Biomedical Engineering Reference
In-Depth Information
the epithelial cells by protecting them from dehydration and scab formation [
12
].
Commonly used wound dressings comprise cotton gauze, foams, sponges, wads or
other fibrous materials. Gauze and other fibrous materials are efficient absorbing
dressings but, when removed, they usually remove new tissue formed causing
wound injury and disturbing new tissue growth, delaying the healing process and
causing pain. Cotton gauze present good absorption properties and soft handle, but
they do not maintain the moist environment that has proved to facilitate faster wound
healing as it allows moisture to evaporate from the wound [
12
,
13
]. Thus, there is
a need for a dressing which is non-adherent while being absorbent and that can
balance the moisture in the wound environment. This has been the driving force in
the development of the large number of products that are currently available and that
include [
14
]:
1.
Semipermeable film dressings
for low to medium exuding wounds: adhesive,
elastic, thin transparent films (allow inspection of wound), permeable to gases
but impermeable to liquid and bacteria. Film dressings are indicated as primary
dressings in minor burns, simple abrasions and lacerations and as a post-operative
layer over dry sutured wounds. Examples of these materials include Opsite,
Flexiguard, Tegaderm, Melfilm and Bioclusive
2.
Foam dressings
for moderately exudating wounds: highly absorbent, cushioning
and protective, and insulate and conform well to body surfaces. Foams facilitate
a moist wound environment and absorb excess exudate to decrease the risk of
maceration. Foams are generally nonadhesive and require a secondary dressing
or tape/bandage to keep in place. Examples of these materials include Allevyn,
Lyofoam, Tielle plus and Biatin Adhesive
3.
Alginate dressings
for medium to heavily exuding wounds and also good
for bleeding wounds: highly absorbent, biodegradable dressings derived from
seaweed. An active ion exchange of calcium ions for sodium ions at the
wound surface forms soluble sodium alginate gel that provides a moist wound
environment. Moreover, it was demonstrated that calcium ions released by this
type of dressing are a natural co-factor in the coagulation therapy promoting
haemostasis in bleeding wounds. Examples of these materials include Kaltostat,
Sorbsan and Algisite
4.
Hydrocolloids
are moisture-retentive dressings, which contain gel-forming
agents such as sodium carboxymethylcellulose, gelatin and pectin. Many
products combine the gel-forming properties with elastomers and adhesives
are applied to a carrier such as foam or film to form an absorbent, self adhesive,
waterproof material. In the presence of wound exudates, hydrocolloids absorb
liquid and form a gel. Examples of these materials include sheets such as Alione,
Combiderm and Duoderm, paste such as GranuGel and hydrofibre such as
Aquacel and Versiva
5.
Hydrogels
for wounds that range from dry to mildly exudating and that can
be used to degrade slough on the wound surface: composed by complex
hydrophyllic polymers have a high water content (90%) which creates a moist
wound surface. Hydrogels are insoluble polymers that expand in water and
