Does exudate viscosity affect its rate of absorption into wound dressings?

Exudate is a vital component of healing wounds. There are differences between acute and chronic exudate, with the latter seen as highly toxic to the healing environment. Wound exudate assessment is not easy for clinicians. The viscosity of wound fluid/exudate is as important as its quantity. Wound fluid viscosity increases when it contains more protein. As wound dressings exhibit a variety of fluid-handling mechanisms, it is important to understand how they interact with the different exudate types, which may alter the wound/dressing interface. This knowledge will ensure a healing wound environment that is beneficial, not one that leaves harmful exudate on the wound surface. This study aimed to evaluate if the viscosity of exudate affected absorption time in four wound dressing types.

This study evaluated the viscosities of two solutions and their effect on the absorption times of four dressing types. The viscosities of the solutions were calculated using Ostwald viscometers, then 2 ml of each of these liquids was applied to each of the four dressing types and repeated 10 times for each dressing, as per British Standards Institution requirements. The parameters for temperature and frequency were applied, and the absorption times recorded. A two-way repeated analysis of variance (ANOVA) was conducted to examine if exudate viscosity and dressing type, or their interaction, affected the absorption time.

The results indicated that the viscosity of the solution alone had a significant effect on absorption time (p<0.01), and that the combined effect of dressing type and viscosity also affected absorption (p<0.01). The type of dressing alone was found to have a significant effect on absorption time (p<0.01). When looking at the between-subject effects of the dressings (between the four types) the only non-significant finding was between two dressings-the superabsorbent and the moderate (foam) absorbing dressing (p=0.097). All other dressings had a between-subject effect of (p<0.01).

A significant difference in absorption times was found in this investigation of dressing types and viscosity of test solutions. The greater the viscosity of the fluid, the longer it took for it to be absorbed into all dressing types tested. This delay was not determined simply by the dressing or by the viscosity of the fluid, but likely to be a combination of the mode of action of the dressing, its pore size and particulate composition of the exudate, all of which require further investigation.