Novel Foam Dressing With Through Holes and Negative Pressure Wound Therapy With Instillation and Dwell Time: A Retrospective Cohort Study

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The clinical benefits of NPWTi-d using a topical wound solution have been reported for a variety of wound types, such as pressure injuries, posttraumatic wounds, and VLUs.^1-3 Traditionally, this therapy is applied via a standard reticulated open cell polyurethane foam dressing (ROCF-V; 3M V.A.C. VERAFLO Dressing, 3M). However, a new reticulated open cell foam dressing architecture with through holes (ROCF-CC; 3M V.A.C. VERAFLO Cleanse Choice Dressing, 3M) became commercially available in 2017 to assist in removal of thick exudate and other infectious materials. In wet conditions, the ROCF-CC foam has a tensile strength approximately 3 times that of the standard NPWTi-d ROCF-V.⁴

ROCF-CC is less hydrophobic than the traditional ROCF-V, with a consequently higher absorption capacity. Particularly during the soak/dwell phase, the main characteristic of ROCF-CC is the presence of through holes, measuring 1 cm in diameter and spaced 0.5 cm apart (Figure 1), on a foam layer that is in direct contact with the wound bed. Upon this contact layer with through holes the clinician places a thin (0.8 cm) or thick (1.6 cm) traditional foam cover layer, depending on patient and wound characteristics,⁴ followed by an occlusive drape. Initial reports on this new dressing suggest that it is suitable for cleansing contaminated wounds by helping to soften, solubilize, and remove viscous exudate, wet slough, fibrin, infectious material, and nonviable tissue.⁴ The dressing may assist wound cleansing of chronic, complex VLUs with areas of nonviable tissue when complete surgical debridement is not possible or appropriate, such as in patients of advanced age or at high risk for complications from anesthesia, when the patients refer a high level of pain during the application of ROCF-V, or when surgical debridement must be delayed.

The authors of the current study conducted a retrospective cohort study to evaluate the efficacy of ROCF-CC dressing vs the standard ROCF-V dressing with NPWTi-d in the adjunctive management of complex VLUs. Outcomes of the 2 treatment groups with respect to mean duration of therapy, hospital length of stay, and wound area reduction are presented.

An observational retrospective cohort study was performed of the records of 22 patients ranging in age from 55 to 95 years. Records of patients with peripheral vascular disease who had a VLU that was present for 6 to 9 months prior to adjunctive management with NPWTi-d (3M Veraflo Therapy; 3M) between January 1, 2017, and December 31, 2020, were extracted from an in-house hospital registry. The registry contained data of all patients who had received NPWT since 2010. Patient records were divided into 2 groups: 11 patients who received NPWTi-d and ROCF-CC dressing (treatment group), and 11 patients who received NPWTi-d and ROCF-V dressing (control group).

To test for the presence of biofilm, microbiological swabs and biopsies were collected for all patients prior to NPWTi-d initiation. Systemic antibiotics were administered as appropriate. Compression was applied before and after NPWTi-d. All wounds were mechanically debrided with monofilament fiber cleansing cloths prior to NPWTi-d initiation. All patients underwent debridement in the operating room. NPWTi-d device settings were the same for all patients, with dwell time of 10 minutes, followed by an NPWT cycle length of 2.5 hours at −125 mm Hg. The 3 topical wound solutions instilled were as follows: 0.05% sodium hypochlorite for patients with high level of exudate and signs of infection with non-Pseudomonas spp, 0.9% normal saline in patients with reported reaction to topical antiseptic solutions or sensitive skin, and betaine plus polyhexanide or hypochlorous acid for patients who initially presented with signs of infection with Pseudomonas spp (abundant blue-green exudate). Dressings were changed every 72 hours. All ulcers in both groups were closed via split-thickness skin graft after wound bed preparation with NPWTi-d.

All codified data were collected from de-identified medical records from a single institution. This study conforms to ethical guidelines of the 1975 Declaration of Helsinki; patient consent to treatment was acquired in accordance with institutional and governmental guidelines. Because of the retrospective nature of the study, no other informed consent or ethical approval was required.

For statistical analysis, the data were divided into subgroups based on sex, topical wound solution instilled, and wound size. Microsoft Excel (Microsoft Corporation) was used for all descriptive statistics. Statistical analysis for significance of both wound surface area reduction and days of application was performed using a 2-tailed t test, with alpha set at .05 as the level of significance.

Patient and wound characteristics

Patient and wound characteristics for the 2 groups are presented in Table 1. There were no significant differences between the groups with respect to sex, age, comorbidities, wound size, or type of bacteria. Mean age was 72 years (range, 46-91 years) vs 76 years (range, 55-95 years), and mean preoperative wound surface area was 94.54 cm² vs 91.27 cm² for the ROCF-CC vs control group, respectively. Patients in both groups had similar comorbidities, including hypertension, obesity, and cardiovascular diseases.

Swab cultures were positive for microorganisms in all 22 patients. The majority of patients had positive culture for Staphylococcus aureus and/or Pseudomonas aeruginosa. In 5 patients in the ROCF-CC group, these bacteria occurred together and/or with other species, including Enterobacter spp, Proteus mirabilis, Escherichia coli, and Alcaligenes xylosoxidans. In 4 patients in the control group, S aureus and/or P aeruginosa bacteria occurred together and/or with other species, including Enterobacter spp, Serratia marcescens, and Morganella morganii.

Study results

Wound surface area reduction was achieved in 7 of 11 patients in the ROCF-CC group and in 8 of 11 patients in the control group. For the remaining 7 ulcers across both groups that did not show surface area reduction, progression toward a healthy wound bed was noted from the first dressing change at 72 hours. In the ROCF-CC group, granulation tissue was evidenced by the presence of macrocolumns of tissue that were formed within the holes of the dressing, and there was residual slough on the top of the microcolumns (Figure 2). The percentage mean wound surface area reduction was 15.7% in the ROCF-CC group (94.54 cm² before therapy vs 79.7 cm² after therapy) and 11.7% in the control group (91.27 cm² before therapy vs 80.54 cm² after therapy) (Table 2).

Overall, due to effective debridement and good granulation tissue as evidenced by the presence of the macroculumns in the ROCF-CC group after the first dressing, mean ± SD duration of therapy was shorter in the ROCF-CC group than in the control group (8.63 days ± 7.05 vs 11.72 days ± 17.41, respectively; P = .05); hospital length of stay was also shorter in the ROCF-CC group (9.9 days ± 2.98 vs 12.81 days ± 4.26; P = .08) (Table 2). These differences were not statistically significant. Additionally, mean wound area reduction was greater in the ROCF-CC group than in the control group (14.64 cm² ± 13.24 vs 10.72 cm² ± 14.60, respectively; P = .51), but this was not significant.

Prior to the initiation of NPWTi-d, bacterial infection was detected in all cases. Of these, more than 1 microbe was detected in 5 cases in the ROCF-CC group and in 4 cases in the control group. MDROs were detected in all 11 cases in the ROCF-CC group and in 1 case in the control group. In the ROCF-CC group, at discontinuation of NPWTi-d all microbiological swabs and biopsies were postive for bacteria persistence, but all showed only 1 microbe, and no microbes were multidrug-resistant. In the control group, at discontinuation of NPWTi-d all microbiological swabs and biopsies were postive for bacteria persistence, but all had only 1 microbe; the 1 MDRO was persistent.

The presence of effective granulation tissue, the almost complete absence of slough, and the negativization of microbiological cultures after the NPWTi-d therapy prompted the authors of the present study to stop treatment and perform the final closure with skin grafts in all patients.

Case study

An 80-year-old female with hypertension and diabetes presented with a chronic VLU that had been present for 9 months (Figure 2A). A preoperative swab sample culture was positive for S aureus. The area of the ulcer measured 300 cm². NPWTi-d was applied with an ROCF-CC dressing. Normal saline was instilled every 2.5 hours with a 10-minute dwell time and negative pressure applied at −125 mm Hg. After 7 days, the wound size had decreased to 270 cm² and the swab culture was negative for S aureus (Figure 2B). NPWTi-d was discontinued, and a split-thickness skin graft was applied. The patient was discharged on hospital day 8.

While the presence of negative pressure has been described since Egyptian times, with cupping therapy and the “wound sucker,” commercialized NPWT systems have been available only since the 1990s.^5,6 Consisting of an interface dressing plus vacuum device, this therapy has become one of the most promising and helpful tools for improving wound healing in the past 30 years. Characterized by specific mechanisms of action such as macro- and microdeformations in the wound bed, fluid removal, and alteration of the wound environment,⁷ new iterations of NPWT have expanded the function of this therapy over time, for example, with the dwelling of a topical wound fluid in the wound bed between NPWT cycles. This technology was introduced in 2011 with the aim of regular cleansing and accelerating wound bed preparation. To optimize outcomes, surgical debridement is generally needed before NPWTi-d application, and the presence of thick exudate can limit its results. To reduce these limitations, in 2015, the new ROCF-CC dressing was introduced to help treat patients with wounds containing a thick exudate or other infectious material who could not undergo surgical debridement or for whom it was necessary to delay surgical debridement.^4,8-10

Although negative pressure of −125 mm Hg is typically used, it has been hypothesized that increasing the pressure might increase granulation tissue formation. This theory remains controversial, however. It has been reported that the effect of increased pressure rapidly dissipates with increased distance from the dressing.¹¹

To the knowledge of the authors of the current study, this is the first comparative study of NPWTi-d outcomes with use of ROCF-CC dressings vs ROCF-V dressings. Unfortunately, there is no national guideline on the use of the ROCF-CC dressing; in the experience of the current authors, foam choice depends only on clinical experience. However, the results of this pilot study suggest that use of the new ROCF-CC dressing may enhance wound bed preparation, as evidenced by a positive trend toward reduced therapy time and greater wound area reduction compared with the standard ROCF-V dressing. For the VLU cases in the ROCF-CC group, a shorter duration of therapy led to reduced time to final skin graft closure. This outcome, coupled with the shorter hospital length of stay, has the potential for cost savings.

From the first dressing change at 72 hours, a peculiar response of the wounds treated with ROCF-CC was noted in terms of both the presence of macrocolumns of tissue on the wound bed and faster removal of nonviable tissue around the columns. The macrocolumns consisted of granulation tissue with a layer of residual slough on the top of the columns. Based on previously published in vitro data, in 2018 an advisory panel of expert ROCF-CC users suggested that the presence of the through holes on the dressing’s wound contact layer could prompt a unique kind of macrostrain-induced macrodeformation with a consequent disruption effect both of slough and thick exudate on the wound bed.¹² They also suggested that the presence of the holes could improve both the delivery of topical solutions and the removal of the thick exudate. The advisory panel also proposed that the presence of slough on the top of the macrocolumns may be indicative of minimum strain on the top of the through holes and maximum strain at the edges of the hole openings.¹²

Regarding bacterial load, in the current study there were no persistent MDROs in any of the 11 wounds in the ROCF-CC group for which culture was positive for MDROs prior to treatment, whereas MDROs were still present after treatment in the 1 wound in the control group with a positive culture for MDROs prior to treatment. This result could be due both to the greater amount of solution that can contact the wound bed through the through holes and to the specific mechanisms of action of the through holes that stimulate formation of macrocolumns.⁴ It also has been reported that the less hydrophobic, more absorptive nature of ROCF-CC allows a more even distribution of instilled fluid throughout the foam,¹² which may enhance the effects of solution delivery to the wound bed during the soak phase.

Although these are hypotheses that require further investigation, they appear to explain the preliminary observations of the authors of the current study that use of NPWTi-d with ROCF-CC results in faster cleansing and removal of devitalized tissue and, consequently, reduced days of hospitalization. In the experience of the authors of the current study, ROCF-CC is a useful tool to obtain faster wound bed preparation and promote healing of VLUs. Patients who received ROCF-CC demonstrated high levels of adherence and reported an almost pain-free treatment. It is the opinion of the current authors that the improved patient comfort may be due both to the larger contact area of the topical solution, which can enhance the quality of cleansing, and to the dressing’s enhanced ability to remove exudate and slough through the holes.

Based on clinical assessment, and consistent with the literature,³ the authors of the current study did not identify a clear relationship between type of topically instilled wound solution and outcome with respect to wound area reduction, swab culture negativization, or duration of therapy. In fact, the same outcomes were obtained in treating bacteria such as Providencia spp or multidrug-resistant P aeruginosa with saline solution vs other topical solutions, such as betaine plus polyhexanide. This supports the idea that the influence of NPWTi-d in these VLUs may have depended more on the mechanical effects of the foam combined with a solution vs the chemical effects of the solution itself. However, it could be quite interesting to analyze the effect of different solutions on the pH of the wounds: chronic wounds are featured by alkaline pH ranging between 7.2 and 8.9; these values can increase matrix metalloproteinases activity and bacterial load.^13-15 Studies suggest that fluids such as 0.05% sodium hypochlorite, polyhexanide (with or without betaine), and hypochlorous acid can reduced pH, thus improving wound healing. This supports the idea that the fluids used in instillation may also affect pH in a manner that results in faster healing, especially when combined with NPWTi-d.

This was a pilot study and therefore was not adequately powered to determine significant differences between the groups. The results could also be limited by record selection bias and inaccuracies in recordkeeping. It is possible that not all relevant risk factors were recorded. Future studies with larger population sizes are needed to determine the effect of NPWTi-d with various dressings on VLUs.

Results of this study suggest improved outcomes with the use of ROCF-CC vs standard ROCF-V dressings in the management of VLU. Compared with ROCF-V dressings, on average, VLUs adjunctively managed with NPWTi-d and ROCF-CC dressings showed greater reduction in wound area, decreased bacteria load, and shortened time to wound healing and final skin graft closure, with resulting reduced hospital length of stay and costs. Due to the low sample size, however, generalizability of these study results to the overall VLU population is difficult.

Authors: Carlotta Scarpa, MD, PhD; Martina Grigatti, MD; Sandro Rizzato, MD; Alberto Crema, MD; Vincenzo Vindigni, MD, PhD; and Franco Bassetto, MD 

Acknowledgments: The authors would like to thank Karen Beach of 3M for providing editorial support.

Affiliation: Plastic Surgery Institute, University of Padua, Padua, Italy

ORCID: Crema, 0000-0001-9875-6129

Disclosures: Dr. Bassetto has served as a consultant for 3M. The other authors disclose no financial or other conflcits of interest.

Correspondence: Carlotta Scarpa, MD, PhD; Researcher, Institute of Plastic Surgery, Neurosciences, Via Giustinani 2, Padua, Padua 35100 Italy; carlotta.scarpa@unipd.it

Manuscript Accepted: January 15, 2024