Biomedical Engineering Reference
In-Depth Information
abrasions, punctured and penetrating wounds) and closed wounds (contusions,
hematoma and crush injuries) [
2
]. The healing of a wound requires a complex
conjugation of biological and molecular actions of cell migration, cell proliferation
and extracellular matrix deposition that result from the interaction of different cells,
mediators and growth factors. This process usually involves four overlapping phases
of coagulation, inflammation, migration-proliferation and remodeling [
3
]. Each
one of these phases is normally characterized by several specific body response
stimuli which are often identified by the generation of some characteristic tissues
and/or secretions that may as well require specific treatment agents/conditions [
4
].
In most cases, wound healing is a natural process which leads to the restoration of
tissue integrity but, in some cases, due to many local (infection, tissue ischemia,
poor surgical technique, formation of hematomas, presence of foreign bodies and
mechanical pressure) and systemic factors (ageing, nutritional status, underlying
diseases, medication), wounds fail to heal and become a complex medical problem
requiring specialized care and treatment [
5
]. In these cases, the use of wound
dressings may help to promote healing by creating proper physiologic wound
environment and acting as a barrier for microorganisms.
2
Wound Dressings
Wound healing is significantly affected by three main factors which include
dehydration of exposed tissues, the status of the blood supply bringing oxygen and
nutrients to the area, and sepsis [
6
]. The main function of wound dressings should
be to help the body's own healing mechanism and to provide clean conditions in
the wound. An
ideal
wound dressing prevents dehydration and scab formation, is
permeable to oxygen, water vapor and CO
2
, is sterilizable, absorbs excess blood and
exudates, protects against secondary infections, supplies mechanical protection to
the wound, is non-adherent, non-toxic, non-allergic and non-sensitizing, economic
and present a long shelf-life [
7
]. The selection of the
best
wound dressing is not
always a simple task as wound healing is a dynamic process in which wounds
undergo different phases of healing. Instead, wounds require different dressings,
depending on the type and dimension of the wound, its positioning on the body and,
in particular, on the depth of tissue damage, stage of healing and level of exudate
[
8
]. Careful monitoring of the exudate can provide information for the application
of systemic and local therapies [
9
].
One of the most important requirements of any dressing system is the capacity
to guarantee the optimal moisture content of a wound and the surrounding skin.
The works published by Winter [
10
,
11
] were the first showing that, under moist
conditions, wounds healed 50% faster than those healed in open air (dry) conditions.
In the case of medium or highly exuding wounds, the dressing should be able to
remove the excess wound fluid but, in dry or lightly exuding wounds, the dressing
should maintain the exposed tissue in the optimum state of hydration. This facilitates
epithelialisation and promotes autolytic debridement also enhancing the viability of
