New information on the use of foam versus gauze in NPWT seldom fails to draw attention. The topic, particularly when presented during major conferences, always seems to arouse close scrutiny of data, passionate debate, and the sharing of personal clinical experiences. A recent presentation by Swedish researcher Malin Malmsjö, MD, PhD, proved to be no exception. Dr Malmsjo, presenting an oral abstract at the Clinical Symposium on Advances in Skin and Wound Care in San Antonio on October 24th, reviewed her work comparing gauze and foam effects on the wound bed related to micro- and macrodeformation, tissue ingrowth, and wound bed histology.*
By itself, the idea that foam and gauze might produce different tissue effects should come as no surprise. Granulation tissue produced by foam routinely has been characterized as having a “beefy red” appearance, and being “thick” in comparison with tissue produced using a gauze filler. What is interesting and remarkable are the ways Dr. Malmsjö and colleagues from Lund University in Sweden sought to take a closer look at the differences in effects, using porcine wound models to compare foam and gauze with respect to the force required to remove each dressing filler, wound contraction, and the histology of the resulting tissue.
The Swedish team employed an interesting and novel instrument to measure the force required for dressing removal. The measurement device, connected to a computer, plotted force over time as it removed the fillers at a uniform speed. The force required for removal of foam was approximately double that for gauze when NPWT at -125 mmHg was used. Dr Malmsjö theorized that the difference resulted from the extensive ingrowth of tissue into foam, which was not observed with gauze. Wound contraction was similar for both groups. She stated, “Foam and gauze result in similar micro- and macrodeformation of the wound bed after NPWT. More force is required to remove foam than gauze after NPWT, which may be due to greater ingrowth into foam.”
Note: In the Q & A session following the presentation in San Antonio, a clinician in the audience described a case of considerable pain upon dressing changes and a lot of difficulty removing foam fragments from the wound when a foam filler was used. After switching to a gauze-based system, he remarked that on subsequent dressing changes he found the gauze did not adhere or allow ingrowth. However, he continued to find problematic residual foam fragments in the wound for quite some time.
Equally if not more interesting were differences observed in tissue morphology. More leukocyte infiltration, tissue disorganization, disruption of contacts between cells, and differences in cell size were seen in the foam-treated tissue, perhaps, according to Malmsjo, as a result of a foreign body reaction. The tissue resulting from foam was found to be thick, but fragile, while that from gauze was found to be thin, but dense.
In what ways might this new research be used to improve patient care and outcomes? Less ingrowth can mean less pain for patients during dressing changes. Knowledge of different granulation tissue characteristics now make it possible to tailor NPWT, selecting the wound filler based on the desired quality of granulation tissue. Foam may be best where thick granulation is desired and where scarring does not pose a problem (ex. sternotomy wounds), whereas gauze may be best for improved cosmetic results and for wound bed preparation for skin grafting.
The foam/gauze dialogue will no doubt continue. We at Prospera find a host of advantages to the use of the AMD gauze filler — among them: microbial control, hydrophilic nature, ability to see and monitor the wound fluid, safe and easy dressing placement, one-piece removal of the dressing, avoidance of in-growth and pain, and reduction in the need for narcotic and other pain medications. These latest findings strengthen our convictions further, by adding a histological piece to the puzzle.
* The research presented was supported by Prospera Technologies, LLC, Fort Worth, Texas USA
