GB2228815A - Enuresis detection device - Google Patents

Abstract

The device comprises a transducer mat for placing beneath the patient, which is formed by screen printing an interdigitated pattern of conductors 20a, 22a on a flexible hydrophobic sheet 12 so as to provide an integral structure. The conductors may be perforated. A layer of electrically-insulating net material may be bonded to the flexible sheet over the conductors so as to isolate the patient from the conductors. <IMAGE>

Description

ENURESIS DETECTION DEVICE The present invention relates to an enuresis detection device and particularly, but not exclusively, to an enuresis detection device for use with incontinent patients lying in bed.

Enuresis, or incontinence of urine, is a condition which often occurs whilst a patient is asleep and unable to exert control over his or her bladder. Various apparatus and methods have been designed to provide an alarm of such enuresis to help patients exert control of their bladder, or alternatively, to allow the bed clothes to be changed by a person taking care of the incontinent patient.

Such apparatus is normally provided by a mat which is disposed below or next to the lower abdomininal portion of the patient. The mat normally includes a substrate sheet having electrical wire tape or a plate sensor apparatus separately manufactured and subsequently secured to the sheet, in which an electrical circuit is closed when urine reaches the mat. When the electrical circuit is closed, a buzzer or a stimulation device is energised to give the patient a warning of the onset of enuresis. A problem associated with such mats is that patients often find them uncomfortable. This is because the pads are generally of a laminated construction of semi-rigid materials, and are consequently not sufficiently flexible to avoid making a crinkling noise when laid on.

Furthermore, there is the possibility of accidental or (in the case of inquisitive children) intentional detachment of the conductive material.

It is an object of the present invention to provide an enuresis detection device which mitigates the aforementioned problems by providing an improved transducer mat.

The present invention provides an enuresis detection device which comprises a transducer mat adapted to be placed beneath a patient for detecting the presence of urine, the transducer mat comprising a soft flexible sheet having printed thereon a pair of spaced conductors so as to be integral with the sheet; and electrical control means connected to said spaced conductors and adapted to produce an output signal in response to the presence of urine.

Preferably, the flexible sheet is formed of a hydrophobic material, and is adapted to be disposed adjacent the lower abdominal portion of said patient.

Preferably, said conductors are screen printed onto said sheet and are of metallic silver, carbon, or conductive ink or other suitably conductive material; so as to provide good flexibility.

Each of said conductors may comprise a pattern of holes, said holes reducing the effective amount and therefore cost of the conductive material required for said strips.

Preferably also, there is provided barrier means coupled to said sheet whereby said conductors are electrically isolated from a patient. Conveniently, said barrier means are provided by an insulating HPE-net which is permanently bonded onto the surface of said sheet over the conductors.

The device may also include warning means coupled to said control means whereby the patient receives a stimulation or warning of the detection of enuresis. The warning means can comprise a light, said light being switched on when enuresis is detected. Alternatively, the warning means may comprise an audible alarm, said alarm being actuable upon detection of enuresis.

Alternatively, the warning means can comprise a tactile sensor,(but notably not of an electrical stimulation nature) adapted to be located adjacent a sensitive part of the nerve system of the patient to provide a warning of enuresis, especially the sole of the patient's foot.

An embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic view of an embodiment of an enuresis detection device, in use, in accordance with the present invention; Figure 2 is a perspective view of the constituent parts of the enuresis detection device shown in Figure 1; Figure 3 is a fragmentary view to an enlarged scale of an electrical conductor of the enuresis detection device shown in Figure 2; and Figure 4 is a circuit diagram of the enuresis detection device shown in Figs. 1 to 3.

Figure 1 of the drawings shows an enuresis detection device generally indicated by reference numeral 10. The detector 10 comprises a soft flexible hydrophobic coated sheet 12 e.g. of polyvinyl chloride or resin bonded cotton mesh, which is adapted to be disposed below the lower abdominal portion of the body of the patient 14. The sheet 12 is coupled to an Electronic Conditioning Unit (ECU) 16 which controls the operation of the detector 10. The detector 10 detects enuresis in a manner which will be described. Upon the detection of enuresis the ECU 16 energises one of three optional output patient warning devices 18, namely (a) a mechanical output device or vibrator 18a such as that described in patent GB 2162980, possibly attached to the sole of the patient's foot, (b) an acoustic output device or buzzer 18b, and (c) a visual indicator 18c.The purpose of each device 18 is to provide the patient 14 with instant warning of the onset of urination. The detector 10 is electrically isolated from the patient 14 and electrical currents in the detector 10 are limited to an acceptable level as will also be described hereinafter.

Reference is now made to Figure 2 of the drawings which is a perspective view of the enuresis detector 10.

The transducer mat comprises flexible sheet 12 screen printed with a conductive silver ink comprising 60% pure silver or other conductive material in a vinyl/acrylic resin carrier to form electrically conductive tracks or conductors 20 and 22, which become an integral part of the transducer. The conductors 20 and 22 comprise elongate portions 20 and 22a which interdigitate with each other. These interdigitated elongate portions 20a and 22a thus form a conductive grid extending across the surface of the sheet 12, each pair of adjacent elongate portions 20a and 22a defining a space 21 therebetween.

During the screen printing process the resinous medium in which the conductive silver or other conductive material is suspended, integrates with the sheet. The completed transducer is impervious to moisture and can be bathed in a sterilising solution, dried and safely reused.

The conductors 20 and 22 are coupled to electrical terminals 23 and 24 respectively. These terminals 23, 24 are coupled to ECU 16 by cable 26. When enuresis occurs, the urine which reaches sheet 12 creates an electrical bridge across at least one space 21 between conductors 20 and 22. This bridging of space 21 completes an electrical circuit and causes ECU 16 to energise one of the output devices 18 as will be described later in detail.

The flexible sheet 12 is conveniently 66 cm long and 47 cm wide and has a thickness of only 0.8 mm and weight of 120 gm. This allows the sheet 12 to be disposed below the patient 14 without causing discomfort. The surface of sheet 12 to which the conductors 20, 22 have been applied is covered with a 0.2 mm thick HPE-net permanently bonded to sheet 12, which electrically isolates the electrical conductors 20 and 22 from the patient 14.

Each conductor 20 or 22 is 12.5 mm wide and the space 21 to be bridged between adjacent conductor forks is 7 mm wide. Each conductor 20 and 22 is screen printed with a pattern of holes 28 as best shown in Figure 3. The holes 28 reduce the amount of silver, and therefore cost, of each fork 20a, 22a without reducing the electrical capability o the sheet 12 to sense the presence of urine.

Reference is now made to Figure 4 of the drawings which is a circuit diagram of the enuresis detection device. As hereinbefore described, the detector 10 comprises a sheet 12, an ECU 16 and an output device 18.

Also shown in Figure 4 is a 6v battery 30, this battery is normally contained within ECU 16 but is shown outside in the Interests of clarity. Alternatively, a mains electrical supply embodying a 6v transformer can be used instead of a battery. When urine is present, it may bridge the conductors leading to a reduction in the resistance of the transducer. The presence of urine will also lead to a change in capacitance of the transducer.

An output signal is generated, which activates an output device to warn the patient. ECU 16 controls current levels used in the detector 10 and ensures that these currents are not above an acceptable level. For example, these currents are below the limits laid down by the British Standards Institution and appropriate health authority requirements.

The ECU 16 is a pulse width modulated system and the electrical input signal to ECU 16 is related to the resistivity, conductivity and capacitance changes in the parameters of the transducer mat. ECU 16 contains a pre-settable level detector to meet the variations in the existence of body moistures of patients thus ensuring that the apparatus is activated only by enuresis. ECU 16 comprises a light emitting diode (l.e.d.) 32 (best shown in Figure 2). This l.e.d. 32 emits a steady green light when the ECU 16 is switched on and emits a flashing red and green signal (at a frequency of 1HZ) when enuresis is detected. The ECU 16 has an output voltage range of 0-3v and a maximum current output of 300mA.

The characteristic parameters of the ECU 16 are as follows: INPUT R - range (1-300)Kohm C - range (10-500)pF Sensitivity 10Kohm/100% OSW 0.5ml/100% OSW Connection Phono socket CONTROL Carrier freq. (1-2)KHz Internal preset 50% duty cycle Trigger level (1.3)V DC Internal preset Output level External potmeter Control with ON/OFF power switch OUTPUT Voltage (0-3)V DC Current 300mA max.

Indicator Green LED when switched ON Red & Green Flashing LED (1Hz) when activated.

SUPPLY Voltage 6V DC internal Penlight Batteries (4) Current lOmA quiscent 15mA LED 40mA Buzzer 300mA Vibrator DIMENSIONS Size L = 150mm W = 82mm H = 50mm Weight 250g with Internal Batteries Each output device 18 requires a different current level to operate and each of these devices 18 may be energised from ECU 16 in response to the detection of enuresis. The output devices 18 are energised and controlled by a digital power circuit. The l.e.d. 32 requires only 15mA current to operate upon the detection of enuresis. The vibrator requires only 300mA to operate. Similarly, the buzzer requires only 40mA.

Each of these output devices 18 are energised by the ECU 16 and supplied with the appropriate current levels. The ECU 16 ensures that a quiescent current of lOmA is not exceeded and that a minimal level of current flow through conductors 20 and 22 is maintained, which together with the lamination of HPE-net obviates the chances of electrical shock to the patient 14.

Various modifications can be made to the embodiment hereinbefore described without departing from the scope of the present invention. The conductors can be arranged In any suitable pattern or grid of varying dimensions which is effective to detect the presence of urine. Any suitable form of output device may be coupled to the ECU rather than the three types specifically described above; for example, an optical output device can be used to provide a patient with a visual indication of enuresis.

In the above described embodiment, the screen-printed transducer is of significant dimensions. If desired, however, the transducer can be of small dimension to form a pad which can be appropriately located and retained in position within underclothing of a patient rather than being positioned below the patient as a sheet.

The enuresis detection device, in accordance with the present invention, can be disposed adjacent the lower abdominal portion of the patient's body without making the patient uncomfortable - due to the soft flexible nature of the conductive sheet. Current flow through the conductors is kept low in order to eliminate the chances of electrical shock to the patient. The transducer is relatively light in weight, flexible and soft.

Further advantages associated with the present invention are as follows: (1) Because the electrical conductors of the detector are screen-printed onto a soft and flexible substrate and become an integral part of the substrate (unlike other types of sensors fitted with a metallic grid made of tapes, wires or plate) the conductors can never become detached, either by accident or intent; thus obviating the risk of electric shock to the patient.

(2) Because the conductive material which will form the conductors is suspended in a resinous medium and is integrated with the hydrophobic sheet at time of manufacture, the sheet having the conductors thereon is impervious to moisture and is highly resistive to the corrosive effects of urine. It can be washed in a sterilising solution and safely used and re-used - which is greatly advantageous in a medical situation.

(3) When the sheet is permanently over-bonded with an HPE insulating net as described above, it provides a safeguard (in addition to the variable control in the ECU) against instant actuation of the warning devices by the presence of body moisture. Additionally, and very importantly, the net layer isolates the patient's skin from the conductors thus obviating the risk of electric shock should the detector sheet be used in conjunction with an electronic control box of different manufacture and with inadequate control limits. The design of the detector sheet or the like is such that it can be positioned next to the patient's skin, either by accident or intent, in complete safety.

Claims (10)

1) An enuresis detection device which comprises a transducer mat adapted to be placed beneath a patient for detecting the presence of urine, the transducer mat comprising a soft flexible sheet having printed thereon a pair of spaced conductors so as to be integral with the sheet; and electrical control means connected to said spaced conductors and adapted to produce an output signal in response to the presence of urine.

2) A device according to claim 1 wherein the flexible sheet is formed of a hydrophobic material.

3) A device according to either preceding claims wherein the conductors are screen printed onto the flexible sheet.

4) A device according to any preceding claim wherein the conductors comprise metallic silver or carbon.

5) A device according to claim 4 wherein the conductors are printed using a conductive ink comprising metallic silver in a resin carrier.

6) A device according to any preceding claim wherein the conductors are arranged in an interdigitated array.

7) A device according to any preceding claim which further comprises a layer of electrically-insulating net material bonded to the flexible sheet over the conductors, so as to isolate the patient from the conductors.

8) A device according to any preceding claim wherein the electrical control means applies a pulse width modulated signal to the conductors, and detects changes in resistance or capacitance due to the presence of urine.

9) A device according to any preceding claim, which further comprises warning means connected to the electrical control means, and responsive to the output signal to warn the patient.

10) A device according to claim 8 wherein the warning means is a light, an audible alarm, or a vibrator.