RECONSTRUCTIVE Biomechanical and Safety Testing of a Simplified Negative-Pressure Wound Therapy Device Gita N. Mody, M.D., M.P.H. Danielle R. Zurovcik, Ph.D. Shahrzad Joharifard, M.D. Grace Kansayisa, M.D. Gemimah Uwimana, B.S.N. Erick Baganizi, M.D. Georges Ntakiyiruta, M.D. Dominique Mugenzi, M.D. Robert Riviello, M.P.H. Boston and Cambridge, Mass.; Vancouver, British Columbia, Canada; and Butare, Rwinkwavu, and Kigali, Rwanda
T
Background: There is a large, unmet need for acute and chronic wound care worldwide. Application of proven therapies such as negative-pressure wound therapy in resource-constrained settings is limited by cost and lack of electrical supply. To provide an alternative to existing electrically powered negative-pressure wound therapy systems, a bellows-powered negativepressure wound therapy system was designed and iteratively improved during field-based testing. The authors describe the design process and the results of safety and biomechanical testing of their simplified negative-pressure wound therapy system. Methods: Simplified negative-pressure wound therapy was tested at two hospitals in Rwanda. Patients with wounds ranging from 2 to 150 cm2 and meeting inclusion and exclusion criteria were enrolled. Wounds were categorized by difficulty of dressing application according to location and contour. Outcomes were maintenance of negative pressure and occurrence of adverse events. Results: Thirty-seven patients with 42 wounds were treated with simplified negative-pressure wound therapy. Eighty-five dressings in total were applied. On average, the final simplified negative-pressure wound therapy dressing maintained negative pressure for 31.7 hours on all wounds (n = 37), and 52.7 hours on wounds in easy-to-dress locations. No unexpected adverse events occurred. Conclusions: This is the first systematic report of the performance of a bellowspowered negative-pressure wound therapy device designed specifically for use in resource-constrained settings. The authors found that elimination of air leaks in the simplified negative-pressure wound therapy dressing is essential, and that their system is safe and feasible for use in these environments. Subsequent trials will study the system’s efficacy. (Plast. Reconstr. Surg. 135: 00, 2015.) CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.
here is a large, unmet need for acute and chronic wound care worldwide. Although the prevalence of all wound types is unknown, the
From the Department of General Surgery, Center for Surgery and Public Health, Brigham and Women’s Hospital; Worldwide Innovative Healthcare, Inc.; the Department of Surgery, University of British Columbia; National University of Rwanda; the Department of Nursing, Rwinkwavu Hospital; Drew Cares International; and the Department of Surgery, National University of Rwanda, Kigali University Teaching Hospital. Received for publication March 23, 2014; accepted September 30, 2014. This trial is registered under the name “Simplified Negative Pressure Wound Therapy,” Clinical Trials.gov identification number NCT01339429 (https://clinicaltrials.gov/ ct2/show/NCT01339429). Copyright © 2014 by the American Society of Plastic Surgeons DOI: 10.1097/PRS.0000000000001101
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global burden of wounds appears to be increasing over time.1 Anecdotally, advanced wound therapies such as negative-pressure wound therapy are sought globally; however, application is limited primarily by cost, availability, and lack of electrical supply. To provide an alternative to existing electrically powered negative-pressure Disclosure: One year after completion of enrollment of study patients, Dr. Zurovcik founded Worldwide Innovative Healthcare, Inc., a for-profit company that develops innovative medical devices that are clinically effective and affordable worldwide. The company will manufacture and sell the simplified negative-pressure wound therapy system as of December, 2015. The other authors have no financial interest in any of the products or devices mentioned in this article.
www.PRSJournal.com
Volume 135, Number 4 • Negative-Pressure Wound Therapy Device wound therapy systems, a bellows-powered, simplified negative-pressure wound therapy system was designed.2 Negative-pressure wound therapy benefits open wound healing by providing macrodeformation and microdeformation of the wound bed, leading to angiogenesis and cell proliferation, removing wound exudate, providing a moist wound environment, and reducing wound surface area.3–6 Improved wound healing rates with both commercial negative-pressure wound therapy systems such as the vacuum-assisted closure system (V.A.C.; Kinetic Concepts, Inc., San Antonio, Texas) and ad hoc negative-pressure wound therapy systems have been demonstrated in both the developed world and the developing world.7–10 Cost-effectiveness of the vacuum-assisted closure system compared with conventional gauze-based dressings also has been demonstrated.11 Historically, negative-pressure wound therapy systems relied on an electrical power supply. More recently, mechanically powered negative-pressure wound therapy devices have been described. The smart negative-pressure system (SNaP; Spiracur, Inc., Sunnyvale, Calif.) relies on a spring-powered suction source and has been shown to be noninferior in its wound healing rates compared to the vacuum-assisted closure system when placed on wounds where an airtight seal was achieved.12–15 However, despite its elimination of electrical requirements, the smart negative-pressure system cost, lack of availability, and limited applicability to all wound types are barriers to its sustainable and widespread use in the developing world. Other mechanically powered ad hoc systems using hospital supplies such as surgical drains have been described; however, these “off-the-shelf” devices cannot continuously maintain negative pressure to a wound on contoured body surfaces because of limitations in the adhesion and compliance of their adhesive drapes that allow air to leak into the system, overwhelming the capacity of the suction supply.16 To overcome barriers to negative-pressure wound therapy use in resource-constrained settings, a novel simplified negative-pressure wound therapy device was developed.17 The device consists of a plastic bellows, which serves as both the negative pressure source and the wound exudate receptacle by means of a drainage tube that is sealed into an occlusive dressing (Fig. 1). The design eliminates air leaks into the system by use of a flexible, semicured polymer to seal edges of the dressing to intact skin (Fig. 2).2,18
This study was a prospective single-arm investigation of the biomechanical parameters and adverse events associated with the simplified negative-pressure wound therapy system in a resource-constrained setting. We hypothesized that simplified negative-pressure wound therapy would be safe and that negative pressure would be maintained for at least 24 hours.
PATIENTS AND METHODS Enrollment Procedures The study took place at two hospitals in Rwanda. Rwinkwavu Hospital is a 110-bed district hospital in rural eastern Rwanda. The 15-bed surgical ward cares for at least 50 patients with chronic wounds per year. The ward was screened for wounds suitable for simplified negative-pressure wound therapy on a weekly basis over a 9-month period. The Kigali University Teaching Hospital is a 513-bed referral hospital in the capital city of Rwanda. The surgery, medicine, and obstetric wards (total, 226 beds) were screened for wounds suitable for simplified negative-pressure wound therapy over a period of 11 weeks. Photographs of wounds ranging in size from 2 to 150 cm2 and the patients’ clinical histories were reviewed for study enrollment eligibility criteria. Inclusion criteria included age 14 years or older, adequate adjacent intact skin and wound location for application of the simplified negative-pressure wound therapy dressing, an effective pain management plan, anticipated clinical stability, and plans to remain hospitalized for the duration of the study. Exclusion criteria were exposed blood vessels, evidence of ischemia, necrotic tissue requiring further débridement, infection, osteomyelitis, and malignancy in the wound. Eligible patients were given 24 hours to review and sign the institutional review board– approved consent form, which had been translated into Kinyarwanda. For patients younger than 21 years, consent was obtained when the patient’s guardian signed the consent form and the patient signed an assent form before enrollment. Wounds were measured for depth and surface area (using a manual tracing onto clean paper) before application of simplified negative-pressure wound therapy. Approval for this study was obtained from the Rwandan National Ethics Committee, the Kigali University Teaching Hospital Institutional Review Board (Kigali, Rwanda), and the Partners Human Research Committee (Boston, Mass.).
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Plastic and Reconstructive Surgery • April 2015
Fig. 1. (Above) Schematic of the simplified negative-pressure wound therapy device dressing and bellows pump. 1, Wound cavity is packed with gauze. 2, Occlusive drape is sealed to surrounding skin. 3, The bellows pump is compressed and barbed drainage tubing is inserted into the pump. (Below) Compression of the bellows pump by hand generates negative pressure.
Dressing and Monitoring Procedures Two dressing types were used sequentially over the course of the study: the initial prototype dressing (without a preattached drainage tube) and the final prototype dressing (with a preattached drainage tube). For both dressing types, the wound was cleansed by the hospital nursing staff with normal saline, and the periwound skin was cleaned with 91% isopropyl alcohol and allowed to dry. Sterile cotton gauze was used to pack the wound. The simplified negative-pressure wound therapy dressing was applied by laying an occlusive adhesive drape over the gauze packing, taking care to avoid wrinkling at the edges. For the initial prototype dressing, a small hole was cut in the drape and the drainage tube was sealed into the hole with additional adhesive drape. The drape of both dressing types was then sealed to
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the surrounding periwound skin using three coats of thinly applied liquid latex. Once the dressing was dry, the barbed end of the drainage tube was inserted into a rubber stopper. The bellows was compressed, and the rubber stopper was inserted snugly into the mouth of the bellows. The bellows drain used in this study delivered 75 mmHg of negative pressure when fully compressed. The bellows was released, and the dressing was monitored for 10 minutes to ensure that it was airtight (if not, the bellows would expand rapidly, signaling air leaking into the system). The dressing was then protected with a light dusting of talc-based, nonmedicated powder and a cloth bandage overwrap. Nursing staff were instructed to compress the pump every 8 to 12 hours as needed to maintain negative pressure.
Volume 135, Number 4 • Negative-Pressure Wound Therapy Device staff to evaluate ease of application and potential areas for design improvements.
Fig. 2. The simplified negative-pressure wound therapy dressing uses an occlusive drape treated with adhesive that is sealed over the gauze packing materials to the periwound skin with a semicured polymer. The drainage tubing is already attached to the drape using a flexible tubing connector, eliminating air leaks at this interface.
An initial pilot of five patients was conducted, during which the simplified negative-pressure wound therapy dressing was applied for a period of 24 hours and removed for inspection of the periwound skin and wound. These dressing applications are not included in the analysis. The enrolled study patients underwent monitoring twice daily to assess the following: (1) amount of negative pressure being delivered, (2) fluid collection beneath the dressing or other disruption of the dressing, (3) quality of wound effluent, (4) erythema of periwound skin, and (5) the patient’s clinical status. If negative-pressure delivery dropped below 75 percent of the starting pressure as indicated by bellows length, fluid accumulated outside of the dressing, or the dressing ceased to adhere to the skin, the dressing was considered to have failed and was removed. If the patient’s clinical status changed, including the development of fever, periwound erythema, or increasing pain, the dressing was also removed. If the dressing remained intact and the patient’s clinical course was stable, the dressing was removed 72 hours after application. When the simplified negative-pressure wound therapy dressing was removed, the wound and periwound skin were inspected for qualitative appearance. The dressing was reapplied after discussion with the patient’s treating clinician. The wound was measured and photographed approximately every week to document wound health. Simplified negative-pressure wound therapy dressing applications at Kigali University Teaching Hospital were observed by a member of study
Statistical Analysis Wounds were classified into three categories based on the contour of the skin surface and accessibility for dressing: easy (flat surface), medium (curved or difficult-to-reach surface), or hard (spanning a joint and/or subject to patient shear, mass movement, or body fluids). The wounds were categorized first by means of independent assessment and then by agreement of two study personnel. Average time to pump failure was recorded and compared by dressing type (initial versus final) and wound difficulty using the Wilcoxon rank sum test and the KruskalWallis test. Cause of dressing failure was reviewed to define targeted areas of dressing and device improvement.
RESULTS Forty-seven patients gave consent for enrollment into the study. Ten were excluded for not meeting inclusion criteria (n = 6), withdrawing voluntarily (n = 1), and other reasons including change in clinical or wound status in the interval between enrollment and the planned treatment (n = 3). Five patients had more than one wound that was treated. Wound location and cause of the 42 treated wounds are listed in Tables 1 and 2. Eighty-five simplified negative-pressure wound therapy dressings were applied in total over the study period. Five dressing applications were excluded from analysis, as the simplified negative-pressure wound therapy was discontinued because of a change in the condition of the patient, unrelated to wound therapy. Nine dressings were excluded from analysis because of concern for occlusion of the dressing drainage tube related to the construction of that particular Table 1. Location of Wounds Treated with Simplified Negative-Pressure Wound Therapy Location
No.
Abdomen Ankle Breast Extremity Foot Labia Sacrum Thigh Trochanter Total
2 1 2 15 5 1 11 2 3 42
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Plastic and Reconstructive Surgery • April 2015 Table 2. Cause of Wounds Treated with Simplified Negative-Pressure Wound Therapy Cause
No.
Decubitus Infection Trauma Total
15 18 9 42
batch of dressings. The study flow diagram is presented in Figure 3. For the remaining 71 analyzed dressings, the average time to dressing failure was 22.2 ± 27.0 hours (range, 0 to 72 hours). In subset analysis, the final dressing delivered negative-pressure wound therapy longer (31.7 hours; n = 37) than the initial dressing type (11.8 hours, n = 34) (p = 0.003) (Fig. 4). The final dressings were analyzed further
by wound location (easy, medium, and hard as listed in Table 3) and were found to deliver negative-pressure wound therapy for longer durations on easy-to-dress wounds (52.7 hours; n = 11) compared with medium- (n = 22) and hard-to-dress (n = 4) wound locations (p = 0.029) (Fig. 5). No serious adverse events were encountered, including no allergic reactions to the latex skin sealant, increases in wound size, or evidence of bleeding or infection. One patient, who was immunocompromised, developed a fever and so device use was terminated (although there was no evidence of wound infection).
DISCUSSION This study demonstrates the safety and feasibility of our simplified negative-pressure wound
Fig. 3. Study flow diagram. Patients with small to medium wounds were enrolled over a 12-month period at two hospitals in Rwanda. sNPWT, simplified negative-pressure wound therapy.
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Volume 135, Number 4 • Negative-Pressure Wound Therapy Device
Fig. 4. The final dressing type delivered a longer duration of simplified negative-pressure wound therapy (p = 0.003) compared with the early dressing type. NPWT, negative-pressure wound therapy.
therapy system for use in resource-constrained settings. The system maintained negative pressure continuously for more than 2 days on wounds located on minimally contoured surfaces and for 1 day on more difficult-to-dress wounds. Since this phase of the study, we have conducted further bench work to refine the dressing materials and application method to target maintenance of negative pressure continuously for 3 days on all wound locations, which is the standard therapy duration provided by commercially available negative-pressure wound therapy systems. The current version of the simplified negative-pressure wound therapy system is undergoing contract manufacturing for commercialization and regulatory approval by means of the U.S. Food and Drug Administration’s 510(k) process. Several important features of the device were qualitatively evaluated by study staff (including local nurses, medical doctors, surgeons, and students) and patients. Both staff and patients voiced enthusiasm about negative-pressure wound therapy in general and the simplified negativepressure wound therapy system specifically, stating that fewer dressing changes were required compared with conventional dressing methods. Table 3. Number of Dressings in Each Wound Difficulty and Dressing Type Category
Wound Dressing Difficulty Easy Final Initial Total
(Extremity, Abdomen)
(Posterior Extremity, Trochanter)
11 10 21
22 16 38
Gita N. Mody, M.D., M.P.H. Department of General Surgery Center for Surgery and Public Health Brigham and Women’s Hospital 75 Francis Street Boston, Mass. 02115 [email protected]
acknowledgments
(Typical Location)
Medium
Financial barriers to simplified negative-pressure wound therapy are anticipated to be low, as the device components are simple and low cost, which was ascertained by our field-based design process. The simplified negative-pressure wound therapy dressing must be prefabricated because of the requirement of a preattached drainage tube, but the remainder of the system can be assembled and even sterilized on site, keeping packaging costs constrained. Clinical and cost-efficacy studies are required to demonstrate benefits in wound healing by the simplified negative-pressure wound therapy system and to formally evaluate patient and provider satisfaction and are being planned. Ultimately, implementing simplified negative-pressure wound therapy in the developing world has the potential to decentralize chronic wound care from secondary and tertiary hospitals, thereby lessening the burden of wounds on health care systems in the developing world.
Hard
(Sacrum, Foot)
Total
4 8 12
37 34 71
The authors would like to acknowledge the Fogarty International Clinical Research Fellowship, the National Institutes for Health and International Clinical Research Fellows Program at Vanderbilt University (R24 TW007988), the Hugh Hampton Young Memorial Fund Fellowship, and the Massachusetts Institute of Technology Legatum Center for financial support of the
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Plastic and Reconstructive Surgery • April 2015
Fig. 5. The final dressing applications were further analyzed by wound type. There was a significant difference in simplified negative-pressure wound therapy delivery duration by wound type, with easy wounds receiving significantly longer therapy (p = 0.029). NPWT, negative-pressure wound therapy.
project. They would like to thank the Ministry of Health of Rwanda for promoting a culture of innovation and equity in patient care. Lastly, they would like to acknowledge the staff at Rwinkwavu Hospital, Inshuti Mu Buzima/Partners In Health, and Kigali University Teaching Hospital for their collaboration and support and their commitment to improving patient care on a daily basis.
references 1. Murray CJ, Vos T, Lozano R, et al. Disability-adjusted life years (DALYs) for 291 diseases and injuries in 21 regions, 1990–2010: A systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012;380:2197–2223. 2. Zurovcik D, Slocum A, Mody G, Riviello R, Sheridan R. Development of simplified negative pressure wound therapy device for low-resource settings. Paper presented at: IEEE Global Humanitarian Technology Conference (GHTC) Proceedings. October 30–November 1, 2011; Seattle, Wash. 3. Kostiuchenok BM, Kolker II, Karlov VA, Ignatenko SN, Muzykant LI. Vacuum treatment in the surgical management of suppurative wounds (in Russian). Vestn Khir Im I I Grek. 1986;137:18–21. 4. Orgill DP, Bayer LR. Negative pressure wound therapy: Past, present and future. Int Wound J. 2013;10(Suppl 1):15–19. 5. Mouës CM, Heule F, Hovius SE. A review of topical negative pressure therapy in wound healing: Sufficient evidence? Am J Surg. 2011;201:544–556. 6. Braakenburg A, Obdeijn MC, Feitz R, van Rooij IA, van Griethuysen AJ, Klinkenbijl JH. The clinical efficacy and cost effectiveness of the vacuum-assisted closure technique in the management of acute and chronic wounds: A randomized controlled trial. Plast Reconstr Surg. 2006;118:390–397; discussion 398. 7. Armstrong DG, Lavery LA; Diabetic Foot Study Consortium. Negative pressure wound therapy after partial diabetic foot
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amputation: A multicentre, randomised controlled trial. Lancet 2005;366:1704–1710. 8. Eginton MT, Brown KR, Seabrook GR, Towne JB, Cambria RA. A prospective randomized evaluation of negative-pressure wound dressings for diabetic foot wounds. Ann Vasc Surg. 2003;17:645–649. 9. Perez D, Bramkamp M, Exe C, von Ruden C, Ziegler A. Modern wound care for the poor: A randomized clinical trial comparing the vacuum system with conventional salinesoaked gauze dressings. Am J Surg. 2010;199:14–20. 10. Mody GN, Nirmal IA, Duraisamy S, Perakath B. A blinded, prospective, randomized controlled trial of topical negative pressure wound closure in India. Ostomy Wound Manage. 2008;54:36–46. 11. Flack S, Apelqvist J, Keith M, Trueman P, Williams D. An economic evaluation of VAC therapy compared with wound dressings in the treatment of diabetic foot ulcers. J Wound Care 2008;17:71–78. 12. Armstrong DG. Discussion: Update on negative-pressure wound therapy. Plast Reconstr Surg. 2011;127(Suppl 1):116S. 13. Fong KD, Hu D, Eichstadt S, et al. The SNaP system: Biomechanical and animal model testing of a novel ultraportable negative-pressure wound therapy system. Plast Reconstr Surg. 2010;125:1362–1371. 14. Landsman A. Analysis of the SNaP Wound Care System, a negative pressure wound device for treatment of diabetic lower extremity wounds. J Diabetes Sci Technol. 2010;4:831–832. 15. Lerman B, Oldenbrook L, Ryu J, Fong KD, Schubart PJ. The SNaP Wound Care System: A case series using a novel ultraportable negative pressure wound therapy device for the treatment of diabetic lower extremity wounds. J Diabetes Sci Technol. 2010;4:825–830. 16. Webster R, Ely PB, Milani A, et al. Alternative materials in vacuum-assisted closure. Plast Reconstr Surg. 2011;128:784e– 785e; author reply 785e–786e. 17. Zurovcik D. Development of a Simplified Negative Pressure Wound Device. Boston: Massachusetts Institute of Technology; 2007. 18. Orgill DP, Bayer LR. Update on negative-pressure wound therapy. Plast Reconstr Surg. 2011;127(Suppl 1):105S–115S.
T
Background: There is a large, unmet need for acute and chronic wound care worldwide. Application of proven therapies such as negative-pressure wound therapy in resource-constrained settings is limited by cost and lack of electrical supply. To provide an alternative to existing electrically powered negative-pressure wound therapy systems, a bellows-powered negativepressure wound therapy system was designed and iteratively improved during field-based testing. The authors describe the design process and the results of safety and biomechanical testing of their simplified negative-pressure wound therapy system. Methods: Simplified negative-pressure wound therapy was tested at two hospitals in Rwanda. Patients with wounds ranging from 2 to 150 cm2 and meeting inclusion and exclusion criteria were enrolled. Wounds were categorized by difficulty of dressing application according to location and contour. Outcomes were maintenance of negative pressure and occurrence of adverse events. Results: Thirty-seven patients with 42 wounds were treated with simplified negative-pressure wound therapy. Eighty-five dressings in total were applied. On average, the final simplified negative-pressure wound therapy dressing maintained negative pressure for 31.7 hours on all wounds (n = 37), and 52.7 hours on wounds in easy-to-dress locations. No unexpected adverse events occurred. Conclusions: This is the first systematic report of the performance of a bellowspowered negative-pressure wound therapy device designed specifically for use in resource-constrained settings. The authors found that elimination of air leaks in the simplified negative-pressure wound therapy dressing is essential, and that their system is safe and feasible for use in these environments. Subsequent trials will study the system’s efficacy. (Plast. Reconstr. Surg. 135: 00, 2015.) CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.
here is a large, unmet need for acute and chronic wound care worldwide. Although the prevalence of all wound types is unknown, the
From the Department of General Surgery, Center for Surgery and Public Health, Brigham and Women’s Hospital; Worldwide Innovative Healthcare, Inc.; the Department of Surgery, University of British Columbia; National University of Rwanda; the Department of Nursing, Rwinkwavu Hospital; Drew Cares International; and the Department of Surgery, National University of Rwanda, Kigali University Teaching Hospital. Received for publication March 23, 2014; accepted September 30, 2014. This trial is registered under the name “Simplified Negative Pressure Wound Therapy,” Clinical Trials.gov identification number NCT01339429 (https://clinicaltrials.gov/ ct2/show/NCT01339429). Copyright © 2014 by the American Society of Plastic Surgeons DOI: 10.1097/PRS.0000000000001101
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global burden of wounds appears to be increasing over time.1 Anecdotally, advanced wound therapies such as negative-pressure wound therapy are sought globally; however, application is limited primarily by cost, availability, and lack of electrical supply. To provide an alternative to existing electrically powered negative-pressure Disclosure: One year after completion of enrollment of study patients, Dr. Zurovcik founded Worldwide Innovative Healthcare, Inc., a for-profit company that develops innovative medical devices that are clinically effective and affordable worldwide. The company will manufacture and sell the simplified negative-pressure wound therapy system as of December, 2015. The other authors have no financial interest in any of the products or devices mentioned in this article.
www.PRSJournal.com
Volume 135, Number 4 • Negative-Pressure Wound Therapy Device wound therapy systems, a bellows-powered, simplified negative-pressure wound therapy system was designed.2 Negative-pressure wound therapy benefits open wound healing by providing macrodeformation and microdeformation of the wound bed, leading to angiogenesis and cell proliferation, removing wound exudate, providing a moist wound environment, and reducing wound surface area.3–6 Improved wound healing rates with both commercial negative-pressure wound therapy systems such as the vacuum-assisted closure system (V.A.C.; Kinetic Concepts, Inc., San Antonio, Texas) and ad hoc negative-pressure wound therapy systems have been demonstrated in both the developed world and the developing world.7–10 Cost-effectiveness of the vacuum-assisted closure system compared with conventional gauze-based dressings also has been demonstrated.11 Historically, negative-pressure wound therapy systems relied on an electrical power supply. More recently, mechanically powered negative-pressure wound therapy devices have been described. The smart negative-pressure system (SNaP; Spiracur, Inc., Sunnyvale, Calif.) relies on a spring-powered suction source and has been shown to be noninferior in its wound healing rates compared to the vacuum-assisted closure system when placed on wounds where an airtight seal was achieved.12–15 However, despite its elimination of electrical requirements, the smart negative-pressure system cost, lack of availability, and limited applicability to all wound types are barriers to its sustainable and widespread use in the developing world. Other mechanically powered ad hoc systems using hospital supplies such as surgical drains have been described; however, these “off-the-shelf” devices cannot continuously maintain negative pressure to a wound on contoured body surfaces because of limitations in the adhesion and compliance of their adhesive drapes that allow air to leak into the system, overwhelming the capacity of the suction supply.16 To overcome barriers to negative-pressure wound therapy use in resource-constrained settings, a novel simplified negative-pressure wound therapy device was developed.17 The device consists of a plastic bellows, which serves as both the negative pressure source and the wound exudate receptacle by means of a drainage tube that is sealed into an occlusive dressing (Fig. 1). The design eliminates air leaks into the system by use of a flexible, semicured polymer to seal edges of the dressing to intact skin (Fig. 2).2,18
This study was a prospective single-arm investigation of the biomechanical parameters and adverse events associated with the simplified negative-pressure wound therapy system in a resource-constrained setting. We hypothesized that simplified negative-pressure wound therapy would be safe and that negative pressure would be maintained for at least 24 hours.
PATIENTS AND METHODS Enrollment Procedures The study took place at two hospitals in Rwanda. Rwinkwavu Hospital is a 110-bed district hospital in rural eastern Rwanda. The 15-bed surgical ward cares for at least 50 patients with chronic wounds per year. The ward was screened for wounds suitable for simplified negative-pressure wound therapy on a weekly basis over a 9-month period. The Kigali University Teaching Hospital is a 513-bed referral hospital in the capital city of Rwanda. The surgery, medicine, and obstetric wards (total, 226 beds) were screened for wounds suitable for simplified negative-pressure wound therapy over a period of 11 weeks. Photographs of wounds ranging in size from 2 to 150 cm2 and the patients’ clinical histories were reviewed for study enrollment eligibility criteria. Inclusion criteria included age 14 years or older, adequate adjacent intact skin and wound location for application of the simplified negative-pressure wound therapy dressing, an effective pain management plan, anticipated clinical stability, and plans to remain hospitalized for the duration of the study. Exclusion criteria were exposed blood vessels, evidence of ischemia, necrotic tissue requiring further débridement, infection, osteomyelitis, and malignancy in the wound. Eligible patients were given 24 hours to review and sign the institutional review board– approved consent form, which had been translated into Kinyarwanda. For patients younger than 21 years, consent was obtained when the patient’s guardian signed the consent form and the patient signed an assent form before enrollment. Wounds were measured for depth and surface area (using a manual tracing onto clean paper) before application of simplified negative-pressure wound therapy. Approval for this study was obtained from the Rwandan National Ethics Committee, the Kigali University Teaching Hospital Institutional Review Board (Kigali, Rwanda), and the Partners Human Research Committee (Boston, Mass.).
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Plastic and Reconstructive Surgery • April 2015
Fig. 1. (Above) Schematic of the simplified negative-pressure wound therapy device dressing and bellows pump. 1, Wound cavity is packed with gauze. 2, Occlusive drape is sealed to surrounding skin. 3, The bellows pump is compressed and barbed drainage tubing is inserted into the pump. (Below) Compression of the bellows pump by hand generates negative pressure.
Dressing and Monitoring Procedures Two dressing types were used sequentially over the course of the study: the initial prototype dressing (without a preattached drainage tube) and the final prototype dressing (with a preattached drainage tube). For both dressing types, the wound was cleansed by the hospital nursing staff with normal saline, and the periwound skin was cleaned with 91% isopropyl alcohol and allowed to dry. Sterile cotton gauze was used to pack the wound. The simplified negative-pressure wound therapy dressing was applied by laying an occlusive adhesive drape over the gauze packing, taking care to avoid wrinkling at the edges. For the initial prototype dressing, a small hole was cut in the drape and the drainage tube was sealed into the hole with additional adhesive drape. The drape of both dressing types was then sealed to
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the surrounding periwound skin using three coats of thinly applied liquid latex. Once the dressing was dry, the barbed end of the drainage tube was inserted into a rubber stopper. The bellows was compressed, and the rubber stopper was inserted snugly into the mouth of the bellows. The bellows drain used in this study delivered 75 mmHg of negative pressure when fully compressed. The bellows was released, and the dressing was monitored for 10 minutes to ensure that it was airtight (if not, the bellows would expand rapidly, signaling air leaking into the system). The dressing was then protected with a light dusting of talc-based, nonmedicated powder and a cloth bandage overwrap. Nursing staff were instructed to compress the pump every 8 to 12 hours as needed to maintain negative pressure.
Volume 135, Number 4 • Negative-Pressure Wound Therapy Device staff to evaluate ease of application and potential areas for design improvements.
Fig. 2. The simplified negative-pressure wound therapy dressing uses an occlusive drape treated with adhesive that is sealed over the gauze packing materials to the periwound skin with a semicured polymer. The drainage tubing is already attached to the drape using a flexible tubing connector, eliminating air leaks at this interface.
An initial pilot of five patients was conducted, during which the simplified negative-pressure wound therapy dressing was applied for a period of 24 hours and removed for inspection of the periwound skin and wound. These dressing applications are not included in the analysis. The enrolled study patients underwent monitoring twice daily to assess the following: (1) amount of negative pressure being delivered, (2) fluid collection beneath the dressing or other disruption of the dressing, (3) quality of wound effluent, (4) erythema of periwound skin, and (5) the patient’s clinical status. If negative-pressure delivery dropped below 75 percent of the starting pressure as indicated by bellows length, fluid accumulated outside of the dressing, or the dressing ceased to adhere to the skin, the dressing was considered to have failed and was removed. If the patient’s clinical status changed, including the development of fever, periwound erythema, or increasing pain, the dressing was also removed. If the dressing remained intact and the patient’s clinical course was stable, the dressing was removed 72 hours after application. When the simplified negative-pressure wound therapy dressing was removed, the wound and periwound skin were inspected for qualitative appearance. The dressing was reapplied after discussion with the patient’s treating clinician. The wound was measured and photographed approximately every week to document wound health. Simplified negative-pressure wound therapy dressing applications at Kigali University Teaching Hospital were observed by a member of study
Statistical Analysis Wounds were classified into three categories based on the contour of the skin surface and accessibility for dressing: easy (flat surface), medium (curved or difficult-to-reach surface), or hard (spanning a joint and/or subject to patient shear, mass movement, or body fluids). The wounds were categorized first by means of independent assessment and then by agreement of two study personnel. Average time to pump failure was recorded and compared by dressing type (initial versus final) and wound difficulty using the Wilcoxon rank sum test and the KruskalWallis test. Cause of dressing failure was reviewed to define targeted areas of dressing and device improvement.
RESULTS Forty-seven patients gave consent for enrollment into the study. Ten were excluded for not meeting inclusion criteria (n = 6), withdrawing voluntarily (n = 1), and other reasons including change in clinical or wound status in the interval between enrollment and the planned treatment (n = 3). Five patients had more than one wound that was treated. Wound location and cause of the 42 treated wounds are listed in Tables 1 and 2. Eighty-five simplified negative-pressure wound therapy dressings were applied in total over the study period. Five dressing applications were excluded from analysis, as the simplified negative-pressure wound therapy was discontinued because of a change in the condition of the patient, unrelated to wound therapy. Nine dressings were excluded from analysis because of concern for occlusion of the dressing drainage tube related to the construction of that particular Table 1. Location of Wounds Treated with Simplified Negative-Pressure Wound Therapy Location
No.
Abdomen Ankle Breast Extremity Foot Labia Sacrum Thigh Trochanter Total
2 1 2 15 5 1 11 2 3 42
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Plastic and Reconstructive Surgery • April 2015 Table 2. Cause of Wounds Treated with Simplified Negative-Pressure Wound Therapy Cause
No.
Decubitus Infection Trauma Total
15 18 9 42
batch of dressings. The study flow diagram is presented in Figure 3. For the remaining 71 analyzed dressings, the average time to dressing failure was 22.2 ± 27.0 hours (range, 0 to 72 hours). In subset analysis, the final dressing delivered negative-pressure wound therapy longer (31.7 hours; n = 37) than the initial dressing type (11.8 hours, n = 34) (p = 0.003) (Fig. 4). The final dressings were analyzed further
by wound location (easy, medium, and hard as listed in Table 3) and were found to deliver negative-pressure wound therapy for longer durations on easy-to-dress wounds (52.7 hours; n = 11) compared with medium- (n = 22) and hard-to-dress (n = 4) wound locations (p = 0.029) (Fig. 5). No serious adverse events were encountered, including no allergic reactions to the latex skin sealant, increases in wound size, or evidence of bleeding or infection. One patient, who was immunocompromised, developed a fever and so device use was terminated (although there was no evidence of wound infection).
DISCUSSION This study demonstrates the safety and feasibility of our simplified negative-pressure wound
Fig. 3. Study flow diagram. Patients with small to medium wounds were enrolled over a 12-month period at two hospitals in Rwanda. sNPWT, simplified negative-pressure wound therapy.
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Fig. 4. The final dressing type delivered a longer duration of simplified negative-pressure wound therapy (p = 0.003) compared with the early dressing type. NPWT, negative-pressure wound therapy.
therapy system for use in resource-constrained settings. The system maintained negative pressure continuously for more than 2 days on wounds located on minimally contoured surfaces and for 1 day on more difficult-to-dress wounds. Since this phase of the study, we have conducted further bench work to refine the dressing materials and application method to target maintenance of negative pressure continuously for 3 days on all wound locations, which is the standard therapy duration provided by commercially available negative-pressure wound therapy systems. The current version of the simplified negative-pressure wound therapy system is undergoing contract manufacturing for commercialization and regulatory approval by means of the U.S. Food and Drug Administration’s 510(k) process. Several important features of the device were qualitatively evaluated by study staff (including local nurses, medical doctors, surgeons, and students) and patients. Both staff and patients voiced enthusiasm about negative-pressure wound therapy in general and the simplified negativepressure wound therapy system specifically, stating that fewer dressing changes were required compared with conventional dressing methods. Table 3. Number of Dressings in Each Wound Difficulty and Dressing Type Category
Wound Dressing Difficulty Easy Final Initial Total
(Extremity, Abdomen)
(Posterior Extremity, Trochanter)
11 10 21
22 16 38
Gita N. Mody, M.D., M.P.H. Department of General Surgery Center for Surgery and Public Health Brigham and Women’s Hospital 75 Francis Street Boston, Mass. 02115 [email protected]
acknowledgments
(Typical Location)
Medium
Financial barriers to simplified negative-pressure wound therapy are anticipated to be low, as the device components are simple and low cost, which was ascertained by our field-based design process. The simplified negative-pressure wound therapy dressing must be prefabricated because of the requirement of a preattached drainage tube, but the remainder of the system can be assembled and even sterilized on site, keeping packaging costs constrained. Clinical and cost-efficacy studies are required to demonstrate benefits in wound healing by the simplified negative-pressure wound therapy system and to formally evaluate patient and provider satisfaction and are being planned. Ultimately, implementing simplified negative-pressure wound therapy in the developing world has the potential to decentralize chronic wound care from secondary and tertiary hospitals, thereby lessening the burden of wounds on health care systems in the developing world.
Hard
(Sacrum, Foot)
Total
4 8 12
37 34 71
The authors would like to acknowledge the Fogarty International Clinical Research Fellowship, the National Institutes for Health and International Clinical Research Fellows Program at Vanderbilt University (R24 TW007988), the Hugh Hampton Young Memorial Fund Fellowship, and the Massachusetts Institute of Technology Legatum Center for financial support of the
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Fig. 5. The final dressing applications were further analyzed by wound type. There was a significant difference in simplified negative-pressure wound therapy delivery duration by wound type, with easy wounds receiving significantly longer therapy (p = 0.029). NPWT, negative-pressure wound therapy.
project. They would like to thank the Ministry of Health of Rwanda for promoting a culture of innovation and equity in patient care. Lastly, they would like to acknowledge the staff at Rwinkwavu Hospital, Inshuti Mu Buzima/Partners In Health, and Kigali University Teaching Hospital for their collaboration and support and their commitment to improving patient care on a daily basis.
references 1. Murray CJ, Vos T, Lozano R, et al. Disability-adjusted life years (DALYs) for 291 diseases and injuries in 21 regions, 1990–2010: A systematic analysis for the Global Burden of Disease Study 2010. Lancet 2012;380:2197–2223. 2. Zurovcik D, Slocum A, Mody G, Riviello R, Sheridan R. Development of simplified negative pressure wound therapy device for low-resource settings. Paper presented at: IEEE Global Humanitarian Technology Conference (GHTC) Proceedings. October 30–November 1, 2011; Seattle, Wash. 3. Kostiuchenok BM, Kolker II, Karlov VA, Ignatenko SN, Muzykant LI. Vacuum treatment in the surgical management of suppurative wounds (in Russian). Vestn Khir Im I I Grek. 1986;137:18–21. 4. Orgill DP, Bayer LR. Negative pressure wound therapy: Past, present and future. Int Wound J. 2013;10(Suppl 1):15–19. 5. Mouës CM, Heule F, Hovius SE. A review of topical negative pressure therapy in wound healing: Sufficient evidence? Am J Surg. 2011;201:544–556. 6. Braakenburg A, Obdeijn MC, Feitz R, van Rooij IA, van Griethuysen AJ, Klinkenbijl JH. The clinical efficacy and cost effectiveness of the vacuum-assisted closure technique in the management of acute and chronic wounds: A randomized controlled trial. Plast Reconstr Surg. 2006;118:390–397; discussion 398. 7. Armstrong DG, Lavery LA; Diabetic Foot Study Consortium. Negative pressure wound therapy after partial diabetic foot
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amputation: A multicentre, randomised controlled trial. Lancet 2005;366:1704–1710. 8. Eginton MT, Brown KR, Seabrook GR, Towne JB, Cambria RA. A prospective randomized evaluation of negative-pressure wound dressings for diabetic foot wounds. Ann Vasc Surg. 2003;17:645–649. 9. Perez D, Bramkamp M, Exe C, von Ruden C, Ziegler A. Modern wound care for the poor: A randomized clinical trial comparing the vacuum system with conventional salinesoaked gauze dressings. Am J Surg. 2010;199:14–20. 10. Mody GN, Nirmal IA, Duraisamy S, Perakath B. A blinded, prospective, randomized controlled trial of topical negative pressure wound closure in India. Ostomy Wound Manage. 2008;54:36–46. 11. Flack S, Apelqvist J, Keith M, Trueman P, Williams D. An economic evaluation of VAC therapy compared with wound dressings in the treatment of diabetic foot ulcers. J Wound Care 2008;17:71–78. 12. Armstrong DG. Discussion: Update on negative-pressure wound therapy. Plast Reconstr Surg. 2011;127(Suppl 1):116S. 13. Fong KD, Hu D, Eichstadt S, et al. The SNaP system: Biomechanical and animal model testing of a novel ultraportable negative-pressure wound therapy system. Plast Reconstr Surg. 2010;125:1362–1371. 14. Landsman A. Analysis of the SNaP Wound Care System, a negative pressure wound device for treatment of diabetic lower extremity wounds. J Diabetes Sci Technol. 2010;4:831–832. 15. Lerman B, Oldenbrook L, Ryu J, Fong KD, Schubart PJ. The SNaP Wound Care System: A case series using a novel ultraportable negative pressure wound therapy device for the treatment of diabetic lower extremity wounds. J Diabetes Sci Technol. 2010;4:825–830. 16. Webster R, Ely PB, Milani A, et al. Alternative materials in vacuum-assisted closure. Plast Reconstr Surg. 2011;128:784e– 785e; author reply 785e–786e. 17. Zurovcik D. Development of a Simplified Negative Pressure Wound Device. Boston: Massachusetts Institute of Technology; 2007. 18. Orgill DP, Bayer LR. Update on negative-pressure wound therapy. Plast Reconstr Surg. 2011;127(Suppl 1):105S–115S.
