Project: JMS-0212 Enteral Feeding Connector Redesign A Major Qualifying Project Report Submitted to the faculty of the WORCESTER POLYTECHNIC INSTITUTE In partial fulfilment of the requirements for the Degree of Bachelor of Science in Mechanical Engineering By: ____________________ Kushlani Sellahennedige ____________________ Talha Riaz In Collaboration with: Boston Scientific Corporation Date: March 13th, 2012 Keywords: Approved: Enteral Feeding ISO 80369 _________________________ Fluid Connector Professor John M. Sullivan Jr., DE
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Project: JMS-0212
Enteral Feeding Connector Redesign
A Major Qualifying Project Report
Submitted to the faculty of the
WORCESTER POLYTECHNIC INSTITUTE
In partial fulfilment of the requirements for the
Degree of Bachelor of Science in Mechanical Engineering
By:
____________________
Kushlani Sellahennedige
____________________
Talha Riaz
In Collaboration with:
Boston Scientific Corporation
Date: March 13th, 2012
Keywords: Approved:
Enteral Feeding
ISO 80369 _________________________
Fluid Connector Professor John M. Sullivan Jr., DE
I
Abstract
Enteral feeding is an important daily task for a patient that is unable to consume food
orally. Due to user errors and the lack of unique medical connectors, in many situations there
have been cases of misconnections. Some of the misconnections have resulted patient death and
to prevent these situations in the future, the International Organization for Standardization (ISO)
has formulated ISO 80369-1. This describes the guidelines for a small-bore fluid connector
design for enteral applications. The team worked on a variety of design concepts to replace
Boston Scientific’s ‘Endovive Enteral Feeding Replacement’ device and the ‘Low Profile Button
Replacement’ device. These designs were subject to critical design reviews coupled with
augmentations which resulted in a final design with a unique rotatable connector for enteral
feeding. The feeding system has a two layer design attached to the abdomen with a unique
connector that fits and locks into the feeding system. The final design also contains O-rings and
silicon seals that ensure the connector does not leak. Prototypes were built to test the various
designs functionalities.
II
Acknowledgement
This project would not have been successful without the support and guidance of many
contributors. Firstly, the group would like to thank Boston Scientific Corporation for sponsoring
this project. Specifically we would like to thank John Genereux (Manager at BSC) and Professor
Eben Cobb (WPI) for the initial acceptance which made this idea into a MQP project, and their
constant assistance throughout the project.
The team would also like to thank the engineering team at Boston Scientific for all their
help with design reviews and for providing the project team with valuable feedback for
improving the designs. The team is also grateful to Erica Stults (WPI) and the Mechanical
Engineering Dept. (WPI) for their help in manufacturing multiple prototype models which led to
critical design changes.
Finally the project team would like to express their deepest gratitude to Professor John
M. Sullivan (WPI) for his role as the project advisor and providing the team with valuable
feedback and guidance throughout the project. His constructive criticism, supervision and
leadership made this project a success.
III
Table of Contents Abstract ............................................................................................................................................ I
Acknowledgement .......................................................................................................................... II
Table of Contents .......................................................................................................................... III
Table of Figures ............................................................................................................................. V
List of Tables ................................................................................................................................ VI
An additional extrusion was added to the bottom opening of the male component (part 2)
which allowed the valve to be pushed open once it was completely inserted into part 1. Due to
this additional feature, the clearance between the male and female component increased giving
part 2 vertical motion within part 1. This terminated the stability of the design as it added extra
space for motion within the device while feeding is taking place. To counter the stability issue, a
friction grip (part 3) was added to the top surface of the male component (Figure 19) which
could move along the slope and engage with the female component’s roof.
Design 6 - Bucket
The bucket design contained three components. The male component (part 1) had
extrusions that were 144 degrees apart which aligned with the grooves in the part 2 as well as
part 3, giving only one orientation for the initial insertion. Once the first process is completed,
the user rotates the male component (this would be guided by the stopper on part 2) and once it
reaches the stopper on part 3, the ports on all three components align. Therefore, this device is
relatively simple to operate and could be done by the patient using one hand.
24
Overall, only minor changes were made to the bucket design during the Phase 2 design
process. Since most of the functions seemed as intended, a prototype was developed using the
rapid prototyping machine at WPI. This gave the team a better understanding on which aspects
of the design needed further improvements.
Figure 20: Exploded Assembly - Design 6
25
Design Review 2-Analysis of the improved top 3 designs
Design 1 proved to be valid design as it was low profile and performed the required
function in a simple manner. However, there still remained some concerns with the design for
compliance with the ISO standard. First off, once the feeding port (part 1) was aligned with the
base component (part 4), there was no method to actuate the duckbill check valve. The male
component could not perform any vertical displacement due to the addition of part 3. Besides
this, there were no design features that would fix part 1 into the assembly. It should be noted that
locking the male component is very crucial to the design as the back pressure from the stomach
during the feeding process can be disengaged. These issues were worked upon in the next phase
of the project.
The team was also faced with a concern regarding the geometry of Design 3. The
rectangular shape had a considerable height when compared to other designs. Several options
were considered in order to reduce the size and to remove the large clearance between parts 1
and 2. The second concern was the method of removal of the male component once the feeding
procedure is completed. Through brainstorming, it was suggested that the base of part 1 could be
made using a lower density material. Therefore, when the user pushes slightly down on the base
of part 1, it would move downwards relative to the rest of the device, providing little room for
vertical motion for the male component. This procedure would allow the extrusion on part 2 to
release, allowing the user to pull it out of the assembly. Although this concept helped to solve the
problem, it also added on to the complexity of the design because of which it was not considered
for further improvements.
The Bucket model integrated both ease of use and safety layers with comparison to
designs 1 and 3. Part 2 provided the strongest safety feature in this design. It blocked the food
port from being accessible to other devices and it also prevented gas/food coming out from the
patient thus avoiding contact with the device. The design was low profile and therefore was
favorable at the design review meeting. Although the design received merit, there were still some
issues that needed to be improved upon. It was noticed that part 2 was rotatable using any device
that could grip to the side grooves. This was observed while testing the functionality of the
prototype, where the user was able to rotate the middle component (part 2) using their fingers.
This raised a major concern due to the safety standards and the ISO guidelines which contradicts
26
this feature and therefore the issue had to be resolved. The reason for this feature was the lack of
friction between parts 2 and 3 which made the rotation simple. There was also a clearance issue
(similar to that of design 3) allowing the device to have vertical motion.
The team brainstormed ideas on how to overcome the concerns discussed above. Many
different approaches were brought to the table by the engineering team from Boston Scientific
and the project advisor. It was suggested that a ‘pin-spring’ locking mechanism that is only
activated by the male component should be integrated, thus it would eliminate the issue. Besides
this, addition of a handle for easy rotation of the male part, sealing the device for any leakages
and dimensions of all the components was discussed. The next step was to integrate these
modifications into the design and develop a second prototype. By completing this, the team was
able to evaluate the design changes which are discussed under the section ‘Modifications made
on Design 6’.
27
Design Phase 3 and Review- Analysis and Improvement of the Top Two
Designs
Modifications made on Design 1
The final assembly for Design 1 can be seen in Figure 21. All individual parts are labeled
1 through 5 and are referenced throughout the next section.
Figure 21: Design 1 - Exploded Assembly
Based on the discussion during the second design review meeting which was held on the
17th
of November at Boston Scientific Corporation, four different changes were implemented to
design 1 in order to make it compatible with the new standard. The first change was the addition
of two ‘pins’ on the male component (part 1-C). A cut was also made on the lock (part 3) and top
28
sliding part (part 2) of the assembly. The pins function was to lock part 1-C to part 2. Next, a 30
degree rotation of part 1-C provided two different functions; first to allow it to lock with the
assembly and secondly to rotate the lock (part 3) so that the part 2 is free to slide. Parts 1-C, 2
and 3 can be seen in Figure 22 in their initial and final positions respectively.
Figure 22: Left: Subassembly showing the male (1-C), lock (3) and slider (2) components, Top Right: Initial position (lock engaged, male free), Bottom Right: Final position (lock free, male engaged)
A subassembly consisting of three different parts were created for the male component; a
body casing (1-C), spring (1-B) and an inner tube (1-A). The subassembly functioned similar to a
clicker ball-point where the inner tube maintained two different positions. In the initial position,
part 1-A rests on a ‘relaxed’ spring within the body casing (1-C). Once the tube (1-A) is pressed
from the top, it compresses the spring. This allows a plastic strip to clip into a hole and a 0.2 inch
portion of the tube protrudes out of the part (1-C) from the bottom (part 4) (Figure 23). This
extra protrusion pushes open the duckbill check valve when the slider (part 2) is in its final
position. The tube (part 1-A) can then be brought back to its original position by pressing the
side clip on the body casing.
29
Figure 23: Working of the male components of Design 1 (Phase 3)
A complete assembly of the final models and its working prototype can be seen in Figure
24 and Figure 25.
Figure 24: Design 1 Section Views, Initial Position (left), Final Position (Right)
30
Figure 25: Design 1 Prototype
Comments
This design included several layers of safety features allowing only the male component
of this device to be inserted into the female component. This is due to the unique shape of the
male and the female ports. There is an additional locking mechanism which allows the slider part
to move back and forth if and only if the lock is rotated be released. Another important feature is
the push-release mechanism on the male component.
Due to these additional features, overall, this design had a lot of merit. However, there
were also negative aspects that arose from these changes. One being that the device had too
many components. One of the design intents of this project was to keep the design simple so that
it could be used by the patient, doctor or nurse with minimal instructions. This design involved
rotational and transverse motion on the same plane, which makes it difficult to operate as
compared to the other designs where the motions were on different planes. The shape and the
height of the device also raised concern since the device would remain on the patient’s body
underneath their clothing. The device also required the use of both hands for a successful feeding
session.
For the reasons mentioned previously it was decided that design 1 should not be pursued
further. Even with reducing the dimensions of the components to minimize the overall height of
the device, there were still a number of components in the final design which added complexity
for the user. These components could not be taken out from the design as that would allow any
other tube to be inserted into the device, thus forcing a misconnection.
31
Modifications made on Design 6
Based on the reviews and observations made from the prototypes, several changes were
implemented for the device to function with minimal human error. The modified final assembly
is shown in Figure 26.
- A handle was added to the male component
- The length of the extrusion on the bottom surface of the male part was reduced to
minimize the clearance
- A pin-spring mechanism was added to the base component to eliminate the free rotation
of the inner component
- Overall, the dimensions were reduced to make the design more low profile