Developers: Hunter Hutchinson, Jenny Egerter
Advisor: Nancy Lelle-Michel
Supervising Professors: Kevin Caves
Abstract
Proper insulin diffusion is crucial for successful blood sugar regulation in Type I diabetes. Our client has a visual impairment and peripheral neuropathy, meaning loss of sensation, in her fingers as a result of long-term diabetes and required the assistance of a neighbor when managing her diabetes with an insulin pump. We’ve designed an insertion device that allows our client to independently insert her insulin pump’s needle at the proper angle and depth for successful blood sugar regulation.
Introduction
Type I diabetes is a chronic condition in which the body produces little or no insulin, a hormone which is needed to produce energy from glucose [1]. Our client is an older woman who has managed her Type I diabetes for over 60 years. She experiences two common long-term complications of diabetes: visual impairment and slight neuropathy (loss of sensation in her fingertips) [2]. Since the advent of insulin-based diabetes treatment is a relatively recent historical phenomenon, there are only about five thousand individuals in the world who have managed Type I diabetes for as long as our client has [3]. Even though visual impairment and neuropathy are common among individuals who have had diabetes for many years, current diabetes management devices like insulin pumps and needle insertion kits have not been designed with these two complications in mind.
Many steps involved in managing diabetes primarily rely on sight. Because our client has years of experience managing her own care, she is comfortable completing the majority of these steps using strategies she has memorized. However, she currently requires assistance from a neighbor when changing her infusion site every 2-3 days. Specifically, our client needs a way to insert the pump’s needle into her abdomen at the right angle and depth, using her sense of touch and feel alone.
Precise insertion of the pump’s needle is required for successful regulation of blood sugar. If the needle is inserted at too shallow an angle and depth, the insulin will diffuse only through the dermal layer of the skin and will not reach the blood stream. This may result in a dangerous blood sugar spike. If the needle is inserted at too deep an angle and depth, the muscle wall may be dangerously punctured, and insulin will not diffuse properly. Our client needs a solution individually tailored to fit her needs: she is thin, requiring a shallower angle of insertion than the industry standard [4], and she has built up scar tissue in her abdomen, requiring an insertion method that allows her to feel resistance at specific spots and adjust infusion sites accordingly.
Statement of Project Goals
The goal of this project is to develop a method and device that will allow the client to independently insert her pump’s needle at the right angle and depth for proper insulin diffusion. A successful device should be compatible with her patented Medtronic system, should be reusable, and should be able to operate from a left or right orientation as infusion sites are rotated. Lastly, it should be simple to use with slight neuropathy and a visual impairment. A successful design will abide by all of these constraints with the ultimate goal of her inserting the needle into her abdomen for proper insulin diffusion simply and independently.
Design and Development
OVERVIEW
We have created a solution that will enable the client to independently change infusion sites. We designed in Solidworks and 3D printed a device that meets the client’s need to insert her needle at the proper angle and depth without sole reliance on vision. The device is compatible with client’s patented Medtronic pump system, and is made to hold her specific brand of Silhouette needles in place. There are three components to the device: the box, the ramp, and the clip holder. Together, these components give the client greater independence and precision when inserting the needle at a depth of 5-6mm and at an angle of 10°. Multiple client tests have demonstrated that our system enables optimal insulin infusion into the body, as the client’s blood glucose levels after using our device to change infusion sites are consistent with levels she has achieved in the past with the help of a neighbor.
PART I. THE DEVICE
Our device is reusable, can be used from both the right and left sides of the body, and is able to be sterilized with an alcohol wipe before use, following clean technique as specified by current clinical practice [5]. As shown in Fig. 1, the device consists of three main parts: the box, the ramp, and the clip.
THE BOX (printed in grey PLA)
The box holds the ramp and clip, and makes contact with the client’s abdomen. It has thumb grips to ensure easy placement on the abdomen and minimizes rocking so that the 10° angle is not compromised. The box also has guards to make sure that the needle is only slid the proper distance of 6mm, and there are rails on the sides to make sure the ramp will stay in place when used vertically on the plane of the abdomen. As per the client’s request, the box also has extended arms to provide added stability when used.
THE RAMP (printed in black PLA)
The ramp part of the device slides along the box to insert the needle at the infusion site of choice. The ramp is fashioned at a 10° angle so that the needle is inserted according to the client’s specifications. It has a raised ellipse-shaped guard that fits with the client’s specific brand of Silhouette needles and holds the needle in place from the back.
THE CLIP HOLDER (printed in red PLA)
Next, the red clip twists to hold the needle in place from the top and has a knob for the client to hold while pushing the ramp a distance of 6mm. The clip is printed in a bright contrasting color of PLA plastic so that the client can easily distinguish between the different parts of the device. The needle clip rotates on and off the needle for easy device removal once the needle has been inserted and the first half of the needle’s adhesive has been secured to the abdomen.
Figure 1. Prototype consisting of the box, the ramp, and the clip.
Evaluation
The device was evaluated against the design specifications and performance criteria, specifically looking at angle and depth of insertion, durability, ease of use, sterilization, and consistency. This consisted of verification testing by the designers without the client and validation testing with the client using the device to insert her needle. Many safety and hazard tests were performed outside of testing with the client to ensure minimal risk during use. All BSI standards were evaluated, such as dropping tests, and were deemed successful. Multiple tests with the client have demonstrated that our system enables optimal insulin infusion into the body. Our client has used the final device over 15 times in a 6 week span and is able to insert the needle easily into multiple sites of her abdomen. She has tested the device both with the assistance of a neighbor and completely by herself with successful blood sugar levels, indicating that the correct angle and depth was reached. Additionally, when asked a series of questions about the ease and design specifications in a client satisfaction survey, the client’s average response was a 9.5/10 (with 10 being “very satisfied”) and testified that it fit her needs.
Discussion and Conclusion
The components of our device come together to produce a successful insertion device that fully complies with all design constraints and criteria. Each component is designed to take into account the client’s visual impairment, neuropathy, and desired conditions for angle and depth of insertion. The final device has been used for over six weeks and the client’s blood sugar has remained normal. This design provides our client with an insertion device that overcomes many issues with current insertion products on the market, such as difficulty to use with motor and visual impairments and inserting at too deep of an angle and depth for our client. Our device has allowed our client to insert her needle at a consistent angle and depth and has allowed her more independence in her diabetes management care process.
REFERENCES
[1] Type I Diabetes. (2017). Retrieved Feb 21, 2017, from http://www.mayoclinic.org
[2] Long-Term Complications of Diabetes. (2017, Feb 7). Retrieved Feb 8, 2017, from https://medlineplus.gov
[3] N. Lelle-Michel, personal communication, Jan 16, 2017.
[4] Inset 30 Infusion Set. (2014). Retrieved Feb 13, 2017, from https://www.animascorp.co.uk
[5] Continuous Subcutaneous Insulin Infusion: Practical Issues. (2012, Dec 16). Retrieved Mar 8, 2017, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3603042/