Ian Sando
Marybeth Jewell
Melissa Kopacz
Cary Berdy
Wound Healing System Development: Improving Current V.A.C. Therapy Methods
Mission
The mission of our project is to provide an affordable medical instrumentation
device to improve patient health by assisting in wound closure. Currently, there are few
devices on the market that use Vacuum Assisted Closure (V.A.C) therapy to remove
interstitial fluid from the wound and facilitate its closure. We hope to design a device
that is less expensive and more efficient that current methods.
Background
Vacuum Assisted Closure therapy devices are composed of a computer-controlled
unit, a canister, and sterile plastic tubing. The device applies a localized negative
pressure to special foam dressing that is positioned in the wound cavity or over a graft or
flap. The wound packing dressing distributes the pressure evenly to remove fluid from
the wound and promote normal healing. The foam is reticulated and can be cut in the
shape of the wound, or it can be layered and placed side by side to treat larger wounds.
With the foam in place, one end of the sterile tubing is connected to the foam, while the
other is connected to a canister. The foam dressing and distal tubing are covered by an
occlusive drape that provides a seal when applying negative pressure to the system. The
canister that is connected to the proximal end of the tubing fits into the microprocessor
vacuum unit and collects the fluid that drains from the wound. The negative pressure that
decompresses the foam dressing is applied either continuously or intermittently,
depending on the type of wound being treated. The pressure can also be adjusted to
provide optimal removal of fluid without risking further injury to the wound tissue.
The V.A.C. therapy systems are advantageous because they provide a moist
wound-healing environment which promotes granulation tissue growth, reduces
contamination from foreign bacteria, and decreases the likelihood of cell-death due to
dehydration. As negative pressure is applied, the wound volume is decreased and the
wound is drawn together. The removal of interstitial fluid helps to reduce oedema, which
improves blood flow to the wound, and it helps to eliminate excess proteinases present in
the periwound environment. Certain growth factors are degraded before their reach their
target tissues do to their binding with metalloproteinases. With such proteinases
removed, the growth factors can stimulate cell proliferation and migration.
Metalloproteinases are known to bind and degrade growth factors before the growth
factor can reach its target tissue. With the inhibitors removed, growth factors can
stimulate cell proliferation and migration. Recent research has also shown that the
stretching and mechanical distraction of the soft tissue, which is caused by the collapsing
of the foam on itself when air is evacuated from the open cells, may result in mitosis (cell
replication).
V.A.C. therapy has proved very useful in assisting in the closure of a variety of
wounds including chronic open wounds, acute and traumatic wounds, meshed grafts,
subacute wounds, and flaps. However, the current devices are expensive and some have
a low incidence of localized superficial skin irritation. The device itself costs about $70 a
day to rent; however, with regards to dressing and nursing expenses, the cost for V.A.C.
therapy is more than $282/day. This is almost four times as much as topical wound
treatment using traditional methods and dressings, which costs approximately $75/day.
Some patients are also allergic to the components which come in contact with the skin,
such as the polyurethane sponge, the adhesive, or the polyvinyl film applied to seal the
system around the wound. In addition, patients with thin skin that is fragile and can be
easily damaged are not able to tolerate the pulling off of the adhesive film, which is done
at the time of sponge removal/change. Our design would eliminate these problems and
prove cost-effective. Not only would the market price of our device be less than that of
our competitors, but by designing a more efficient design when removing infectious fluid
and closing the wound, healthcare costs would altogether be less due to the decrease in
the duration of hospital stay of the patients who use our V.A.C. therapy device.
Market Research
A majority of the current wound healing systems tend to focus on collecting
drainage of exudates from wounds. One such system is the Youki Wound healing system,
which works by applying a spray or cream to the surface of a wound and allowing a
membrane to form. This semi-permeable membrane allows exudates to flow easily out of
the wound and prevents re-entry1. Another approach utilizes hydrocolloid hydrofiber
dressings. This method is geared toward ulcer wounds and ensures a moist healing
environment while allowing unwanted drainage to exit to wound2 as well.
The major competitive disadvantage for systems that simply facilitate drainage of,
and separation from, exudates is that such fluid is allowed to sit on the healing wound for
substantial period of time. Healing inhibiting substances, such as matrix
metalloproteinases, are often leaked from wounds3. Decreasing the presence of such
matter rapidly would increase the healing speed dramatically.
The wound healing technology we are improving is the KCI wound healing
system. The Vacuum Assisted Closure (V.A.C.) Therapy System, manufactured by KCI,
is designed to physically remove infectious materials and other unwanted fluids from
wound sites to aid in the healing process. Sub-atmospheric pressure is applied to the
wound in either a continuous or discontinuous fashion to accomplish this task and to
advance the healing process3. This concept is advantageous in that it decreases healing
time which is not only satisfying to the patient, but decreases costs to both the patient and
medical community as well.
Wound types suitable for this application include chronic open wounds, diabetic
ulcers, pressure ulcers, acute and traumatic wounds, flaps and grafts, dehisced wounds,
and partial thickness burns. The V.A.C. Therapy System, however, cannot be used over
exposed blood vessels or organs, active bleeding sites, untreated Osteomvelitis, nonenteric and unexplored fistulas, or necrotic tissue with eschar present3 since it would most
likely cause further trauma in such cases.
Group Description
Our team is composed of three biomedical engineers and one mechanical engineer
who have competent knowledge in biomedical instrumentation, biomechanics and
biomaterials, electrical engineering, thermodynamics, fluid transport phenomena, fluid
dynamics, and systems physiology. We have researched extensively the designs of our
competitors and have set forth a plan to design and implement a better device. In order to
fully study other designs and determine the necessary steps to improve on these designs,
however, we require access to our competitors’ designs and additional funding to back
our project.