Team Under Pressure Presents:

A Novel Approach to Preventing Pressure Ulcers

Biomedical Engineering Senior Projects I Final Report

Biomedical Engineers: Robert Karas and Corina MaloneUDM Mechanical Engineers: Bobby Lorenz, Frank McClosky, and Jacob Dodman UDM Nurses: Victoria Murad, Lydia Jacob, and Christina Osterhout 12/15/17

Table of Contents

Abstract............................................................................................................................................2

Introduction......................................................................................................................................3

Details of Design Concept...............................................................................................................8

Methods.........................................................................................................................................13

Project Relevance/Broader Impact................................................................................................16

Timeline.........................................................................................................................................17

Budget............................................................................................................................................18

References......................................................................................................................................20

1

AbstractIn collaboration with University of Detroit Mercy, our team at LTU has identified a need to

provide a cost-efficient device which is more effective at lowering risk factors of pressure ulcer

formation in patients confined to a wheelchair for an extended period of time. The goal of the

team is to use our engineering and collaboration skills to develop a product that will help people

who are at risk for pressure ulcer formation, and reduce the chance of developing or further

injuring a pressure ulcer. In the U.S. over 2.5 million people develop pressure ulcers annually.

Also, 25% of people who have suffered a spinal cord injury (SCI) develop a pressure ulcer.

There are 65,000 wheelchair bound individuals like our client, who suffer from a SCI, that have

an increased risk of forming ulcers. Our client is a Vietnam War veteran that was injured from a

gunshot wound leaving him paralyzed from the waist down. The idea was formed during a

meeting with the client whose chief complaint was that he experienced a lot of pain and

discomfort from pressure ulcers. Our client has expressed that he’s tried a variety of pads,

mattresses and other pressure relieving devices, however his pressure ulcers ultimately kept

progressing until they became a stage 4 pressure ulcer. Our team is proposing a device that will

alternate pressure to injured areas and offer a tilt feature to allow blood to circulate in the area

where pressure is relieved. The device will be a pad that is specifically designed for a

wheelchair to address main risks in pressure ulcer formation including pressure reduction,

moisture decrease and minimizing friction. The seat will alternate positions to relieve pressure

and recirculate blood to the area of interest. To decrease moisture the top layer will be a

moisture wicking material to prevent any fluids from seeping into the pad. Finally, a low friction

coefficient material, such as lyocell, will be ideal to prevent further injury and ultimately

decrease the chance of pressure ulcer formation.

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IntroductionOur patient suffers from pressure ulcers due to his prolonged use of the wheelchair

throughout the day. He suffered a spinal cord injury due to a gunshot wound to his back that is

still lodged in his spine. After the war, our patient was also a victim of post-traumatic stress

disorder (PTSD) so it’s very important that the design of the device doesn’t evoke any abrupt

movements or loud noises that could potentially alarm him. The patient lost his lower limbs

after gangrene set in and stage four ulcers caused him to have several flap surgeries to help with

pressure ulcers. He is confined to a wheelchair to ambulate making him high risk of ulcer

formation so he has tried several pressure relieving pads and devices in earlier stages of the

disease. Our patient also lives with his grandson who cares for him and a wife who is also his

caretaker but suffers several illnesses herself. Therefore, our device needs to be mindful of the

caretakers and be effective in that no further injury occurs to his untreatable ulcers. Currently, he

is treating the pressure ulcers with pain medication and frequent massages from caretakers. Most

patients who spend 8 or more hours in a wheelchair tend to stay in the same position majority of

the time causing prolonged pressure to an area of the body. The area of the body which is in

contact with the surface will create friction and moisture increasing the risk of the formation of

pressure ulcers. Treatment is complicated and dependent upon the stage of the ulcer it is difficult

to determine if the skin will heal. Pressure ulcers are classified in 4 stages which regulate the

healing process and classifies the health of the tissue. Beginning with the first stage, the site of

the ulcer may be tender, painful, firm, soft, warm or cool compared with the surrounding skin.

Stage 2 presents blisters which can be ruptured and if left untreated will accelerate to stage 3.

Stage 3 is the point where skin is compromised and fat can be exposed that can include yellowish

dead tissue with possible craters. For paralyzed individual’s injuries are more likely to advance

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to stage 4 which usually results in surgery to remove damaged tissue and prevent infection. The

fourth stage is hardest to heal and is indicated by a large-scale amount of tissue loss which can

expose tendon, tissue, muscle or bone. If the injury is left untreated it could be classified as

unstageable where the surface is covered by yellowish, black, brown or dead tissue and the

severity of the wound is impossible to see. Spinal cord injury patients have a few extra factors

that make developing pressure ulcers easier for them. One factor is the inability to regulate heat.

Studies have shown an increase of one degree Celsius can increase the chance of getting a

pressure ulcer by as much as 10%. Another factor is that some spinal cord injury patients have a

compromised nervous system which affects fight or flight instincts and leads to increased

perspiration. Increased perspiration and wheelchair confinement lead to formation of pressure

ulcers near the bony areas of the body. When we heard about this undesirable problem that our

patient had, we knew that something had to be done in order to relieve his pain and try to help

reduce any further injury of his wound site. Another tragic state that he has to face is his PTSD.

Often times even his own wife feels unsafe around him, and the only thing that ever seemed to

calm anxiety was the water. If there is a way to incorporate water either by sound or by massage

into the design, he could not only have the benefit of pressure therapy but also therapy to help

with his devastating PTSD. It was easy to identify the need of pressure ulcers because it is a

major problem for many Americans however it was very difficult to govern how to address this

problem. Patients who are wheelchair bound usually are in the chair for over a period of 8 hours

and are more likely to be in the same position. The prolonged pressure causes irritation, friction,

and increased moisture to the injury site. Clinicians advise that patients who are in a wheelchair

for over 8 hours should change their position every 15 minutes to relieve pressure allowing blood

to re-circulate in that area. After conducting interviews with 10 patients of varying stages of

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ulcer formation the answers were carefully analyzed and assisted with confirming the need for

prevention and treatment of pressure ulcers. Many of the patients described extreme discomfort

and pain in relation to pressure ulcers. Most of them treated the pain with oral medications and

physical therapy that was described as “temporary relief”. In an interview with a spinal cord

injury patient confined to a wheelchair expressed the interest in devices that provide more

independence and less reliance on the caretaker for weight shifting. There were a large

percentage of patients who were not managing their pressure ulcers with any medical devices

and when asked about previous treatment methods responses indicated there were none. There

were also questionnaires given to physical therapist, RN, and doctors that revealed a need for a

device that effectively redistributes pressure but allows that patient some level of comfort. An

RN working for Receiving Hospital discussed how she sees patients not receiving the proper care

due to a lack of staff available to reposition patients as needed based on severity. Having a

device that reduces the need of another individual to assist in the weight shifting process will

provide an environment for prevention of pressure ulcers. Currently there are several medical

devices on the market that offer pressure redistribution through air loss, patient turning and

pressure alternation. There are several beds that circulate air or water and use gel or foam pads

to alleviate pressure and obtain a more balanced pressure or monitor applied pressure. Many of

these existing solutions are primarily for beds and recliners that intends to redistribute pressure.

The issue with many of these devices is that they still show chances of forming pressure ulcers

because of ergonomics or the device main purpose being predictive pressure ulcer devices. The

devices currently on market are pads and coverings for mattresses and chairs which are no slip

covers trying to keep the body still but no concern for shear forces applied to the skin. There are

also microclimate controlled covers for chairs and beds in attempt to keep the body cool and dry

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to prevent excess dampness from developing and leading to increased tissue damage. There are

some other treatment solutions to pressure ulcers such as special dressings, negative pressure

therapy, hyperbaric chambers, ointments and Band-Aid. Most technology on the market focus

on determining how where and how much pressure is applied to a given area. The main existing

solution for wheelchairs is the Geri Chair Alternating Pressure pad. It has air interwoven

channels that will inflate a set of alternating channels to relieve pressure and rotate the channels

that are blown up to relieve pressure. There is an opportunity to innovate existing solutions by

developing a cost-effective device that is effective and helps to reduce pressure ulcer formation.

We have identified the stakeholders as being primarily the patient but also nursing staff,

clinicians, hospitals, medical equipment companies, caregivers, insurance companies, wound

care facilities and home healthcare agencies. These influential stakeholders do not pose any

conflict of interest because all above mentioned will tend to benefit from this product. Our target

audience would be wheelchair bound individuals who are also the decision makers because they

will provide the demand. We have identified 3 market segments that include pre-hospital,

hospital, and post hospital which provides a map of the stakeholders. All segments include the

patient while also included in pre-hospital are caretakers and medical device companies where

the patient is treated and therapeutic devices are purchased in hopes of healing/preventing

pressure ulcer formation. In the hospital segment nursing staff, clinicians, and insurance

companies are concerned with treatment of pressure ulcers as well as preventing patients from

getting pressure ulcers once they were admitted. In post-hospital, medical device companies,

insurance companies, and caretakers search for wound care and treatment options in attempts of

preventing ulcers from progressing to further stages or preventing infection.

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In the U.S. pressure ulcers cost anywhere between $9.1 and $11.6 billion per year and the cost

for an individual patient care ranges from $20,900 to 151,700 per pressure ulcer. In a 2015 study,

there were 2.5 million pressure ulcers in the U.S. alone where 25% of all people with spinal cord

injury develop pressure ulcers every year. Per a report by the Medicare services the average cost

of pressure ulcer treatment is $43,180 also reporting an estimated 65,000 individuals that are

wheelchair bound and develop pressure ulcers annually. The 65,000 people who suffer from a

spinal cord injury and are wheelchair bound multiplied by the cost of pressure ulcer treatment

gives a $2.8 billion market available in this product. The device that we are anticipating on

creating will help the pre-hospital, hospital and the post-hospital market. The device will prevent

the ulcer from worsening and will also slow the development of pressure ulcer formation

eliminating the main factors associated with pressure ulcers. The prevention of further injury is

the main goal of the project and to alleviate pressure at the injury site providing more comfort to

the patient.

7

Details of Design ConceptWhen coming up with a design, the first step was to see what the market already has on

it. When looking at the treatment or prevention of pressure ulcers there are two main categories,

hospital equipment and then at home equipment. Hospital equipment to treat and prevent

pressure ulcers mainly includes mattresses and mattress pads. Since hospitals are actively trying

to figure out how to stop pressure ulcer formation, there are quite a few options including low air

loss beds, alternating pressure mattress pads, and patient turn devices. Low air loss beds use a

simple idea that if air is circulating under the body, then the pressure will distribute evenly

throughout the body. Alternating pressure pads try to make sure that the pressure points that the

patient feels shift about every 15 minutes to alleviate the pressure. Also, patient turning devices

believe that turning the patient will result in reduced pressure and increased blood flow to the

injury site, resulting in less pressure ulcers. These forms of treatment are widely used in many

hospital settings, however are rarely used outside of the hospital. Wheelchair bound individuals

suffer a great risk for pressure ulcers due to the fact they have to be in a seated position for most

of the day putting pressure on both the hip bones and the tail bone. Many different seats are used

including pressure relieving pads and pressure alternating pads. Pressure relieving pads are

designed in an ergonomic manner to try and even out the pressure distribution of the patient.

This results in a more even spread of pressure to try and normalize the pressure distribution to

alleviate any pressure points. The other type of wheelchair pad in the market is pressure

alternating pads. These pads try to change the pressure points every 5, 10, or 15 minutes to try

and stop pressure from building up on certain areas.

After reviewing these devices it became clear that little was being done on the market to

build a device that not only relieved pressure, but promoted blood to recirculate to the injury site.

8

Three design concepts were created including an inflatable pad that would be able to redistribute

pressure as well as make major adjustments to the patient to allow for blood to recirculate to the

injury site(s), a reclining wheelchair integrated with a pressure sensor to automatically adjust the

patient to relieve high pressure areas, and a water pad for a wheelchair that would feature cold

water as well as circulation to try and promote healing and injury site microclimate control. A

decision matrix was designed using what our group thought was the most important criteria, see

table below, and a design idea was then solidified.

Table 1: Decision Matrix for three design concepts

The inflatable recliner pad was chosen due to the interest from our client. When deciding

between air, water, or gel to inflate the pad with we went with air because it is lightweight, easy

to use, and will not weigh down the wheelchair with a tank holding the liquid or gel. In order to

ensure that our idea was novel, we researched all sorts of cushions and found the area for

improvement. No matter what wheelchair/cushion combination someone chose they still

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Concept 1 Concept 2 Concept 3Inflatable Wheelchair Recliner Pad Wheelchair w/ Tilt Function Water Circulating Cushion

Criteria Weight

Patient Interest 0.1 1 0 0Mobility 0.1 1 1 1Comfort 0.15 1 1 1

Pressure Reducing 0.2 1 1 1Temperature Reducing 0.1 0 0 1

Friction Reducing 0.1 1 0 0Marketing Potential 0.15 1 1 1

Manufacturing Feasibility 0.1 0.5 1 10.85 0.7 0.8

DescriptionConcept

Concept Decision Matrix

Total

recommend the patient to do certain stretches like shown in the figures below to ensure proper

blood circulation and skin proliferation.

Images 1 & 2: Stretches to ensure blood circulation and prevent skin deterioration

Once this was realized, a design of the pad was made so that the patient wouldn’t have to

make these stretches a part of his routine. Many patients forget about doing stretches after about

a week or two post treatment. Our device will help the patient recirculate his blood to the injury

areas so the device should be more effective at preventing pressure ulcers than previously made

devices. To do this we brainstormed an idea that the pad can have eight pads, to ensure no

pressure points are created, that will not only alternate but lift up the patient in various directions

to ensure proper circulation to prevent further degeneration of the skin.

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Images 3, 4, 5 & 6: CAD drawing of design at different inflation settings

These images show how we intend to inflate the balloons to ensure that pressure will not

only be redistributed, but the pad will allow the patient to have full recirculation during inflation

patterns designed to tilt the patient at a fifteen degree angle. This will ensure proper recirculation

and will occur every fifteen to thirty minutes depending on the user’s preference. To ensure

comfortability a very slim piece of foam will be placed above the inflatable balloons. This foam

will in no way hinder the effect of the balloons due to the thin aspect of the foam.

After the concept was designed we knew we had to figure out the outer material for the

seat. After deliberation with nurses of various specialties, we decided to go with a waterproof

material in order to prevent water from sitting on the seat which can increase the chances of

pressure ulcer development.

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After all the materials and concepts were finished, the actual mechanics were taken into

account. In order to get our desired fifteen degree tilt, we need the balloons to raise about four

inches from the seat. The amount of pressure these balloons will feel will be a maximum of three

pounds per square inch. This was calculated by taking the highest weight allowed, 300 pounds

which a standard wheelchair is regulated for, and dividing by the area of balloons that will be in

contact with the patient. However, when looking at the tubes they will see a much higher

pressure due to the small area of the tube. This is why when we chose our valves and pump to

include in our design we had to make sure they can withhold a high PSI rating in order to work

for our application. We went with an air compressor, because most pumps will not allow the

balloons to inflate. Also, we went with solenoid valves because they will control each tube

independently. Lastly, we chose an Arduino to operate our system because we don’t need any

computing power like raspberry pie microcontrollers and the Arduino can control the compressor

and the valves to ensure proper function.

With all this in mind the final product will have to be made for our client and his manual

wheelchair. The design includes two loops at the top that will fit over the caretaker handles on

the back of the wheelchair. The pad will then tie into the armrests to ensure that the pad is

secure. Pressure is to be reduced at least every fifteen to twenty minutes according to the nurses

we interviewed, so we will have the user be able to adjust their position every ten, fifteen,

twenty, or thirty minutes depending on their preference. The thirty minute option is for those

who are without a pressure ulcer that are just trying to prevent one from forming. The sequence

of pressure redistribution will occur every five minutes regardless of user input to ensure no

pressure points are created, and then will shift them to the left, the right, forward, and backward

depending on the time step they indicate. With all of these pressure redistributive patterns, this

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wheelchair pad should be more effective than any other pad designed to reduce the chance of

pressure ulcers, and should improve healing of pressure ulcers.

13

MethodsNot only is it important to have a great design that should accomplish the desired task,

but there needs to be testing already specified to make sure that the product can work for its

desired function. These tests would include usability testing, materials testing, pressure testing,

weight testing, and safety testing. All of these types of testing will ensure that our product will

meet not only our client’s needs, but any future investor’s needs as well.

The first step to usability testing would be to contact LTU’s IRB and get approval for

human testing. This will need to be done in order to let our patient try out our chair, and give us

feedback on our design. This step is crucial because the designers always know how they intend

their product to be used, but sometimes how to function the device isn’t clear to the user. Since

our project is very client based, it is essential that our client can be able to use our device

intuitively in order to reach our intended market.

After our device is tested by the user for function we will do materials testing. This is to

ensure that the outer material we chose is both low friction and water resistant. A simple

coefficient of friction can be done with a force sensor tied to a certain amount of mass in order to

obtain the coefficient of friction. Then we can compare our material to other known material on

the market to ensure our material has a lower coefficient of friction. If it is not, then some simple

surface modification can be done, or a new material can be chosen. To test the hydrophobicity a

contact angle measurement can be done on the fabric. If there is a contact angle than the fabric is

considered water resistant. If the water is able to be wiped off of the surface and there is no wet

residue, then the material can be classified as waterproof.

Pressure testing is another aspect of testing that we will need to do in order to classify our

product. This can be done with simple pressure sensors hooked up to the motion capture

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equipment to see if the patient’s pressure is properly redistributed. If the pressure is noticeably

not shifting, then the size of balloon or pressure from the pump will have to be increased to meet

the required goal.

Since standard wheelchairs are standardized to accept any weight until three hundred

pounds, our pressure pad should be able to withstand the same amount of weight. To do this we

need to test one and a half times the maximum weight desired for the product to be rated for.

This means our pad will have to be tested with someone weighing four hundred and fifty pounds.

This can be done with the weights from the weight room to ensure proper function when the

maximum weight capacity is reached.

Throughout these steps safety is our number one concern. If there is any potential hazard

or possible are for error, our job is to correct the error. This includes making sure our circuitry is

closed and unable to shock the patient. Also, preventing kick back from some of our components

to protect the Arduino. Lastly, we need to ensure that our device is usable without a seatbelt. If a

seatbelt is needed, some slight modification to our design will get the desired effect and once

again our product will be easy to use for our patient.

Product testing is very crucial for the development of a product. If your product is either

not safe or not effective, then your product will not be able to make it to market. Below is a risk

assessment exercise to try and find any potential risks that could be associated with our design.

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Line #

Hazard

Situation

Harm

Severity

Occurrence

Risk

Acceptability

Controls

Verification

Occurrence

Residual R

isk

Acceptability

Pain/Concussion

4 1 4 Acceptable 1. limit the amount of inflation 2. possible seatbelt

1. User manual; user testing2. Design docs 3. Test tilt of device

1 4 Acceptable

Broken Bone 2. Possible seatbelt

Disease state progression

20 Disease state

progression

3 3 9 Caution 1 3 Acceptable

10 Balloons inflate too much in back,

causes patient to fall out of chair

Pressure Points

Triggered

Not enough Pressure

Distribution which causes pressure

points

1. Better materials2. Higher number of balloons

1. Pressure Test

2. User test3. Design docs

Degree of Tilt being

exteme

Probability Unlikely Remote Possible ProbableSeverity 1 2 3 4

Catastrophic Intolerable

5 Caution

Severe Acceptable

4

Major

3

Minor

2

Negligible

1

Table 2: Risk assessment chart with risk criteria below for under pressure decubitus ulcer pad.

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Project Relevance/Broader ImpactThis project relates to many people because of its intent to heal pressure ulcers by reducing

friction, redistributing pressure and decreasing moisture. Per a report by Transparency Market

Research the pressure relief market is expected to experience a compound annual growth rate of

5.2 percent from 2014 to 2020. These numbers show that there is an identified need to prevent

pressure ulcer formation which can ultimately lead to death. It is important to understand the

broader impact this device will have on the medical industry due to the amount of people

suffering from pressure ulcers. Pressure ulcers can be acquired in the home setting, hospital or

even long term care facilities which is the reason prevention is so vital. Along with knowledge,

there is a need for medical equipment that reduces the risk factors in the formation of these

wounds. Our portable product which effectively prevents pressure ulcers will be an innovative

solution to the identified need. Patients confined to wheelchairs express awareness about the

importance of prevention and concern about the effect, if left untreated. This problem is a threat

to all patients who are subjected to a wheelchair or bedridden for a long period. The impact of

this condition results in many people being affected due to fatalities and decreased activities of

daily living for patients. The fatal environment for causes patients to get progressively worse

with time and increased lack of mobility which increases risk factors for pressure ulcer

formation. Stakeholders are equally interested and concerned with the pressure relief market and

how it will affect them directly.

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TimelineTo successfully complete the project our team anticipates to complete all objectives and goals

within the structured time frame. Our first task is to meet with our faculty advisor to in the

beginning of the 2nd semester to receive feedback and guidance to help organize our efforts in

developing a prototype. This task will continue until the project is completed to ensure deadlines

are being met. Materials will be bought no later than February 1st and prototype build will be

begin no later than February 1st as well. The task will proceed until no later than March 1st to

guarantee testing will begin by March 1st. Testing will be completed no later than March 15th to

assure that modifications can be made if necessary. Modifications must be complete by April 1st

so that a robust prototype is achieved in time for the final deadline. This timeline is intended to

provide direction for the senior project, allow deadlines to be met and be conducive to a

prototype which delivers a solution to the identified need.

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BudgetItem Quantity Needed Price/unit (US$) Total Cost (US $)

RolAir FC2002 - Portable Air Compressor 1 70 70Arduino Board & Accessories 1 78 78Crydom DC Relay to Arduino 11 20 220

Batteries (9V & 12V) 1 30 30Solonoid Valves 10 15 150

Pneumatic Tubes 4 5 20Foam Pad 1 25 25

Material for Air Bladders 16 5 80Outer Shell Material 1 100 100

TOTAL COST 773

The group decided on doing an Arduino based design because the Arduino has been used

in previous projects and wo do not need computing power that the raspberry pie gives. The air

compressor is used because pumps that were able to get to a high enough psi rating were very

expensive compared to the air compressors. These can all be controlled via relays to the Arduino.

The relays is the most expensive item and if we need to cut our costs, then the relays can be

wired in differently, but may not be as effective. The batteries are 9V to power the valves and the

Arduino, and 12V to power the air compressor. The solenoid valves are chosen because they

allow for control over each bladder separately in order to get the proper balloons inflated to

achieve the desired task. Only ten are needed, eight can control the bottom and two will control

the top. Pneumatic tubes are chosen because they were recommended for the air compressor and

they are relatively low cost. The foam pad needs to be a slight foam pad that can provide

ergonomics, so a relatively cheat piece. An air mattress material can be used for the balloons and

they will hold up to the weight that we expect to put on the pad. Lastly, the outer shell is a

waterproof material that surrounds the device in order to allow the patient to be separate from

our device, as well as lower friction and water that will gather on the surface. The funding source

for this project will be the UDM budget of one thousand dollars, which allows us to purchase all

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of the above items with about two hundred and twenty five dollars left for incidental needs and

items that were not intended.

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Appendix

Block Diagram of our design

Cross sectional view of the seat cushion

Solidworks Drawing of our Initial Idea

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Tenative Schedule for the Senior Projects II

Team Structure

ReferencesFu, Jicheng, Yih-Kuen Jan, and M. Jones. "Development of Intelligent Model to Determine

Favorable Wheelchair Tilt and Recline Angles for People with Spinal Cord Injury." 2011

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TEAM UNDER PRESSURE

UDM NURSES

Disease State Fundamentals

Background Information

Design Parameters

LTU ENGINEERS

Methods Design Ergonomics Market Research

UDM ENGINEERS

Fabrication Methods Manuafacturing

Annual International Conference of the IEEE Engineering in Medicine and Biology

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Ischial Tuberosity in People With Spinal Cord Injury." Archives of Physical Medicine

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Moore, Zena Eh, and Seamus Cowman. "Repositioning for Treating Pressure Ulcers." Cochrane

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Wounds: A Major and Snowballing Threat to Public Health and the Economy." Wound

Repair and Regeneration 17.6 (2009): 763-71. Web.

Thiers, B.h. "Preventing Pressure Ulcers: A Systematic Review." Yearbook of Dermatology and

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