Pressure Ulcer Prevention and Treatment Following Spinal Cord Injury - 7

CLINICAL PRACTICE GUIDELINE

inflammatory cells and vacuolated fibroblasts
(the cells that secrete the collagen). Fibrin
appears to supplant the collagen matrix seen in
intact tissues. Edema is also present near the
surface of the ulcer, and there is often partial to
full occlusion of blood capillaries (Vande Berg
and Rudolph (1995).

Susceptibility of skin and soft tissue
to pressure and shear
The first visible indication that a pressure
ulcer is developing usually is a change in the skin
surface or change in temperature or tugor in
darker skinned individuals, which can be assessed
by palpation. However repeated investigations
have shown that muscle tissue is more sensitive
than skin to pressure-induced ischemia and that
this is where the tissue damage is initiated which
ultimately leads to pressure ulcer development
(Daniel et al., 1981; Nola and Vistnes, 1980;
Salcido, 1994).

Vascular deformation by direct
pressure and shear
Support surfaces contacting the body are
for the great proportion of the contact surface,
oriented obliquely at the contact area. This
causes both direct pressure and shear stress to
occur at the same time. The orientation of the
blood vessels relative to the load-bearing skin
surface determines the response of the vessel
to the surface loads. In general, the major vessels
and their branches are oriented either parallel or
perpendicular to the skin surface. This pattern
repeats for successive branches of the arterial
and venous circulation (Agris and Spira, 1979).
Vessels parallel to the surface collapse easily from
pressure loads whereas vessels perpendicular to
the surface bend and collapse from shear loads
applied to the weight-bearing tissue. Vessels most
vulnerable to occlusion by shear stress are those
penetrating through the interfaces between the
tissue planes. Blood flow to the distal capillaries
is impaired when capillaries collapse and occlude
as a result of tissue layers that slip and vessels
that bend between tissue layers. Thus, both
pressure and shear loads can cause ischemia
and necrosis in the layers of the skin and
subcutaneous tissues.
The deformative mechanical effect of
external loads on tissue is resisted by the
internal cellular and interstitial pressures and the
strength of the collagen network within the tissue
structure. With the application of external
pressure, internal tissue pressure builds up first

within the interstitial fluid trapped between the
cells and the collagen network. Pressure
gradients cause the fluid to move from the highto low-pressure regions, causing local volume
and contour change in the cells and supporting
structural tissues stroma, which can lead to
alterations in cellular metabolism (including
collagen synthesis) and, if extreme, cell
boundary and collagen network destruction
(Reger et al., 1986; Reddy et al., 1981).

Category/Staging of Pressure Ulcers
Pressure ulcers are described by a category/
staging system based on the extent of anatomical
tissue loss. The category/staging system for
pressure ulcers most commonly used is the
consensus classification developed by the National
Pressure Ulcer Advisory Panel in 1989 and
updated in 2007 and illustrated below (Black et
al., 2007).
CATEGORY/ STAGE I

Category/Stage I damage is defined by nonblanchable redness of a localized area usually
over a bony prominence. Darkly pigmented skin
may not have visible blanching; however, its color
may differ from the surrounding area. The area
may be painful, firm, soft, warmer, or cooler as
compared to adjacent tissue. Category/stage I
damage may be difficult to detect in individuals
with dark skin tones.

CATEGORY/ STAGE I I

Moisture or incontinence-associated
dermatitis should not be confused with a pressure
ulcer. The anatomical location of the lesion, e.g.,
whether or not it is located over bony
prominence, can often help in making this
determination.
A category/stage II ulcer is the partial loss
of the dermis presenting as a shallow open ulcer
with red pink wound bed, without slough. It also
may present as an intact or open/ruptured serumfilled or sero-sanguineous-filled blister. It presents

Pressure Ulcer Prevention and Treatment Following Spinal Cord Injury

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