Automated Syringe Dosing - University of Wisconsin–Madisonhomepages.cae.wisc.edu/~bme400/asd/documentation/Final... · 2005-05-05 · 2. Wash medicine bottle top with cotton ball

Automated Syringe Dosing

Hanson, E.E., Weisshaar, C.L., Wentland, A.L.

BME 402 Department of Biomedical Engineering

University of Wisconsin-Madison May 4, 2005

Advisor

Willis J. Tompkins, Ph.D., Professor Department of Biomedical Engineering

Abstract

Many people, especially elderly individuals, have afflictions along with diabetes, including poor

eyesight, tremors, loss of dexterity, arthritis, multiple sclerosis, and other neuromuscular

disorders. These disabilities make it difficult for patients to measure and administer medications

with a syringe. We have developed a device that electronically drives the plunger on a standard

syringe, reducing the dexterity normally needed with dosing a syringe. We have constructed a

prototype that demonstrates the feasibility of driving the syringe on a screw-based system with a

bimodal stepper motor. We have begun to program a microprocessor for controlling a keypad,

motor, and digital display.

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Table of Contents Page

Abstract 1 Table of Contents 2

Problem Statement 3

National Student Design Competition 3

Schoofs Prize for Creativity 3

Background 4

Current Products 6

Contacts 7

Design Constraints 7

Design Approaches 8

Design Evaluation 10

Our Chosen Design 11

Syringe Dosing Device: Operation 12

Prototype 13

Construction of the Prototype 13

Syringe Dosing Device: Advantages 15

Syringe Dosing Device: Disadvantages 15

Syringe Calibration and Preliminary Testing 16

Schoofs Prize for Creativity: Claims and Marketing Information 17

Smaller Motor 19

Microprocessor 20

Future Work 23

Ethical Considerations 23

Conclusions 24

References 25

Appendix A: PDS 28

Appendix B: Expenses 32

Appendix C: BASIC program for counting zero through nine 33

Appendix D: Master BASIC program for the design 37

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Problem Statement

Our goal is to develop a syringe delivery device that uses standard 1 cc syringes (BD

Ultra-FineTM Needles [1]) and sets the dosage on those syringes within 0.01 cc accuracy. This

device should minimize the dexterity typically needed with dosing a syringe, along with being

easy to use for elderly patients and those with poor eyesight. Ideally, this machine is geared

towards patients who use syringes on a daily basis, such as those diagnosed with diabetes.

Patients afflicted with maladies in addition to diabetes, such as neuromuscular disorders and poor

eyesight, would also benefit greatly from this device.

National Student Design Competition

This project is part of the 2004-2005 National Student Design Competition, an

undergraduate competition funded by the Rehabilitation Engineering Research Center on

Accessible Medical Instrumentation [2]. In conjunction with Marquette University, Professor

John Enderle of the University of Connecticut chairs the competition. The competition is open

to students predominantly in biomedical engineering and industrial design. In the 2004-2005

competition, student teams have a choice of three projects: a weight scale, a syringe dosing

device, or an ergometer, all to assist patients of diabetes, obesity, paralysis, and neuromuscular

disorders. At the University of Wisconsin – Madison, another team is working on an ergometer

[3] while our team is working on a syringe dosing device.

Schoofs Prize for Creativity

The team also chose to participate in the Schoofs competition. Part of this competition

incorporated market research to develop a marketing plan. As part of this research, we

determined the market, insurance costs and coverage, and future prospects for this type of a

device. Marketing research will be provided later in this paper.

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Background

Diabetes is one of the leading causes of disability in the United States, causing dementia,

low testosterone levels in males, excessive thirst, frequent urination, fatigue, changes in vision,

blindness, stroke, nerve damage, and the need for amputation [4, 5]. Diabetes is typically treated

with insulin injections, where the amount of insulin is determined by eating habits, exercise, and

ultimately a patient’s blood glucose level. While the changes in vision make it difficult for

patients to see and set the dosage on the syringe, elderly diabetes patients commonly acquire

neuromuscular diseases, albeit unrelated to diabetes. Nevertheless, these diseases make it

difficult for patients to control syringes.

Type 2 diabetes is the most common form of diabetes, affecting 18.2 million people in

the United States alone. This type is found in 90-

95% of the diabetes patients [6]. Those most often

afflicted with this disease are older people. The

Center for Disease Control [6] has predicted that the

number of American diabetes patients will increase

as Baby Boomers grow older and more sedentary.

Type 2 diabetes is characterized by a high blood

glucose level, a high insulin level, and a resistance

to insulin (Figure 1). Contrary to type 1 diabetes,

where insulin does not get produced in proper quantities, type 2 diabetics cannot use their insulin

effectively [5].

A person with diabetes must take daily precautions to maintain optimal health. These

include healthy eating, exercise, and blood glucose testing. Blood glucose testing will tell if the

Figure 1. Type 2 Diabetes. In this disease, users develop a resistance to insulin, and therefore, blood glucose levels rise [7].

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blood sugar levels are too low (hypoglycemia) or too high (hyperglycemia) [4]. Irregular blood

sugar levels can cause illness, dizziness, nervousness, confusion, fainting, and/or impaired

judgment [4]. Depending on the blood sugar level, insulin may be administered.

The injection procedure should be done as recommended by an endocrinologist and is as

follows [8]:

1. Wash hands and area where injecting (usually a fatty subcutaneous tissue area such as the stomach).

2. Wash medicine bottle top with cotton ball and alcohol.

3. Draw air into the syringe equal to the volume of fluid needed.

4. Insert needle into medicine bottle and depress plunger, pushing all air out of the syringe. This action creates a vacuum and allows for easier and smoother filling and delivery.

5. Invert medicine bottle and fill syringe, making sure the needle is not exposed to air.

Air bubbles in the barrel will lead to an incorrect amount of medication.

6. Once the syringe has been filled to the proper amount, keep the bottle and syringe upside down and flick the syringe barrel. This moves air bubbles that may have formed at the top of the syringe.

7. Push the plunger to move the air bubbles into the vial.

8. Check medication dosage.

9. Insert needle into skin at a 90-degree angle and deliver medicine at a slow, steady rate. All medication should be released within 5 seconds.

10. Dispose of needle properly.

It is evident that this is a complicated and involved procedure, requiring a fair amount of

dexterity in controlling the syringe and perspicacity in detecting bubbles. This process should be

simplified for the elderly and individuals with neuromuscular disorders and/or poor vision.

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Current Products

Research was done on current devices available to diabetes

patients. Most diabetes patients administer insulin using either an

insulin pump or a syringe. An insulin pump, like the Medtronic

MiniMed [9] (Figure 2), provides a constant supply of fast-acting

insulin throughout the day [10, 11]. Additionally, the device must

be programmed to accommodate eating and exercising habits.

While an insulin pump provides many advantages in terms of convenience, flexibility, and

accuracy, the pump also has some drawbacks. Many patients do not enjoy having a pump

attached to their body. Older patients are often wary of the new, computer-driven technology

and don’t want to feel attached to a device. There are still many users of syringes. However,

proper syringe operation requires concentration, dexterity, and good eyesight.

Many currently available devices assist in administering the medication, not setting the

dosage. Owen Mumford offers a product called the Autoject 2 [12]. To use this device, the user

fills the syringe to the proper level and places the syringe inside the Autoject 2 (Figure 3). With

the touch of a button, a spring pushes the syringe into the patient and administers the medication.

The device does not assist the patient in

filling the syringe. Consequently, the device

does not increase the accuracy of the dosage

or compensate for the user’s disabilities to a

significant degree.

Another device that assists the user is the Novo Nordisk NovoPen® [13] (Figure 4). The

device uses cartridges of insulin and disposable needles. The NovoPen® itself is disposable after

Figure 2. Medtronic MiniMed insulin pump. A user programs this device to deliver fast-acting insulin based on the diet and activity of the user. [9]

Figure 3. Autoject2 syringe device by Owen Mumford [12]. This device assists in injection, but does not assist in setting the dosage on the syringe.

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a month or when the cartridge is empty, whichever occurs first. The

device is used by clicking the top for each unit of insulin. While

patients find this easier to use than a syringe [14], it still takes a fair

amount of dexterity to click the device, and particularly to not

overshoot the desired dosage. Furthermore, if the user needs a

large dosage, the device would require a lot of clicks, making it

cumbersome and liable to losing count.

Contacts

We have accumulated a few contacts concerning different aspects of our project. They

are listed below:

1) Missy Midbon [11] – UW student; diabetes patient using a Medtronic MiniMed pump.

2) Kara Yaeger [15] – diabetes educator and nurse.

3) Doug Haist [14] – a 79-year (2004) old diabetes and Parkinson’s disease patient.

4) Bern Jordan – a graduate student in the Trace Center familiar with universal design.

5) John Puccinelli – a biomedical engineering graduate student with diabetes.

The evolution of our design and first prototype is described below.

Design Constraints

On average, the device will be used twice daily with slow-acting insulin and several more

times with fast-acting insulin to accommodate the eating habits of the user. The device should

function for at least five years under normal use. The device will be designed to accommodate

BD UltraFineTM II 1 cc syringes, which have 80% of the market share [16]. Furthermore, the

device should be easy to use for people with poor eyesight, dexterity, and fine motor control.

Figure 4. Novo Nordisk NovoPen®. This device uses insulin cartridges. The dosage is set by clicking the device for each unit desired. [13]

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Creating a syringe dosing device with universal design in mind is a very important aspect

of this project. The device must be small and portable, yet have features accommodating

presbyopia and individuals with poor neuromuscular control. The device should be easier to use

than the NovoPen® and reduce the amount of interaction a patient has with syringes.

Should a user, and not an insurance company, pay for the device, the device should be

inexpensive, especially compared to the price of insulin pumps (>$5,000). We would like the

design to sell for between $300-$500, with manufacturing costs between $150-$200.

Please refer to Appendix A for our Product Design Specifications, a list of requirements

particular to our final design. See Appendix B for a list of this semester’s expenses.

Design Approaches

We brainstormed two major methods in which we could design a syringe dosing device.

One such way was to have a device that not only controls the syringe, but also an insulin bottle at

the same time. A device like this would be prohibitively large to be considered portable and is

therefore described in the Tabletop portion of this section. Another way of designing the device

would be to control the syringe alone and let the user continue to control the insulin bottle. This

device would be portable and is therefore described in the Portable portion of this section.

Tabletop

With a tabletop device, a user inserts an

insulin bottle and a syringe into the device

(Figure 5). A user would then type in the

needed dosage of insulin. This input will trigger

the microprocessor to move the syringe towards

Figure 5. Tabletop syringe dosing device. The device can hold an insulin bottle and syringe, where a user types in a dosage, the syringe itself moves into the insulin bottle, a motor pulls the plunger of the syringe backwards to draw fluid, and the syringe moves back into its starting position. [17]

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the insulin bottle, then to run a motor that pulls the plunger of the syringe backwards, drawing

fluid into the insulin chamber of the syringe. With that process complete, the syringe will move

back to its starting position where it can be taken out of the device. A user would then remove

the syringe and inject the insulin into the body without assistance.

Advantages: Completely eliminates the dexterity needed to dose a syringe and control an

insulin bottle at the same time.

Disadvantages: This design is not portable and provides no assistance in pushing the

plunger while also inserting the needle into the body. Pushing the plunger for injection takes a

fair amount of dexterity because the thumb must be used while also holding the syringe in place.

The authors acknowledge that it would be possible to combine this device with the Owen

Mumford Autoject 2 to assist in the injection.

Portable

A portable device would be useful for all users. While users claim that it is difficult to

hold an insulin bottle at the same time as holding the syringe [14], the difficulty truly arises when

a user needs to hold the bottle but also maneuver the plunger of the syringe at the same time.

Our supposition is that a user would have no trouble holding an insulin bottle and a device at the

same time, because only a single button would need to be pressed on the device. Therefore, one

hand would hold the bottle while the other would hold the device, pressing a button to cause the

plunger to draw fluid into the chamber of the syringe.

Below are two methods of controlling the plunger of a syringe in a portable device.

Hydraulics-driven: In a hydraulics-driven design, a piston would be connected to the

plunger of the syringe (Figure 6). This piston would be controlled by a hydraulic pump, which

in turn is regulated by a control device, e.g. a microcontroller. While this device would provide

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plenty of power for controlling the syringe, it may be difficult to fit all of

the components in a portable device without making it prohibitively

expensive.

Motor/screw-driven: In a motor and screw-driven design, a

bracket would be attached to the plunger. This bracket would translate

along a screw that rotates according to a motor with or without gears.

While this design doesn’t provide as much power as a hydraulics

system, it would be considerably cheaper to build. It would also be

easier to fit this design into a small portable device. (Please see Figure 8

in Our Chosen Design for a representation of the motor/screw-driven system).

Advantages: The authors consider the portability of this design to be very advantageous.

Setting the dosage on a syringe could then be done anywhere and would not rely on the location,

such as the tabletop design.

Disadvantages: The fact that the user still needs to hold the insulin bottle is a noteworthy

flaw in the design, but is considered outweighed by portability.

Design Evaluation

To determine whether to design a tabletop or portable device, we constructed a design

matrix to quantitatively assess the two categories (Table 1). Although this matrix gives equal

weight to all of the criteria, cost and portability are the most important factors. Nevertheless, the

handheld device achieved a lower score than the tabletop design (where a lower score is more

desirable). Qualitatively, a portable device would be more useful, as it provides assistance in any

environment. However, it must be noted that we still suppose that users will not have trouble

holding a device and insulin bottle simultaneously.

Figure 6. A hydraulics-driven plunger. The plunger of the syringe is controlled with a piston. [17]


Table 1. Design matrix evaluating handheld and tabletop designs, where a lower score is desirable and each criterion is evaluated on a scale of 1-3. Handheld Tabletop Portability 1 3 Cost 1 2 Ease of Use 1 1 Accuracy 1 1 Total 4 7

To determine whether to control a syringe in a handheld device with a hydraulics-driven

system or a motor/screw-driven system, we constructed a design matrix to quantitatively assess

the two designs (Table 2). Although the matrix gives equal weight to all of the criteria, cost and

simplicity are the most important factors. Nevertheless, the motor/screw-driven design achieved

a lower score than the hydraulics-driven system (where a lower score is more desirable).

Qualitatively, a motor/screw-driven device will be much simpler to construct than a hydraulics-

system.

Table 2. Design matrix evaluating hydraulics-driven and motor/screw-driven designs, where a lower score is desirable and each criterion is evaluated on a scale of 1-3. Hydraulics-Driven Motor/Screw-Driven Cost 3 2 Simplicity 2 1 Reliability 2 1 Size 2 1 Strength 1 2 Total 10 7

Our Chosen Design

Based on the criteria we used to evaluate our designs (Tables 1 & 2), we chose to design

a portable device driven with a motor/screw system (Figure 7). A key factor in choosing this

design was that it not only satisfied the requirements of the National Student Design

Competition, but that it will be easy to manufacture. Additionally, the mechanical components

of the device are very cheap. The operating steps of this device are provided in the following

section.


Syringe Dosing Device: Operation

Taking the normal procedures to sterilize a syringe, a user will insert the syringe into our

device. The syringe is held in place with collapsible brackets (Figures 7 & 8, shown in red); the

plunger of the syringe will fit into a bracket. The user will then use the numeric keypad to type

in the dosage, pressing Enter when complete. The digital display (top of Figure 7) will instruct

the user to insert the needle into a bottle of insulin. Having done so, the user will press a Fill

button located on the right side of the device (not shown in Figures 7 & 8) where a user’s thumb

will typically be located. This button will cause the motor to run and the bracket to pull on the

plunger, therefore drawing fluid into the chamber of the syringe. The digital display will notify

the user when the process is complete. The display will then instruct the user to insert the needle

into the body. Having done so, the user will press the Inject button located adjacent to the Fill

button. This button will cause the motor to run in the opposite direction as before, therefore

pushing on the plunger and expelling the fluid. Again, the user will be notified when the process

is complete.

Figure 7. 3D model of our final design. A syringe can be inserted into the device with the plunger controlled by a motor. The interface includes a numerical keypad for setting the dosage on the syringe. [18]

Figure 8. 3D model of the inner components of our final design. As shown, a screw is attached to a motor. A bracket translates along this screw to move the plunger simultaneously. [18]


Prototype

The fall semester was devoted to constructing a large-scale model of our design,

mastering its mechanics and feasibility. This prototype was constructed without regard to

dimensions and is therefore much larger than a portable device. As a note: the specific

dimensions of our chosen design (Figure 7) have not been determined. Roughly, the device will

measure the length of two syringes (~10”) and have a diameter that fits in the palm of the hand

(~3”). The exact dimensions of the final prototype will be determined when the device is

dimensioned with CAD.

Construction of the Prototype

Figure 9. Picture of our constructed prototype. Annotations are shown for the description below. This model includes a syringe with its plunger controlled by a bracket. This bracket translates along a screw based on the direction the motor is turning. The motor is controlled by a PC with the shown microcontroller. [19]

The long base platform (Figure 9 – 1) and syringe support block (Figure 9 – 2) both

began as large pieces of kiln-dried carving wood. A table saw and band saw were employed to

cut the pieces to the desired dimensions before they were sanded and stained. General purpose

cement was then used to bond the pieces together. Next, the syringe (Figure 9 – 3) was mounted

to the support block using two brackets (Figure 9 – 4) purchased at a local hardware store. With

the syringe affixed, attention was turned toward the screw and its supports.


Two screw supports (Figure 9 – 5) were machined from a block of scrap wood using a

drill press, band saw, and an electric powered sander. Wood was chosen instead of other

materials such as steel or aluminum due to the ease at which it could be machined. The supports

were mounted to the base platform using cement. The threaded rod (Figure 9 – 6) was selected

from an assortment of small diameter threaded rods at a hardware store. One end of the rod was

cut to the desired length and filed flat.

The bracket (Figure 9 – 7) that holds the syringe plunger was machined from a small

block of aluminum. This material was chosen because a high degree of precision was required

for this part and a threaded hole needed to be cut into the piece to accept the threaded rod. An

end mill was used to machine most of the piece geometry. A drill press and a tap were used to

create the threaded hole.

The two-phase step motor (1.8°/step) and controller circuit (Figure 9 – 8) were purchased

as a kit from online [20]. The kit also included the software required to control the motor from a

personal computer. The motor was mounted to the base platform using a pair of L-shaped

brackets, screws, and bolts (Figure 9 – 9). A small block of wood (Figure 9 – 10) also was

mounted under the motor to provide additional support. The controller circuit was affixed with

contact cement. Following the instructions that came with the kit, the motor was wired to the

controller.

The last piece of the prototype to be constructed was the sleeve (Figure 9- 11) that would

mechanically link the shaft of the motor to the threaded rod. A small section of aluminum rod

was machined with a lathe. A hole with a diameter slightly larger than the diameter of the motor

shaft was drilled halfway into the rod, along the centerline. Another hole, matching the diameter

of the threaded rod, was drilled through the other end of the sleeve to connect the two holes. A


pair of set screws, placed in threaded holes, was used to apply pressure to the shafts and ensure

that a snug fit was obtained.

Overall, the construction of the prototype was relatively straightforward. A fair amount

of machining was required but it was accomplished without much difficulty.

Syringe Dosing Device: Advantages

The motor/screw prototype has a number of advantages over other designs. First of all,

using a two-phase step motor with a step size of 1.8° offers a high degree of accuracy. The step

size is sufficiently small enough to reach the level of accuracy required for the design

competition. The second advantage to this design is that the design itself and the underlying

principles of its operation are very straightforward. While sufficient testing has yet to be done,

the design has shown early indications that it will be quite accurate. A final advantage is that the

final prototype will be very user friendly. All of the complexities of the device will be out of

sight. The user will interface with the device solely through a simple keypad with feedback

provided by a series of LEDs. It is our goal to make the device as user friendly as possible.

Syringe Dosing Device: Disadvantages

While the prototype has many advantages, the design has a few drawbacks as well. One

of the major disadvantages is that the motor and other electrical components will require a

significant power supply. Motors in general require relatively high start-up current. Since the

device is to be portable, the power must come from a battery source. This is a concern due to

obvious spatial limitations. Another disadvantage to the device is that the motor creates some

degree of noise and vibration. Proper motor selection should minimize this problem. Finally, the

cost of the device has the potential to be high. The motor and the microprocessor could drive the


price of the final prototype up, making the device unaffordable to a sufficient group of the

expected users. Again, motor selection will be crucial to ensure that this is not a major issue.

Syringe Calibration and Preliminary Testing

A microprocessor will control

the motor and determine how long it

needs to run for a given dosage. It is

therefore important to determine if the

syringe is approximately linear.

Calipers [21] were obtained to

measure the distance the plunger

moved from a baseline for every ten

units of the syringe. These

measurements were performed along the

length of the syringe, for all 100 units,

and repeated three times. A linear regression was performed showing approximate linearity,

with 0.224 inches between every ten units of the syringe and an error of +/- 0.00049 inches.

Since the motor moves in steps of 1.8°, there are 200 steps/revolution. It was discovered

that approximately 300 steps of the motor correspond to the plunger moving the length of 1.06

units on the syringe. Since we can control the motor to the step, the system will be easily within

the accuracy of 1 unit.

Figure 10. Linear regression of the average distance the plunger moves for every ten units on a 1 cc syringe. These measurements were made along the length of the syringe and repeated three times. The average distance between 10 units was 0.224 +/-0.00049 inches; R2 = 0.99. [22]


Schoofs Prize for Creativity: Claims and Marketing Information

The first half of the spring 2005 semester was devoted towards market research and

developing a preliminary disclosure paper.

Claims

In disclosing our design for patent submission, we make the following claims:

1. An automatic syringe wherein said apparatus is handheld and portable. 2. The invention as defined in claim 1 wherein said device is powered by stepper motor. 3. The invention as defined in claim 1 wherein said device automatically measures medicine

by pressing numbers on a keypad. 4. The invention as defined in claim 1 wherein said device is more intuitive than insulin

pumps. 5. The invention as defined in claim 1 wherein said device shows a digital display of the

medication to be administered, offering a visual user interface. 6. The feature as defined in claim 5 will not be necessary for operation and said device will

include tactile and auditory clues. 7. The invention as defined in claim 1 wherein said device is accurate to 0.01 milliliter,

offering better accuracy than a person or other marketed devices. 8. The invention as defined in claim 1 wherein said device requires minimal dexterity. 9. The invention as defined in claim 1 where said device assists users with poor vision,

users with poor motor control, and users who need assistance injecting the fluid into the body.

Marketing Information

Our product will be marketed towards persons who have difficulties with fine motor

skills and who also have the need to accurately administer medication via a syringe. These users

will most likely be 65 years or older and have some sort of chronic illness, such as diabetes. In

2002, 12.4% of the U.S. population was represented by the 65 and older age group. This group

represented 40% of the total healthcare costs [23]. The U.S. Census Bureau expects this age

group to expand to approximately 17% of the population by 2020, due to the presence of the

baby boomer generation [24]. Because our product is designed mainly for consumers in this age

group, there is a favorable future for marketing our product. In addition, the World Health

Organization expects the prevalence of chronic disease (such as diabetes) to increase due to


unhealthy lifestyles [25]. A product that seeks to aid patients suffering with diabetes or other

illnesses that require daily injections would therefore be increasingly necessary.

In addition to an expanding market for our product, there are also pricing trends within

the medical industry that are favorable. Overall pricing in the U.S. medical product industry will

remain competitive in future years [23]. Furthermore, the American population of peoples over

age 65 is 34,974,000 [24]. With 1% of Americans over 65 having Parkinson’s disease [26] and

18.37% of Americans over 60 having diabetes [27], an estimated 0.18%, or 62,247 people, have

both diabetes and Parkinson’s disease, and therefore, desperately need assistance. These

statistics exclude the numerous people with poor eyesight that need assistance with syringes. It

also excludes nurses and doctors who could appreciate the accuracy the device provides.

Although entry into the medical products industry is difficult due to many barriers of

entry and government regulations, our device’s classification as a Class I [28] medical device is

advantageous. Our automated syringe dosing system poses little patient risk and therefore

requires less government approval than Class II or Class III devices. Before manufacturing our

device we would need to register with the FDA, notify the FDA 90 days before any marketing

campaigns, and uphold good manufacturing practices [28]. Endorsement by a major medical

corporation would be necessary for competitiveness, manufacturing, and advertisement.

While the Minimed pump costs $6,195 [29], the Owen Mumford Autoject 2 costs $32.99

[30], and the Novopen costs $31.99 [31], we estimate our device to cost around $300, with $100-

200 being at cost. Initial costs are high due to the need for a small motor, the keypad, and the

circuitry involved. While this price may seem expensive compared to the Autoject 2 and the

Novopen, our device is much more accurate and vastly aids the user over these devices.


Our device is much less expensive than a pump. Pumps are typically covered by

insurance companies and Medicare [15]. Should our device achieve corporate sponsorship, it

would be a good alternative to any patient wary over using pumps and a strong alternative to

insurance companies who would appreciate the lower cost. Furthermore, our device will be less

prone to wasting medication than a person using a syringe alone. Initial costs may be high for

our device, but saving medication may allow patients to come out ahead in the long term.

Smaller Motor

The team began designing a prototype with a smaller motor. This motor provides

7.5°/step, which has a significantly reduced resolution from the previous motor. However,

granted the excessively high resolution of the larger motor, as shown in Figure 9, resolution can

be sacrificed to get a smaller motor and yet still yield the required accuracy of 0.01 cc.

The bipolar motor purchased came with a controller kit [32], which the team constructed

and soldered. Time ran out in the spring 2005 semester, preventing the team from incorporating

this motor into the prototype with a new fitted sleeve (Figure 9 – 11). The motor and its

controller, along with the electronic connections, are shown in Figures 11 and 12, respectively.

Figure 11. LNS Technologies motor and our soldered controller circuit for this bipolar stepper motor [32].


Figure 12. LNS Technologies bipolar stepper motor controller circuit diagram with wiring [32].

Microprocessor

In the second half of the 2005 Spring semester, our team began working on the

electronics side of the project. Using a microprocessor kit [33], we taught ourselves how to

program a BASIC Stamp 2 embedded system using PBASIC 2.5. Our first program was a lesson

in using a push button and a seven-segment LED. Each time the button was pressed, the LED

was increment by one. A later version of the code included a sound chip that would beep upon

the LED displaying ‘nine.’

The seven-segment LED button works by using a different pin from the microprocessor

for each segment. In the code, you can light up a segment with ‘HIGH A,’ where A is the pin

number corresponding to a segment on the LED. Subsequently, a segment can be turned off with


‘LOW A.’ Programming the push button uses a ‘listening’ technique, where a loop cycles every

fourth of a second to see if a signal came through in the microprocessor pin linked to the button.

In the code at hand, a signal from the push button would instruct the seven-segment LED display

to increment one number, where the number to be displayed was determined with a counter. The

actual process of displaying a number worked by using the ‘GOSUB B’ command, which calls a

function B. A function was used for displaying each number, with each

function setting the appropriate pins HIGH and the appropriate pins LOW

from the previous number displayed on the LED. When the number ‘nine’

was reached, the sound chip would beep with the following code,

‘FREQOUT p, t, f,’ where p is the pin number, t is the length of time, in

milliseconds, for the beep to occur, and f is the frequency of the sound.

This code is provided in Appendix C.

The team attempted to incorporate

a numeric keypad [34] and a digital

display, but ran out of time. We ordered a

keypad (Figure 13) and began to

understand the coding, which is described

in Figure 14. Furthermore, we ordered a

10-digit length LCD display, which is

much bigger than desired for a final

device, but was used to begin learning

the programming aspect of the display.

Figure 13. 12-key numeric keypad with ten pins, programmed in a matrix format

Figure 14. 10-pin matrix format of a 12-key keypad [34].


Further programming of the microprocessor will need to include error handling for the

following situations (Figures 15 and 16).

Figure 15. Microprocessor Error Handling Flow Chart. If the user realizes that he or she entered an incorrect dosage during the filling or injecting stages, the user can stop the device and start over.

Figure 16. Microprocessor Error Handling Flow Chart. If the user realizes that he or she entered an incorrect dosage before filling, the user can press clear and re-enter the correct dosage.

The first flow chart (Figure 15) demonstrates the path followed by a user who realizes an

input error before the filling stage. The device allows the user to clear the entry and restart the


process. The second flow chart (Figure 16) demonstrates the path followed by a user who

realizes an input error during the filling or injecting stage. The user can stop the syringe’s

current action and view the current volume. The user would then decide the appropriate course

of action.

The team also worked on a master code that would be used in the final product. This code

begins to handle every aspect of the design, including the motor, display, and keypad buttons.

Error-handling is scant at this point. This code is provided in Appendix D. Please note that the

actual code is not meant to work with all components because it doesn’t, for example, include the

proper coding for controlling a motor. This code is meant to outline the true program to be

uploaded onto the microprocessor.

Future Work

Future work includes finishing the microprocessor program, incorporating the coding of

the keypad and digital display (seven-segment LEDs). Further construction is needed to house

the microprocessor and motor in a small compartment. Finally, the team has until 12/3/06 to file

a patent disclosure, which will be done through the Wisconsin Alumni Research Foundation

(WARF).

Ethical Considerations

Delivery of the incorrect amount of insulin or other medication could be very dangerous.

Consequently, there must be a way for the patient to easily check that the correct amount of

medication is being administered, and most importantly, that there are no bubbles in the chamber

of the syringe. Even though the chamber of the syringe will be openly exposed, the patient with

poor eyesight will be unable to check for bubbles or an incorrect dosage. If a mechanism was


used to detect these errors, such as a laser checking the passage of light along the length of the

syringe, the device would become prohibitively expensive.

Conclusions

Our team has proposed a device that is beneficial to diabetes patients, particularly those

with poor motor skills and/or poor eyesight. The device aids patients in measuring and

administering medication via a syringe. It would be competitive in the current market and more

so in the future with this expanding market. Compared to current products, the device is an

attractive alternative to both patients and insurance companies.


References

[1] BD Diabetes. BD Ultra-FineTM Insulin Syringes. http://www.bddiabetes.com/us/product/thin wall_consumer.asp. 2004. [2] RERC-AMI. 2004-2005 National Student Design Competition. http://www.rerc-ami.org/rerc ami/r2d2/d22-yr2.htm. 2004. [3] Swift, J., Mehta, A., Millin, J., Poper, R. National Design Competition: Ergometer. http://ww w.cae.wisc.edu/~bmedesgn. 2004. [4] Medline plus: National Library of Medicine. Diabetes tutorial. http://www.nlm.nih.gov/med lineplus/tutorials/diabetesintroduction/id029102.html. 2004. [5] Medline plus: National Library of Medicine. Diabetes. http://www.nlm.nih.gov/medlineplus /diabetes.html. 2004. [6] Center for Disease Control. Diabetes: Frequently Asked Questions. http://www.cdc.gov/diab etes/faq/index.htm. 2004. [7] Health. Diabetes Symptom. http://www.diabetes-immune-system.com/. 2004. [8] NIH Clinical Center. Giving a Subcutaneous Injection. http://www.cc.nih.gov/ccc/patient_ed ucation/pepubs/subq.pdf. 2004. [9] Medtronic. MiniMed. http://www.minimed.com/. 2004. [10] Canadian Diabetes Association. Insulin: Things you Should Know. http://www.diabetes.ca/S ection_About/insulin2.asp. 2004. [11] Midbon, Missy. Diabetes patient interview. 9/10/04. [12] Owen Mumford. Autoject 2: Self injection made simpler…http://www.owenmumford.com /autoject2.html. 2004. [13] Novo Nordisk. NovoPen® 3 – An unsurpassed range. http://www.novonordisk.com/diabete s/public/insulinpens/novopen3/default.asp. 2004. [14] Haist, Doug. Diabetes and Parkinson’s disease patient interview. 10/06/04. [15] Yaeger, Kara. Diabetes educator and nurse interview. 09/14/04. [16] BD. Prefilled Syringes Brochure. http://www.bd.com/pharmaceuticals/products/BDPS_bro chure.pdf. 2004. [17] Wentland, A.L. Drawn in Deneba Canvas 9.0.3. 2004.


[18] Lienau, W. of Flite Productions, Madison, WI, USA. Drawn and rendered in 3D Studio Max. 2004. [19] Wentland, A.L. Picture taken with a 5.0 MegaPixel EasyShare DX4530 Kodak Camera. Annotations constructed in Deneba Canvas 9.0.3. 2004. [20] Stepper World. MS-1 Microstepping Motor Control Project: Advanced Microstepping Control. http://www.stepperworld.com/. 2004. [21] Enco. Enco Vernier Calipers. 2004. [22] Wentland, A.L. Linear regression using Matlab Student ed. 6.5. 2004. [23] Healthcare Products & Supplies Industry Survey: Industry Trends. Standard & Poor’s Industry Surveys. Sept. 23, 2004. [24] US Census Bureau. Percent Distribution of the Population by Age: 1990 to 2050. http://www.census.gov/prod/1/pop/p25-1130/p251130b.pdf. 2005. [25] World Health Organization. Obesity and Overweight. http://www.who.int/hpr/NPH/docs/ gs_obesity.pdf. 2005. [26] Center for Disease Control. National Center for Health Statistics: Data on Parkinson’s Disease. http://www.cdc.gov/nchs/data/factsheets/Parkinsons.pdf. 2005. [27] American Diabetes Association. National Diabetes Fact Sheet. http://www.diabetes.org /diabetes-statistics/national-diabetes-fact-sheet.jsp. 2005. [28] Food and Drug Administration. Device Classes. http://www.fda.gov/cdrh/devadvice/ 3132.html. 2005. [29] Medtronic Minimed. The Paradigm® Platform FAQ. http://www.minimed.com/patientfam/ pf_ipt_paradigm_faq.shtml. 2005. [30] Diabetic Express. Autoject 2 Fixed Needle Device. http://www.diabeticexpress.com/content /ProductDetail.aspx?CategoryID=0&SubCategoryID=0&ItemID=08-14. 2005. [31] Walgreens. Novopen 3 Insulin Delivery System. http://www.walgreens.com/library/ finddrug/druginfo1.jhtml?id=14415. 2005. [32] LNS Technologies. Part Number: BISTEP-MAN. Bipolar Stepper Motor Controller Kit. 2004. [33] Parallax, Inc. Parallax #27207 BASIC Stamp Discovery Kit. Oct., 2004.


[34] Ellis, J.R. Embedded Systems & Test Equipment. ElectronicBrains.com. 2005.


Appendix A PDS Function:

The device will accept a standard 1 cc syringe of ¼” diameter and automate the process of

measuring and delivering medication. After a syringe is inserted into the device, a user can type

in the number of units that should be drawn into the barrel of the syringe. The user will then

insert the needle into a bottle of medication, such as insulin, and press the “Fill” button. A motor

will drive the syringe’s plunger back via a screw mechanism, drawing the medication into the

barrel. Afterwards, the user will insert the needle into the body and press the “Inject” button.

The motor and screw will drive the plunger in and push the medication into the user. Since the

only manipulation required by the user is pressing numbers on a keypad and inserting the needle

into the body, the amount of dexterity is reduced dramatically.

Client Requirements:

The device should accept 1 cc syringes ¼” in diameter.

The device should dose to the nearest 0.01 cc.

The device should be easy to use for people with poor vision, low dexterity, diminished

motor control, Parkinson’s, and/or other neuromuscular disorders.

Design Requirements:

1. Physical and Operational Characteristics

a. Performance requirements

i. On average, the device will be used twice daily with slow-acting insulin and

several more times with fast-acting insulin to accommodate the eating

habits and varying blood sugar levels of the user.

ii. The device will be modeled to fit BD Ultra-Fine II 1 cc syringes (BD has 75 –

80% market share).

iii. The device should be easy to use for people with poor eyesight and/or

dexterity.

b. Safety


i. Standard syringe safety measures should be taken, including proper sterility

procedures and disposal.

ii. The device will contain batteries, so the batteries should not be left in the

device if they have exceeded their expiration date.

iii. Being electronic, the device should comply with FCC standards.

c. Accuracy and Reliability

i. The device will use 1 cc syringes and dose to the nearest unit, where a unit is

1/100 of a cc.

ii. With the stepper motor in the prototype, the shaft of the motor can move in

steps of 1.8°. In initial testing, 300 steps of the motor corresponded to 1.06 units

being expelled from or drawn in to the plunger. Therefore, the prototype is

accurate to a minimum accuracy of 1/100 of a cc.

iii. This accuracy will be true as long as the syringe dimensions, screw pitch, and

motor increments do not change.

d. Life in Service

i. The device should function for at least five years around five times per day at

five minutes per usage under normal functionality (low-viscosity fluid, such as

insulin, and careful handling).

e. Shelf Life

i. Being electronic, the device should not be left in the sun or in freezing

temperatures. Direct contact of the electrical components with liquids should be

avoided.

ii. The batteries should not be left in the device for more than three years or

beyond their expiration date, whichever comes first.

f. Operating Environment

i. The device should operate and remain accurate at temperatures above freezing

and below 100 °F.

ii. The device should not be affected at different pressures or humidity.

iii. The device will be inoperable if dust, dirt, or water has gotten into the device.

iv. The device can be used by able people of any age above seven.

g. Ergonomics


i. This device seeks to overcome the typical problems that patients with poor

muscular control, tremors, Parkinson’s, and poor eyesight have operating a

syringe.

ii. Anyone who has some control of the hands should be able to use the device,

because the device only requires the pressing of a few buttons with low resistance.

h. Size

i. The device should fit into a single hand.

ii. The device should not exceed the length of two syringes (~10”) or a width of

3”.

iii. It should be completely portable, such as being able to fit into a purse.

i. Weight

i. Ideally, the device should weigh less than a pound.

j. Materials

i. There are no restrictions on the materials, although non-slippery materials are

best.

ii. Materials that are smooth are ideal, so as to ensure comfort of the user.

k. Aesthetics

i. The color of the device should be mild, so as not to attract attention. A colorful

appearance may bring too much attention to a user that prefers discretion.

ii. The device should have a smooth texture, but not too smooth to slip out of the

hands. Rubber grips in key locations would be best.

iii. The device should contour to the hand in a natural fashion.

2. Production Characteristics

a. Quantity

i. Potential for thousands of units, depending on the number of patients/companies

that desire the device. For the National Student Design Competition, one

prototype is needed.

b. Target Product Cost

i. Suggested retail price: $300 - $500

ii. Manufacturing costs: ~$150-200

iii. Existing devices that don’t assist in dosing:


- MiniMed pump ~$5000

- Novopen ~$34

- AutoJect ~$44

3. Miscellaneous

a. Standards and Specifications

i. FDA approval required

b. Customer

i. The device should be portable, lightweight, and fit in one hand.

ii. The device should completely eliminate the need to manually set the

dosage on the syringe.

iii. The device should be easy to use, especially for individuals with tremors, poor

muscular control, Parkinson’s, and poor eyesight.

c. Patient-related concerns

i. The device itself will not need to be sterilized, but for each usage, a new syringe

should be used with proper sterilization and swabbing of the skin.

ii. Proper disposal procedures should be taken.

d. Competition

i. Aside from the items listed above, there are no other devices that assist in

dosing syringes to the degree that ours does.


Appendix B

Expenses Budget: $2,000

Costs to date:

℘ $13.82 – Supplies at Home Depot (screws, brackets, and glues)

℘ $125 – MS-1 Motor Kit [20] from StepperWorld.com

℘ $178 – Parallax BASIC stamp 2 kit [23]

℘ $39.95 – ZiLog microprocessor kit from DigiKey.com

℘ $25.95 – 8-digit LED driver from Parallax

℘ $264.52 – 2x Board of Education (USB) from Parallax

℘ $8.80 – 12-Button Keypad from ElectronicBrains.com

℘ $39.00 – 10 seven-segment LEDs from LC Led Inc.

℘ $4.00 – 10-digit LCD from AllElectronics.com

℘ $5.50 – 5 seven-segment LEDs from Parallax _______________

Total: $704.54

Remaining Budget: $1,295.46


Appendix C

BASIC program for counting zero through nine

'What's a Microcontroller - ZeroThruNine.bs2 ' {$STAMP BS2} ' {$PBASIC 2.5} counter VAR Nib counter2 VAR Word pulses VAR Word duration VAR Word GOSUB set_Zero DO IF IN3 = 0 THEN counter = counter + 1 IF counter = 1 THEN GOSUB set_One ELSEIF counter = 2 THEN GOSUB set_TWO ELSEIF counter = 3 THEN GOSUB set_Three ELSEIF counter = 4 THEN GOSUB set_Four ELSEIF counter = 5 THEN GOSUB set_Five ELSEIF counter = 6 THEN GOSUB set_Six ELSEIF counter = 7 THEN GOSUB set_Seven ELSEIF counter = 8 THEN GOSUB set_Eight ELSEIF counter = 9 THEN GOSUB set_Nine 'FREQOUT 6, 1000, 2000 FOR counter2 = 1 TO 150 PULSOUT 5, 1000 PAUSE 20 NEXT FOR counter2 = 1 TO 150 PULSOUT 5, 500 PAUSE 20 NEXT FOR counter2 = 1 TO 150 PULSOUT 5, 750 PAUSE 20 NEXT


ENDIF DEBUG ? counter PAUSE 250 ENDIF LOOP set_Zero: HIGH 15 HIGH 14 HIGH 13 HIGH 10 HIGH 9 HIGH 8 RETURN set_One: HIGH 15 HIGH 10 LOW 14 LOW 13 LOW 9 LOW 8 RETURN set_Two: HIGH 15 HIGH 14 HIGH 12 HIGH 9 HIGH 8 LOW 10 RETURN set_Three: HIGH 15 HIGH 14 HIGH 12 HIGH 10 HIGH 9 LOW 8 RETURN set_Four: HIGH 15 HIGH 13


HIGH 12 HIGH 10 LOW 14 LOW 9 RETURN set_Five: HIGH 14 HIGH 13 HIGH 12 HIGH 10 HIGH 9 LOW 15 RETURN set_Six: HIGH 14 HIGH 13 HIGH 12 HIGH 10 HIGH 9 HIGH 8 RETURN set_Seven: HIGH 14 HIGH 15 HIGH 10 LOW 13 LOW 12 LOW 9 LOW 8 RETURN set_Eight: HIGH 15 HIGH 14 HIGH 13 HIGH 12 HIGH 10 HIGH 9 HIGH 8 RETURN set_Nine: HIGH 15 HIGH 14


HIGH 13 HIGH 12 HIGH 10 LOW 9 LOW 8 RETURN


Appendix D

Master BASIC program for the design

' {$STAMP BS2} ' {$PBASIC 2.5} keypadInput VAR Nib flag VAR Boolean degrees VAR Nib drawn VAR Boolean injected VAR Boolean display VAR String degrees = 295 flag = false drawn = false injected = false DO IF IN3 = 0 THEN IF keypadInput = 1 & flag = false THEN GOSUB set_One ELSEIF keypadInput = 2 & flag = false THEN GOSUB set_TWO ELSEIF keypadInput = 3 & flag = false THEN GOSUB set_Three ELSEIF keypadInput = 4 & flag = false THEN GOSUB set_Four ELSEIF keypadInput = 5 & flag = false THEN GOSUB set_Five ELSEIF keypadInput = 6 & flag = false THEN GOSUB set_Six ELSEIF keypadInput = 7 & flag = false THEN GOSUB set_Seven ELSEIF keypadInput = 8 & flag = false THEN GOSUB set_Eight ELSEIF keypadInput = 9 & flag = false THEN GOSUB set_Nine ELSEIF keypadInput = 0 & flag = false THEN GOSUB set_Zero ELSEIF keypadInput = ENTER THEN GOSUB set_Return ENDIF ENDIF IF IN4 = 0 THEN IF !flag THEN display = 'Press enter.' ELSEIF flag THEN GOSUB draw ENDIF


ENDIF IF IN1 = 0 THEN IF !drawn THEN display = 'Draw fluid.' ELSEIF GOSUB inject ENDIF ENDIF LOOP set_Zero: HIGH 15 HIGH 14 HIGH 13 HIGH 10 HIGH 9 HIGH 8 RETURN set_One: HIGH 15 HIGH 10 LOW 14 LOW 13 LOW 9 LOW 8 RETURN set_Two: HIGH 15 HIGH 14 HIGH 12 HIGH 9 HIGH 8 LOW 10 RETURN set_Three: HIGH 15 HIGH 14 HIGH 12 HIGH 10 HIGH 9 LOW 8 RETURN set_Four:


HIGH 15 HIGH 13 HIGH 12 HIGH 10 LOW 14 LOW 9 RETURN set_Five: HIGH 14 HIGH 13 HIGH 12 HIGH 10 HIGH 9 LOW 15 RETURN set_Six: HIGH 14 HIGH 13 HIGH 12 HIGH 10 HIGH 9 HIGH 8 RETURN set_Seven: HIGH 14 HIGH 15 HIGH 10 LOW 13 LOW 12 LOW 9 LOW 8 RETURN set_Eight: HIGH 15 HIGH 14 HIGH 13 HIGH 12 HIGH 10 HIGH 9 HIGH 8 RETURN set_Nine:


HIGH 15 HIGH 14 HIGH 13 HIGH 12 HIGH 10 LOW 9 LOW 8 RETURN set_Return GOSUB set RETURN set flag = true RETURN draw DONE VAR Nib DONE = keypadInput*degrees FOR counter = 1 TO DONE IN2 = 1 NEXT drawn = true RETURN inject DONE VAR Nib DONE = keypadInput*degrees FOR counter = 1 TO DONE IN0 = 1 NEXT injected = true display = 'Complete' PAUSE 1000 GOSUB set_Zero RETURN

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Automated Syringe Dosing - University of Wisconsin–Madisonhomepages.cae.wisc.edu/~bme400/asd/documentation/Final... · 2005-05-05 · 2. Wash medicine bottle top with cotton ball