Discussion
Topical NPWT involves active drainage of chronic over-exudative wounds. In this technique, a porous material (antimicrobial gauze or foam) is placed in the wound bed and enclosed using polyurethane films to form an airtight seal. This kind of dressing has been shown to be beneficial in a wide variety of wounds, including pressure ulcers, leg ulcers, skin grafts, sternal and abdominal wounds, traumatic injuries, postfasciotomy closures, and lymphorrhea. Although the bulk of the literature regarding NPWT describes one vacuum-assisted closure system (V.A.C. Therapy®, KCI, San Antonio, TX), the use of alternative dressing interfaces and vacuum sources also has been presented. The first use of gauze as a medium was reported by Chariker et al in 1989. They reported that negative pressure enhanced the closure of incisional fistulae by improving drainage control, reducing skin damage, improving wound granulation and contraction, and reducing nursing costs. The technique uses moistened gauze as a wound interface and 80 mm Hg of negative pressure. Campbell et al published a retrospective analysis in 2008, which proved the effectiveness of gauze as a wound filler material and applied the pressure at −80 mm Hg for the duration of therapy. Generally, pressures are targeted at −125 mm Hg, although no clinical data identify an optimum pressure. However, in a recent report, reduction in wound volume was suggested to be unrelated to pressures between −50 mm Hg and −125 mm Hg. In this study, the authors used continuous 125 mm Hg of negative pressure in wounds for the first 48 hours. After the wounds were properly cleaned by continuous and high pressure, the authors continued dressings with intermittent 80 mm Hg of negative pressure at 24- to 48-hour intervals. The pressure delivered to the wound bed by a suction tube and a wound filler—gauze, or foam—creates the mechanical stress on the surface of the wound. In the cells exposed to negative pressure, integrin bridges in their cytoskeletons are disrupted; thus, cell proliferation is stimulated. The other effect of negative pressure is elimination of proteases that inhibit healing of the lesion. The most important effect of negative pressure is provided by the mechanical pump. Therefore, a useful wound filler material should transduce the negative pressure to the wound bed equally.
As evidence of granulation tissue appears, wound management guidelines can be divided in terms of 3 groups of patients: Group A wounds must be closed with either local flaps or free tissue transfer.; these include wounds with exposed joints, tendons, and fractures. Group B wounds are amenable to closure with a skin graft; these wounds are typically larger than 5 cm and require 2 to 4 weeks to close by secondary intention. Group C wounds are amenable to closure by secondary intention; these are smaller wounds that can be managed with other moist, nonadherent dressings. In the present series, only 5 cases were in Group C, and they healed secondarily. The duration of vacuum therapy averaged 12.98 days to secondary closure. Granulation was clinically noted in all patients by day 5, illustrating the short time needed to produce a healthy, granulating tissue bed. In a similar study of 75 patients with open wounds of the lower extremity (of which 49 were the result of trauma), granulation tissue was present by day 4 of vacuum therapy, with decreased edema and bacterial counts. Another study reported results of 21 consecutive patients with high-energy, soft-tissue wounds who underwent vacuum therapy for an average of 19.3 days. Bollero et al likewise reported rapid granulation tissue formation in 35 patients with lower limb traumatic wounds who underwent vacuum therapy. In another study by Chariker et al, this method was used in 24 pediatric patients with upper and lower extremity injuries. The duration of vacuum therapy averaged 10 days to primary closure and 17 days for secondary closure. Granulation was noted in all patients by day 4, illustrating the short time needed to produce a healthy, granulating tissue bed.
Clare et al used NPWT with growth factors in 17 cases of persons with diabetes and vascular insufficiency in their extremities. They accomplished treatment without any need for surgery in 6 cases. De Franzo et al needed surgery for only 12 of 75 patients with wounds on a lower extremity treated with the same procedure. Also, De Lange et al did not need any surgical procedure to cover the wounds in 29 of 100 cases. In that study, the defect was left for secondary healing in only 1 case because of its decreased dimensions. In the present study, 6 cases did not undergo an operation, and these wounds were left to secondary healing; however, these wounds were relatively smaller in dimension than that of others at the beginning of treatment. Other wounds required various reconstructive surgery procedures.
In the present study, average pre-treatment wound size was 90.21 cm, while the post-treatment period averaged a wound size of 35.71 cm, a statistically significant difference (P < 0.001). The authors observed that the wound areas decreased at a rate of 64.61%, and in all wounds granulation tissue formation and increased contraction were observed.
Gauze-based NPWT may be more practical and useful in smaller undermined wounds, such as DFUs. Following surgical debridement, patients were effectively treated and prepared for surgery by topical NPWT with antimicrobial gauze dressings. Although the foam-based system is preferred in large and deep wounds in many centers, gauze as a wound filler seems to be easier to apply and conform to complicated geometries of the wounds. In a study by Dunn et al, the gauze-based system was used during the pre-and post-grafting period at a continuous negative pressure of −80 mm Hg. The authors suggested that split-thickness skin grafts might provide the ideal indication for the adoption of gauze-based NPWT. According to the author's experiences, the gauze-based system seems to be more useful and feasible for group B or grade 1 and 2 wounds. The gauze medium may require using more material to fill in a large and deep wound compared to foam. This can raise cost of treatment. However, recent reports indicated that the type of interface material does not affect the pressure transduction to the wound.
Comparative and prospective studies are needed to assess the efficacy of a gauze-based system on large and deep wounds. The aim of NPWT is to prepare the wounds for surgery. The excessive use of this method can lead to extended duration of hospitalization and increased cost of treatment. NPWT should be considered a temporary or bridge technique for management of wounds, meaning it is used to promote wound healing before closure, either by secondary intention or by grafting or flap placement.
In the postoperative period, sufficient and proper wound care, as well as passive and active exercises, are essential for providing long-lasting positive results and reducing recurrence rate. The patients should not lie down or sit down on their flaps for 3 weeks. At the end of the 3-week period, patients can sit down on the flap for only 15 minutes a day. In the authors' study, 3 patients required secondary surgery in postoperative 6 months. These patients had SPS (1 case) and IPS (2 cases) pressure ulcers. The gauze-based NPWT was reused in only 1 patient with an IPS because of total dehiscense.
IPSs have a high incidence of recurrence despite successful reconstructive treatments. In the literature, it is reported that the reoccurrence rate ranges from 27.8% to 63%. In IPSs, myocutaneous flaps can be used to reduce recurrence rate and the wounds should be protected from long-lasting pressure and shearing forces as an important factor in decubitis ulcers, especially in paraplegics.
In their study of 51 pediatric patients, Caniano et al reported the cost-effectiveness of NPWT with foam therapy on nonhealing wounds. Although cost-effectiveness was not the focus of the current report, NPWT was shown to be an economical treatment for adult patients, especially those with pressure ulcers. According to Vidrine, cost is a major disadvantage in foam-based NPWT. Even in developed countries, the cost of wound care has exorbitant rates. Therefore, when deciding on the method of treatment, the efficiency as well as the cost of treatment should be considered.
The current study suggests use of gauze-based dressings is an effective method of NPWT. In the authors' study, polyurethane foam dressing was found to be insufficient for cost-effectiveness compared to the gauze-based dressing. The cost of the polyurethane foam dressing in total is $75,500 for 50 patients, while the gauze-based dressing is $30,000 for 50 patients. From the patient perspective, NPWT may be associated with reduced discomfort due to pain, medication usage, and costs. Most NPWT dressings need only to be changed every 2 to 5 days, sometimes less. Therefore, the method reduces material resources, staff time, and patient discomfort during painful dressing changes. Pain depends on many clinical variables, including the presence of analgesic, neuropathy, and paraplegia. In the present study, the number of the patients who complained of pain was very low.
In this study, the authors found a statistically significant correlation between age and proportional change in wound areas for women, but no significant correlation for men. An area for future exploration is that one of the most important results of hormonal changes is the age-related delay in cutaneous wound healing. Reduced estrogen levels play a negative role on cellular and tissue response to injury. This effect includes impaired cytokine signal transduction, unchecked inflammation, and altered protein balance, and can have a major impact on the rate of wound healing.