STUDY OF LIGHT TRANSMISSION THROUGH THE

UNDERWEAR FOR DEVELOPMENT OF A URINARY

INCONTINENCE SENSOR

Kai Ishida

, Toshiya Habata

, Akihiro Takeuchi

, Harukazu Tsuruta

Minoru Hirose

and Noriaki Ikeda

Graduate School of Medical Sciences, Kitasato University, Kitasato, Sagamihara, Japan

Department of Occupational Therapy, School of Allied Health Science, Kitasato University, Kitasato, Sagamihara, Japan

Department of Medical Informatics, School of Allied Health Sciences, Kitasato University, Kitasato, Sagamihara, Japan

Department of Medical Safety Engineering, School of Allied Health Science,

Kitasato University, Kitasato, Sagamihara, Japan

Keywords: Urinary incontinence, Photosensor, Dementia, Light transmission.

Abstract: Urinary incontinence is a troubling disease that makes it difficult for patients to live a normal life. Rapid

detection of urinary incontinence could allow many patients with this condition to feel more confident about

going out. Therefore, our goal is to develop a urinary incontinence detector based on a light-emitting diode

and a photodiode. Here, we describe the development and testing of a prototype model. The photosensor is

driven by a 9 V battery and consists of an ordinary electrical circuit, a light-emitting diode (lambda max =

950 nm), a photodiode (spectrum 750-1200 nm), a comparator and, a compact motor. Light transmission

through the underwear was changed by soaking with liquids. This phenomenon was measured using a

digital voltmeter. The urinary incontinence sensor was placed on a dummy. Liquids were drained into the

shorts. These increased in voltage from 3.73 V to 8.78 V, which caused the motor to vibrate. These results

show that the prototype sensor can be used to detect urinary incontinence.

1 INTRODUCTION

In recent years, Japan is rapidly becoming an aging

society. According to the report by the Japanese

Ministry of Internal Affairs and Communications, as

of August 2011, the number of elderly people in

Japan aged 65 or more was 2971 million (23.2%).

Of these, aged 65 or older women were 1702

million. It is reported that about 11 percent of

women need to have surgery related to urinary

incontinence or genital prolapse one or more times,

which means about 187 million women are applied

(Olsen et al., 1997).

In studies of epidemiology or health screening,

lower urinary tract symptoms are highly prevalent

(Homma Y, Yamaguchi O, Hayashi K, 2006; Terai

A et al., 2004). Currently, about 4 to 5 million

people suffer from urinary incontinence in Japan. It

is estimated that the number of urinary incontinence

patient will increase 10 million people after 15

years.

Cause for urinary incontinence includes, the

person who is elderly, patients with dementia,

patients who have undergone radical prostatectomy

due to cancer, patients who injured spinal cord,

patients who have schistorrhachis, females after

delivery of a baby or at the menopausal stage, and

one in four otherwise healthy women who develop

urinary incontinence. Such incontinence decreases

quality of life in various situations in society.

Patients with chronic incontinence have no urge to

urinate, and so it is difficult to use public facilities

and continue to work. For example, Spinal cord

injury (SCI) patients with normal upper body

function have a desire to return to society, but their

concern that urinary incontinence may occur at any

time often causes patients to avoid going out.

Therefore, urinary incontinence disrupts human

relationships and increases isolation, and in extreme

cases patients may commit suicide because of this

condition.

At a hospital, care facility and home, a diaper is

commonly used to prevent urinary incontinence.

311

Ishida K., Habata T., Takeuchi A., Tsuruta H., Hirose M. and Ikeda N..

STUDY OF LIGHT TRANSMISSION THROUGH THE UNDERWEAR FOR DEVELOPMENT OF A URINARY INCONTINENCE SENSOR.

DOI: 10.5220/0003741103110314

In Proceedings of the International Conference on Biomedical Electronics and Devices (BIODEVICES-2012), pages 311-314

ISBN: 978-989-8425-91-1

 2012 SCITEPRESS (Science and Technology Publications, Lda.)

Patients with SCI may also use intermittent self-

catheterization using a balloon catheter, and male

patients can use a condom remodeled as a urine bag.

However, these methods have several problems:

condoms remodeled as urine bags require a long

time to fit, and patients dislike wearing diapers.

Furthermore, the artificial urinary sphincter, which

is the only definitive therapy for urinary

incontinence, is not covered by the Japanese

National Insurance system and thus is uncommon in

Japan, despite its approval by the Japanese Ministry

of Health, Labour and Welfare (Arai et al., 2009).

Several sensors have been described for

prevention or detection of incontinence, including

monitoring of temperature changes in diapers

(Matsushita et al., 1993), detection of conductance

changes in diapers after incontinence (Nakajima et

al., 1994), and use of the characteristics of

radiofrequency that prevent its transmission if water

is present on clothes (Tamura et al., 2007). A device

that measures urinary volume in the bladder using

ultrasound is also on the market (Yuririn, USH-052,

Takashiba Electric Ltd., Japan, Retrieved Aug 26,

2011). However, these devices are not commonly

used in Japan. In addition, some of the reported

sensors are intended for use at the bedside for

elderly patients or patients with dementia. In

contrast, we have been unable to find a report of

practical use of a portable urinary incontinence

sensor in normal life situations. Therefore, we have

started development of a urinary incontinence sensor

that is portable, works on a battery, senses urinary

incontinence quickly, is diaper-independent, and has

a low cost.

2 METHODS

2.1 Basis and Structure of the

Incontinence Sensor

Our sensor is based on the venous needle

dislodgement sensor that we have described for use

during hemodialysis (Takeuchi et al., 2010). This

sensor utilizes light transmission through a cloth and

changes voltage after liquid osmosis. We modified

the sensor by changing the diode to emit infrared

light, adding a monitoring circuit, and using a dry-

cell battery to drive the sensor. The sensory module

consists of a light emitting diode (LED, lambda max

= 950 nm, SFH4110), a photodiode (PD, spectrum

750-1200 nm, BP104FS), and a comparator

(LM2903) with a compact motor on a simple circuit

(Figure 1). The PD changes its resistance depending

on the intensity of the transmitted light. The LED

and PD are attached at the edges of a plastic clip and

sealed with bonding to avoid a short-circuit that

could be caused by urinary incontinence (Figure 2).

The voltage across the R2 resistor (12 kohm)

increases when the light is bright and decreases

when it is dark. The voltage is not changed by

background illumination such as that from a

fluorescent lamp because the strong LED light is

directly targeted to the PD through the cloth. The

comparator receives a certain voltage from variable

resistors (Rv, 1 kohm) and R2 (variable due to light

transmission). When urinary incontinence occurs,

the R2 voltage increases to slightly higher than the

Rv voltage, and the resulting current drives the

transistor (BC373G) and causes the motor to vibrate.

Figure 1: The circuit of the sensor module.

Figure 2: Components of the incontinence sensor.

2.2 Experimental Methods and

Statistics

First, to measure the characteristics of the sensor,

several liquids were infused and light transmission

was measured. The sensor is attached by clipping

underwear made of cotton at the bottom of the front

BIODEVICES 2012 - International Conference on Biomedical Electronics and Devices

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surface. Infusion tube is inserted into the inner side

of the underwear (Figure 3). The liquids are infused

by the infusion pump (SYRINGE PUMP 1235N

Atom Medical., Ltd., Japan) at a rate of 200ml per

hour. Normal human urine, tap water, or

physiological saline were manually infused into the

underwear, and the R2 voltage change between dry

and wet conditions of the shorts was measured with

a digital voltmeter. We measured the interval of time

between the infusion of liquid and the beginning of

motor vibration. For each liquid, seven independent

measurements were performed. The results are

presented as a mean ± SD. A probability level of P <

0.05 was considered to be statistically significant. To

confirm the effect of thickness of the cloth on light

transmission we used three kinds of cloth with the

thickness of 0.2mm, 0.4mm and 0.6mm. We then

tested the sensor using a dummy patient that was set

to external underwear assumes incontinence may

occur (Figure 4).

3 RESULTS

With a dry underwear, the mean voltage across R2

was 3.58 ± 0.12 V under control conditions. The

threshold of the comparator was set at about 8 V by

adjusting Rv. Infusion of liquid to wet the underwear

caused the R2 voltage to increase from 3.73±0.41V

to 8.78±0.31V with unimpaired urine, from 8.78 ±

0.11 to 5.9 ± 0.06 V with tap water, and from 3.46±

0.13 to 9.08 ± 0.05 V with physiological saline. In

all cases, the values after liquid infusion were

significantly higher (P<0.01) than the Rv voltage

which caused the motor to vibrate about 4.5 to 6

seconds after the liquid was infused (Figure.5).

Figure 3: Positioning of the sensor and infusion tube.

By the experiment that changed thickness of

cloth, the R2 voltage increased from 5.7± 0.2 to

8.38±0.07V with 0.2mm cloth, from 3.41±0.2V to

7.96±0.3V with 0.4mm cloth, and from 1.92±

0.12V to 6.47±0.31V with 0.6mm cloth (Figure 6).

In all cases, the changes were statically significant

(P<0.01).

Similarly, in testing on the dummy patient, the

motor vibrated a few seconds after infusion of tap

water.

Figure 4: Experimental dummy showing the positioning of

the sensor.

Figure 5: Effect of liquid type on the R2 voltage.

Figure 6: Effect of thickness of cloth on the R2 voltage.

4 DISCUSSION

The prototype sensor described in this work is

compact, works on a battery, is suitable for use at

the bedside and outside the house, and has a low cost

because the sensor is washable and sterilizable. Our

STUDY OF LIGHT TRANSMISSION THROUGH THE UNDERWEAR FOR DEVELOPMENT OF A URINARY

INCONTINENCE SENSOR

313

results show that the sensor can respond to a small

amount of urine, which allows detection of

incontinence before a flood of urine occurs. We

think this sensor is suitable for patients with

dementia, patients use a wheelchair such as SCI

patients, and training for young patients with

enuresis. With use of the sensor, younger patients

will be able to avoid wearing diapers and can choose

to wear any type of shorts. Soaking of the shorts due

to incontinence will drive vibration of the motor, and

positioning of the motor on the normal upper body

will allow the patient to detect incontinence at an

early stage.

From the results, we confirmed that the light

transmission through the cloth increased

significantly by human urine, tap water and physical

saline. When the thickness of the cloth was 0.4-

0.6mm, the R2 voltage increased by more than 4V.

This indicates that adjusting Rv resistance and

setting the threshold properly, this sensor is

applicable to detecting urinary incontinence.

In this study we used the underwear made of

cotton. The motor vibrated even when the sensor is

attached at the thickest position. If we adjust the

variable resistors and control threshold voltage,

different type of underwear can be used. In the

experiment, we used dummy patient, but for

practical use it will be necessary to examine the

effects of walk and roll-over, etc. Therefore, as the

next step in development of the sensor, we will work

toward its practical use through testing and

evaluation in a patient with urinary incontinence.

5 CONCLUSIONS

In this article, we described development of a

urinary incontinence sensor, which utilized light

transmission through cloth. This sensor is compact,

works on a battery, can be used at the bedside and in

ordinary life, and frees the patient from wearing a

diaper.

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