Matching dressing properties to wound requirements is a fundamental part of any good protocol of care, but the mechanics of exudate handling are complex and many factors need to be considered. This paper introduces these factors, giving examples of their effects in conjunction with dressing products and materials. It discusses one modern material (Hydrofiber® Technology) in more depth, using scientific and clinical evidence to illustrate how it has been engineered to retain many of the best attributes of traditional wound dressing materials, while addressing some of their shortcomings.

Caring for and healing chronic wounds is often a long and expensive process. It has been estimated that the annual costs of wound care to the UK's National Health Service is in the region of £2.3-3.1bn which, according to figures for 2005/06, is equivalent to 3% of the total expenditure on health [1]. However, evaluating the true cost is difficult because it involves more than simply the price of a dressing. A wound care audit [2] (of approximately 590,000 members of a local population in the north of England) revealed that one person in 360 had a significant wound and that a relatively high proportion of these (24%) had wounds that had lasted for longer than six months. Another key finding of the audit was that around 80% of the total cost of care was attributable to factors not related to dressing costs but to wound complications (and delayed healing). In particular, the authors suggested: '... that seeking to reduce wound care cost simply by reducing the cost of dressings is likely to have a limited impact'.

Selecting an appropriate protocol of care is an important factor in achieving the best possible clinical outcome. The protocol should include guidelines that ensure that dressing selection is based on scientific principles, including consideration of the type and condition of the wound and the dressing's attributes and performance characteristics [3]. However, this is not an easy task as no two wounds are alike, they may have complex anatomy and their behaviour can change rapidly. Therefore, the selected dressing needs not only to generate and maintain an environment that is conducive to healing, but also to respond and adapt to manage the changing demands.

ROLE OF DRESSINGS IN EXUDATE MANAGEMENT AND WOUND PROGRESSION

Since Winter's landmark paper on moist wound healing [4], it has been recognised that the control of fluid in the wound environment is pivotal. In a consensus document issued by the World Union of Wound Healing Societies (WUWHS), it was stated that dressings should have the ability to absorb and retain fluid, control its evaporation and transmission rates, while ensuring that there is sequestration of exudate's harmful components (eg proteolytic enzymes and bacteria) [5].

Dressings differ significantly in their fluid-handling characteristics. Matching these characteristics to the wound's exudate profile is important when trying to establish and maintain a moist wound environment [6]. The strength, rate and capacity of absorption, the rate of conversion of unretained to retained absorption (or retention), the rate at which absorbed and retained fluid can be lost by evaporation and how a dressing can modify the rate of exudate production, should all be considered.


POTENTIAL EFFECTS OF THESE FACTORS

Too vigorous absorption, for example one generated by a superabsorbent polymer, may desiccate the wound and result in the wound bed drying out and unwanted adherence to healing tissue[5]. If absorption is slow, such as that provided by hydrocolloid adhesive dressings, use on a heavily exuding wound will be inappropriate. The dressing adhesive will fail and unabsorbed exudate may cause maceration and wound deterioration. However, used appropriately on superficial and partial-thickness wounds (which tend to be dry or only lightly exuding), hydrocolloid dressings have been shown to be more effective in improving healing, reducing pain and levels of infection, when compared with dressings that have minimal fluid retention, eg gauze [7].

A dressing's absorption capacity is a compromise between conflicting needs. Insufficient capacity (for the level of exudate being formed and the dressing change frequency indicated) will result in leakage and maceration, requiring more frequent dressing changes [5]. Alternatively, a dressing with an excessive absorption capacity will be bulky and may become heavy before coming to the end of its useful life; this can lead to issues with fixation, change frequency and patient discomfort. Thin gauzes, films and waxy or oily dressings can fall into the former category, and thicker foams and gauze wadding dressings can fall into the latter [8].