11 / 20
JCN supplement
2015,Vol 29, No 5
11
Granulation tissue formation
Stabilisation of wounds, i.e.
sternotomy wounds.
Using a standard device and pressure
higher than -80mmHg
When using NPWT in wounds with
high volumes of exudate, a traditional
negative pressure device and pressure
higher than -80mmHg can be used
(Malmsjö et al, 2009).
It is important to note that wound
exudate volume is a symptom and
can provide clues as to the wound’s
condition, i.e. if it is infected — its
bacterial load (World Union of Wound
Healing Societies [WUWHS], 2007;
Morgan, 2014). To manage exudate
effectively, it is essential to establish
the underlying cause. If the volume
is simply related to wound size,
choosing NPWT to help achieve other
goals, as well as to contain exudate
is acceptable. However, exudate
management alone should never
be the primary reason for choosing
NPWT, as failing to address the
underlying cause of exudate
will lead to prolonged and
unsuccessful treatment, and
potentially increase costs.
When to use lower pressures
A pressure lower than -80mmHg can
be used in the following situations
(Malmsjö et al, 2009):
Poorly vascularised wounds
Paediatric patients
If the patient reports pain.
Figure 1.
Typical NPWT
treatment pathway.
Establish aetiology
Baseline measurement
Reassess —
measurement/goals
Initiate NPWT
Set goals/start
treatment
Failure to progress/
prepare wound bed
Reassess —
measurement/goals
›
NPWT facts...
NPWT systems consist of a:
Wound contact layer and dressing: traditionally foam or gauze that fills the
wound cavity
Film: this is applied over the foam or gauze filler to form an air-tight seal
Drainage tube: this is connected to a suction device with a canister that
collects and evacuates exudate.
Standard devices consist of a pump which is attached to a canister to collect
exudate, this in turn is connected to non-collapsible tubing that is attached
via a port to the patient’s dressing. These devices have a choice of incremental
pressure settings that can be selected by the clinician. As discussed, generally
-80mmHg is sufficient to give optimal benefit.You may wish to vary the
pressure settings to optimise NPWT therapy based on individual patient need
and the lead clinician’s guidance. Negative pressure may be increased by
10mmHg increments if:
High volumes of exudate/excessive drainage are present
Wound volume/size are large
There is a tenuous seal/positional difficulties maintaining the seal.
It is generally accepted that pressure
levels below -40mmHg are sub-
optimal, and, as such, therapy should
be discontinued in favour of more
appropriate treatment options that
are matched to the primary treatment
objectives and licenced/designed to
address presenting signs and symptoms.
There is no evidence of any therapeutic
benefit below 40mmHg (Malmsjö et al,
2009) and continued use will result in
increased overall treatment costs (Searle
and Milne, 2010).
Intermittent, variable or
continuous therapy
Intermittent and/or variable NPWT
can be set on standard devices and is a
means of applying and removing the
pressure delivered by automatically
switching on and off the suction applied
to the wound bed at pre-set or clinician-
defined intervals.The most commonly
used setting is five minutes on and two
minutes off.
Intermittent and/or variable
NPWT can be used in the following
circumstances:
All wounds, except those producing
excess exudate
To achieve greater blood flow in the
periwound tissue
To achieve greater mechanical
shearing forces at the wound
dressing interface (the NPWT acts by
‘massaging’the wound surface)
To achieve more granulation
tissue and faster healing (Saxena et
al, 2004).
NPWT IN THE COMMUNITY
Continuous NPWT should be
used for:
Wounds that are producing a high
volume of exudate
Large wounds that require
stabilisation of structures, i.e.
sternotomy wounds, as NPWT
provides splinting and stabilisation
as the pressure is applied
continuously to the tissue and
offers support.
DISPOSABLE NPWT
For small-to-medium sized wounds
with low-to-moderate volumes of
exudate, disposable NPWT systems
(such as PICO
™
) combine the benefits
of negative pressure with the simplicity
of advanced wound care dressings.
For instance, the dressing used in
PICO comprises:
A silicone adhesive wound contact
layer which helps establish an
effective seal, yet is gentle on the
periwound area
An airlock layer that distributes
the negative pressure across
the dressing