Executive Summary



Project Description



Engineering Design Specifications



Prototype Development



Performance Testing



Design Solutions



Discussion & Recommendations










This report summarizes the design process of the proposed “Urinary Catheter Valve with Pressure Release Mechanism”. The device aims to allow patients suffering from urinary incontinence to control and manage urine flow.

Urinary incontinence is a condition in which a person is unable to control his or her bladder1. Solutions to this problem typically involve an indwelling Foley catheter that continuously drains into an attached urine bag2,3,4. The indwelling Foley catheter is inserted through the patient’s urethra until it reaches the bladder, where it remains to collect urine. Because the urine is constantly draining, a collection bag must remain with the patient at all times 5. Many patients complain that this is highly inconvenient, uncomfortable, and causes embarrassment in social settings 6. A patient’s quality of life is compromised due to the inconvenience and social embarrassment that stems from carrying a urine bag at all times. This constant drainage also causes the bladder to lose its normal function as a collection unit and its muscle may atrophy7. Infection of the bladder and urinary tract are also common among catheterized patients due to urine stasis and introduction of pathogens by the catheter itself 8,9.

The main goal of the project is to create an inexpensive device that will be practical and convenient for the patient, while at the same time reducing the health hazards associated with current solutions for incontinence. The intended functions of the proposed design are as follows: to eliminate the need for an attached urine collection bag, to allow the patient to manually empty the bladder when desired, to maintain the bladder’s natural function and muscle tone, and to have compatibility with the widely used and accepted Foley catheters. In addition, the new design will introduce an emergency pressure relief mechanism, designed to leak small amounts of urine into a low capacity bag when the internal bladder pressure rises to critical levels. This will eliminate the danger of ureter reflux.

This project proposes an improved solution to urinary incontinence. Taking patient complaints and health hazards into consideration, the proposed solution aims to eliminate the need for an attached urine bag, and allow patients to regain control of emptying their bladder. Additional customer requirements call for the device to remain small and discrete, as well as comfortable and easy to use.

The proposed valve design is intended to work in conjunction with a standard Foley Catheter. The valve attaches to the distal end of a Foley catheter, essentially stopping the flow of urine until manually activated. To prevent ureter reflux, a dangerous condition in which overfilling of the bladder can lead to urine backflow into the kidneys, the valve allows the release of urine at high bladder pressure. This release is regulated by the “tightness” of the valve seal, which is determined by the degree that the valve is twisted. Because the fluid conduit in the valve is a soft, flexible liner, twisting will slowly occlude the passageway until no fluid will pass. However, high pressures may force small amounts of fluid through the liner. This pressure relief mechanism allows the release of small amounts of urine from the catheter when sustained bladder pressure reaches critical levels. This then requires a small emergency release bag (smaller and less cumbersome than a standard urine bag) to collect any leaked urine.

Performance testing of the valve prototype indicated appropriate pressure sensitivity. When set at an intermediate seal tightness, the valve remained closed at average physiological pressure (40-80 cm water). The valve continued to remain closed at slightly elevated pressure (100 cm water). However, the valve did release fluid at sustained critical pressures (120-160 cm water), and released enough fluid to lower pressures to within a much safer range (102-110 cm water). The seal tightness may also be adjusted to raise or lower to pressure sensitivity for individual patient needs.

Project Description

Urinary incontinence is a condition in which a patient loses control of his/her bladder. When severe, this condition requires continuous drainage of urine through an indwelling Foley catheter into an attached urine bag. Because the urine is constantly draining, the bag must remain with the patient at all times. Many patients complain that this is highly inconvenient, uncomfortable, and causes embarrassment in social settings. More importantly, however, it may lead to two serious health conditions. First, urine stasis within the bag and backflow of urine into the catheter may result in urinary tract or bladder infections. Secondly, a lack of constant distention associated with normal filling and emptying of the bladder may lead to bladder muscle atrophy.

The main goal of the project is to create an inexpensive device that will be practical and convenient for the patient, while at the same time reducing the health hazards associated with current solutions for incontinence. The intended functions of the proposed design are as follows: to eliminate the need for an attached urine drainage bag, to allow the patient to manually empty the bladder when desired, to maintain the bladder’s natural function and muscle tone, and to have compatibility with the widely used and accepted Foley catheters. In addition, the new design will introduce an emergency pressure relief mechanism, designed to leak small amounts of urine into a low capacity bag when the internal bladder pressure rises to critical levels. This will eliminate the danger of urine backflow into the kidneys when the bladder is overfilled, a condition known as ureter reflux.


There are currently 19 million adults in the United States suffering from some form of urinary incontinence10,11. Out of these, 10 million control incontinence with an indwelling Foley catheter, attached to a urine drainage bag. It is estimated that 50% of Foley catheter users are over the age of 65, 25% are short term users (less than three months), and the remaining 25% are long term users under the age of 6510,11. In order to reach as much of this market as possible, the target product cost is less than $10.

The principle product user will be the patient, but physician assistance may be required to determine the patient’s needs and to instruct the patient on proper use. In some cases, licensed caregivers may be the primary user as they control the device for their patients. Patients suffering from incontinence range in age and may be of either gender. However, incontinence typically becomes more common with age, so a large percentage of users may be geriatric. The target market for the project includes both short-term and long-term incontinence patients. However, the proposed design will particularly appeal to post-operative patients that are required to use a Foley catheter for a few weeks to a few months as ordered by a physician.

Because it is a medical device, the design solution must be in compliance with regulation by the Food and Drug Administration Center for Devices and Radiological Health. The device is categorized under panel 876 – “Gastroenterology and Urology.” Its seven-digit classification code is 876.5130 – “Urological Catheter and Accessories.” Under these classifications, it is considered a type II device. Its 3-alpha code is KNY – “Accessories, Catheter G-U.”

The device is noninvasive and operates outside the body. However, indirect interaction with the internal environment may occur through the Foley catheter. Therefore, steps must be taken to ensure sterility of the device to prevent introduction of bacteria and other pathogens. The device will be made of plastic, and therefore will be sensitive to heat. This eliminates the possibility of using any type of heat sterilization. To sterilize the device, the device will be exposed to Ethylene Oxide (EtO) at a concentration of 200 mg/L at a temperature of 30 °C for at least three hours using the gas chamber method. Aeration of the chamber post sterilization will allow for the removal of toxic residue on the device. To ensure that the sterilization has succeeded, Bacillus subtilis will be used as a biological indicator. After four hours of incubation at 37 °C, the bacteria will fluoresce. This bacterium is highly resistant to EtO, so if sterilization did not occur, the indicator will fluoresce.

The sterile paper package containing the device will be made of bleached white sulfate kraft, which has been formulated and produced on a Fourdrinier machine. This ensures uniform fiber formation, high wet strength, and good air porosity5. The cellulose fibers of the paper form a “torturous” network that prevent transmission of bacteria, but allow permeation of air and EtO. The result is a package that serves as a bacterial filter.

Another important aspect governing the design of the device is the biocompatibility. The device will be connected to the distal end of the catheter, and as such will have minimal contact with the skin. The materials from which the device is made already have established test data for biocompatibility for the intended method of manufacture, packaging, and sterilization. This established data confirms the biocompatibility of the device, and satisfies the criteria for the International Standard ISO – 10993.

The design solution should address both convenience and health-related customer requirements. The device should provide greater physical comfort, ease of use, and ease of concealment than current catheterization and urine collection methods. The design solution should decrease the incidence of harmful bladder atrophy linked to long term catheterization. The design also should not impose added risk to health issues currently associated with catheterization, such as risk of urinary tract infection. Lastly, the solution should offer a means by which to prevent bladder overfilling.

In order to maintain patient comfort, the device is small and lightweight. The recommended length is approximately 2-3 inches, with a diameter of approximately 0.5 – 0.65 inches. The expected weight of the device (excluding the tubing to which it is attached) should be approximately 5-6 grams. The device should allow for the disposal of urine volumes comparable to that of normal, complete evacuation (400-600cc). If urine is released to prevent over-distention of the bladder, this volume should be relatively small (20-100 mL). The greatest constraint is the necessity for the device to interface with a standard Foley catheter. The device should work in conjunction with a Foley catheter, which is a widely accepted method of incontinence management, and provide solutions to the problems associated with it.


When designing a prototype, it was necessary to fulfill several criteria so that accurate testing could be completed. First, the prototype needed to fit into the end of a standard catheter to allow for a realistic testing environment. The prototype also needed to be pressure sensitive so that the pressure relief function of the final product could be tested. Finally, it needed to have a strong screw mechanism so that additional pressure to the internal tubing would not cause the cap to unscrew thus reducing the pressure sensitivity.

Figure 1: Side View of Completed Prototype

The final prototype (Fig 1) was made of a cryovial (rigid polypropylene vial), polypropylene, plastic pipe fittings and soft latex tubing. The first step in construction was cutting off the end of the cryovial and hollowing out the cap so that the pipe fittings could be connected to the ends. The next step was to modify the pipe fittings so that they could be inserted into the ends of the cryovial. This involved cutting off the excess piping so that just the fitted end remained. This end was then sanded down so that it could be fit into the ends of the cryovial, and then glued into place. From here, latex tubing was run through both ends, and glued in place using Krazy glue.

In order for the design to fulfill all of the design criteria, several steps were taken. First, measurements of the catheter end were taken to ensure the use of the correct size pipe fitting. This allowed for no leakage between the end of the catheter and the prototype. The pressure sensitivity was achieved by using expandable latex tubing. When the pressure increased, the tubing was allowed to expand, causing fluid release and pressure reduction. The amount the tube was able to expand was based on the extent of twisting, therefore creating the different degrees of pressure sensitivity. Finally, the screw mechanism was made more effective by utilizing the elastic properties of the latex tubing. By stretching the tubing to make it pull on the screw end, the screw mechanism is much tighter and will not automatically unscrew due to increased pressure.


To imitate sustained bladder pressure, the valve was attached to a vertical water column. The column was constructed of 1-inch clear, rigid tubing and filled to designated heights to achieve the desired pressure at the bottom of the column. The water column was filled to simulate both normal physiological pressures (40-80cm water) and critically high pressures (100-160cm water). The valve was set to an “intermediate tightness”, approximately halfway between completely open and completely closed (so tight that the valve can not twist further). This method allowed for the determination of the following performance testing criteria:

1) Pressure Sensitivity – Does the valve release fluid at the pressure tested?

2) Volumetric Flow Rate – At the start of fluid release, what is the flow rate?

3) Volume Released – What is the total volume released until the valve reseals?

The results of performance testing are displayed below in Table 1. At physiological pressures (40-80 cm water), the valve remained sealed. The valve continued to remain sealed at 100mL, which is acceptable because the bladder may briefly reach these pressures through natural means such as sneezing or coughing. The valve began to release fluid at more elevated pressures. At 120 cm water, fluid initially flowed at 3mL/min and the valve resealed after releasing 18mL. At 140 cm water, fluid initially flowed at 10mL/min for a total of 35 mL released. A max flow of 21 mL/min was achieved at 160 cm water with a total of 50 mL released.

Table 1: Performance Testing Results


(cm water)

Pressure Sensitivity

Volumetric Flow Rate


Volume Released (mL)














Releases Fluid




Releases Fluid




Releases Fluid



These results therefore show that the proposed valve exhibits appropriate pressure sensitivity for use in conjunction with a Foley catheter. The valve remains closed at physiological pressure levels, but opens at critically high pressures to release fluid and therefore lower the pressure.


The intended device (Fig 2) aims to help control urinary incontinence via a valve mechanism, while also allowing for the emergency release of urine during periods of critically high, sustained pressures. A short length of rigid polypropylene tubing has, at its proximal end, a hollow, ridged adaptor that interfaces with the distal end of the Foley catheter tubing. The distal end of this tubing has a “male” thread pattern. Another short length of rigid tubing with a “female” thread pattern is attached to the “male” end. The distal end of this length of tubing is open at the end to allow fluid flow. Spanning the two lengths of tubing is an internal cylindrical latex liner. By default, the liner is in an open configuration, which allows free flow of fluid through the device. When the distal section of tubing is rotated, the latex liner twists and contracts (similar to the human iris), occluding the passageway. The threads serve to gauge the pressure sensitivity of the valve. The more the tubing is twisted, the tighter the liner is wound, resulting in a stronger seal.

Fig 2: Outside, Side View of Valve

Fig 3: Side View of Valve Channel – Opened and Closed

Fig 4: Cross-Sectional View of Valve Channel – Opened and Closed

The desired degree of pressure sensitivity can be determined between the patient and his or her physician through common urodynamic testing. For example, if a patient does not need the pressure release function, then he or she may wish to simply twist the valve to its maximum tightness level and therefore completely halt urine flow until the valve is opened. However, if a patient is less aware of the sensation of fullness, then the valve should be set to an intermediate level so that urine may be released if the bladder overfills.

The prototype also showed the important of using a material for the liner that is not too flexible. If the liner twists too easily, then the valve closes completely with very little twisting. However, by using a more stiff material (such as thicker latex tubing), the liner does not twist shut as quickly and allows for more accurate pressure settings.


The current solution for patients suffering from urinary incontinence involves the connection of an indwelling catheter to a continuous drainage urine collection bag. This system is embarrassing and cumbersome, and can increase the risk several health complications. The direct connection of the bladder to the urine collection bag via the catheter tube creates the risk of urine backflow into the catheter, creating the risk of a urinary tract infection. The complete disuse of bladder contraction muscles causes extreme muscle atrophy inevitably leading to total catheter dependence.

The proposed Urinary Catheter Valve with Pressure Release Mechanism can eliminate or greatly reduce these problems. By removing the necessity for an external visible urine collection bag, the patient experiences greater comfort and less social anxiety. The inclusion of a valve system allows for convenient and voluntary evacuation of the bladder when desired. This also reduces some of the major health risks associated with current catheter use. By preventing backflow, the risk of non-sterile urine flowing back into the catheter is completely removed, eliminating the potential for urinary tract infections. Because the bag prevents continuous flow of urine, the cyclical distension and relaxation of the bladder prevents muscle atrophy. The valve also provides a pressure relief mechanism that allows a small amount of urine release, preventing urinary reflux into the ureter due to bladder overfilling. The attachment of a small capacity bag also prevents any unwanted external leakage from the valve. This design is compatible with the widely accepted standard indwelling Foley catheter, therefore making it very easy to implement into standard treatment of urinary incontinence.

The late implementation of a twisting mechanism into the design solution allows for greater control of pressure levels as opposed to the original design solution in which pressure levels were predetermined. Using this mechanism, patients can adjust pressure levels based on physiological requirement, time of day, or specific activities. In addition, a twisting motion applied onto the device rather than a squeezing motion greatly reduces the chances of the device opening unintentionally. Performance testing indicated that this twisting and pressure relief mechanism successfully allowed for the release of fluid at critically high pressures while remaining closed at physiological pressures.

The valve’s threaded connector port also leaves room for the future development of additional attachments. For example, the valve cap and the full-sized disposable, expandable bag that were originally considered as design solutions could eventually be developed as optional attachments for the device. These developments could further improve the functionality and practicality of the valve.

Pressure sensitivity could potentially be improved with the use of different liner materials or a reinforced liner. A thicker liner will require more twisting to completely close it. A reinforced liner, such as a double liner or a ribbed liner, will also require more twisting to seal. By increasing the amount of twisting required to close the valve, the patient will be able to better customize the valve pressure sensitivity.


The proposed Urinary Catheter Valve With Pressure Release Mechanism employs the widely accepted method of catheterization, while significantly reducing the health risks and inconvenience associated with it. By replacing a continuously draining bag with a manual valve and introducing a pressure release mechanism, patients may experience improvements in mobility, comfort, and safety. The twisting mechanism for pressure release is effective, simple, and convenient for a patient to use and allows for accurate pressure controls at varying pressure levels. This pressure release mechanism distinguishes the proposed design from existing catheter valves. Appropriate performance testing has proved the functionality of the twisting pressure release mechanism. Furthermore, the valve’s connector port allows for the development and introduction of additional attachments. In conclusion, the proposed device offers a practical approach to managing incontinence while decreasing the discomfort, inconvenience, and health risks associated with the use of an indwelling Foley catheter.


1 “Nerve Disease and Bladder Control”. National Kidney and Urologic Disease Information Clearinghouse 2005. [cited 9/20/2007]

2 Jahn P, Preuss M; et al. “Types of indwelling urinary catheters for long-term bladder drainage in adults”. Cochrane Database of Systematic Reviews (COCHRANE DATABASE SYST REV), 2007(4).

3 Hutton, J. “The role of catheter valves in urinary incontinence”. Geriatric Medicine. 2004 Aug; 34 (8): 16-8.

4 Addison R. Product focus. “Catheter valves: a special focus on the BARD FLIP-FLO catheter”. British Journal of Nursing. 1999 May 13-26; 8(9): 576, 578-80.

5 Munnings L., Cawood C. “Clinical study of a new urine collection bag”. Urologic Nursing. 2003 Aug; 23(4): 287-91.

6 Fraczyk L., Godfrey H.; Feneley R. “A pilot study of users’ experiences of urinary catheter drainage bags”. British Journal of Community Nursing. 2003 Mar; 8(3): 104, 106-7, 110-1.

7 Xiaoyan N. “Observation of effects of disposable plastic urine bags”. Shanxi Journal of Nursing. 1995 Aug; 9(4): 174-5.

8 Wilson M., Coates D. “Infection control and urine drainage bag design”. Professional Nurse. 1996 Jan; 11(4): 245-6, 248-9, 251-2.

9 Keerasuntonpong A., et al. “Incidence of urinary tract infections in patients with short-term indwelling urethral catheters: a comparison between a 3-day urinary drainage bag change and no change regimens. American Journal of Infection Control”. 2003 Feb; 31(1): 9-12.

10 Fultz N, Girts T, Kinchen K, Nygaard I, Pohl G, Sternfeld B. Prevalence, mangament and impact of urinary incontinence in the workplace. Occupational Medicine. 2005;55:552-557.

11. Wilson L, Brown JS, Shin G, Luc K, Subak L. Annual Direct Cost of Urinary Incontinence. America College of Obstetricians and Gynecologists. 2001; 98,3: 398-405.

2 Responses to “Full Report”

  1. Marc Euschen Says:

    Dear project group.

    Has this product been manufactured or reached it’s final engineering stages?

    What about a mechanism to completely Empty urinary blather before the valve seals again?

    Marc euschen

  2. g harper Says:

    Hi was emailing bard about something like this for users of foleys etc that a produce urine in larger amounts/gush opposed to ones that more of a dribble type.
    Has someone like me at night wouldn’t be realy able to use a bag as 1 can’t sleep on my back(more on front to side sleeper) plus turn over/around alot due to spine problem.
    So something like this would be great if like it would stay “sealed”? so to speak but let amounts out say at night when you could wear diaper for instance that would protect you/contain urine but let you go in a managable way thats safer that has some ive read of that have had enough of problem with the pain/sudden urge to urinate at night and have left on freeflow so to speak.
    As for someone like me at i can go from going all the time to not for realy long periods?.i don’t get feeling of bladder filling till late (900mls+)or dribble/leak for no the excersises for it.
    nurse has said about using a foley sometimes and if had something like this would be great esp for in sumertimes when weathers warmer and not so comfortable with inco wear etc with summer clothes.

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