flexibility to the user.

BRIEF SUMMARY OF THE INVENTION

These and other goal are accomplished in the embodiments of the invention providing a body fluid sensor for remote volume reading of the presence and volume of body fluids in a patient environment. In the sensor, a first layer provides support for and has on it a conductor pattern having at least a first electrode of at least a given length and a second electrode of at least said given length. The first and second electrodes extend the given length in closely spaced relationship to define a sensing length between them. The electrodes are electrically isolated one from the other and extend to connection terminals at one periphery of the sensor.

These provide electrical contact external of said sensor to interface and processing electronics which can further include a central patient monitoring station that displays messages and warnings indicative of the presence and volume of sensed body fluids.

An apertured cover sheet is adhered over the first layer and the conductor pattern thereon and has plural apertures aligned with the sensing length at staggered intervals. A fluid absorbent skin is applied over the cover sheet whereby fluids applied to the skin migrate through one or more of the apertures of the cover to provide an electrical bridge of a resistance characteristic of the fluid between electrodes.

The processor and interface signals the sensorto read resistance. In an embodiment where additional electrodes are provide with additional connector terminals, the size and dimensions of the sensor and its intended use are communicated. These goals are achieved by use of a conductor pattern applied with a partially conductive or semi-conductive ink applied in regions independent of the fluid sensing areas so the resistance is a size indicator. An additional ink element can be deposited in an area away from the fluid sensing area with predetermined resistance indicative of the use of the sensor.

The incontinence sensor assembly according to the invention is simple and inexpensive to manufacture in various configurations. It is comfortable to use and operate and is designed to be disposable.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof and from the claims, taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a side view of an incontinence sensor assembly according to the invention;

Fig. 2a is a plan view of the circuit layer of multiple incontinence sensors of the invention according to Fig. 1; Fig. 2b is another embodiment of the circuit layer of an incontinence sensor according to the invention;

Fig. 3 is a plan view of the die cut adhesive layer of multiple incontinence sensors of the invention according to Fig. 1 ; and Fig. 4 is a circuit diagram of the incontinence sensor of Fig. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION In one embodiment, the incontinence sensor of the invention is used in conjunction with a Patient Activity Monitoring System as described in co-pending Application No. , filed this day, entitled Patient Activity Monitor, the whole of which is incorporated by reference herein. A Patient Activity Monitoring System allows caregivers of multiple patients to work more efficiently and with reduced cost, while increasing the quality and level of patient care. The incontinence sensor according to the invention is exemplified herein by two sensor configurations, which differ in their physical dimensions. A wheelchair incontinence sensor is in the form, e.g., of a thin strip, e.g., 7/8" x 12" x less than 1/64", which can be laid down on a wheelchair seat or among the patient's wheelchair pads. A bed incontinence sensor is physically in the form, e.g., of a two-dimensional pad covering the appropriate portion of the bed of the user. In one version, a sensor strip similar in configuration to that used for a wheelchair runs diagonally across the pad. In another version, the elements of the sensor circuit are designed to occupy the major portion of the pad. In all configurations, the incontinence sensor of the invention provides an indication of the "area of wetness" sensed.

As will be described in more detail below, when in use with the Patient Activity Monitoring System, the incontinence sensor is plugged in at the smart sheet sensor remote monitoring unit. (The connection point is adjacent to the smart sheet connection point, which provides patient activity feedback. ) The incontinence sensor is connected to the monitoring unit with a common telephone jack and its connection detected by the monitoring unit electronics via a sensor configuration bit. The electronics then determines a dry resistance reading, which can be associated with and indicative of different sensor configurations, e.g., as a wheelchair or bed sensor, or different sensor shapes. The configuration determination also indicates that the sensor is connected to the reading electronics.

The incontinence sensor incorporates a variable resistor (as will be described in detail below) , the resistive value of which is read by one of several, e.g., A to D, inputs of a microcontroller in the monitoring unit, or processor. The measurable resistive range of the sensor is generally between 10M ohms (typical dry resistance) and 130K ohms for the wheelchair configuration. This resistive range accommodates various areas of wetness of the sensor. The sensor can be made in different lengths and widths, but the measured resistance of a 100% wet (e.g., urine) sensor is typically set to be near 130K ohms. Due to the sensor design, the decrease in resistance is a function of the percent wetness. The volume creating the wetness for different sensor lengths can be calculated by calibrating the sensor dimensions in processor memory to the start of resistance change. The sensor length can always be calculated by using an additional circuit electrode pattern of known unit resistance so that an applied signal, which travels the length of the sensor and back, indicates the total resistance of the sensor.

Referring to Fig. 1, a side view of a preferred embodiment, it can be seen that an incontinence sensor of the invention 10 includes a 0.010" thick, typically polyester sensor sheet layer 15 on which is laid down a carbon ink, or other semiconductive or partially conductive circuit 20, described in detail below; a die cut adhesive layer 30 (3M Company No. 467) over the sensor circuit layer; and a thin absorbant sheet layer 40 (e.g., Crane & Company S-10 cotton Saturating Base Paper, 0.010" thick) over the die cut adhesive layer, which is placed next to the patient or wearer. On the underside of sensor sheet 15 is a medium tack adhesive layer 42, which provides for easy release of the sensor from clothes or bedding after use, and a release paper cover layer 44, which is removed prior to sensor use so as to expose the tack adhesive layer. Circuit 20 is connected to a two wire telephone cable lead 46, in the embodiment of Fig. 2a, via a connection 48 such as crimped pins or soldering, and padded with protective tape 50. Lead 46 is terminated with a standard four pin telephone jack 52, for connecting with a processor 25 having a resistance interface.

Fig. 2a is a plan view of multiple versions of sensor 10 showing circuits 20, which are laid down on polyester sensor sheet strips 15. As shown in Fig. 2a, multiple versions of the sensor can be manufactured simultaneously in one sheet, and then the sensors can be separated. An individual circuit 20 consists of semiconductive or partially conductive elements 22 and 24, having end terminals 21 and 23, respectively, that are electrically isolated from each other. Portions of elements 22 and 24 are formed as parallel adjacent thin lines, which are very closely spaced but not touching, arrayed along one edge of each sensor strip 15. In Fig. 2b, an alternative embodiment of the circuit 20" is shown in which interdigitating circuit elements 22" and 24" occupy a two dimensional, substantially rectangular, area. A sensor having this circuit configuration is particularly suitable for covering large areas, e.g., as a bed incontinence sensor.

Fig. 3, also a plan view of the embodiment of Fig. 2a, shows adhesive layers 30 of sensors 10 laid down on top of circuits 20. As can be seen in Fig. 3, in each sensor 10, multiple die cut apertures 32 are made in the adhesive layer 30 to expose adjacent segments 22' and 24' on circuit elements 22 and 24 and serve as "wick wells" for absorbent sheet 40.

The sensor is attached, e.g., to a wheelchair pad or bedsheet sensor by peeling back the release paper 44 to expose the medium tack adhesive 42 and then pressing it to the wheelchair or bedsheet sensing pad. In operation, fluid wicking into or absorbed by absorbent sheet 40 migrates into individual die cut apertures 32 and forms a resistive bridge between each of the conductor circuit segments 22' and 24' at each aperture 32 where there is liquid. In effect, this causes the resistance between the end terminals 21, 23 to decrease a predetermind quantum for each aperture where a resistive bridge is created between circuit segments 22', 24'. A linear change reflective of the fluid volume (the wetted length of the sensor) is thus produced, making a simplified measurement by a processor 25 of not only the presence of a body fluid (urine in the case of an incontinence sensor) but also its volume.

In the embodiment of Fig. 4, shown here in the form of a circuit diagram, a sensor is designed having four external connections 31, 33, 35, 37. Connections 31 and 33 connect via inked patterns to a length of facing conductor elements in region 39, such as provided by conductor elements 22 and 24 (Fig. 2), and in which region the migration of fluid causes a resistive bridging therebetween. Additional connections 35 and 37 allow for the measurement of further indicia by the processor 25. For example, a printing of ink of a specified width and/or depth in a region 41 between connections 35 and 37 can impart a predetermined resistance that can be read by processor 25 to reflect various characteristics of the sensor such as size, one or two dimensional extent of the circuit pattern, and/or intended use including bed or wheelchair use. In this case, it is preferable for the inked conductive pattern to have a resistivity greater than that of the connections to the processor so that the resistance can be used for this measurement. Additionally, the resistance between connections 31 and 37 can be used to indicate the length of the sensor from the resistance of the conductive (partially or semi) pattern between them. This resistive measurement, furthermore, is an indication that the sensor is actually connected to the processor.

Referring again to Fig. 1, it can be seen that sensor assembly 10 is connected by telephone jack 52 to the monitoring unit, or processor, 25. The telephone jack provides a polarized connection for the 4-signal connector interface. An isolation op amp with a gain of one can provide an interface buffer in processor 25 between the sensor and the micro-controller operation. This interface can also protect the sensor from static discharge and misalignment of the connector (4 pins) . The circuitry as a whole is typically a simple voltage divider, but a current driven op amp may provide a measurement of the total wetness of a variety of sensor configurations.

As described, one embodiment of the incontinence sensor assembly according to the invention is made with a thin polyester stock as the substrate. In general, any base material that is thin, flexible, easy to handle, inexpensive and stable to water can be used as the substrate for the sensor system of the invention. In an alternative embodiment, both sides of the sensor substrate layer are absorptive and provide for fluid access to the conductive circuit.

In general, an incontinence sensor assembly according to the invention can be used with any type of processor control box that will provide a notification mechanism (such as a CRT display, an audible alarm, a call button, a wireless page, a flashing light or a vibration) to either the user or caregiver, as is described herein. Connection to the control box processor can be by a direct connection or by any type of wireless connection. In the most general case, a microprocessor in the control box can process the information and route it anywhere via the internet or via wireless modem.

While the present invention has been described in conjunction with a preferred embodiment, one of ordinary skill, after reading the foregoing specification, will be able to effect various changes, substitutions of equivalents, and other alterations to the compositions and methods set forth herein. It is therefore intended that the protection granted by Letters Patent hereon be limited only by the definitions contained in the appended claims and equivalents thereof.

Claims

CLAIMS What is claimed is:

1. A body fluid sensor for remote volume reading comprising: 5 a first layer for supporting a conductor pattern; a conductor pattern on said first layer, said pattern having at least a first electrode of at least a given length and a second electrode of at least said given length, said first and second electrodes extending said given length in closely spaced

L0 relationship to define a sensing length and being electrically isolated one from the other; said pattern including conductive strips from said first and second electrodes to first and second connections for electrical contact external of said sensor;

15 an apertured cover over said first layer and the conductor pattern thereon with plural apertures in said cover aligned with said sensing length at staggered intervals thereof; a fluid absorbent skin over said cover whereby fluids applied to said skin migrate through one or more of the apertures

20 of said cover to provide an electrical bridge of a resistance characteristic of said fluid between said electrodes in the area of each aperture having said fluid migrated therethrough.

2. The sensor of claim 1 wherein said first layer is a dielectric 25 or insulating layer.

3. The sensor of either of claims 1 or 2 wherein said conductor pattern is a printed pattern.

30 4. The sensor of claim 3 wherein said printed pattern is an ink pattern.

5. The sensor of claim 4 wherein said ink is a carbon ink.

6. The sensor of any of claims 1 to 5 wherein a plurality of separated sensing lengths are provided on said first layer.

7. The sensor of claim 6 wherein said plural separated sensing lengths have respective electrodes electrically connected together.

8. The sensor of claim 6 or 7 wherein said plural separated sensing lengths are in an interdigitated relationship on said first layer.

9. The sensor of any of claims 1 to 8 wherein said fluid absorbent skin is a paper layer.

10. The sensor of any of claims 1 to 9 further including a third connection to one of said first and second electrodes via a conductive strip so as to provide a resistance between said third connection and one of said first and second connections representative of a length of said sensor.

11. The sensor of claim 10 further including a forth connection and a resistive bridge between said fourth connection and one of said first, second and third connections of a resistance predetermined to indicate a characteristic of said sensor.

12. The sensor of claim 11 wherein said characteristic includes an indication of one or more of sensor use and sensor configuration.

13. The sensor of claim 12 wherein said use includes bed or wheel chair use.

14. The sensor of claim 12 or 13 wherein said configuration is substantially one dimensional or substantially two dimensional.

15. The sensor of any of claims 1 to 14 wherein said first layer includes an apertured cover covered by a skin.

16. The sensor of claim 15 wherein said apertured cover is substantially nonconductive and has apertures aligned with one or more of the apertures of said first mentioned cover.

17. The sensor of any of claims 1 to 16 further including processing means for sensing a resistance between any of said connections .

18 The sensor of claim 17 wherein said processor applies a resistance of a predetermined value across said first and second electrodes .

19. The sensor of claim 18 wherein said predetermined value is substantially greater than the characteristic resistance of one or more electrical bridges.

20. A method of manufacturing a body fluid sensor for remote fluid volume reading comprising: forming a first layer for supporting a conductor pattern; forming a conductor pattern on said first layer, said pattern having at least a first electrode of at least a given length and a second electrode of at least said given length, said first and second electrodes extending said given length in closely spaced relationship to define a sensing length and being electrically isolated one from the other; forming said pattern to include conductive strips from said first and second electrodes to first and second connections for electrical contact external of said sensor; forming an apertured cover over said first layer and the conductor pattern thereon with plural apertures in said cover aligned with said sensing length at staggered intervals thereof; forming a fluid absorbent skin over said cover whereby fluids applied to said skin migrate through one or more of the apertures of said cover to provide an electrical bridge of a resistance characteristic of said fluid between said electrodes in the area of each aperture having said fluid migrated therethrough.

21. The method of claim 20 wherein said first layer is formed of a dielectric or insulating layer.

22. The method of either of claims 20 or 21 wherein said conductor pattern is formed by printing said pattern.

23. The sensor of claim 22 wherein said printing is of an ink pattern.

24. The method of claim 23 wherein said ink is a carbon ink.

25. The method of any of claims 20 to 24 inclueing the step of providing a plurality of separated sensing lengths on said first layer.

26. The method of claim 25 including the step of electrically connecting said plural separated sensing lengths together.

27. The sensor of claim 25 or 26 including the step of forming said plural separated sensing lengths in an interdigitated relationship on said first layer.

28. The method of any of claims 20 to 27 wherein said fluid absorbent skin is a paper layer.

29. The method of any of claims 20 to 28 further including the step of forming a third connection to one of said first and second electrodes via a conductive strip so as to provide a resistance between said third connection and one of said first and second connections representative of a length of said sensor.

30. The method of claim 29 further including the step of forming a forth connection and a resistive bridge between said fourth connection and one of said first, second and third connections of a resistance predetermined to indicate a characteristic of said sensor.

31. The method of claim 30 further including the step of predetermining said characteristic to provide an indication of one or more of sensor use and sensor configuration.

32. The method of claim 31 wherein said use includes bed or wheelchair use.

33. The method of claim 31 or 32 including the step of providing said configuration as substantially one dimensional or substantially two dimensional.

34. The method of any of claims 20 to 33 including the step of forming said first layer to include an apertured cover covered by a skin.

35. The method of claim 34 including the step of forming said apertured cover to be substantially nonconductive and having apertures aligned with one or more of the apertures of said first mentioned cover.

36. The method of any of claims 20 to 35 further including the step of providing processing means for sensing a resistance between any of said connections.

37. The method of claim 36 including the step of applying a resistance of a predetermined value across said first and second electrodes.

38. The method of claim 37 including the step of forming said predetermined value substantially greater than the characteristic resistance of one or more electrical bridges.

39. An incontinence sensor comprising a layer of a flexible substrate, said substrate being impervious to moisture; a circuit comprising a variable resistor laid down on a surface of said substrate; and an absorbent layer laid down over said circuit.