Accessible Incontinence Control Device

Biomedical Engineering Senior Design Group 17Zach HawkinsKristen HeckAmy Klemm

Amanda Streff

AdvisorsProfessor Paul King

Dr. Doug MilamDr. John Enderle

Abstract

Urinary incontinence, which is the inability to control urine flow, directly affects

twenty-five million adults in the United States. Incontinence is caused by a number of

conditions including loss of muscle tone, neurological disorders, or obstruction of the

urinary pathway. Inspired by the current gold standard, the AMS 800TM, the design

presented here is an artificial urinary sphincter. However, unlike the AMS 800TM, the

sphincter is controlled remotely using a radio signal, which rotates a servo. The rotation

of the servo causes a syringe to increase the pressure in tubing leading to a cuff, which

is secured around the patient’s urethra. The increased pressure results in the pinching-

off of the urethra, therefore, preventing urine flow. The device is a proof-of-concept that

requires a few modifications to ensure biocompatibility before being implanted. A plan

is laid out to further develop the device to include a bladder status indicator. The

highlight of the design is that it is easily operated by either the patient or a caregiver

allowing for better control and management of urine flow.

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Introduction

Urinary incontinence, which is the inability to control urine flow, negatively affects

both men and women and occurs more frequently with age. Incontinence is typically

due to weakened pelvic floor or bladder muscles, neurological disease, or an

obstruction in the urinary tract.1 Regardless of the cause, the patient's quality of life is

greatly reduced. Sufferers will experience an increased chance for infection, skin

irritation, and embarrassment.

Urination, also known as micturition or voiding, is the process of excreting urine

from the urinary bladder through the urethra to the outside of the body. The process is

primarily under voluntary control and involves the

urinary bladder, urethra and two sphincters. The

bladder walls contain smooth muscle tissue called

the detrusor muscles, which are innervated by the

sympathetic and parasympathetic nerves.2 Located

at the base of the bladder, the internal sphincter

(Figure 1) consists of smooth muscle and is under

involuntary control. The external urethral sphincter

is located at the distal inferior end of the bladder, is composed of skeletal muscle, and is

under voluntary control. To urinate, the detrusor muscles contract, the sphincters relax,

and the abdominal muscles are voluntary contracted.

There are four main types of incontinence; urge incontinence, stress

incontinence, overflow incontinence and functional incontinence. Urge incontinence is

the involuntary loss of urine associated with an abrupt or strong desire to void. The

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Figure 1: The bladder has two sphincters to prevent urine flow: an internal involuntary sphincter and an external voluntary sphincter.Gerard J. Tortora (1999) Principles of Human Anatomy (eight edition) John Willy & Sons Inc. , New York (Click image for larger version)

involuntary loss of urine during coughing, sneezing, and laughing is known as stress

incontinence. The other two types are overflow incontinence, the involuntary loss of

urine associated with over distension of the bladder, and functional incontinence, where

the individual has no recognition of need to void or the inability to make it to the toilet in

time. The main focus for this project is to address patients with urge and stress

incontinence.

There are a variety of conditions that lead to urinary incontinence. Neurological

disorders such as Parkinson’s disease, Multiple Sclerosis, and Alzheimer’s along with

strokes, brain tumors and spinal injuries can all result in incontinence problems.3

Hormone imbalances during menopause can also cause urinary issues in females. In

males, prostate cancer can result in incontinence symptoms. Finally, the loss of muscle

tone, either from old age or child birth, is another cause of urinary incontinence.

Urinary incontinence affects one in ten people over the age of sixty-five, but is

not limited to the elderly. The National Association For Continence (NAFC) estimates

that about twenty-five million adults in the United States experience urinary

incontinence. Both men and women are subject to incontinence, but women are twice

as likely to have issues.4 Incontinence can lead to medical problems such as infection or

skin irritation from the increased dampness. In addition, the embarrassment that

patients may experience can negatively affect their quality of life and prevent them from

leading a normal life. For example, some patients suffer from loss of self-esteem,

restriction of social and sexual activities, depression, and, in more severe cases,

dependence on caregivers. A device to manage urinary incontinence will allow patients

to function independently without the worry of embarrassment.

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The goal of our project is to design a device that is easily operated by either the

patient or a caregiver that allows for better control and management of urine flow. The

design is intended to be capable of being controlled by patients with disabilities and it

will allow for the desired and controlled emptying of the bladder while indicating to the

patient or caregiver the status of the bladder.

Considering the size of the population with incontinence and that our design can

be used for most cases of incontinence, the market potential of a male and female

accessible incontinence control device is high. Our implantable device design will assist

incontinence patients in urge retraining and discretionary urination, which are the two

most common concerns. Doctors may recommend using this device for all their

patients, for this product has a large competitive advantage over most other clinical

options, which often involve an indwelling catheter. The fact that this device does not

require a catheter is an advantage because it minimizes infections and does not require

frequent check-ups to insert a clean catheter. Therefore, we believe patients will prefer

this type of implant. In addition, because the device is patient controlled, discrete and

does not require a catheter, it will allow them to control their symptoms with more

comfort and privacy.

Methodology

The Design Process

The current gold standard for urinary incontinence control is the AMS 800TM

Urinary Control System. Completely implantable and made of silicone elastomer, the

AMS 800TM is an artificial urinary sphincter controlled by a fluid filled pressure reservoir.

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Figure 2: The AMS 800TM is made of silicone elastomer and is implanted with the cuff around the urethra.http://www.st-josef-moers.de/fachabteilungen/ uro/53252197a91257606.html

The device is manually controlled

by the patient. In men, the pump

is located in the scrotum, and, in

females, the pump is located in the

labia. To void, the patient must

squeeze the pump three to four

times to release the pressure in the cuff that is around the urethra. After urination, the

cuff automatically refills with the saline stored in the reservoir.

An alternative option for incontinence control is the male sling

InVance/AdVance. However, this option is only good for moderate incontinence. If a

patient needs more than two to three pads a day they then require a device such as the

AMS 800TM. 5

Despite the success of the AMS 800TM, there are still areas where it could be

improved. For example, the device is problematic for people with disabilities and

dexterity issues. Also, since many surgeries require catheterization, patients with the

device that go into surgery can have complications. The urethra may erode due to

excessive constriction if the device is not disabled when the patient is catheterized.

In order to make the device easier to use for all patients and to avoid urethral

erosion, our goal is to make a device that is electronically controlled and easily turned

on and off. Our initial design was to complement the AMS 800TM by placing an

1 http://www.mayoclinic.com/health/urinary-incontinence/DS00404/DSECTION=3

3 http://www.mayoclinic.org/urinary-incontinence/types.html

4 http://www.fda.gov/fdac/features/2005/505_incontinence.html

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Figure 3: Design Idea II - The orange circle represents the urethra and the gray areas are all electromagnets.

electronically controlled cuff around the pump. Instead of having the patient manually

pump the device when they needed to void, they would externally activate the pumping

of the device. The wireless signal from pressing a button outside the body would

communicate with an RC receiver connected to a mechanism strapped around the

pump. The RC receiver would send an electrical pulse to electromagnets that would

compress the pump. Therefore, instead of the patient manually pumping the device,

they would simply press the button four times to electronically release the fluid from the

pressure cuff. The distance the cuff needed to be depressed was measured and the

force necessary to accomplish this depression was calculated. The force was found to

be too great to control the pump with electromagnets considering the restricted space.

Based on this realization, we decided to use electromagnets in a different way.

We changed our project direction from building upon

the AMS 800TM to designing our own unique device, shown

in Figure 3. Our initial cuff design used the same concept

of electromagnets, but for the purpose of collapsing the

urethra. A similar silicone elastomer cuff would be used to

encase the electromagnets. A latching system with springs

would be used to keep the urethra compressed, so a

constant power source would not be needed. All the

supporting electronics would be housed in a silicone elastomer bubble with the wires

going to the device also encased in silicone. Again, an external button would trigger a

current pulse in the electronics bubble. The pulse would travel through the wires and to

the electromagnet. The pulse would cause the electromagnet to attract the opposing

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magnet. After the attraction, the notches would latch the magnets in place and the

power would no longer be required. Once the patient needs to void, they again would

press a button to administer a current pulse. This current pulse would attract the

magnets that release the spring loaded latches.

While working with our electromagnets, we experimented with a servo and push

rod as the collapsing device. In the most primitive form, a dial connected to the servo

was turned to rotate the servo, which moved the push rod. A small, solid cylinder was

attached to the end of the push rod. A similar sized piece of plastic, in the shape of a

half cylinder was used in the cuff to surround the urethra. When the servo was

activated, the push rod was propelled toward the plastic half cylinder and the urethra

was collapsed.

The push rod design appeared to have more potential than the electromagnetic

cuff, so our work focused on improving this design. Two initial problems were identified:

first, the servo was not strong enough, and, second, a straight metal push rod was not

realistic for a biological application. A more powerful servo was ordered, and new push

rod ideas were brainstormed. It was decided that the new design needed to be

powerful enough to collapse the urethra, yet flexible enough to enable easier

implantation of the device. The thrusting mechanism needed to travel from the

electronics housing to the urethral cuff. Looking back towards the AMS 800TM, it was

decided that using fluid as the driving source would work best. In addition, the device,

including all the electronics, needed to be small and implantable. According to Dr. Doug

Milam, a urological surgeon at Vanderbilt University Medical Center, the current location

where AMS 800TM reservoir is placed has room for something about the size of a tennis

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Figure 4: The RC receiver acquires the radio signal and sends an electrical signal to the servo, which rotates and pushes the fluid through the tubing to force the plunger in the cuff to pinch the urethra closed.

ball. Therefore, the entire device’s supporting electronics needed to fit inside a tennis

ball. Also, there was still the desire to control the device remotely, so a radio signal was

used for communication between the implanted device and the external control.

Results

Prototype Function

First, the device would be surgically implanted. The cuff would be secured

around the urethra at the neck of the bladder. The cuff is rigid and has a hinge on one

side. The cuff can be opened far enough to

allow the urethra to pass through. Similar to

how the current gold standard cuff operates, a

silicone tab on the outside of the cuff has a

small hole. The tab is pulled around the cuff

and secured in place by pushing a knob

through the button hole in the cuff. The

electronics housing is implanted in the

peritoneal cavity of the patient.

The prototype operates by simply moving the throttle stick of a radio controller up

causing the controller to send out a radio signal, as shown in Figure 4. Strong enough

to penetrate multiple layers of tissue, the signal is picked up by the RC receiver, which

generates an electrical signal to the servo. The servo rotates clockwise about 100

degrees. Attached to the servo is a push rod, which is also attached to a plunger inside

a stationary syringe tip. The moving servo and push rod compress the plunger forward

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Figure 5: The prototype’s electronics were housed in a tennis ball to demonstrate the amount of space used.

to force fluid out of the syringe tip and into the

tubing. The pressure increases inside the tubing

and forces the fluid into the other syringe tip. As

the fluid fills the syringe tip, the plunger attached to

the cuff moves away from the tubing and deeper

into the cuff. The urethra collapses between the

pushing plunger and reinforced cuff, preventing

urine flow.

When voiding is desired, the servo must be

rotated counterclockwise. To move the servo in

the opposite direction, the throttle stick on the radio

controller is pulled down initiating the same sequence of events. A radio signal is

transmitted from the controller to the RC receiver. An electrical signal is sent to the

servo, which causes it to rotate counterclockwise. The rod attached to the servo pulls

the plunger back creating a drop in pressure inside the syringe tip. The pressure drop

causes fluid to fill the syringe tip. The pressure change pulls the fluid out of the syringe

tip attached to the cuff. Therefore, the plunger releases the urethra and urine is able to

flow freely.

Cost

The prototype was fairly inexpensive to make costing less than $100.00. The

primary costs were the servo, RC receiver, and batteries. The servo and RC receiver

each cost approximately $35.00. Because the batteries were Lithium ion rechargeable

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batteries, both cost about $20.00 each. The tubing, wiring, and hardware that were

used for the construction of the prototype were donated samples, so there was no cost

incurred. The syringes all cost under a dollar each. The tennis ball used to show the

approximate size of the electronics was donated. Tools used during construction were

provided by the Vanderbilt University Biomedical Engineering department at no cost.

Market Analysis

Last year, 8,200 AMS 800TM artificial urinary sphincters were sold in the United

States, each costing roughly $8500 for the device alone.5 The production cost for the

AMS 800TM was estimated at $4000. It is estimated that the costs associated with the

final design of the device presented in this paper will be approximately double those of

the AMS 800. The AMS 800 does not have a cost of maintenance because re-

implantation with revision is the only form of correction for failure. Likewise, the device

design described here will also have no maintenance costs. Of the devices implanted,

25% are revised in five years, which is fairly high compared to 7-9% revisions for

Implantable Penile Prosthesis (IPP). A portion of the entire cost, the device and

surgical implantation, is covered by insurance. Blue Cross Blue Shield, the largest

insurance provider, pays Vanderbilt University Medical Center the cost of the device,

10% of the cost of the device, plus typical charges. The total amount paid is about

$19,000-$20,000. Since complete replacement is the only option for correcting a

malfunction, this cost is the same for every revision.5

Since our device is more advanced, the cost would be much greater. Based on

the complex electronics, batteries and wireless control, we project our device to cost

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$14,000. We expect the production cost to be around $8000. We expect insurance to

use the same plan for coverage for our device since we expect a long implantation and

battery life, and few possibilities for malfunction.

Safety Issues

As with any implantable device, there are many safety and biocompatibility

issues that need to be considered. First, a silicone coating on the implanted device

helps ensure biocompatibility. In addition, the tubing should be filled saline solution and

sealed properly to prevent fluid exchange between the device and the body.

Safety issues occur within other facets of the device as well. The cuff must be

tight enough to guarantee no unnecessary leaks, but not so tight as to cause urethral

erosion. Similarly, no excessive pressure should occur in the system.

The electronics also pose a few concerns. Safety issues such as electrical

hazards, for example shock, should be considered. The batteries can also malfunction

and circuit errors can occur. With the proper trouble shooting and clinical trials, the

main safety issues can be evaluated and corrected. In order to ensure that the receiver

hears the correct radio signal, both the receiver and radio are set to a specific

frequency. The crystal that is selected tunes the frequency. There are other receivers

that have a code that will sync with a radio. There are also specific channels that are

reserved along with radio bands specifically for medical devices.

FDA Approval

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Once our device is up to standards for an implantable incontinence control

device it would be considered a Class III device. The most regulated devices are in

Class III. The amendments define a Class III device as one that supports or sustains

human life or is of substantial importance in preventing impairment of human health or

presents a potential, unreasonable risk of illness or injury.6 Therefore, a Pre-market

Approval (PMA) application would be necessary to gain FDA approval. If the PMA is

approved, it essentially gives the company desiring to market the device, a license to do

so. The AMS 800 received their original PMA approval on June 14, 2001. They applied

for another PMA to make improvements on their device on October 13, 2006. Since the

original PMA was approved, up until April 1, 2008, ten reports have been posted on the

MAUDE database. MAUDE data represents reports of adverse events involving

medical devices.7 Examples of some of the complaints include necessary device

removal due to urethra erosion, need for re-implantation because of a leaky implant,

device malfunction, improper fitting of cuff due to urethral atrophy and tubing erosion.

Four of the ten complaints came after the device revision. Our device aims to correct

for such malfunctions and safety concerns.

Discussion

Final Design Ideas

Clearly, the prototype cannot be implanted as is. However, it is well on its way.

First, the electronics housing, currently a tennis ball, would need to be replaced with a

6 http://www.fda.gov/cdrh/pmapage.html

7 http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfMAUDE/search.CFM

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biocompatible silicone casing that is approximately the same size and seals off the

electronics from the body. Furthermore, the cuff itself will need to be miniaturized a bit

further and coated with a biocompatible silicone. Of course, the patient is not expected

to carry around a remote control that is normally used for model airplanes, so the

technology in the remote control will need to be transferred to a more manageable

controller. Ideally, a wristwatch-like control will be utilized to send the radio signal to the

implanted device. The wristwatch would also have a screen alerting the patient of

bladder capacity, as well as whether or not the device is activated.

Two possible concepts were generated to measure bladder capacity feedback

system. One idea was to suture tiny transmitters on the exterior of the bladder. The

transmitters would be placed in such a way that triangulation could be used to

determine how much the bladder has expanded and thus how full the bladder is. The

other idea incorporates an existing technology, but modified. Portable ultrasound

devices are available to measure bladder capacity. If this device is modified to be worn

continuously under the patients clothing the bladder status would always be available to

the patient. Modifications required include developing a strap to hold the device in

place and flattening the device to make it less noticeable while being worn.

Of all the people with incontinence problems, 85% have intact normal bladder

sensation, compliance and contractility. Less than 15% have functional incontinence.

Once the bladder status indicator is integrated into the current design, the device will be

suitable for all types of incontinence.5 For example, patients with functional

incontinence, who do not recognize the need to void, will be notified when the bladder

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reaches capacity. Therefore, not only will the device be useful for patients suffering

from stress and urge incontinence, but also form functional incontinence.

Testing

Upon completion of our device, testing will ensue. The first step will be to use an

animal model. Male dogs are the most suitable model for incontinence device testing.

First a S/P sphincterotomy5 will be necessary to make an incision of the sphincter

muscles so they are no longer functional. Our device can then be implanted and tested

for proper functioning. If positive results are found after a six month study, human

testing can occur. A one year human study is then necessary to demonstrate safety

and efficacy of the device. As demonstrated by the AMS 800, most failures occur within

the first year of implantation. As

depicted in Figure 6, the failure curve

follows the trend of a bathtub curve.

Multiple failures are not common again

until ten years after the device has been

implanted. Therefore, a one year

human study should be sufficient to

determine if the device can properly and safely function in humans.

Hypothetical Clients

Figure 6 The failure curve for the AMS 800 was used to determine the time length necessary for a suitable human study with a new device.

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The greatest feature of this design is its ease of use. Once the device is

implanted and calibrated, the patient only needs to push a button to activate and

deactivate the device. The button could be adapted to the patient, too. For example,

an individual with more severe dexterity issues, such as Jerry who suffers from

Parkinson’s disease, could simply use a larger button. On the other hand, patients like

Jamie, a serious wheelchair basketball athlete, may prefer a more discrete system. In

addition, the fact that the device is clearly activated or deactivated is beneficial to both

patients and doctors. Patients will not have to question the status of the device.

Doctors and nurses can be sure that the device is deactivated if catheterization is

required for any reason, such as a surgical procedure. Therefore, the urethral erosion

that occurs when the AMS 800TM is not properly deactivated during catheterization can

be eliminated.

Conclusions

We succeeded in accomplishing the design goals that were set for us by the

RECR competition. We improved on the current gold standard device, the AMS 800,

by creating a push button to operate our device. With the external, wireless control, the

device is easier for patients with disabilities to operate. The device successfully

empties and prevents urine flow from the bladder when the patient desires. After a few

modifications, based on the life of the batteries available, the device has the potential to

be implanted within a patient, and can remain there for at least thirty days.

Future Directions and Recommendations

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In the future, our device needs to be further miniaturized. It must also be brought to

standards for implantable devices by making it biocompatible and reducing safety

concerns. The external control must also be integrated with an interface that will display

the status of the bladder volume. After success is seen with the urinary system,

treatment of fecal incontinence with this device may be possible.

Appendix

Design Purchases

Hobby lobby: servos, receiver, servo adjuster, crystal, batteryServos: HS-55 Sub Micro Servo and HS-85 "Mighty Micro" Plus Metal Gear, Ball BearingReceiver: Hitec Micro 05S 5 Channel Receiver with Auto-ShiftCrystal: Hitec Crystal for Micro 05

P.E.P. Specializing in Plastic Engineered Products: silicone medical tubing

References

2 de Groat, William C., “Anatomy of the Central Neural Pathways Controlling the Lower Urinary Tract” Functional Urology towards the Next Millennium. Proceedings of the 4th International Congress of the Dutch Urological Association (DUA-IV). November 5-7, 1997, Maastricht, The Netherlands

5 Dr. Doug Milam, Vanderbilt University Medical Center Urology Department

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