Wound Healing Device Volume 2
University of Minnesota – Twin Cities
ME 4054W, Spring 2013
Team: John Braun, Christopher Hanson, Bryan Horvat, Daniel Knox, Nick Tassoni
Advisers: Laura Paulsen, Chris Rolfes
Sponsor: University of Minnesota Medical Devices Center
May 7th
, 2013
2
Contents
1.1 Annotated Bibliography ....................................................................................................... 3
1.2 Patent Search ........................................................................................................................ 8
1.2.1 – Patent Search – Objectives .............................................................................................. 8
1.2.2 – Patent Search – Search Criteria ....................................................................................... 9
1.2.3 – Patent Search – Findings ................................................................................................. 9
1.3 User Need Research ........................................................................................................... 12
1.3.1 – Customer Interviews ..................................................................................................... 12
1.3.2 – Customer Needs and Design Specifications.................................................................. 19
1.4 Concept Alternatives .......................................................................................................... 20
1.4.1 – Patch .............................................................................................................................. 20
1.4.2 – Wound Vac Integrated Device ...................................................................................... 21
1.4.3 – Foot Application ............................................................................................................ 22
1.4.4 – Moisture Devices........................................................................................................... 22
1.5 Concept Selection .............................................................................................................. 23
1.5.1 – Screening Process .......................................................................................................... 23
1.5.2 – Criteria Definitions ........................................................................................................ 24
1.5.3 – Selection Process ........................................................................................................... 24
1.5.4 – Selection Results ........................................................................................................... 25
2.1 Manufacturing Plan ............................................................................................................ 25
2.1.1 – Manufacturing Overview .............................................................................................. 25
2.1.2 – Part Drawings ................................................................................................................ 26
2.1.3 – Bill of Materials ............................................................................................................ 30
2.1.4 – Manufacturing Procedure .............................................................................................. 31
3.1 Evaluation Reports ............................................................................................................. 32
3.1.1 – Delivers AC Electric Field Therapy .............................................................................. 32
3.1.1.1 – Electric Field Intensity............................................................................................ 32
3.1.1.2 – Electric Field Distribution ...................................................................................... 34
3.1.2 – Delivers Ultrasound Therapy ........................................................................................ 38
3.1.2.1 – Ultrasound Intensity ............................................................................................... 38
3.1.2.2 – Ultrasound Distribution .......................................................................................... 41
3.1.3 – Patentable ...................................................................................................................... 51
3.1.4 – Short Setup Time ........................................................................................................... 55
3.1.5 – Maintains a Low Profile ................................................................................................ 57
3.1.6 – Petri Dish Biofilm Inhibition......................................................................................... 58
3.2 Cost Analysis ..................................................................................................................... 59
3.3 Environmental Impact Statement ....................................................................................... 62
3.4 Regulatory and Safety Concerns ........................................................................................ 63
3
1.1 Annotated Bibliography
After researching numerous articles about the field of wound closure, the main types of
chronic wounds found were pressure ulcers, venous ulcers and diabetic ulcers. Many different
technologies which appear to be viable solutions to this problem have been brought forth,
including electric fields (AC and DC), ultrasound, plasma, negative pressure, mechanical fixture
and offloading. Many devices have been created using some of these technologies with the hope
of aiding wound healing, but each device has its own issues which leave room in this field for
improvement.
[1] Sen CK, Gordillo GM, Roy S, Kirsner R, Lambert L, Hunt TK, Gottrup F, Gurtner GC,
Longaker MT, 2009, “Human skin wounds: A major snowballing threat to public health
economy,” Wound Repair Regen, 17(6), pp. 763-771.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2810192/
This article discusses the patient population and costs behind chronic wounds in the
United States. It also gives brief explanations of the different types of chronic wounds.
[2] Kruse I, Edelman S, 2006, “Human Evaluation and Treatment of Diabetic Foot Ulcers,”
Clinical Diabetes, 24(2), pp. 91-93. http://clinical.diabetesjournals.org/content/24/2/91.full
This article discusses costs associated with diabetes. More specifically, it details costs
and frequency of amputations in patients with diabetes. The article goes on to explain the
etiology, evaluation and treatment of diabetic foot ulcers.
[3] Mayo Clinic Staff, 2011, “Bedsores (pressure sores),”
http://www.mayoclinic.com/health/bedsores/DS00570
This article describes numerous facts about pressure ulcers. It defines a pressure ulcer,
talks about symptoms and causes, risk factors, complications and treatments.
[4] WebMD, 2009, “Skin Problems & Treatments Health Center,” http://www.webmd.com/skin-
problems-and-treatments/tc/venous-skin-ulcer-topic-overview
This article describes how venous ulcers are formed in the body. It also describes what
activities supplement the formation of this type of ulcer and what the symptoms are.
[5] Mayo Clinic Staff, 2011, “Amputation and diabetes: How to protect your feet,”
http://www.mayoclinic.com/health/amputation-and-diabetes/DA00140
This article describes how diabetic ulcers are formed and how diabetes damages the feet.
It also talks about ways in which the patient can take care of themselves in the hope of
preventing the formation of a diabetic foot ulcer.
[6] Johnson, A. MD, 2013, “Otolaryngologist, Medical Devices Center Innovation Fellow,”
Interview.
The interview with Dr. Johnson gave the team a solid understanding behind the basics of
wounds and ulcers. Also, Dr. Johnson described terminology commonly used in the field and
talked about what types of doctors typically deal with wounds.
[7] Kern, S. MD, 2013, “General Surgeon, Chief of Surgery,” Interview.
4
The interview with Dr. Kern allowed the team the opportunity to pick the brain of an
experience surgeon with a questionnaire. The major takeaway of this discussion was the
importance of increasing blood flow to the wound site and debridement to wound healing.
[8] Buckley, M. MD, 2013, “Plastic and Reconstructive Surgeon,” Interview.
The interview with Dr. Buckley was another opportunity for the team to use a
questionnaire to gather information from an experienced surgeon. Dr. Buckley was very
educated on current technologies and had great input. Also, team was invited to observe
procedures in her OR or wound clinic.
[9] Mrs. Daniels, 2013, “Wound Patient,” Interview.
The interview with Mrs. Daniels allowed the team the opportunity to use a questionnaire
in order to gather information from the perspective of a patient. Mrs. Daniels had major surgery
on a wound on her leg following a side-by-side accident.
[10] Physics Classroom, “Electric Fields,”
http://www.physicsclassroom.com/class/estatics/u8l4d.cfm#Q4Answer, 2013(2/21).
This article describes the physics behind electric fields. It goes on to detail the theoretical
equations which govern electric fields and how these fields act.
[11] Costerton J, Ellis B, Lam K, Johnson F, Khoury A, 1994, “Mechanism of Electrical
Enhancement of Efficacy of Antibiotics in Killing Biofilm Bacteria,” Antimicrobial Agents and
Chemotherapy, 38(12)pp. 2803-2809.
This article describes how the use of DC electric treatment works in combination with
antibiotics to kill biofilm bacteria. This data is compared against a control, only electric and only
antibiotic, showing that the combined treatment is most effective.
[12] Giladi M, Porat Y, Blatt A, Wasserman Y, Kirson E, Dekel E, Palti Y, 2008, “Microbial
Growth Inhibition by Alternating Electric Fields,” Antimicrobial Agents and Chemotherapy,
52(10)pp. 3517-3522.
This article describes how the use of AC electric worked in combating bacteria. The
study uses a frequency of 10 MHz, and an intensity of 2 to 4 V/cm. It also talks about the
limitations of using DC, those being can stimulate nerves, need too high of an intensity, and can
produce electrolysis, metal ions and free radicals which can damage healthy tissues.
[13] Rubin C, Bolander M, Ryaby J, Hadjiargyrou M, 2001, “The Use of Low-Intensity
Ultrasound to Accelerate the Healing of Fractures,” The Journal of Bone & Joint Surgery, 83(2).
This article describes how the use of low-intensity ultrasound improved the healing rate
of fractures of bones in clinical healing. The article describes what ultrasound is and said it used
an intensity of 30 mW/cm2 for 20 min/day.
[14] Giladi M, Porat Y, Blatt A, Shmueli E, Wasserman Y, Kirson E, Palti Y, 2010, “Microbial
Growth Inhibition by Alternating Electric Fields in Mice with Pseudomonas aeruginosa Lung
Infection,” Antimicrobial Agents and Chemotherapy, 54(8)pp. 3212-3218.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2916302/
5
This article describes how the use of high frequency, low intensity AC electric fields with
insulated electrodes inhibits the growth of bacteria. The study uses a frequency of 10 MHz and
ceftazidime antibiotics. The article also describes how AC makes deep treatment possible.
[15] Cutting K, 2006, “Electrical Stimulation in the Treatment of Chronic Wounds,” Wounds,
2(1).
This article describes what chronic wounds are, and how wounds are healed. Article
details moist wound healing and how an endogenous electric current is naturally present in
wounds. Discusses how electric stimulation increased rate of chronic wound healing by 144%
and how it produced directional cellular migration (required in wound healing).
[16] Covington S, Adams G, Dixon K, 2012, “Ultrasound-Mediated Oxygen Delivery to Lower
Extremity Wounds,” Wounds, 24(8)pp. 201-206.
http://www.woundsresearch.com/article/ultrasound-mediated-oxygen-delivery-lower-extremity-
wounds
This article describes how using oxygen mediated ultrasound to lower extremity wounds
increased the partial pressure of oxygen at the wound site by a median of 59.7% and by a
maximum of 116%. The medium was hyper-oxygenated saline.
[17] Byl NN, McKenxie A, Wong T, West J, Hunt TK, 1993, “Incisional Wound Healing: a
Controlled Study of Low and High Dose Ultrasound,” J Orthop Sports Phys Ther, 18(50)pp.
619-628. http://www.ncbi.nlm.nih.gov/pubmed/8268965
This article gives important functional specifications for use in ultrasound. High dose
ultrasound (HUS) uses a frequency of 1 MHz, an intensity of 1.5 W/cm2, and 5 minutes of
continuous application. Low dose ultrasound (LUS) uses a frequency of 1 MHz, an intensity of
0.5 W/cm2, and a 5 minute pulsed application with a 20% duty cycle. Article suggests using
LUS when treatment is more than 2 weeks long.
[18] Dyson M, Moodley S, Verjee L, Verling W, Weinman J, Wilson P, 2003, “Wound Healing
Assessment Using 20 MHz Ultrasound and Photography,” Skin Research and Technology,
9(2)pp. 116-121. http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0846.2003.00020.x/full
This article gives important functional specifications for use in ultrasound. This study
used a frequency of 20 MHz with a polyvinylidene difluoride transducer. It also used opsite
dressing for its ultrasound transmitting capability. Also, this dressing protected the wound from
direct exposure to the coupling gel (sonogel).
[19] Taskan I, Ozyazgan I, Tercan M, Kardas Y, Balkanli S, Saraymen R, Zorlu U, Ozugul Y,
1997, “A Comparative Study of the Effect of Ultrasound and Electrostimulation on Wound
Healing in Rats,” Plastic & Reconstructive Surgery, 100(4)pp. 966-972.
http://journals.lww.com/plasreconsurg/Abstract/1997/09001/A_Comparative_Study_of_the_Effe
ct_of_Ultrasound.20.aspx
This article gives information about a study done using DC electrostumulation. The
functional specifications were a current of 300 microamps and an intensity of 0.1 W/cm2.
Electrostimulation was found to be superior to ultrasound in this study.
6
[20] Most RS, Sinnock P, 1983, "The Epidemiology of Lower Extremity Amputations in
Diabetic Individuals," Diabetes Care, 6(1)pp. 87-91.
This article uses data from diabetes control programs in 20 states to study the prevalence
and causes of foot ulcers in diabetic patients. It concludes that diabetic patients are at a 15 times
higher risk of lower extremity amputation than non-diabetic patients.
[21] Poltawski L, Watson T, 2007, “Transmission of Therapeutic Ultrasound by Wound
Dressings,” Wounds, 19(1)pp. 1-12.
This article describes how ultrasound has been used for treatment of venous ulcers. The
transmissivity of different dressings for ultrasound applications is discussed.
[22] Hess CL, Howard MA, Attinger CE, 2003, “A Review of Mechanical Adjuncts in Wound
Healing: Hydrotherapy, Ultrasound, Negative Pressure Therapy, Hyperbaric Oxygen, and
Electrostimulation,” Ann Plast Surg., 51pp. 210-218.
This article describes different therapies to be considered in the process of wound
healing. It talks about hydrotherapy, ultrasound, negative pressure therapy, hyperbaric oxygen
and electrostimulation.
[23] ECRI, Centers for Medicare & Medicaid Services, 1996, "Electrical Stimulation for the
Treatment of Chronic Wounds." http://www.cms.gov/medicare-coverage-
database/details/technology-assessments-details.aspx?TAId=13
This report documents extensive analyses of studies of electrical stimulation therapies for
the treatment of chronic wounds (those lasting longer than 30 days). The therapies studied
included direct current, pulsed current, alternating current, pulsed electromagnetic induction, and
spinal cord stimulation. The report concludes there is evidence that AC therapy improves the
normalized healing rate of decubitus ulcers (pressure ulcers).
[24] Butcher M, 2007 "How to Use POSiFECT(R) Bio-electric Stimulation Therapy in Chronic
Wounds." http://www.wounds-uk.com/pdf/content_9416.pdf
This document describes the design of the POSiFECT® system, how it works, and how it
is properly applied. The document also describes clinical findings with the device and discusses
the positive effect on wound healing that applied bio-current has.
[25] Anonymous, "MIST Therapy." http://www.celleration.com/mist-therapy/
This page describes how the Mist Therapy® works. It shows a mock animation of the
saline mist being applied to a cross section of a wound. It describes how the device removes
barriers to healing and stimulates cells to promote healing.
[26] Liu Y, Shu XZ, Gray SD, Prestwich GD, 2004, “Disulfide-Crosslinked Hyaluronan-Gelatin
Sponge: Growth of Fibrous Tissue in Vivo,” Journal of Biomedical Materials Research,
68(1)pp. 142-149.
This article talks about a newly developed gelatin sponge that would assist the human
ECM to successfully nucleate across the wound bed. The sponge is biocompatible so it can be
absorbed after the body creates its own scaffolding to support the final stages of wound healing.
7
[27] Wells W, 2006, “Electric Healing,” Journal of Cell Biology, 174(4)pp. 477.
http://jcb.rupress.org/content/174/4/477
The article demonstrates how DC electric current can direct cell mitigation during healing
to either open or close a wound. The tests were done in vivo.
[28] Brighton C, 1979, “Electric Healing Batteries for Bone Breaks,” Time, 113(6)pp. 139.
http://www.ahrq.gov/legacy/research/pressureulcerhealing/pruhlit.htm
In this article, a 70 year old man is shown to have healed from a major bone fracture
thanks to electric stimulation applied directly to the bone fracture site.
[29] Sample I, 2006, "Healing Power of Electricity Raises Hope of New Treatments," The
Guardian. http://www.guardian.co.uk/science/2006/jul/27/uk.health
The article talks about how studies have been found to speed the process of healing. It
provides proof that electric stimulation technology may reduce the time that a wound takes to
heal.
[30] Hirshon B, “Electric Healing.” http://sciencenetlinks.com/science-news/science-
updates/electric-healing/
This article claims that a little electricity may dramatically speed up the healing of skin
wounds. The article focuses on giving evidence on why electricity helps wounds close. The team
learned that an electric field is created when the body has a wound, and this electric field attracts
healing cells to the wound site to close it.
[31] Ly M, Poole-Warren LA, 2008, “Acceleration of Wound Healing Using Electrical Fields:
Time for a Stimulating Discussion,” Wound Practice and Research, 16(3)pp. 138-151.
http://www.awma.com.au/journal/1603_05.pdf
This article looks at electric fields and talked about what these fields do within the body
to cause wound closure. It also talks about the advantages and disadvantages of each type of
electric field: AC, DC, and pulsed DC. The article came to the conclusion that AC fields seem to
be the most promising technology due to the fact that DC fields have a potential to create toxins
in the wound.
[32] Yao M, Hasturk H, Kantarci A, Gu G, Garcia-Lavin S, Fabbi M, Park N, Hayashi H, Attala
K, French MA, Driver VR, 2013, “A Pilot Study Evaluating Noncontact Low Frequency
Ultrasound and Underlying Molecular Mechanism on Diabetic Foot Ulcers,” International
Wound Journal.
This pilot study explores the relationship between the dose and duration of treatment for
subjects with non-healing diabetic foot ulcers, and the correlation between wound healing and
change of cytokine/proteinase growth factor profiles. This study took place over 5 weeks on
patients that were effectively offloaded for the duration of the study.
[33] Litzelman D, Marriott D, Vinicor F, 1997, “The Role of Footwear in the Prevention of Foot
Lesions in Patients with NIDDM,” Diabetes Care, 20(2).
This case study evaluates footwear characteristics as predictors of diabetic foot wounds.
In practice, many variables have been cited as protective measures in footwear for diabetic
patients that were not prospectively predictive when controlling for physiological risk factors.
8
[34] Horn S, 2009, “Pressure Ulcer Healing Literature Review,” Agency for Healthcare
Research and Quality. http://www.ahrq.gov/legacy/research/pressureulcerhealing/pruhlit.htm
A review and summary of the technology and therapies that have been researched and
tested related to improving pressure ulcer healing. This literature review gave the team a good
idea of all the different techniques that are being researched for closing ulcers. The review also
had a results and conclusions sentence under each technology that stated how well each
technology performed on certain ulcers. Review also showed evidence of the AC electric fields,
ultrasound, and negative pressure all working to increase healing time on ulcers.
[35] Horton A, 2010, “The Standard of Care for Evaluation and Treatment of Diabetic Foot
Ulcers,” Barry University, pp. 1-28. https://www.barry.edu/includes/docs/continuing-medical-
education/diabetic.pdf
This is a publication created by Barry University with the assistance of a grant that
studies the standard ways to detect and treat diabetic foot ulcers. It is written to be a self-study
tool for physicians, podiatrists and nurses working on wound healing related to diabetic foot
ulcers.
[36] Ul-Muqim R, Driffin S, Ahmed M, 2003, “Evaluation and Management of Diabetic Foot
According to Wagner’s Classification,” Peshawar and Department of Surgery, Ayub Medical
College. http://www.ayubmed.edu.pk/JAMC/PAST/15-3/rooh.htm
This paper studies the prevalence of diabetic foot ulcers in 10 surgical patients at Khyber
Teaching hospital. The Wagner’s classification was used to describe the wounds and the
prevalence of each grade of chronic wound is reported. This is useful because it describes the
Wagner’s classification of chronic foot ulcers and gives some data on how common each level of
severity is in a post-surgical diabetic population.
[37] Perlman, H. (2013, January 10). The Water in You. Retrieved 04 22, 2013, from
http://ga.water.usgs.gov/edu/propertyyou.html
[38] Wu, Stephanie., “Foot ulcers in the diabetic patient, prevention and treatment,” 2007.
[39] Nather, Aziz., “Effectiveness of Vacuum-assisted Closure (VAC) Therapy in the Healing of
Chronic Diabetic Foot Ulcers,” 2010.
1.2 Patent Search
1.2.1 – Patent Search – Objectives
The purpose of the patent search was to explore the current state of electric field and
ultrasound wound healing technologies to see what would be considered a novel device.
Searching patents also helped spark ideas in brainstorming and to see what has been tried, what
looks successful, or what is not possible or applicable for this device.
The design of the wound closure device is intended to deliver both AC electric field and
ultrasound therapies to the wound site. The device is unique in that it combines both of these
therapies in a single device. The electric field could be delivered through a wide variety of
electrode types, shapes, and sizes; including wires, strips, and disks. The ultrasound therapy
needs a medium to travel through to get from the transducer to the skin. Options for this medium
include saline, gel applied to the wound site, or through a gel wrap. The idea for this device is to
9
incorporate the electrodes into a gel wrap that could have a separate “wand” with the ultrasound
transducer inside to apply the therapies together when needed.
1.2.2 – Patent Search – Search Criteria
The Google Patents search engine was used to search for patents. Phrases that were
searched include ultrasound wound therapy, electric wound therapy, facilitating wound healing,
and wound healing. Classes and sub-classes searched include 601/2, 128/200.16, 600/439,
604/22, and 607/50.
1.2.3 – Patent Search – Findings
Rafael Victor Andino, Christopher J. Brooks, Michael J. Keating, Courtney F. Morgan, Donald
Van Royen, 2009, “Apparatus and methods for facilitating wound healing and treating skin”,
Google patents from http://www.google.com/patents/US20100174343?dq=posifect&ei=qrs3Uf_-
KMTR2QXFjYHwCA
Figure 1.2.3.1: Apparatus for facilitating wound healing and treating skin
This patent’s original assignee is Biofisica LLC, the company that produces the
POSiFECT® system. The patent describes an electrode system and methods for using them to
apply electrical stimulation to a wound or skin. The electrode system could also receive feedback
from the wound site to detect wound healing factors and adjust the therapy accordingly creating
a closed-loop system. The outer electrode is a strip that runs around the outside of the wound.
The inner electrode is placed in the middle of the wound bed. If the wound is large enough,
multiple inner electrodes could be used. The control module is attached to the electrodes as a
flexible circuit that can conform to the shape of the area it is applied to. This patent uses a patch
style device with electrodes and a flexible control module attached to it to increase the range of
successful application locations. Since the idea of the design team is to create a wrap with a
separate power source with different electrode designs and incorporating ultrasonic therapy as
well, it should differ enough from this patent to not be a significant threat to novelty.
10
Eilaz Babaev, 2011, “Ultrasonic method and device for wound treatment”, Google patents from
http://www.google.com/patents/US7914470
Figure 1.2.3.2: Ultrasonic device for wound treatment
This patent’s original assignee is Celleration, Inc., the company that produces the Mist
Therapy® system. This patent describes an apparatus and method for applying ultrasound
therapy to desired tissue area through a medium. The device delivers therapy from a non-contact
distance. The ultrasonic energy delivered has enough intensity to penetrate the wound tissue to a
deep enough level to provide a therapeutic effect to the tissue. This device gave us an idea of the
possible mediums available to transmit ultrasound through, and to investigate the healing
capabilities of the therapy. The design team’s design uses a contact through the wrap or gel to
transmit the ultrasonic waves and incorporates electric field therapy, so it should be different
enough from this patent to not be a significant threat to novelty.
11
Brian Fahey, 2009, “Systems and methods for automated muscle stimulation”, Google patents
from
http://www.google.com/patents/US20100004715?dq=607/50&ei=m_I3UbOBM8y02AWv4YGQ
DA
Figure 1.2.3.3: System for automated muscle stimulation
This patent describes a patch-like device used for neuromuscular electrical stimulation to
muscle tissue. This device can use both therapy delivery and sensor probes so that therapy can be
applied and feedback can be received, creating a closed-loop system. The system may also
include temperature sensing probes to prevent over heating of tissue for patients who may not be
able to feel or react to the sensation. The device uses a separate control box connected to the
therapy delivery patch by wires similar to the concept proposed by the design team. However,
this device uses electrical signals to stimulate muscle tissue, which requires greater voltages and
serves a different purpose than the device proposed by the design team. This patent should not
pose a threat to novelty.
Andruw Burd, Michael Wing Wai Tsang, 2008, “Wound healing dressing and methods of
manufacturing the same”, Google patents from
http://www.google.com/patents/US20100196448?dq=wound+healing&ei=dPU3UcyABI762AW
floGIDg
This patent describes a hydrogel dressing for covering or treating a wound, and the
method for doing so as well. The dressing described includes a matrix structure of a cross-linked
mixture, and an elastic sheet coated with an elementary metal or ionic metal embodied in the
matrix structure. In the process for treating wounds with the dressing, a possible method is
described where electrical current is applied to the wound with a positive electrode in the
dressing and a negative electrode attached to skin close to the wound. The device proposed by
the design team would like to use a hydrogel dressing with electric therapy, but the electrodes
would not have to be in contact with the wound in order to use the AC electric field. This fact,
along with the device also using ultrasound therapy should set the device apart from this patent
enough to not be a threat to novelty.
12
1.3 User Need Research
1.3.1 – Customer Interviews
To understand the needs of our customers, interviews were conducted with different
specialists and a survey was sent to an individual who had just undergone surgery and had a
large open wound. Through these interviews and survey the most important customer needs for
our device were determined.
Date: January 24th
, 2013
First Meeting: Christopher Rolfes, Ph.D.
Advisor title: Fellow at the Medical Devices Center at the University of Minnesota.
Location: 5th
Floor of Shepherds Lab at the University of Minnesota
Members Present: John Braun, Bryan Horvat, Daniel Knox, Nick Tassoni, and
Christopher Hanson (caught the end of the meeting)
Notes from first meeting:
Christopher Rolfes, our advisor, introduced himself and then gave us incite to the
previous work that had led to this project.
The Senior Innovation Fellows at the University of Minnesota’s Medical Devices Center
have completed needs finding to identify opportunities for a new medical device. They had
begun researching electric fields and ultrasound and saw the potential for creating a device that
applies these therapies to the wound bed. Chris went into how wound closure is a huge problem
for both surgical and non-surgical patients. Chris also mentioned that there was no gold standard
for treating open wounds in patients with diabetes, pressure ulcers, and bed sores. “Clearly there
is a need for an effective way to promote wound closure.”
Chris explained that this project will involve designing and building prototypes for a
novel method of incorporating ultrasound and electric field. Chris emphasized the need for the
device to be novel and patentable and mentioned that no device has attempted to incorporate
both ultrasound and electric field together.
Date: February 5th
, 2013
Interview with: Alan W. Johnson, M.D.
Interviewee title: Otolaryngologist
Location: Brainstorming Room in Shepherds Lab at the University of Minnesota
Members Present: Christopher Hanson, John Braun, Bryan Horvat, Daniel Knox, and
Nick Tassoni and Advisors: Christopher Rolfes and Laura Paulsen
Notes from Interview:
Dr. Johnson came into our meeting in the Brainstorming room to meet with the team to
discuss wounds and talk about what causes a wound to be chronic. There are generally two
reasons a wound will not close these are the lack of oxygen to the wound or infection in the
wound bed, or a combination of both.
There are a few basic types of wounds.
Pressure Ulcers (located on back and bottom)
Venous Stasis Ulcers (located on limbs)
Diabetic Ulcers (generally on the foot and lower legs)
13
Acute trauma
Post Surgical
Infection/Abscess
Malignancy
Dr. Johnson then went into a discussion on the two different categories wounds are put
into to describe how they will heal. The categories are 1st intention and 2
nd intention wounds. 1
st
intention wounds are incisions or wounds where none of the flesh has been removed. 2nd
intention wounds are wounds where flesh is missing, meaning there is a gap in the skin or a
pocket where skin or flesh is missing.
The best environment for healing wounds is a wet and moist environment where the
wound is completely sterile. Silverdene is a solution that is used to create this environment. It has
antibiotics in it to create a sterile environment and it also keeps the wound site moist.
Dr. Johnson then went into a discussion about debridement. Debridement is commonly
done using gauze in the wound bed, this process of putting wet gauze in the wound and removing
it when it is dry is called wet-to-dry dressing. When the gauze is dry the gauze is pulled out and
debris, which is attached to the gauze, is pulled out of the wound.
Wounds are categorized in three general sterile levels. The first category is clean wounds
(typically found in surgical wounds). The second is clean/contaminated wounds. These wounds
are initially sterile but then an incision is made into a bacterial laden area such as the liver or
spleen. The third and last sterile level is dirty. This means the wound is already dirty and
debridement must be used to remove the bacteria and biofilm. These are typically ulcers and
trauma wounds.
Dr. Johnson provided us with a great background in how wounds heal and the conditions
necessary to get a chronic wound to heal. Dr. Johnson’s final thoughts were to select a specific
type of wound to try and close as the wound types vary so much. Also 1st intention wounds
already have a pretty good wound closure process. Stitches have the market on 1st intention
wounds.
Date: February 6th
, 2013
Interview with: Dr. Steven J. Kern, M.D.
Interviewee title: General Surgeon, Chief of Surgery at Maple Grove Hospital
Location: Trauma Surgeon’s house
Members Present: Christopher Hanson, John Braun, Bryan Horvat, Daniel Knox, and
Nick Tassoni
Notes from Interview:
Dr. Kern invited us over to his house to talk with him about wounds and his experience
with wound closure devices.
Group asked Dr. Kern about his familiarity with wound closure devices and procedures:
Dr. Kern mentioned that he was familiar with a product that sewed Velcro into the skin to
assist wound closure. It is an attempt to find an alternative for stitches. Had heard of the wound
VAC and used it. Dr. Kern was really impressed with the wound VAC. Dr. Kern said that in his
experience the wound VAC was not as effective for healing chronic wounds, but it is really easy
14
to apply to the wound site. Mechanical closure has also been used by many devices to facilitate
closure. Mechanical closure basically pinches the wound.
What is the key to healing a chronic wound:
Dr. Kern said the key to healing a wound is getting oxygen to the wound. If you get
oxygen to the wound site, the wound will heal.
How much money would this device save patients if it decreased hospital stay time:
Dr. Kern saw huge market potential for a device of this type. A day in the hospital is
$15,000 - $20,000 a day. A product that could decrease even one day off of the hospital stay time
of the patient would save the insurance company and patient a huge amount of money.
What are some indications that a patient has to stay in the hospital for a chronic wound:
Usually hospital tries to get wound under control and send patient on their way. The key
for the hospital is to seal the wound and then have checkups with the patient to ensure the wound
is closing. Dr. Kern also recommended making the device easy to use and intuitive. These house
nurses are used to doing things a certain way and for our device to succeed, it needs to be easily
adapted into the way they dress wounds.
Dr. Kern’s final thoughts:
No perfect device on the market for healing chronic wounds. There are some processes
for healing chronic wounds that are somewhat barbaric such as skin grafts. A solution to these
processes is highly desired by the healthcare industry. The key to getting wound closure is that
our device gets and increases oxygen to the wound. Also mentioned that the device would have to
be covered by insurance in order for hospitals to use it.
Dr. Kern wanted to be kept in the loop as we moved forward with the project as he will
be very interested in the solution we come up with for chronic wounds.
Date: February 18th
, 2013
Interview with: Dr. Marie-Claire Buckley, M.D.
Interviewee title: Plastic and Reconstructive Surgeon at Fairview Southdale Hospital in
Edina
Location: Brainstorming Room in Shepherds Lab at the University of
Minnesota
Members Present: Christopher Hanson, John Braun, Bryan Horvat, Daniel Knox, and
Nick Tassoni and Advisors: Christopher Rolfes and Laura Paulsen
Notes from Interview:
Group asked Dr. Buckley about what technologies she was familiar with:
Dr. Buckley was very excited about the potential stem cell research has with wound
healing. She said that it was the “way of the future,” where the body heals itself. She had heard
of the electromagnetic spectrum being used to close chronic wounds. Also, she liked the idea of
inserting an extracellular matrix into the wound site to heal the wound. This type of technology
is used in products like the Wound VAC. Dr. Buckley mentioned a few future improvements to the
wound closure process.
15
“A device that provides an alternative to debridement would be nice.” Dr. Buckley hates
having to remove tissue in order to clean the wound. Also the device should be very lightweight
to avoid creating new wounds or pressure ulcers. Dr. Buckley had also used an electromagnetic
device. Dr. Buckley’s favorite chronic wound closure device that is on the market is the wound
VAC that uses negative pressure in the wound to facilitate debridement. This device still has
some issues however. The wound VAC still uses classic debridement of the wound site. Because
the extracellular matrix in the wound is not biodegradable, the wound VAC has to be removed
every so often and when it removes the extracellular matrix rips out tissue along with bacteria
and other biofilms that build up in the wound bed. A wound VAC with a biodegradable matrix
would be great!
Dr. Buckley mentioned that a device that removes pressure from wound site would also
be helpful for wounds such as chronic pressure or diabetic foot ulcers. Mentioned that some
research is being done with vertebra tension to have the device support and remove pressure
from the wound and surrounding tissue. She gave an example of the spine of a dinosaur to
explain how vertebra tension works. Lastly, Dr. Buckley knew of a device called SURECLOSE
which uses mechanical closure of the wound. Device uses tension on the edges of the wound to
try and force them together. Device looks like a shoelace across the wound and every so often
they tighten the laces.
What are the pros and cons involved in making the device a take home device:
Dr. Buckley went into how sometimes an in-home nurse is used when the procedure for
wound dressings is too complicated. Some technologies such as mist therapy would be harder to
incorporate in a take home device whereas a device that uses an electromagnetic spectrum
across the wound would be easier to incorporate into a take-home device.
What are some indications that patient needs to stay in hospital for a wound:
Usually based on if they can take care of it themselves, usually doctors can quickly get
wound under control and send them on their way. Dr. Buckley then expounded on some of her
ideas on best way to apply a device. Silver and iodines when used in a solution applied to the
wound are good at getting rid of microbials and biofilm.
Is there special care for diabetic ulcers:
With diabetic ulcers perfusion is very important. There is fancy footwear usually used to
prevent the ulcers. These footwear devices focus on offloading the foot. In general (with any type
of wound) you do not want the wound too wet or too dry. Doctors usually check the moisture
content of the wound visually. If wound is weeping (seeping with water) it is too wet and if it
looks crusty then it is too dry. Might be interesting to determine the ideal moisture content for
the wound bed to be at to heal.
With diabetic ulcers, old cells are not responding. Glucose interferes with calling cells so
you cannot feel pain from the wound and also there is no call to the cells necessary for closing
the wound.
Overall, care of this demographic is similar, but it is important to be extra aware of
potential complications.
What types of technologies have you used to attach devices to the wound site:
16
Topical oxygen has been used. These topical oxygen solutions are applied through
gauzes. These gauzes are applied soaked in the oxygen rich solution and then the particles are
released from the gauze into the wound. To get wound closure you need to get endothelial cells
to the wound site.
Negative pressure is very easily applied to any location on the body. Patient can sit on
the negative pressure. The negative pressure runs constantly. Dr. Buckley had a great idea. She
mentioned that it would be cool to have a self run device, where as the patient puts pressure on
the device it would provide electrical field to the tissue and stimulate wound closure.
The easiest method of application would be a wrap or compression sleeve. You can wrap
almost any area of the body. She also mentioned that one technology or therapy cannot be
applied 24/7 because body will become tolerant and the device will become ineffective for wound
closure.
Is diabetic ulcer treatment done in the ICU/ward or at home:
Categorizing whether a diabetic ulcer needs to be treated in the ICU or can be treated at
patient’s home, is done on a patient-by-patient basis. If patient develops gangrene then ICU care
is needed. Usually they end up amputating part of the limb.
What would help the hospital save money:
In order for hospital to save money on treating diabetic ulcers the therapy needs to be
covered by insurance. Devices that incorporate electric field therapy and mist therapy are not
covered by insurance. The wound VAC, which incorporates negative pressure, is covered by
insurance. That is why this technology is most frequently used. Hospitals don’t want to pay for
treating diabetic ulcers. Usually the hospital will try to do whatever they can to get it under
control and then send the patient along on their way.
Dr. Buckley’s final comments:
No current device that monitors and controls the moisture content of the wound.
Angiogenesis, which is needed for wound closure, needs moisture. The important factors for a
device used on an ulcer are maintaining moisture, elevating the ulcer, and removing pressure
from the ulcer.
To reach Dr. Buckley
Call her secretary: 612-625-0697
Survey sent to: Mrs. Daniels
Survey returned: February 10th
, 2013
Survey-taker’s reason for completing survey: Mrs. Daniels recently had surgery done and
it left a large open wound. Mrs. Daniels
received common wound closure methods
used by the hospital
SURVEY QUESTIONS:
1. What area of the leg was injured?
17
Left front of leg, knee to ankle.
2. How large was the wound?
1 ½ feet long and 8 inch wide.
3. What procedures were performed to repair leg injury?
(First Surgery) Reattached muscle, stitched leg together for hope it would recover (it
didn’t), (Second surgery) so they removed the dead skin. Had to wait 4 days to make sure muscle
underneath the wound didn’t get infected and blood flow stayed consistent. (Third Surgery) Next
step was a skin graph, after skin graph had a pump with saline solution onto the new skin to keep
skin moist and to flush out any infection. The term used for the whole process was partial de-
gloving of the lower left leg.
4. Was there a sizeable wound left on leg after surgery?
Pretty much the whole wound will be a scar.
5. What methods/devices were used in the healing process of the wound?
Wrapping, antibiotics, cleaning, moisturizing, physical therapy, stretches, compression
stocking.
On crutches/walker for 4 weeks. 4 months of physical therapy then 2 month break now
doing physical therapy again (3 times a week). Still in the healing process to get motion back in
foot and ankle.
6. Was there anything you disliked about the methods/devices used to heal the wound?
Disliked the whole thing, but the worst was peeling off foam pad that was adhered to skin
donor area (upper thigh on left leg). Skin donor area ended up being the worst part of the whole
process.
7. Was there anything you liked about the methods/devices used to heal the wound?
Pain pills
8. How long was your stay in the hospital?
3 ½ weeks
9. What portion of your hospital stay was after surgery, during the wound healing process?
After first surgery 4 days in hospital then went home for a week then readmitted because
skin died then had second surgery to remove dead skin stayed in hospital for a week and after
that week also had a third surgery and stayed at the hospital 2 more weeks after that.
10. Was any part of the wound healing process done at home? If so, what methods/devices were
used?
See answer to question 5 same processes done at home.
11. Additional comments (if any)
18
Email sent to: Dr. Marie-Claire Buckley, M.D.
Email sent: February 25th
, 2013
Email returned: February 26th
, 2013
Emailed Dr. Buckley with questions specifically directed towards finding more about
diabetic ulcer wounds that are located on the ball/heel of the foot.
What is the current practice for treating a diabetic ulcer located on the foot:
Because many diabetics are neuropathic, off-loading is very important. They also
develop calluses around the wound edges that must be shaved down to free up the epithelial cells
from the perimeter. Debridement of the slough in the base is also important since many diabetic
wounds have polymicrobial flora. Once it’s clean, then it’s a matter of stimulating granulation
tissue formation which can be tricky since there are a number of molecular and cellular defects
associated with poor sugar control and effects on perfusion.
Is the wound VAC device used on patients with diabetic ulcers on the heel or ball of the foot:
The VAC can be used anywhere you can get a seal as long as vital structures aren’t
exposed.
How mobile are patients when the doctor is treating these ulcers on their foot:
Mobility is allowed but some of the off- loading shoes are awkward.
Are offloading devices used on the foot while the doctor is treating the diabetic ulcer:
You should probably connect with a podiatrist for more on that!
19
1.3.2 – Customer Needs and Design Specifications
Based on information obtained through the patent searches, the customer interviews, the
survey, and research done by the team a list of customer needs related to our design was created.
Each team member ranked the importance based on what their takeaway was from the user needs
research and the average value is shown. The customer needs are listed in Table 1.3.2.1 below.
Table 1.3.2.1: Customer Needs
Customer Needs
# Need
Importance
(out of 5): Source
1 Device speeds the process of healing wounds 5 Advisors
2 Device reduces the cost of healing wounds 5 Dr. Kern
3 Device allows patient to shower 2 Dr. Buckley
4 Device reduces risk of infection 5 Dr. Johnson
5 Device fits in a hospital room 5 Advisors
6 Device is easy to operate 3 Dr. Kern
7 Device has a low profile 2 Dr. Buckley
8 Device is easy to store 2 Advisors
9 Device is comfortable for patient 4 Dr. Buckley / Dr. Kern
10 Device operates on standard household outlet 4 Dr. Buckley / Advisors
11 Device is aesthetically pleasing 1 Dr. Buckley / Advisors
12 Device attaches securely to the desired area 3 Advisors
13 Device is applied with minimal pain 4 Dr. Buckley
14 Device contains reusable parts 2 Dr. Buckley
15 Therapy is applied with minimal pain. 5 Dr. Buckley
16 Device will keep surrounding healthy tissue intact 5 Dr. Buckley
17 Device is easy to manufacture 2 Dr. Kern
18 Device is intuitive for healthcare provider to use 4 Dr. Kern
19
Device is adjustable for different sizes/anatomical
locations of wounds 3 Advisors
20 Device is safe 5 Dr. Buckley / Advisors
21
Device decreases hospital stay time due to wound
closure problems 5 Advisors
22 Device is portable 3 Dr. Buckley / Advisors
23 Device increases blood flow to wound site 5 Dr. Kern
24 Device is easily detached from patient 4 Advisors
25 Device facilitates wound debridement 3 Dr. Buckley
26 Device allows visibility of wound when attached 3 Advisors
27 Device is lightweight 3 Dr. Buckley
28 Compatible with Negative Pressure Wound Therapy 2 Dr. Buckley / Dr. Kern
29
Device is easily adoptable by healthcare providers
and patients 4 Dr. Buckley / Dr. Kern
30 Device is novel and patentable 5 Advisors
31 Device is sterile 5 Dr. Johnson
20
These customer needs were then transformed into a list of design requirements for our
design. These design requirements are metrics by which we can measure our success of
satisfying our customer needs. Table 1.3.2.2 summarizes those specifications.
Table 1.3.2.2: Design Specifications
Customer Design Specifications
Need #’s Metric Importance Units
Marginal
Value
Ideal
Value
2, 21,14,17 Device Cost 4 US $ <200 50
6,18,24 Number of operators 4 Integer 2 0-1
5,8,22 Storage Area 2 m^2 <4 <0.25
5,8,22 Storage Volume 2 m^3 <8 <0.125
10 Power Source 2 Volts <240 120
19,1,15 Current Delivered 3 milliAmperes <1000 <1
2,18,29 Setup Time 5 Minutes <60 5-10
7,9,12,13,15 Comfortable 4 Subjective Yes Yes
20,31 Meets applicable ISO standard 4 Binary Yes Yes
7,11 Aesthetics 2 Subjective Yes Yes
1,4,23 Delivers required therapy 5 Binary Yes Yes
24,25,26,28 Ease of Access to wound site 3 Subjective Yes Yes
3 Moisture Resistant 3 Binary Yes Yes
16 Healthy tissue unaffected 5 Binary Yes Yes
19 Covers different sizes 4 mm^2 100-200 <1000
24,26 Facilitates doctor checkup visits 4 Subjective Yes Yes
27 Weight on patient 3 lbs <20 <1
19
Covers different anatomical
locations 4 Binary Yes Yes
7 Height 4 inches <24 <1
6,18,25,28,2
9
Easily incorporated with current
methods 5 Subjective Yes Yes
30 Patentable 5 Binary Yes Yes
1.4 Concept Alternatives
1.4.1 – Patch
With this sort of device, a single unit of material with all major needed components can
be applied to the wound area. The device would be either circular or modular in shape in order to
fit around the wound. The device is then adhesively attached to the wound and wrapped into the
wound. An electric field or DC current can then be applied to the wound. A similar product has
been developed called POSiFECT® [24].
The device is largely made of standard dressing materials, and the bio-current therapy is
integrated into the dressing matrix and is powered by a small electric module assembly. The
anode of the device is a flexible metal ring attached to the outer part of the dressing, and the
cathode is on the end of a wire that is attached to the power unit under the dressing flap. The
21
cathode is placed on the wound bed during use. Both are covered in a sodium-rich hydrogel to
ensure good electrical contact. This device uses a changing DC current to promote healthy tissue
growth and prevent infection, and so requires contact with the wound bed and skin. This concept
has advantages of being easy to apply, simplicity and proven success in the field.
Figure 1.4.1.1: Patch Concept Drawing with Gel Ground
As shown in Figure 1, we considered applying the therapy using a patch design with a
central electrode and grounding the tissue around the wound using conductive gel contacting the
ground wire. The advantage of this is that the conductive gel can be applied in any shape
necessary so that the wound is treated properly. However, even if we were to use the same basic
concept for the device and add ultrasound therapy treatment options to the device, the team
decided that our design and POSiFECT® were too similar. Therefore, the concept was thrown
out.
1.4.2 – Wound Vac Integrated Device
The wound vac is used as a method of debriding the wound and pulling the wound
together. The wound vac is applied by first laying down a sponge on the wound. A layer of
plastic is laid over the wound and the sponge that prevents air from flowing into the wound. A
vacuum hose is attached to the plastic above the wound and the device is turned on drawing the
wound together and removing infectious material. Based on the interviews with Dr. Buckley and
Dr. Kern, a wound vac is often an important tool used in the treatment of chronic wounds. Both
Dr. Buckley and Dr. Kern stated that they use wound vacs as part of the treatment for chronic
wounds. [7,8]
Conductive Gel Alternating Field
Electrode
22
Figure 1.4.2.1: Wound Vacuum integrated with Ultrasound and Electric Field
As shown in Figure 2, we considered concepts that might allow all three technologies to be
applied at the same time. The challenge of applying wound vac technology to this wound and
also allowing for the ultrasound technology and electric field therapy to be applied to the wound
at the same time led the team to the decision that the wound vac should be applied when our
device is not applied to the wound.
1.4.3 – Foot Application
In many cases, diabetes can lead to neuropathy in the extremities including the hands and
feet of the patient [7,8]. Because of this, the feet are a common area for chronic wounds to form
and therefore provide a great opportunity for providing a targeted market solution. The primary
concept in this category was to apply a gel sock that would allow for offloading of the wound
area while the patient walked.
Figure 1.4.3.1: Offloading Gel Sock
The biggest challenge for this concept was that the specific technology for the offloading gel has
not been developed yet and applying offloading solutions is outside of the scope of our project.
1.4.4 – Moisture Devices
Through the interviews with Dr. Kern and Buckley, we determined that a large limiting
factor in the rate that a chronic wound would heal was the amount of oxygen and nutrients that
Wound Vacuum
Hose
Outer Electric
Field Ring
Ultrasound
Transducer
23
the cells around the edges of the wound are receiving. We came up with several concepts
including pumping oxygen rich fluid through the wound.
Figure 1.4.4.1: Wound Bubbler Concept
As shown in Figure 4, we considered applying a device that delivered oxygen and fluid to the
wound bed. This concept and other similar ideas require an addition of expensive equipment
normally not included in wound care so the concept was not chosen.
1.5 Concept Selection
1.5.1 – Screening Process
The concept selection process began by identifying the pertinent screening criteria. Eight
criteria were taken from the product design specifications and customer needs and then used to
rate each of the six concept categories. The selection criteria are listed in the first column in
Table 1.5.1.1 while the six basic categories are listed across the second row. Concepts were
given a plus, or one point, if they excel in the criteria. Concepts received a minus, or negative
one point, if it failed to meet the criteria. Lastly, concepts received a zero, or zero points, if they
were merely on par with the standard method of treatment, debridement. The points were then
added up and the concepts were ranked based on those values. Table 1.5.1.1 shows the results of
this analysis.
Table 1.5.1.1: Concept Screening
Air and Fluid
Delivery
Ultrasound
Transducer
Electric Field
Ring
24
From Table 1.5.1.1, three concept categories were rated significantly higher than the remaining
three and were further investigated. Patentability was a key criterion for the final concept. It
was decided that the best way to achieve that would be to evaluate combinations of the top
concept categories. Table 1.5.4.1 below uses a weighted analysis to differentiate between these
combined concepts.
1.5.2 – Criteria Definitions
The eight criteria used to evaluate concepts in Table 1.5.1.1, in addition to
Manufacturability and Patentability, were used for the weighted concept analysis in Table 1.5.4.1
below. They are: Speed healing, reduce hospital time, reduce risk of infection, low profile, safe,
increase profusion, applied with minimal pain, intuitive to use, patentable, and manufacturable.
“Speeds healing” means that the device will heal the wound faster than the medical industries
standard method of treatment, debridement. This is important because the goal is to actually treat
patients and return them to their normal lives as soon as possible. “Reduce hospital time” means
that the technology will either reduce staff time spent treating the wound or get the patient out of
the hospital faster. This is important because reducing hospital stays amount to huge savings and
make our product more competitive in the marketplace. “Reduce risk of infection” means the
device will reduce the risk of infection more so than the standard method of treatment. This is
important because infections, especially in diabetic patients, can substantially increase the time
to heal the wound and even lead to amputations. “Low profile” means that the device should not
take up much space, make too much noise, or inhibit the abilities of staff to treat the patient.
Small device size saves on the cost of storage; reduced noise allows patients to relax, and
allowing staff to easily treat the patient is crucial for getting the product adopted. “Safe” means
that the device has no adverse side-effects such as damaging healthy tissue. “Increase perfusion”
means that the device will facilitate in bringing blood and nutrients to the wound bed. Without
that, there is no healing. “Applied with minimal pain” means that the device can be applied
without requiring pain medication. This definition was chosen in lieu of a pain scale because of
the variability of patient pain tolerances; whereby the subjectivity of the scale would require a
product to account for extremes and therefore cost more. “Intuitive to use” refers to having a
device that can be applied without special training. A device that is easy to use is more likely to
be adopted by medical professionals. “Patentable” means that the device could be patented and
marketed. This is the ultimate goal of the project and solutions need to have that prospect.
Lastly, “Manufacturable” refers to the ease of actually building the device for commercial use.
This is important because even a device that works exceptional will not be adopted if it costs too
much to manufacture.
1.5.3 – Selection Process
The four possible combinations from the top three concepts above were evaluated in
Table 1.5.4.1 below. They are: E-field Wrap with Wound Vac; E-Field Wrap with Ultrasound;
Wound Vac with Ultrasound; and E-field Wrap with Ultrasound and Wound Vac. Each
selection criteria was given a weight between 1 and 5; 1 being the least important and 5 being the
most important. A higher importance was given to criteria from the customer needs such as being
patentable rather than to criteria from the product design specifications such as being low profile
because the device is for the client, not the engineers. Then the concepts were given a rating
between 1 and 7 for each of the criteria. Again, a higher number signifies that the concept better
adheres to the selection criteria. This scale was chosen over the traditional 1 to 5 scale, because
25
it incorporates a human factors recommendation for obtaining a more accurate representation.
On a 1 to 5 scale, most people tend to avoid the extreme cases denoted by 1 and 5, thus limiting
the team’s ability to differentiate the concepts. After values were assigned, the rating and the
weight were multiplied to give the weighted score. Weighted scores were then summed to give
the total score for each concept. The largest total score denotes the best concept according to the
criteria.
1.5.4 – Selection Results
Table 1.5.4.1: Weighted Analysis of Concepts
As seen in Table 1.5.4.1, the “E-field Wrap with Ultrasound” and “E-field Wrap with
Ultrasound and Wound-Vac” have significantly larger scores than the remaining two concepts
and were chosen for further evaluation. The approach taken was on a common sense basis. Both
concepts incorporated E-field wraps and Ultrasound, but one had an additional component; the
wound vac. Common sense tells us that if they both accomplish the same thing, go with the
simpler concept. The project advisors, both of whom are Senior Fellows at the Institute for
Medical Devices, unanimously agreed. Therefore, client input, expert opinion, and common
sense lead to the conclusion that incorporating and E-field wrap with ultrasound was the best
choice among the concepts tested. Most importantly, this final concept was never below par
with the most common industry method of treatment; debridement. In addition, it excelled in
several key areas such as reducing the risk of infection; increasing perfusion; speeding wound
healing; and maintaining patentability.
2.1 Manufacturing Plan
2.1.1 – Manufacturing Overview
The novel wound closure device incorporates wires, conductors and a transducer inside
of a wrap. Vitality Medical’s Coban Self Adherent Wrap will be purchased as the wrap material.
This choice was made in order to make prototyping quick, cheap and easy. Also, the self-
adherent properties of the wrap will be able to secure the wires, conductors and transducer in
between the two layers of the wrap.
26
The electrical portion of the device will contain many of the parts. A function generator
from B&K Precision will be used to supply the voltages, currents and frequencies needed in the
device. Stainless steel shim stock purchased from McMaster-Carr will be the material used for
the conductors. This is because the shim stock is cheap and malleable which will allow the
conductors to be made into long, narrow and thin strips to run the length of the wrap. The
conductors will create the AC electric field therapy delivered by the device. Also, BNC male
plug with two hook electrical connectors from McMaster-Carr will be used to connect these
conductors to the function generator. The transducer will be purchased from STEMiNC, and
will be attached to the wires by securing the self-adherent wrap around the transducer. The wires
will be 24 gauge speaker wire purchased from Jameco. The BNC male plug with hook electrical
connectors will also be used to connect these wires to the function generator. This transducer
will supply the ultrasound therapy delivered by the device.
Beneath the transducer, a medium is needed to transmit the ultrasound. To do this,
ultrasound gel from the Medical Device Depot will be purchased. This gel will rid the gap
between the transducer and the wound of air, which greatly disrupts the transmission of the
ultrasound pressure waves.
This manufacturing overview is for the generation one prototype. These materials do not
account for the readily available materials from the Medical Devices Center that the team used to
construct the actual prototypes. Also, the materials described may change in a future generation
prototype or if an industrial manufacturing setting becomes a reality.
2.1.2 – Part Drawings
Note: All dimensions are in inches unless otherwise noted. Dimensions and drawings are
preliminary.
27
Figure 2.1.2.1: Electrode Drawing
Figure 2.1.2.2: Wrap Hole Drawing
28
Figure 2.1.2.3: Transducer Drawing
Figure 2.1.2.4: Assembly Drawing
29
Figure 2.1.2.5: Layout Drawing
Figure 2.1.2.6: Exploded View Drawing
30
2.1.3 – Bill of Materials
Table 2.1.3.1: Rev 1 Bill of Materials
Part
Description
Model
Number
Supplier,
Manufacturer Quantity Unit Cost Total Cost
Coban Self
Adherent Tan
Wrap 1584 Vitality Medical 1 Roll $2.95 $2.95
Stainless Steel
Shim Stock 2317K11 McMaster-Carr 1 Sheet
$7.83 $7.83
24 Gauge
Speaker Wire 100280 Jameco 1 Roll $7.95 $7.95
Ultrasonic
Transducer
SMD20T2
1F1000R STEMiNC 1 Item $7.43 $7.43
Function
Generator 4017A
Zoro Tools, B&K
Precision 1 Device $415.84 $415.84
Ultrasound Gel G150 Medical Device Depot 1 Bottle $2.95 $2.95
BNC Male Plug
With Two Hooks 6934K73 McMaster-Carr 2 Item $27.63 $55.26
Grand Total
Cost
$500.21
This Bill of Materials is quoted for what a remake of the prototype of the device will cost
someone who wishes to build this product. It does not account for tools used to create the
prototype or the materials that were readily available to the team from the Medical Devices
Center which were used to create the prototype. Also, it should be noted that the function
generator would be a one-time cost for a facility that would use this device. After the function
generator has been purchased, the materials to build a prototype will cost about $84.37.
However, some of the other components contain enough material to build more than one
prototype, so this is an overestimation of the true cost of a prototype.
31
Table 2.1.3.2: Rev 2 Bill of Materials
Part Description
Model
Number
Supplier,
Manufacturer Quantity Unit Cost Total Cost
Coban Self
Adherent Tan
Wrap 1584 Vitality Medical 1 Roll $2.95 $2.95
Aluminum Shim
Stock 9574K72 McMaster-Carr 1 Sheet
$9.28 $9.28
24 Gauge Speaker
Wire 100280 Jameco 1 Roll $7.95 $7.95
Ultrasonic
Transducer
SMD20T21
F1000R STEMiNC 1 Item $7.43 $7.43
Transducer
Housing N/A N/A 1 Item $7.50 $7.50
Function
Generator 4017A
Zoro Tools, B&K
Precision 1 Device $415.84 $415.84
Ultrasound Gel G150
Medical Device
Depot 1 Bottle $2.95 $2.95
BNC Male Plug
With Two Hooks 6934K73 McMaster-Carr 2 Item $27.63 $55.26
Grand Total Cost
$509.16
This Bill of Materials is quoted for what a remake of the second generation prototype of
the device will cost someone who wishes to build this product. It does not account for tools used
to create the prototype. Also, it should be noted that the function generator would be a one-time
cost for a facility that would use this device. After the function generator has been purchased, the
materials to build a prototype will cost about $93.32. However, some of the other components
contain enough material to build more than one prototype, so this is an overestimation of the true
cost of a prototype.
2.1.4 – Manufacturing Procedure
The following manufacturing procedure is a step-by-step guide to fabricate the generation
one prototype. Details of how to obtain or fabricate individual components have not been
included in this procedure.
1. Insert Electrical Components
A. Unroll the full length of the wrap on a flat surface.
B. Cut two long strips out of the shim stock to be 12” long and 1.39” wide for the
electrode conductors.
C. Place the electrode conductors 1/16” from each long edge of the full length of the
wrap.
D. Measure 3” from right end of the wrap and using a scissors cut a 0.5” diameter
hole.
E. Place transducer centered between the two conductors and 3” from right end of
the wrap.
32
F. Create a 0.7” diameter circle with two bare speaker wires and place one circle on
each side of the transducer.
G. Securely fasten the wires to the top and bottom of the transducer by squeezing the
two layers of self-adherent wrap together around the transducer.
H. Run the transducer wires along the middle of the wrap to the edge of the left end.
I. Place a new wrap layer over existing wrap layer and press together over each area
without component interference to adhere wraps together.
2. Prepare Wrap For Use
A. Roll wrap back up tightly.
B. Connect a BNC male plug with two hooks electrical connector to the left end of
both electrode conductors, and to the wires from the transducer when therapy is to
be applied.
C. Place ultrasound gel between transducer and skin to rid of air gap.
3.1 Evaluation Reports
3.1.1 – Delivers AC Electric Field Therapy
3.1.1.1 – Electric Field Intensity
Abstract
Having an electric field intensity of 3 V/cm was one of the important design requirements
for the wound healing device. Literature has shown that electric field intensities in the range of
2-4 V/cm are effective in combating biofilm and infection in the wound [12]. This requirement
was evaluated using a test method which required finding the distance between the electrodes of
the prototype and the voltage difference between the two electrodes. After the distance of
separation was found and the required voltage to produce the correct electric field intensity was
calculated, the prototype was attached to a function generator and oscilloscope. Once the data
was collected and evaluated, it was found that the prototype produced an electric field intensity
of 3.03 V/cm. This evaluation proved that the prototype is indeed capable of producing the
required electric field intensity.
Introduction One of the major therapies produced by this device will be an alternating electric field.
Literature was found showing that an electric field intensity from 2-4 V/cm was effective in
combating biofilm and infection in the wound, which led to an intensity of 3 V/cm becoming an
important design requirement [12]. This test has the purpose of verifying that the required
electric field intensity is being applied by the device. This will be done by finding the distance
between the two electrodes of the prototype and then checking if the applied voltage is what is
measured by an oscilloscope. The device must deliver the proper voltage to meet the
recommended therapy proven to be effective by literature. Table 3.1.1.1 shows the equipment
required to perform the test.
33
Method
Table 3.1.1.1: Equipment
Name Description
Wound Healing Prototype Team’s designed prototype
Function Generator Power source for the prototype
Oscilloscope Record and display voltage difference
Probes Probes with exposed tip to measure voltage
Caliper Used to measure distance between the two electrodes
A caliper was used to find the distance between the electrodes on a given point on the
wrap. After this was found, the voltage difference between the two electrodes was needed.
Equation 3.1.1.1 below was used in order to find what this required voltage difference was.
Equation 3.1.1.1: Electric Field Intensity
In this equation, E is the electric field intensity (V/cm), V is the voltage difference between
the two electrodes (V), and d is the distance between the two electrodes (cm). Using this
equation after already having the distance between the electrodes and the required electric field
intensity allows one to find the required voltage difference. The experimental procedure
performed is detailed below.
1. Use ruler to measure distance “d” between the electrodes shown in Figure 3.1.1.1.
Figure 3.1.1.1: Distance Between Electrodes
2. Use Equation 3.1.1.1 to determine required voltage value needed.
3. Connect prototype to function generator with one electrode the cathode (ground) and the
other the anode (required voltage value).
4. Connect prototype to oscilloscope with one probe on each electrode.
5. Turn on function generator with 2 MHz sine wave and required voltage.
6. Record peak voltage difference displayed on oscilloscope.
d
34
Results The distance found between the two electrodes (from inner face of each electrode) was
2.15 cm. Equation 3.1.1.1 was used and it was found that a voltage of 6.45 V was required to
produce the 3 V/cm electric field intensity. The voltage input of the function generator was 6.45
V, and the reading out from the oscilloscope was 6.52 V. Some error involved in the
measurement equipment as it doesn’t make sense that the read voltage was higher than the
required voltage.
Discussion The prototype was found to be able to produce the correct electric field intensity shown
effective in literature. The required voltage difference was found (6.45 V) based on the distance
of separation of the electrodes (2.15 cm) and was applied to the prototype with a function
generator. The function generator available to the team was only capable of producing a 2 MHz
sine wave, but the electric field intensity should be the same based on the voltage used regardless
of the frequency. An oscilloscope took the voltage measurements of the prototype which found
the voltage to actually be 6.52 V. Also, a reading was taken of the leads from the function
generator which was shown to be 6.4 V. When the leads from the oscilloscope weren’t connected
to anything, a small, non-zero reading of about 30 mV was seen. This shows that some error was
introduced into the experiment by the measurement equipment. Since the electric field intensities
shown effective in literature were from 2-4 V/cm and the actual voltage reading had an intensity
of 3.03 V/cm, it was verified that the prototype was capable of producing the correct electric
field intensity.
3.1.1.2 – Electric Field Distribution
Abstract
An important functional element of the design of the device was the COMSOL
simulations of the electric field distribution. Both the device and flesh were modeled in
COMSOL and a constant voltage was applied to the electrodes so that the distribution of the
voltage and therefore the electric field can be studied. The device was tested by attaching it to a
pig leg and measuring the voltage at various points along the length of the wrap and below the
surface of the flesh. The voltage was collected at each of the same points on a pig leg. The
voltage was measured using a wire attached to a function generator that was pierced into the skin
at various locations and depths along the wrap. The primary goals of this test was to verify that
the actual depth of penetration of the electric field along the wrap and verify that the model used
in COMSOL is similar to the actual built device so that further development of the design can be
done through virtual prototyping.
As shown in Figure 3.1.1.2.6, the voltage plots showed a qualitatively similar voltage
field structure underneath the electrodes of the device. The model may need to be adjusted to
account for the difference in the resistance of the wrap, but overall the COMSOL results and
physical testing results are quite similar.
Introduction
Comsol:
A program called COMSOL Multiphysics was used to simulate the electric field
distribution. This is a multipurpose FEA program with capabilities similar to ANSYS. The
program allowed the geometry and material properties to be modeled in 3D, and apply an electric
35
field to the electrodes and visualize the electric field lines and voltage field around the
electrodes.
Device Testing:
In order to verify the COMSOL model so that virtual development could be complete and
to verify that the depth of electric field penetration is acceptable, the distribution of the electric
field was tested. This was done using a pig leg. In order to directly test whether or not the
COMSOL model matches the actual testing of the device, the voltage at various points in the
flesh beneath the skin was tested. Since the electric field can be defined as electric potential
between two points separated by a distance, arrangement of the voltage in the flesh can tell
whether the electric field penetration is the same.
Equation 3.1.1.2.1: Electric Field
Methods
Comsol:
The COMSOL model for the device was developed by forming the physical shape of the
Revision 1 device as shown in Figure 3.1.1.2.1.
Figure 3.1.1.2.1: COMSOL Electric Field Model
The electrodes modeled above are 35.89 mm x 1 mm x 100 mm. At the time the
simulations were completed, much of the design of the device had not been complete. Therefore,
the electrodes were modeled to float 1mm off the service of the skin to simulate the effect of a
good insulator between the electrodes and the skin. The electrode design was also modified
several times before it reached its final geometry as shown in Figure 3.1.1.2.1. The skin is 1 mm
thick and was modeled to be 200 mm wide and long to minimize edge effects. The flesh is 600
mm tall, 500 mm wide and 500 mm deep. A 400 mm radius sphere of air was placed around the
whole set up. The material properties used are shown in Table 3.1.1.2.1:
Air Volume
Skin
Flesh
Electrodes
36
Table 3.1.1.2.1: COMSOL Material Properties
Components
affected: Material:
Electrical
Conductivity
(S/m):
Relative
Permittivity:
Relative
Permeability:
Electrodes Copper 5.96×107 1 1
Skin
Some
properties
same as skin
and others
water
0.001 80 1
Air Air 3×10−15
1 1
Flesh
Some
properties
same as skin
and others
water
0.01538 80 1
The properties of air and copper are well known and easy to find through various sources.
The resistivity used for both the skin and flesh were based on moderately wet conditions found
from literature values. The relative permeability and permittivity of both the skin and flesh were
assumed to be the same as water since lean tissue contains 75% water by mass [37].
For the COMSOL modeling, the literature recommended 3 V/cm was applied to the
electrodes of the device and the results were saved. The COMSOL model was evaluated to
provide adequate electric field penetration by varying the separation between the electrodes and
qualitatively viewing the electric field lines to verify that the field penetration appears to be
skewed into the skin. The electric field intensity is already assumed to be correct based on
another test. Based on qualitative judgment, the electrode geometry is varied until the electric
field penetration is deemed acceptable. Figure 3.1.1.2.2 shows the output of COMSOL:
Figure 3.1.1.2.2: Electric Field Output in COMSOL
37
Device Testing:
The device was secured to the pig leg in a manner that would be similar to how the device is
designed to be applied to a patient. Next, a wire was placed into the pig leg at various points and
the voltage was measured using an oscilloscope. Figure 3.1.1.2.4 shows a view of the pig leg
test specimen from the back.
Figure 3.1.1.2.4: Test Setup Sketch
Figure 3.1.1.2.5 shows the test as it was conducted.
Figure 3.1.1.2.5: Electric Field Testing
Revision 1 Wrap
Probe Penetration
Point
Section of Pig Leg
Flesh
38
The depth and Y location of the wire was varied with each data point. The X locations were
measured out using a caliper and marked on the pig leg using a black marker. The depth of wire
penetration into the flesh was controlled by marking the wire at 2 mm increments and shoving
the wire in until the requested line is parallel with the surface of the pig skin. The collected data
is then compared to the COMSOL simulation results. The following plot shows the voltage field
was measured in the flesh compared to the COMSOL simulation. The voltage applied in both
cases was 22.4 Volts.
Figure 3.1.1.2.6: Voltage Measured Beneath Electrodes
COMSOL results (Left) | Physical results (Right)
Discussion
The Figures 3.1.1.2.6 both show a qualitatively similar voltage field structure underneath
the electrodes of the device. In both cases, the voltage field penetrates straight into the pig flesh
and the field does not lose much magnitude as it penetrates deeper. In the COMSOL case, under
the positive electrode the magnitude does drop off a little with depth but overall, the rest is the
same. Even though the voltage applied in both cases is the same, the voltage read in the pig leg is
much greater than in the COMSOL model. This indicates that the resistance in the actual wrap is
less than what is simulated in COMSOL. The model may need to be adjusted to account for this
difference but overall the COMSOL results and physical testing results are quite similar.
3.1.2 – Delivers Ultrasound Therapy
3.1.2.1 – Ultrasound Intensity
Abstract
One of the two major therapies that is produced by the device is ultrasound therapy. This
therapy has proven to be effective by literature when the appropriate frequency and signal
intensity is applied to the transducer. Therefore ensuring the appropriate signal intensity of
is being applied to the piezoelectric transducer in the wrap is an important design
requirement for the device. Research articles have shown evidence that when a signal is
applied to a transducer with an intensity of
produces pressure waves within the wound
that can help stimulate cell growth and promote angiogenesis [19][17]. This design requirement
0
1
5
10
15
20
25
30
0 20 40 60 80 100
De
pth
into
fle
sh (
mm
)
Y-distance Along the Wrap (mm)
Voltage Field Under Electrodes- COMSOL
0-2 2-4 4-6 6-8 8-10
0
1
2
3
4
0 1 2 3 4 5 6 7 8 9
De
pth
into
fle
sh (
cm)
Probe Y Location (cm)
Pig Leg Voltage Field Under Electrode - Pig Leg
0-5 5-10 10-15
39
was evaluated using a physical test that involved measuring the piezoelectric transducer and
calculating the surface area of the transducer. After the calculation of the surface area of the
transducer was done, this surface area was multiplied by the required signal intensity (
to
find the power that must be delivered to the piezoelectric transducer. The necessary power was
then applied to the transducer inside the built prototype. A function generator was used to apply
the signal to the transducer and an oscilloscope was used to confirm the transducer was
indeed experiencing this signal at the required intensity.
After the distance of separation was found and the required voltage to produce the correct
electric field intensity was calculated, the device was attached to a function generator and
oscilloscope. Once the data was collected and evaluated, it was found that the device produced
an electric field intensity of 3.03 V/cm. This evaluation proved that the device is indeed capable
of producing the required electric field intensity.
Introduction
This test method confirms that the piezoelectric transducer in the design will receive the
signal that has been shown by research to produce ultrasound waves inside the wound that
promote angiogenesis and stimulate cell growth [19][17]. The signal that is necessary for these
waves to be produced has a frequency of and an intensity, which defines how much
power should be transmitted to the transducer based on its surface area, of
Therefore if the transducer has a surface are equal to , of power would need to be
provided to the piezoelectric transducer. This test verifies the appropriate signal is being applied
to the transducer in the prototype by first measuring the transducer and calculating its surface area.
Based on this surface area the required power to the transducer is calculated. This power is
applied to the transducer at a frequency of and an oscilloscope is used to verify the
frequency of the signal received by the piezoelectric transducer in the design as well as the
power applied to it. The device must have the transducer inside the wrap receive the specified
signal in order for the therapy to be effective as shown by literature. Table 3.1.2.1.1 below shows
the equipment necessary to perform this test.
Table 3.1.2.1.1: Materials and Equipment
Method
To perform this test, the diameter of the transducer needs to be found. A caliper is used to
find the diameter of the transducer by sliding the caliper grips around the transducer until the
maximum value is obtained. This value is the diameter of the piezoelectric transducer. When that
value is known the surface area of the transducer can be determined and multiplied by the
required intensity specified by the clinical studies and research in order to be effective
(
[19][17].
Name Description
Wound Healing Prototype The team’s designed and built prototype
Function Generator Power source for the prototype
Oscilloscope Utilized to record and display the voltage across and
current running through the transducer
Caliper Utilized to measure the diameter of the transducer in
order to determine the surface area
40
The function generator is then attached to the transducer and the necessary frequency and
calculated power is set on the function generator and delivered to the transducer inside the
device. The oscilloscope probes are then attached in series with the transducer to measure the
peak current through the transducer, and the probes are attached across the transducer to measure
the peak voltage across the transducer. Using these peak values for current and voltage as well as
the fact that the transducers used have an impedance of 4Ω, the power delivered to the transducer
can be calculated (
). This value is then divided by the previously determined surface area
of the transducer to find the intensity that the transducer is experiencing (
). This value is
then recorded and compared against the specification for the intensity given by the research
articles [17].
The experimental procedure performed is outlined below.
1. Use the caliper to measure the diameter of the transducer as shown in Figure 1.
Figure 3.1.2.1.1: Transducer Measurement
2. Calculate the surface area of the transducer ( ).
3. Multiply the required intensity given by research by the surface area of the given
transducer to determine the power that needs to be provided by the function generator to
the transducer ( )
4. Turn on the function generator and set it to deliver the necessary power at the required
frequency ( ).
5. Attach the oscilloscope in series with the transducer and set it to measure current.
6. Record the peak value displayed for current to the transducer.
7. Attach the oscilloscope across the transducer and set it to measure the voltage signal.
8. Record the peak value displayed for the voltage across the transducer.
9. Calculate the peak value for power applied to the transducer ( ).
10. Calculate the intensity of our signal to the transducer (
).
11. Record the value for the intensity of the signal read across the transducer and compare it
against the intensity value specified by the literature (
[17].
Results
The diameter of the transducer was measured to be , yielding an area of .
The power needed to be applied to the transducer knowing the appropriate intensity is
D
41
was then calculated to be 1.6W[17]. The function generator was set to produce this power and
connected to the transducer wires. The oscilloscope was then used to measure the voltage across
the transducer. The oscilloscope read a peak value of . The impedance of the transducer
given in the specification sheet is . The power was calculated to be . This yielded a
reading higher than the power being outputted by the function generator. This is not possible so
there is some small error in the readings of either the oscilloscope or function generator. The
intensity was calculated to be
.
Discussion
This test found that the prototype of the device was able to supply the correct intensity to
the transducer shown to be effective in literature. The required intensity from the design
specifications was
and the measured intensity from the physical test was found to be
[17]. The power was measured to be higher than the power that the function
generator was set to provide to the device. When the leads from the oscilloscope were not
connected to anything, a small voltage ( ) was shown by the oscilloscope. This shows that
there is a small amount of error introduced into the readings taken by the oscilloscope. The
design requirement for the intensity to the transducer was given by literature to be
and
the intensity measured in the physical tests was
[17]. This test verified that the
device supplies the appropriate intensity to the transducer to meet the design requirement.
3.1.2.2 – Ultrasound Distribution
Abstract
Additional analysis was performed to ensure that there were pressure waves being
produced within the skin when the wrap was applied. This involved computer simulations
conducted using the FEA package COMSOL as well as a physical test to validate these models.
An important consideration with the ultrasound therapy was to ensure the design would produce
pressure waves and that the pressure waves would penetrate deep enough into the skin to affect
the maximum amount of tissue surrounding the wound bed. The computer simulated the
piezoelectric transducer in the wrap when placed on skin and the required signal was applied.
The simulation showed the pressure waves that would be generated within the skin as well as the
intensity and depth of these waves. These COMSOL results were used to determine the design
for the first generation of the device. Prototypes of the first generation of the device were then
built and a physical test was performed to confirm the COMSOL simulations the design was
based off of were valid. The prototype was placed on a pig’s leg to simulate human skin and the
appropriate signal was applied to the transducer within the wrap. A different transducer was
placed on the opposite side of the pig’s leg to measure the intensity of the ultrasound once it had
reached that depth. The test was conducted at numerous depths and axial locations to obtain the
pressure and intensity profile of the ultrasound waves the transducer inside the wrap was
producing. Figure 5.1.2.2.12 shows the intensity profile at the center of the transducer that was
found using the COMSOL model (left) and the intensity profile that was found in the physical
experiment (right).
42
Figure 5.1.2.2.12: Intensity Profiles at Centerline of Transducer
COMSOL results (Left) | Physical results (Right)
Figure 5.1.2.2.13 shows the pressure values throughout the tissue surrounding the wound
obtained using the COMSOL simulation (left) and the voltage values throughout the tissue
obtained from the physical experiment (right). These voltage values provide a qualitative plot of
the pressure since the voltage has a linear relationship with pressure. The higher the voltage that
is read the higher the pressure the transducer is experiencing.
Figure 5.1.2.2.13: Pressure Contours Throughout Tissue Surrounding Wound
COMSOL Results (Left) | Physical Results (Right)
The primary goal of the physical test was to verify the ultrasound therapy would indeed
penetrate into the wound as well as to confirm the COMSOL models for the transducer and flesh
were correct so further development of the device could be done using simulations in COMSOL.
The COMSOL model proved to be useful as the design of the device was being formulated, and
depth [mm]
axia
l positio
n [
mm
]
5 10 15 20 25 30 35 40 45 500
5
10
15
20
25
30
35
40
50
100
150
200
250
300
350
mV
43
the qualitative results obtained from the physical experiment confirmed the presence of pressure
waves when the device is attached. The experiment also verified that the pressure and intensity
profiles obtained from the COMSOL model were correct. In order to quantitatively prove the
COMSOL model a more accurate test method using an expensive point transducer would have to
be done.
Introduction
Comsol Modeling:
The FEA package called COMSOL Multiphysics was used to simulate the pressure
waves that would be produced when a transducer was placed on top of the skin. The program
modeled the transducer and the size and location of the transducer on the skin could be varied in
order to determine the best design for the 1st generation device. When the frequency and
magnitude of the signal were applied to the transducer the simulation would show the pressure
waves that were produced and the depth and distribution of these waves could be analyzed. This
modeling allowed the testing of different design features to see how they would affect the therapy
that would be applied in the skin.
Physical Testing:
The physical tests were required to verify the results that were obtained from the
COMSOL simulations. A major focus with the physical test was to confirm the depth and width of
the pressure waves shown by COMSOL did exist when the device was applied to skin. To
confirm the results obtained by these simulations the prototype was applied to a pig’s leg. The
pig’s leg simulated the skin or flesh the ultrasound would have to propagate through when
applied to a patient’s leg. The device was attached to the pig’s leg and the therapy was delivered.
Another transducer was placed on the opposite side of the pig’s leg and this transducer output a
voltage based on the deflection it felt from the waves propagating from the transducer in the wrap.
This voltage value could be converted to pressure and by placing the transducer at different
locations in the pig’s leg the pressure profile can be realized. This pressure profile was then
recorded and compared against the pressure profile received from the COMSOL simulations in
order to confirm their validity. Table 3.1.2.2.1 below shows the equipment necessary to perform
this test. Table 3.1.2.2.1: Materials and Equipment
Method
Comsol Modeling:
The COMSOL model for the device was developed using the Acoustic Package in
COMSOL, specifically the Piezoelectric, Frequency Domain package. The skin was modeled as
a hemisphere and the transducer was placed on top of the skin as shown below:
Name Description
Wound Healing Prototype The team’s designed and built prototype
Function Generator Power source for the prototype
Oscilloscope Utilized to record and display the voltage values picked up
by the transducer opposite the one inside the wrap.
Piezoelectric transducer The transducer will be used to measure the magnitude of
the pressure waves given off by the transducer in the wrap
at various locations in the pig’s leg.
Pig Leg Pig leg to simulate human skin and flesh
44
Figure 3.1.2.2.1: COMSOL Pressure Waves Model
Simulations were then run to determine the optimal size and location (on the skin or on
open flesh) for the transducer to be placed on in the design. Also, the effect ultrasound gel had
when placed between the transducer and the skin was analyzed. The use of focused versus
unfocused transducers as well as the transducer material was also analyzed. The pressure
distribution for each of these simulations was analyzed and parameters were changed to
determine the best location and size for the transducer as well as the use of gel or no gel to give
us pressure waves that propagated deep into the wound and spread out quickly.
Some of the key material properties that needed to be defined are shown below:
Table 3.1.2.2.2: Material Properties
Physical Testing:
To perform the physical test and confirm the COMSOL simulations of ultrasound
propagating through skin or flesh a pig’s leg was obtained. Ultrasound gel was then applied to
the location on the pig’s leg where the transducer in the wrap was to be placed. The 1st
Generation prototype was placed on top of the pig’s leg and connected to the function generator.
A piezoelectric transducer was then placed on the side opposite of the pig’s leg and connected to
the oscilloscope. The function generator was turned on and the signal was delivered to the
Material: Speed of sound
through material
[m/s]
Density [ Layer Thickness
[mm]
Epidermis 1550 976 1
Dermis 1580 976 3
Fat 1440 917 20
Muscle 1587 1060 50
Open Flesh 1500 1400 7.4
Ultrasound gel 1620 1020 0.2
45
transducer inside the wrap at the required intensity (
and frequency ( ). The voltage
value displayed by the oscilloscope was recorded. This process was repeated at various locations at
that depth. The pig’s leg was cut thinner and the process was repeated at that depth while each
voltage value read from the oscilloscope was recorded. This gave a profile of the voltage values
inside the pig’s leg. This profile was then compared to the COMSOL simulation to verify the
results.
The experimental procedure performed is outlined below.
1. Apply ultrasound gel to the bottom and top of the pig’s leg at the locations where the
transducer from the wrap and the transducer used to read the pressure will be in contact
with the pig’s leg.
2. Place the wrap on the pig’s leg and attach the cables leading to the transducer to the
function generator.
3. Place the other piezoelectric transducer on the side opposite the wrap and attach it to the
oscilloscope.
4. Turn on the function generator and set it to deliver a signal to the transducer inside the
wrap at the required intensity (
and the required frequency ( ). This signal
was tested and confirmed in section 3.1.2.1, the Ultrasound Therapy Test that was
performed.
5. Record the voltage value displayed by the oscilloscope from the deformation of the
transducer opposite the wrap.
6. Place the transducer opposite the wrap at various axial locations and record the voltage
values at these locations.
7. Cut the pig’s leg a little thinner and apply ultrasound to that depth of the pig’s leg.
8. Repeat steps 4, 5, 6, and 7 at various depths and axial locations to obtain voltage values
that give us the pressure profile.
9. Compare the pressure and intensity profile obtained from the physical test to the pressure
and intensity profile obtained through the COMSOL model and verify the validity of the
COMSOL simulations.
Results
Comsol Modeling:
The Acoustic Package in COMSOL was used to create the geometry shown in Figure
3.1.2.2.1. Through research it was determined that the device would work best if the ultrasound
therapy was applied to the tissue surrounding the wound. This discovery led to the placement of
the transducer in the device to be just to the side of the wounded area as shown in Figure
3.1.2.2.2.
46
Figure 3.1.2.2.2: Placement of Transducer in Relation to Diabetic Ulcer
The model was constructed so the layers of skin had the depths and material properties
shown in Table 3.1.2.2.2 for the epidermis, dermis, fat, and muscle layers. Also since the device
was to apply the transducer to the edge of the wound bed an area of open flesh deep
with a surface area of was constructed in the model using the properties for flesh shown
in Table 3.1.2.2.2. This model provided an accurate representation of the area the transducer
would be applied to.
After running multiple simulations it was determined that an unfocused transducer
provides a pressure field that extends out faster. Also through the simulations it was shown that
when a smaller transducer was used the pressure waves extended out more quickly than when a
larger diameter transducer was used (compare Figure 3.1.2.2.3 and Figure 3.1.2.2.4). This led the
design to have a smaller, unfocused transducer placed inside the wrap. The smallest transducer
that the team was able to purchase was a transducer constructed out of SM111. The
dimensions of the transducer and material of the transducer were updated on the model and the
appropriate power and frequency to the transducer was set on the simulation.
Figure 3.1.2.2.3: Simulated Pressure Field, 20mm Diameter Transducer
Piezoelectric
Transducer
Neuropathic Skin
Diabetic Ulcer
Wrap
47
Figure 3.1.2.2.4: Simulated Pressure Field, 25mm Diameter Transducer
After the final design was obtained by using the COMSOL simulations to determine
specifications, the prototype was built and more accurate dimensions were found. The COMSOL
model was updated to represent the design of the Rev1 device. The model had a diameter
and the material for the transducer was updated to match the material of the purchased
transducer. Also a layer of ultrasound gel was inserted between the transducer and the skin
domain. The ultrasound gel had the property values specified in Table 3.1.2.2.2. The model now
reflected the current design of the device and the results obtained from these simulations
represent the pressure and intensity waves that will be produced when the required power is
supplied to the transducer inside of the device. Figures 3.1.2.2.5 through 3.1.2.2.8 show the
results of the simulation.
Figure 3.1.2.2.5: Pressure Waves Simulation
48
Figure 3.1.2.2.6: Intensity of Pressure Waves vs. Depth
Figure 3.1.2.2.7: Pressure Values vs. Depth.
49
Figure 3.1.2.2.8: Voltage Potential Across Transducer
Physical Testing:
Once the prototype was built it was applied to a pig leg in a manner similar to how the
device is designed to be applied to a patient. Another transducer was then placed on the opposite
side of the pig’s leg and used to pick up the pressure waves from the transducer inside the wrap.
The pressure waves deform the transducer on the opposite side of the pig’s leg and this
deformation of the transducer produces a voltage reading on the oscilloscope. Figure 3.1.2.2.9
shows pictures of the setup for the test.
Figure 3.1.2.2.9: Ultrasound Test Setup
The pig leg was then cut at different depths and the transducer was placed at different
axial locations. A marker and ruler were used to draw lines along the pig leg to show where the
transducer in the wrap was located. A caliper was used to measure the depth and location the
50
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0 10 20 30 40 50
Inte
nsi
ty [
W/c
m^2
]
Depth [mm]
other transducer was at in relation to the transducer within the wrap. The pig’s leg was cut in
increments that varied because it was difficult to cut the pig leg at specific depths. The voltage
produced by the sensing transducer was then measured by the oscilloscope at each location and
depth and recorded. The intensity was then calculated using the fact that the sensing transducer is
the same material and size as the one used in the wrap. Figure 3.1.2.2.10 shows the intensity plot
that was found from the experimental results. Figure 3.1.2.2.11 shows how the voltage values
varied at the different depths and at different axial locations.
Figure 3.1.2.2.10: Intensity of Pressure Waves vs. Depth in Physical Test
Figure 3.1.2.2.11 shows the voltage values obtained at different axial locations at each
depth. These voltage values give a qualitative plot of the pressure since the voltage has a linear
relationship with pressure. The higher the voltage that is read the higher the pressure the
transducer is experiencing.
Figure 3.1.2.2.11: Voltage Values at Varying Axial Locations and Depths
depth [mm]
axia
l positio
n [
mm
]
5 10 15 20 25 30 35 40 45 500
5
10
15
20
25
30
35
40
50
100
150
200
250
300
350
51
Discussion
When Figure 3.1.2.2.10 is compared against the graph of Figure 3.1.2.2.6 both show the
same profile of intensity as the pressure waves penetrate deeper into the wound bed. However
the actual value of intensity at each depth varies between the two graphs. The experimental graph
(Figure 3.1.2.2.10) has a smaller intensity at each point than the intensity the COMSOL model
found after the simulation. This could be to a number of factors. The COMSOL model had exact
thickness values for each layer of skin whereas the pig leg had varying layers of skin. Also the
transducer was attached by pinning the sensing transducer to the pig leg until it was tight so this
introduced human error and variability between measurements. Also the sensing transducer
could not pick up a reading unless a thin layer of ultrasound gel was placed between it and the
pig leg. This was because no air can be allowed between the transducer and the medium in which
it is measuring pressure so the ultrasound gel was needed. Of course since it is passing through
another medium this produces a small amount of error. Therefore the experimental results will be
taken for their qualitative value.
Comparison of Figure 3.1.2.2.11 and Figure 3.1.2.2.5 shows that the experimental values
obtained at different axial locations and at different depths has the same contour as the
COMSOL model. The same errors mentioned in the previous paragraph caused the physical
measurements to have some error. Also it is important to note that the lines in Figure 3.1.2.2.11
are very sharp due to the fact that the voltage drastically changed at some locations and not
enough measurements were taken at different axial location. This was due to the fact that the
measurements were taken using a transducer with a large surface area ( ) to measure the
pressure. If a point transducer (a transducer with a very small area) could have been obtained
more measurements could have been taken axially and the contour would have smoother lines.
However, looking at the results qualitatively it can be seen that the voltage was greater closer to
the surface where the transducer was applied but decrease drastically as the axial location from
the transducer increases. Deeper in the wound bed the voltage values are smaller but more
uniform as the axial location from the transducer is increased. At a depth of 20mm the voltage
values are uniform out to a distance between 20 and 25mm. At a depth of 40mm the voltage
values are uniform out to a distance of 40mm. Comparing this profile against the COMSOL
model, the experiment yielded a very similar profile to the COMSOL model. Looking at the results of the COMSOL model as compared to the physical test, the
profile of intensity at different depths and the contour of pressure values matched up well. The
quantitative results obtained from the experimental tests are of no use as there was too much
error associated with the measurements. However, the quantitative results obtained confirm the
profile that the COMSOL model obtained and confirmed that the device is indeed creating
pressure waves inside the wound when it is applied. In order to gain experimental quantitative
results to confirm the COMSOL model a more accurate method must be used. This method
would have to use a point transducer to allow measurements to be taken inside the pig leg and
allow more axial locations to be measured at each depth.
3.1.3 – Patentable
Abstract
A medical device was designed with the intention of taking it to market. Preliminary
patentability of the device was determined to gage whether the device was worth spending
additional resources pursuing. Three main criteria the device had to meet to be considered
52
patentable was that it is new, useful, and non-obvious. Following the guidance of a book titled
Patent Pending in 24 Hours, seven main questions were answered. The answers to those
questions led to the determination that the device is likely new, useful, and non-obvious. As a
result, a provisional patent was applied for by the project advisors. A professional patent search
is advisable before a patent is applied for, but the $125 provisional patent gives credit to the
likelihood of the device being patentable.
Introduction
Medical devices are created with the intention of taking them to market. Therefore, it is
necessary to test whether or not a proposed solution is patentable, early on in development, so
that time and money can be saved in the event that it fails the requirements for patentability.
Methods
Patentability was evaluated using two tools. Firstly, the book titled “Patent Pending in 24
Hours” was read through for understanding of the patent process. The content in the book
included when and how to a provisional patent, the advantages of filing, and the disadvantages of
filing. This book listed all the questions that need to be considered before patenting a device.
Answering these does not guarantee a patent will be granted, but if they cannot be answered, it
may be best not to spend more time and money pursuing the device. As part of answering these
questions, it is necessary to gain access to a patent search engine such as Google Patent Search.
A summary of the materials and equipment used are listed in Table 3.1.3.1.
Table 3.1.3.1: Materials and Equipment
Name Description
Computer An electronic device used to access the internet.
Patent Search Engine Either Google Patent Search or USPTO. Used for finding prior art.
Patent Pending in 24
Hours
Book about the patent process.
The seven questions that were answered are listed below:
1. Is it commercially viable?
2. Did you invent it?
3. Do you own it?
4. Is it useful?
5. Does it fit in one of the five patent classes?
6. Is it new?
7. Is it non-obvious?
Finally, the results of these questions were taken to the project advisors for final approval.
Results
Commercial Viability
A solution doesn’t have to be commercially viable to be patented. However, it is the only
reason for patenting in the first place. Five sub-factors were considered in determining
commercial viability. The evaluation of these factors is summed up below in Table 3.1.3.2.
53
Table 3.1.3.2: Commercial Viability
Factor Explanation Pass/Fail
Cost
The cost of the final product isn’t known, but we expect it to be
significantly lower than the cost of commonly used devices for
chronic wounds such as the Wound-Vac, which can run around
$800 per day (Buckley). Pass
Market
Competition
There is no gold-standard for treatment of chronic wounds.
Therefore the market is still open. Pass
Ease of Use
The device is a wrap which is very intuitive for medical and non-
medical professionals so it can even be applied by the patient in
the comfort of their own home. Pass
Market Demand
There are millions of diabetic patients with an average annual cost
of over $15000 per patient. There is a huge demand. Pass
Safety
This will have to be further investigated. According to literature,
this is safe. Pass
Each of these factors received a pass, so the device is considered commercially viable.
Who Invented It
The device was invented independently of anyone else. However, it has many co-
inventors; the ones who contributed to at least one novel and nonobvious concept that makes the
invention patentable. In patent drafting terms, the co-inventor must contribute something
substantial to one of the patent claims. This receives a pass.
Who Owns It
All intellectual property rights are owned by the University of Minnesota. However, the
names of the inventors can still be put on the patent. Since the University will be the one paying
for a patent, this receives a pass.
Usefulness
The usefulness of the solution was determined by answering two sub-questions. Firstly,
does the device produce a result? Secondly, is it legal?
To determine if the device produces results, simple tests were conducted to measure the
electrodes that produce electric fields and if ultrasound emanates from the transducer as
expected. It was concluded that the device both produced electric fields and ultrasound waves.
Case studies will be required to confirm if the literature values assumed for this device are
consistent with the values needed to properly treat patients.
The legality of the device really comes down to whether or not it is safe. By all accounts,
the device is both sterile and applies a treatment that literature deems as safe. The final decision
will be determined by the FDA, but at this time, the results of the aforementioned tests along
with the safety level indicate that this device can be useful. It receives a pass.
54
Patent Class
The device was determined to fit in several of the five patent classes by referring to
Patent Pending in 24 Hours. The classes it fit into include: Processes and Methods, Machines,
and Articles of Manufacture. This receives a pass.
Is It New
The newness of the device was determined by conducting a patent search using the
Google Patent Search. A sample of the patents viewed is shown in Table 3.1.3.3 below.
Table 3.1.3.3: Sample of Patents
Patent Title
Publication
number File Date
Pulsed electromagnetic field and negative pressure
therapy wound treatment method and system EP2421575 A1 23-Apr-10
Ultrasound wound treatment device using standing
waves EP1355696 B1 30-Jan-02
Electrical wound healing system and method EP2274047 A1 19-Jan-11
Portable ultrasound system EP2519323 A2 7-Nov-12
Oxygen therapy with ultrasound EP2035082 A2 18-Mar-09
Ultrasound bandages EP1076586 B1 11-Oct-06
Device and method for ultrasound wound debridement EP1526825 A1 4-May-05
Ultrasound wound care device and method EP2032112 A2 11-Mar-09
Chronic wound treatment (unbound polyphosphate) EP2254585 A1 1-Dec-10
Microbial cellulose wound dressing for treating chronic
wounds EP1356831 B1
16-Mar-05
There were devices that used electrical fields, and there were devices that used
ultrasound, but no devices could be found that included both of these.
A new device is mostly likely non-obvious. This factor is achieved if the device meets a
new and unexpected result. Additionally, it can be non-obvious if others have praised the
invention in the field, if others fail to achieve the same results, or there has been a need in the
industry for the invention. Further testing is required to determine that the device works as
expected on humans. Assuming the literature values that were used are good, the device will
certainly achieve a result that hasn’t been achieved in industry.
This category should be re-examined before a patent is filed. However, for the purpose of
filing a provisional patent, this section receives a pass as well.
Advisor Opinion
The advisors were consulted. After presenting the concepts and test results, they filed a
provisional patent to protect the device before our first public disclosure.
Discussion
Seven main questions were answered to determine the patentability of the solution. The
answers to those questions led to the conclusion that the device is worth protecting. After
55
consultation with the advisors of the project, a provisional patent was filed. The filing of the
provisional patent validates the quality of this test method. However, several sections require
further attention before a patent is filed. For example, FDA approval will be needed to carry out
human testing. Before the device goes to market, this testing is required.
3.1.4 – Short Setup Time
Abstract A design requirement for the device was to have a setup time of less than 5 minutes. A
short setup time increases the ease of use of the device and makes it more likely that a medical
professional will use it. The test was recording the amount of time it took for an operator to takes
the device from a wrapped stage, similar to how it would be packaged, on a table, wrap it around
the patient’s foot and connect it to the function generator so that therapy was ready to be applied.
Three operators were used and each performed the test five times. Using three different operators
gave an indication of inter-operator variability, and having them do the test five times each gave
enough data points to have a good idea of the mean time. The data points were plotted with 95%
confidence intervals for the mean of each operator, and the data points were run in a capability
analysis with an upper specification limit of 300 seconds (5 min). The interval plots for each
operator overlap at some point and are not statistically different. This shows that different
operators can produce the same results. The overall mean setup time was 39 seconds with a Cpk
of 27.96. A Cpk greater than 1.33 is generally accepted as a capable process, so 27.96 meets the
requirement and shows that the device setup process will consistently be less than 5 minutes.
Introduction The purpose of this test method is to determine the average setup time for the designed
wound healing device. A short setup time is beneficial to have in a new device to increase ease
of use and the likelihood that a medical professional will use it.
Method
Table 3.1.4.1: Materials and Equipment
Name Description
Wound Healing Device Team’s designed wound closure wrap
Function Generator Power source for the wound closure device
Stopwatch Stopwatch to keep track of elapsed time
Timer A third party person to run the stopwatch
Simulated Patient Test subject to simulate placement of device on foot
1. Remove shoe of seated patient if still on.
2. Place calf of patient on raised stool so foot hangs over the edge.
3. Have timer start stopwatch.
4. Place first layer of wrap so that the transducer is just below the outside ankle.
5. Wrap full length of device around and secure to foot.
6. Attach function generator to device.
7. Have timer stop stopwatch.
8. Record result.
56
Results The test was run using 3 different operators, each performing the test 5 times. The raw data and
statistical analyses are shown below:
Table 3.1.4.2: Setup Time Data
Operator 1 Operator 2 Operator 3
40.8 46.2 37.6
30.9 39.9 40.8
39.0 44.5 38.7
32.8 41.3 37.3
34.0 39.8 38.7
Figure 3.1.4.1: Interval Plot of Time
Figure 3.1.4.2: Process Capability of Time
57
Discussion The data points were plotted with 95% confidence intervals for the mean of each
operator, and the data points were run in a capability analysis with an upper specification limit of
300 seconds (5 min). As seen in Figure 3.1.4.1, the interval plots for each operator overlap at
some point and are not statistically different. This shows that different operators can produce the
same results. The overall mean setup time was 39 seconds with a Cpk of 27.96 as shown in
Figure 3.1.4.2. A Cpk greater than 1.33 is generally accepted as a capable process, so 27.96
meets the requirement and shows that the device setup process will consistently be less than 5
minutes. Future tests should include medical personnel to accurately profile the users.
3.1.5 – Maintains a Low Profile
Abstract A design requirement for the device was to have a profile of less than 1 inch. A low
device profile increases comfort for the patient, reduces the risk of new wounds developing, and
makes it compatible with other necessary therapies such as additional wrap or an off-loading
boot. The device was measured at its thickest point, where the ultrasound transducer is placed.
The device was measured with a caliper 10 times to ensure the thickest point was found. A
maximum thickness of 0.111 inches was found, which meets the requirement of being less than 1
inch. In the future it would be beneficial to measure the maximum heights of many devices, but
because of limited resources one device was available to test.
Introduction The purpose of this test method is to determine the device profile. A low device profile
increases comfort for the patient, reduces the risk of new wounds developing, and makes it
compatible with other necessary therapies such as additional wrap or an off-loading boot.
Method
Table 3.1.5.1: Materials and Equipment
Name Description
Caliper Used to measure the profile of the wrap
Wound Closure
Device
Team’s designed wound healing wrap
1. Determine the points on the wound healing device that protrudes the most above and
below the wrap.
2. Use the caliper to measure the distance between the lower and upper surface of the wrap
at the widest point. See d in Figure 1.
3. Record the result.
Figure 3.1.5.1: Device Profile Measurement
d
58
Results
10 measurements were taken of the device to ensure the maximum height was found. The
maximum height measured was 0.111 in. The measurements are shown below:
Table 3.1.5.2: Device Profile Measurements
Measurement (in)
0.097
0.105
0.107
0.106
0.110
0.105
0.108
0.111
0.110
0.108
Discussion The device had a maximum height of 0.111 inches, which satisfies the requirement of
being less than 1 inch. In the future it would be beneficial to measure the maximum heights of
many devices, but because of limited resources one device was available to test.
3.1.6 – Petri Dish Biofilm Inhibition
Introduction The purpose of this test method is to demonstrate the effectiveness of a prototype at inhibiting
bio-film development both with and without the presence of antibiotics compared to a control.
Testing prototypes on animals is expensive and time consuming. It is necessary to be able to test
prototypes quickly and cost effectively. The following test method accomplishes this by
targeting the common bio-film producing strains of bacteria that commonly infect chronic
wounds. This is an outline for a test to be done in the future, so results and discussion are not
available at this time.
59
Method
Table 3.1.6.1: Materials and Equipment
1) Purchase necessary equipment.
2) Grow each test strain in 3 ml of LB medium at 37°C for 16 h in an orbital shaker at 220
rpm and then, in fresh LB broth, dilute it to an optical density (OD) corresponding to
bacterial counts to the desired CFU per ml (Perhaps 107 CFU/ml).
3) Take some preliminary tests to determine the lowest antibiotic concentration necessary to
completely inhibit the growth of the organism. A range of concentrations up to this limit
can be tested to compare the effects of the prototype combined with antibiotics and
without it.
4) Prepare the antibiotic by following the CLSI guidelines.
5) Take three petri dishes for each strain you’re testing; one for the control, one for testing
the prototype alone, and one for testing antibiotics in combination with the prototype.
Add 7 ml of the diluted cultures to each of the petri dishes.
6) With one of the petri dishes, add the antibiotics. Then apply the prototype to both the
petri dish with and without antibiotics. Place all three of the petri dishes inside an
incubator set to the proper culture temperature of 37°C so that the control dish isn’t
affected by the prototype.
7) At the end of treatment, suspend the cultures by pipetting.
8) Disburse the pipetted cultures into a microwell plate and determine the each optical
density at 750 nm (OD750) spectrophotometrically with a microplate reader.
9) Calculate the percentage of growth for each well as the OD750 of the treated wells
divided by the OD750 of the control well.
10) Assess the drug interactions with the prototype according to the checkerboard method.
11) Record all processes and final results.
3.2 Cost Analysis
Abstract
Each year there are over 1.5 million documented cases of diabetic foot ulcers [38]. The
proposed device was compared against the leading wound closure device, the wound vac. A cost
savings analysis was conducted. It found that the proposed device saves $10,800 per treatment
Name Description
Prototype Device to test.
Bacterial Strains Common bio-film producing strains common to chronic wounds.
Lysogeny Broth (LB) (1.0% Bacto tryptone, 0.5% yeast extract, 1.0% NaCl)
Petri dishes Medium for growing the test strains.
Incubator Device for maintaining bacteria at near human body temperature.
Antibiotic Topical chemical commonly applied to clean wounds. May use a general
purpose one, chloramphenicol.
Microwell Plate A flat plate with multiple indentations or “wells” used as small test tubes.
Microplate Reader Device for spectrophotometrically reading suspensions in microwells.
Orbital Shaker Device that moves solutions in an orbital pattern as to keep mixtures
suspended.
60
when compared with the wound vac. In an ideal situation where 100% market share is achieved,
these savings then amount to $16.2 billion annually.
Introduction
Closing chronic wounds can lead to increased hospital stay time which is a huge cost for
patients, insurance providers, and hospitals. Even outpatients incur enormous expenses as the
treatments often require them to visit a wound clinic. $25 Billion spent yearly to treat chronic
wounds, with the average yearly patient cost of about $15,000. No gold standard to treat these
wounds has been established, providing a huge market potential.
Methods
It was decided that the most common wound closure device should be used for
comparison to our device because it is the most likely competitor. This device was discovered
by interviewing medical professionals. The typical duration of treatment for the common device
was then found through internet research. These values were compared to estimated values for
our device based on literature values. Cost savings were calculated on a per treatment basis.
Equation 3.2.1: Cost Effectiveness Equation
Where the costs are the monetary values corresponding to the total duration of the wound
healing and treatment refers to the average number of days it takes a wound care professional to
deem the wound healthy, clean, and granulating. The cost savings per treatment was then
multiplied by the number of diabetic foot ulcer cases each year. This yielded the savings over
the period of one year.
Results
The duration for wound vac treatment varied tremendously. One study followed patients
that applied the wound vac for over 8 months for the treatment of refractory ulcers. However,
most studies applied the negative wound pressure between 2 and 6 weeks. A median value was
sought after, and an average treatment duration of 24 days was taken from a single case study
[39].
According to Dr. Buckley, a plastic surgeon, wound vac treatments can cost 700 to 800
dollars per day. A conservative value of $700 was used in the analysis. Depending on
economies of scale, the cost of the proposed device could be significantly lower than that. Table
3.2.1 below displays educated guesses derived from knowledge gained while researching and
developing the new would closure device.
61
Table 3.2.1: Cost of Wound Healing Device
Factor Description
Cost per 1000 units
[$]
Materials
Wrap, Transducer, Ultrasound gel,
electrodes. Assume control unit lasts
for thousands of applications and price
is negligible compared to wraps. 25000
Manufacturing Simply application of layers. 15000
Distribution
Each wrap is very small and easy to
ship. Get bulk discounts and use
FedEx. 10000
Hospital staff
time
Assume the price will be based on the
time you sit in an evaluation room, that
this time is about 30 minutes, and the
costs of that time is at an hourly wage
of $100. The wrap will be changed
once per day. 50000
Markup
Margin added for company and
hospital profit (2x) 2x
Total 300000
The daily cost of the treatments and the effect of each device were compared. Table 3.2.2
shows the values of comparison.
Table 3.2.2: Cost Comparison
Device Cost/day [$] Effect [days]
Wound Vac 700 24
Proposed Device 300 20
The effect does not indicate the time it takes to completely heal the wound. Instead, it
measures the average amount of time it would take until a professional determined the wound
was healthy, clean, and granulating.
The main factor by which the wound vac heals the wound is by keeping bacteria out of
the wound bed. Secondly, it reduces edema by pulling fluid out. The proposed device also
keeps the bed free from infection but instead uses ultrasound to stimulate blood flow. It is
expected to reach the desired results faster than the wound vac because it leaves fibroblasts and
macrophages, the body’s natural wound healers, in the wound bed.
Substituting the values into equation 3.2.2 yields the cost effectiveness ratio:
Equation 3.2.2: Savings of proposed device compared to industry leading device
62
The Advanced Medical Technology Association reports that more than 1.5 million
diabetic foot ulcers occur in the U.S. annually. If each of those ulcers were treated with the
proposed device as opposed to a wound vac then the savings would amount to:
Equation 3.2.3: Total Annual Savings
Discussion
This analysis lacked a lot of information. No manufacturers were consulted to get
estimated pricing for our device. It is not reasonable at this time, because the final device could
be significantly different from our prototype. Also, Dr. Buckley’s estimation for the wound vac
may not be representative of other hospitals or clinics. When information could not be obtained
from research, educated guesses were made. This leads to greater uncertainty in the analysis.
The total savings per year assumed the device would enjoy a perfect monopoly over the
market. In reality, medical technology is slow to propagate into industry even if it is better than
existing products. Even if the CE ratio is accurate, the total savings per year is likely not because
it was only compared to one device and assuming that device was used to treat all diabetic foot
ulcers.
3.3 Environmental Impact Statement
The device described in this document provides a great service by closing chronic
wounds that have not responded to normal treatment thus reducing cost and waste associated
with treating the patient for potentially several additional weeks. Like any other device or
process, however it should be designed with the environment in mind. The Revision 1 design
described in this document has only a small negative environmental impact while it is produced
in small quantities. Even in the disposal phase, the device is relatively clean. The wires and
stainless steel can be recycled. The transducer can be easily reused if cleaned properly. The
Coban wrap is the only component that will have to be thrown away. Since very few of the
Revision 1 prototypes have been built, waste created by old discarded prototypes is negligible
but it should still be properly disposed of when the prototype has run its course. However, the
Revision 2 design may be produced in a much larger volume, so disposal should be considered.
For the patient’s safety, every Revision 2 wrap should be responsibly disposed of after one
application. This includes wrap material, and any other non-recyclable components. For proper
disposal, the components should be placed in a container labeled “Hazardous Waste.” Since
Revision 2 will be applied within a hospital setting, recycling is not an option since medical
personal cannot be expected to separate the hazardous material from the recyclable. Since the
waste from the wrap will be classified as “potentially infectious,” the wrap will eventually be
incinerated. To help protect public health, the wrap will not be treated with any toxic adhesives
or other substances that may be emitted from the incinerator. To save some waste, the function
generator can be re-used for multiple treatments. The device could be made even more
environmentally friendly by using aluminum shim stock in place of the stainless steel shim stock
because it takes less energy to manufacture. The second device could also be designed to use
local suppliers thus reducing the energy required to transport the materials for the device.
63
3.4 Regulatory and Safety Concerns
Medical devices applying therapy to the human body are strictly regulated by the FDA.
Medical devices are typically designed to meet certain FDA and ISO standards, and tested to
ensure they do so. The largest concern with the wound healing device is the voltage that needs to
be applied to the electrodes and ultrasound transducer in order to deliver the therapy. The
voltages are designed to be applied in the range of less than 12 volts with small currents relative
to those dangerous to the body. Bare wire or electrodes can cause damage to the skin if they
come in direct contact, so the device must be designed so that electrical contacts are isolated
from the patient’s skin. This can be done with coating, electrical tape, or a properly designed
connection. As this device is intended for proof of concept and non-human testing, it is not
regulated by these standards, but they should be kept in mind during the design and development
of the device. An overview of the FDA’s device regulations is given here: http://www.devicewatch.org/reg/overview.shtml
