Use of Disposable Negative Pressure Wound Therapy in 16 Podiatry Clinic Patients with Chronic Wounds

As the population ages, the incidence of wounds being managed in different health care settings is also increasing.¹ Patients with chronic wounds presenting for outpatient care may require the use of negative pressure wound therapy (NPWT), though traditional NPWT is not always suitable due to small wound size and the patient’s desire to maintain normal daily activities without the constant need of electrical power. Disposable mechanical NPWT (dNPWT) devices could provide the required negative pressure therapy while allowing the patient to resume daily activities.

dNPWT devices are mechanically powered, small, quiet, and off-the-shelf and deliver negative pressure to small- to medium-sized wounds with mild to moderate exudate.² One company’s dNPWT system with foam dressings (3M Snap Therapy, 3M) has been shown to be comparable to traditional, electrically powered NPWT. The use of dNPWT was associated with higher rates of wound size reduction and similar wound closure rates and adverse events compared with traditional NPWT in an RCT of 132 patients with diabetic foot ulcers (DFUs) or venous leg ulcers (VLUs).³ When the VLU subset (n = 19) was further analyzed against traditional NPWT controls (n = 21), higher rates of wound closure and significant wound size reduction were observed in the dNPWT group.⁴ However, despite randomization, the initial wound size was significantly greater in the traditional NPWT group than in the dNPWT patients (11.60 vs 4.85 cm², P < .05).⁴

dNPWT has previously been shown to be successful in managing lower extremity wounds, with reported wound size reduction and wound healing without complications.^4-8 To further assess the potential clinical benefits of dNPWT use, we examined wound healing outcomes in 16 patients managed with dNPWT at a podiatry clinic with outpatient care.

Study design

Approval for this study was granted by the institutional review board of Prisma Health (970271935). All patients provided written informed consent prior to study enrollment. This study was performed in accordance with the Declaration of Helsinki. Patients with lower extremity wounds presented for care at the outpatient clinic between October 31, 2019, and December 16, 2021. Only patients that received dNPWT were included in the study. Patient and wound assessments were conducted to obtain patient demographics, previous medical history, wound type, wound age, previous treatment information, wound size and volume, and wound condition.

Wound care provided

Sharp debridement was performed, and antibiotics were initiated as necessary. All patients received dNPWT with dressing changes every 2 to 3 days. A hydrocolloid ring, applied to the periwound skin during dNPWT application, was utilized in some patients with wounds in difficult anatomical locations to help maintain a negative pressure seal. dNPWT use was discontinued when the wounds were healed or displayed 100% healthy granulation tissue and minimal to no exudate. Standard of care dressings (SOC, such as hydrocolloid dressings or foam dressings) or oxidized regenerated cellulose (ORC)/collagen (C)/ silver-ORC dressings (3M Promogran Prisma Collagen Matrix with ORC and Silver, 3M)) were utilized, if necessary, after dNPWT was discontinued. SOC or ORC/C/silver-ORC dressings were changed or reapplied according to manufacturer’s instructions and at the discretion of the health care provider. All patients received offloading through either an all-purpose postoperative shoe, heel suspension boot, controlled ankle motion walking boot, or patella tendon bearing orthosis. Patients received follow-up care at the outpatient clinic or from a home health service.

Outcome measures

Patient demographics, wound measurements (length, width, and depth), and subsequent wound visit data and treatments were recorded. Wound outcomes were defined as healed (complete wound closure), almost healed (76%-100% wound bed coverage of healthy granulation tissue), or not healed (<76% granulation tissue wound bed coverage). The percentage of granulation tissue was visually estimated based on granulation tissue color and wound depth measurements by the clinician during wound assessments at follow-up visits. Outcome measures, including wound area and volume, duration of treatment, and healing status were assessed. Descriptive statistics were generated using Excel (Microsoft).

Patient population and wound
demographics

A total of 16 patients (8 male and 8 female) presented for care. The average age of the study patients was 59.6 ± 8.9 years old. Multiple comorbidities were present, including poor nutritional status, diabetes, obesity, hypertension, and coronary artery disease (Table 1). Wound types managed consisted of DFU, surgical wounds, and one pressure injury (PI) (Table 1). Half of the patients (n = 8) underwent amputation prior to wound treatment. Baseline wound characteristics included an average wound age of 15.6 weeks, average wound area of 5.5 cm², and average wound volume of 3.3 cm³.

Type of follow-up care and
treatment duration

A majority of the patients received follow-up care at the outpatient clinic (n = 12); the remaining 4 patients received follow-up care in the home health setting. The average total treatment length was 128.6 ± 67.4 days, which corresponds to 22.3 ± 12.4 days of dNPWT and 106.3 ± 67.0 days of SOC dressings (Table 2). The average time from presentation to end of dNPWT was 45.5 days. During use of dNPWT approximately 8.4 dressing changes were performed, while use of SOC dressings required approximately 11.3 dressing changes (Table 2). A majority of patients (9 of 16, 56%) had at least 1 home health visit between follow-up visits to the outpatient clinic.

Wound healing outcomes

A significant reduction in average wound area was observed during dNPWT use (P = .046, Figure 1A). A reduction in wound volume was also observed with dNPWT use, though this was not significant (Figure 1B). Within the dNPWT use time frame, 81% of wounds showed an increase in granulation tissue amount, 63% showed wound area reduction, and 69% showed wound volume reduction. At the start of treatment, a majority of patients (56%) had little to no (≤25%) wound bed granulation tissue. By the end of treatment, most patients (88%, n = 14) had developed healthy granulation tissue covering ≥76% of the wound bed. One patient showed an increased amount of granulation tissue within the observation period (≤25%- ≥50%). The remaining patient did not respond to treatment as the amount of granulation tissue remained ≤25% at the end of the observation period.

Representative Case 1

Surgical wound following amputation. A 71-year-old male with chronic osteomyelitis of the first metatarsal and sesamoids underwent a first ray amputation. Previous medical history included former tobacco use, diabetes, coronary artery disease, hypertension, autoimmune disorder, and poor nutrition status. The wound was left open after amputation and antibiotics were initiated. At presentation to the clinic (2 weeks after amputation), the wound measured 7.0 x 3.1x 0.5 cm³. dNPWT was initiated with dressing changes every 2 to 3 days (Figures 2A, 2B). A hydrocolloid ring was applied on the periwound skin during dNPWT application to help maintain a negative pressure seal. Wound off-loading was provided by the use of an all-purpose postoperative shoe. dNPWT was discontinued after 16 days due to the presence of healthy granulation tissue and reduced wound area (5.5 x 1.0x 0.4 cm³, Figure 2C). ORC/C/Silver-ORC dressings were applied and continued for 28 days. The wound was fully healed 44 days after presentation (58 days after amputation, Figure 2D).

Representative Case 2

A 54-year-old male presented with a Wagner Stage 2 DFU (Figure 3A). Previous medical history included diabetes, obesity, and poor nutrition status. At presentation, wound maceration and undermining/tunneling was observed. A sharp debridement was performed resulting in a 2.5 x 1.5x 0.7 cm³ wound (Figure 3B). dNPWT was initiated with dressing changes every 2 to 3 days. A hydrocolloid ring was applied during dNPWT application to help maintain a negative pressure seal (Figure 3C). An all-purpose postoperative shoe was utilized for wound off-loading. After 28 days, dNPWT was discontinued due to the development of healthy granulation tissue and reduced wound area of 1.7 x 1.3x 0.3 cm³ (Figures 3D and 3E). ORC/C/Silver-ORC dressings were applied with reapplications occurring every 2 to 3 days. After 21 days (49 days after presentation), the wound was fully healed.

Traditional NPWT is more suited to managing large wounds and utilizes electrical power to deliver negative pressure. However, for patients with small, low-exudating wounds, traditional NPWT systems may not be the best NPWT option. dNPWT can offer patients wound management without the use of a bulky, noisy NPWT system, or electricity. In this retrospective study, 14 of 16 patients displayed improvement in wound area, volume, and granulation tissue amount during dNPWT. Most wounds (87%) were healed at, or shortly after, discontinuation of dNPWT.

Previous studies have reported improved wound healing outcomes with the use of dNPWT.^4-9 Klein reported wound size reduction and increased development of granulation tissue in a patient with wound dehiscence following a transmetatarsal amputation.⁹ A 3-patient case study on dNPWT use in VLU and wound dehiscence reported improved granulation tissue development in all patients and wound closure in 2 of 3 patients.⁵ Fong et al reported wound healing in all 12 patients with chronic wounds, including VLUs and neuropathic wounds, without serious adverse events and no pain in a majority of the patients (9 of 12).⁶ Another 12-patient study assessed dNPWT use for DFU management in the home care setting.⁷ In these patients, wound closure and wound size reduction without complications were observed.⁷ Bradbury et al reported decrease in wound area, exudate, and patient-reported pain along with increased granulation tissue development in 37 patients with chronic lower extremity wounds.¹⁰ One study compared the use of dNPWT in wound healing against standard of care dressings. Lerman et al reported that patients receiving dNPWT displayed a statistically significant healing trend and significantly shorter time to healing compared with the matched controls in the dressing group (P < .05).⁸ When the VLU subset was further analyzed from an RCT, significant wound size reduction at 4, 8, 12, and 16 weeks was observed in the dNPWT group along with higher rates of wound closure than the traditional NPWT patients.⁴ The wound size reduction and wound healing rates reported in the literature were similar to those observed in our patient population.

In our patient population, time from clinic presentation to the end of dNPWT was longer than the treatment duration of dNPWT. This indicates that non-dNPWT treatment methods were employed first, most likely due to initial use of more conservative methods (ie, use of dressings) while the clinician managed patient comorbidities to help remove barriers to wound healing.

dNPWT provides negative pressure therapy with a lightweight, portable, and quiet system. These features often appeal to patients as they represent minimal intrusion into their daily life while providing the needed wound management. Three previously published studies have reported improved quality of life with the use of dNPWT.^5,7,10 All 3 studies noted that patients with lower extremity wounds were able to resume daily activity due to the quietness of negative pressure delivery, the device’s light-weight design, and ability of the canister to be concealed underneath clothing.^5,7,10 In our study, patients were able to resume daily activities with the appropriate wound off-loading following application of dNPWT. Additionally, all patients were able to inconspicuously receive dNPWT as the canister was easily hidden underneath clothing.

The use of dNPWT has been slowly increasing; however, few studies have assessed the potential cost-savings benefits from dNPWT. A cost-minimization analysis comparing the use of dNPWT and traditional NPWT was conducted using Medicare paid claims in 2018.¹¹ Delhougne et al reported reduced average payments of $1564 for dNPWT compared with $3501 for traditional NPWT, indicating that dNPWT may provide potential cost savings compared with traditional electrically powered NPWT.¹¹ Fout et al reported that home health use of dNPWT increased between 2016 and 2019 leading to fewer home health visits and lower total Medicare payments than traditional NPWT.¹² However, the home health Medicare payment per episode of dNPWT was nearly twice the amount for traditional NPWT, most likely driven by the increased number of dNPWT units used per episode.¹² Future studies are needed to more fully assess the potential health economic benefits of dNPWT use in the outpatient setting.

Limitations for this study include the retrospective design and lack of a control group. Larger, randomized controlled trials and health economics assessment are necessary to fully characterize the potential benefits of dNPWT use in the outpatient setting. Additionally, the use of a single manufacturer’s dNPWT was assessed in this outpatient population. As such, these results may not be indicative of all dNPWT systems. Clinicians should review all available literature, device indications for use, and limitations before selecting a dNPWT system for the management of outpatient wounds.

In patients with small, low exudating wounds, traditional NPWT may not be the most appropriate negative pressure system due to its size, noise level when in use, and requirement for electrical power. dNPWT can offer comparable negative pressure therapy in an outpatient setting while allowing patients to resume daily activities. In this retrospective study, outpatient dNPWT use along with SOC dressings or ORC/C/silver-ORC dressings in patients with lower extremity wounds resulted in wound healing, and wound size and volume reduction without complications. The author and his clinical team see many advantages of using dNPWT in the out-patient setting including ease of use, a low learning effort required for dNPWT application, and the ability to add dNPWT without significant delay as it is an off-the-shelf negative pressure system. In our experience, use of dNPWT in small, low-exudating wounds have shown similar outcomes as traditional NPWT. dNPWT offers an off-the-shelf, mechanically powered, advanced wound care modality to our toolkit for treating hard-to-heal wounds.

R Klein is a consultant for 3M. L Soloway and C Bongards are employees of 3M.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

The authors thank Julie M. Robertson, PhD (3M) for assistance with manuscript preparation and editing.

¹University of South Carolina School of Medicine, Greenville, SC
²PRISMA Health Upstate, Greenville, SC
³Furman University, Greenville, SC
⁴3M, St. Paul, MN
⁵3M, 3M Deutschland GmbH, Neuss, Germany

Robert Klein, DPM, FACFAS, CWS, FFPM RCPS (Glasgow).
Prisma Health Upstate Greenville, 200 Patewood Drive, Suite C300, Greenville, SC 29615, Email: robklein63@gmail.com