Oxygen levels during negative pressure wound therapy

Palliative care with negative pressure wound therapy application in malignant wounds: a systematic review

OBJECTIVE

To synthesise and appraise the evidence for and benefits of palliative application of negative pressure wound therapy (NPWT) in malignant wounds.

METHOD

We performed a systematic review according to Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA). MEDLINE, Embase, Cochrane Library and trial registers (www.clinicaltrials.gov) from inception to 1 June 2021 were searched. Quality was assessed using the tool of methodological quality and synthesis from the 2018 BMJ Evidence-Based Medicine article on case series and case report synthesis.

RESULTS

Of 765 articles screened, 14 eligible studies were included in the review. All were case reports and included a total of 22 patients. The mean age of the patients was 60.7 (range: 33-77) years. The location of the hard-to-heal wounds was widely distributed: five wounds on the scalp; three wounds over the anogenital area; and the remaining wounds on the trunk and extremities. The reported outcomes included: improvement of wound healing; decreased exudation and malodour of the wound; decreased pain sensation; eligibility for further treatment; and a shift to the homecare system.

CONCLUSION

The findings of this study suggested NPWT could be a choice in palliative care for patients with malignant wounds. However, more studies are needed to evaluate the efficacy of NPWT in these wounds.

Adjunctive hyperbaric oxygen therapy and negative pressure wound therapy for hard-to-heal wounds: a systematic review and meta-analysis

OBJECTIVE

Negative pressure wound therapy (NPWT) and hyperbaric oxygen therapy (HBOT) have been widely used in the treatment of hard-to-heal (chronic) wounds, but there is still a lack of sufficient evidence for their combined use for the treatment of hard-to-heal wounds. This systematic review aimed to identify the clinical efficacy and safety of adding adjunctive HBOT to NPWT for hard-to-heal wounds.

METHOD

Embase, PubMed, Cochrane Library, Web of Science, China National Knowledge Infrastructure and Wanfang were searched from the establishment of the database to March 2022. The literature was screened according to the inclusion criteria and exclusion criteria. We assessed the quality of each included study with the Cochrane Collaboration Risk of Bias tool and Newcastle-Ottawa Scale. A meta-analysis was performed using R programming software version 4.1.0 (R Project for Statistical Computing, US). The PRISMA 2020 guidelines were used to report data from systematic reviews and meta-analysis.

RESULTS

A total of 15 studies were identified, including nine randomised clinical controlled trials and six retrospective studies. Meta-analysis results showed that NPWT combined with HBOT had better outcomes compared with the NPWT alone with regards to: wound healing rate (odds ratio (OR)=6.77; 95% confidence interval (Cl): 3.53-12.98; p<0.0001); bacterial positive rate of wound (OR=0.16; 95% CI: 0.05-0.55; p=0.0037); wound healing time (mean difference (MD)= -3.86; 95% Cl: -5.18 - -2.53; p<0.0001); wound area (standardised mean difference (SMD)=1.50; 95% Cl: 0.35-2.65; p=0.0104); hospitalisation time (MD= -3.14; 95% Cl: -4.93 - -1.36; p=0.005); and hospitalisation cost (OR= -202.64; 95% Cl: -404.53 - -0.75; p=0.0492). There was no significant difference in pain score (MD= -0.43; 95% Cl: -1.15-0.30; p=0.25).

CONCLUSION

The findings of this study demonstrated that adjunctive HBOT with NPWT is safe and effective in the treatment of hard-to-heal wounds. However, these findings should be interpreted with great caution given the limitations of the studies included.

Negative Pressure Wound Therapy-A Vacuum-Mediated Positive Pressure Wound Therapy and a Closer Look at the Role of the Laser Doppler

Background: Negative pressure wound therapy (NPWT) is an intensely investigated topic, but its mechanism of action accounts for one of the least understood ones in the area of wound healing. Apart from a misleading nomenclature, by far the most used diagnostic tool to investigate NPWT, the laser Doppler, also has its weaknesses regarding the detection of changes in blood flow and velocity. The aim of the present study is to explain laser Doppler readings within the context of NPWT influence. Methods: The cutaneous microcirculation beneath an NPWT system of 10 healthy volunteers was assessed using two different laser Dopplers (O2C/Rad-97®). This was combined with an in vitro experiment simulating the compressing and displacing forces of NPWT on the arterial and venous system. Results: Using the O2C, a baseline value of 194 and 70 arbitrary units was measured for the flow and relative hemoglobin, respectively. There was an increase in flow to 230 arbitrary units (p = 0.09) when the NPWT device was switched on. No change was seen in the relative hemoglobin (p = 0.77). With the Rad-97®, a baseline of 92.91% and 0.17% was measured for the saturation and perfusion index, respectively. No significant change in saturation was noted during the NPWT treatment phase, but the perfusion index increased to 0.32% (p = 0.04). Applying NPWT compared to the arteriovenous-vessel model resulted in a 28 mm and 10 mm increase in the venous and arterial water column, respectively. Conclusions: We suspect the vacuum-mediated positive pressure of the NPWT results in a differential displacement of the venous and arterial blood column, with stronger displacement of the venous side. This ratio may explain the increased perfusion index of the laser Doppler. Our in vitro setup supports this finding as compressive forces on the bottom of two water columns within a manometer with different resistances results in unequal displacement.

Does Negative Pressure Wound Therapy Impact the Outcome for Patients With Necrotizing Soft Tissue Infection Infected With Anaerobic Bacteria?

Background: A notable improvement in the treatment of necrotizing soft tissue infections (NSTIs) is the development of negative pressure wound therapy (NPWT). Clinicians are still debating whether NPWT is as successful as conventional wet-to-dry dressings at removing bacteria. Recent research has revealed potential oxygen deprivation effects of NPWT in underlying wound tissues, although clinical trials regarding the effects of reduced oxygen on anaerobic bacterial soft tissue infections remain noticeably lacking. Hypothesis: We hypothesized that NPWT-treated patients with NSTIs who were solely infected by anaerobic bacteria would have worse outcomes than those who were infected with other bacterial species. Patients and Methods: Our study included a retrospective examination of the 2008-2022 period of our Acute and Critical Care Surgery database. Patients who had been identified as having necrotizing fasciitis, Fournier gangrene, or gas gangrene and who had their conditions verified by positive wound cultures acquired during the initial debridement and subsequently received NPWT made up the study cohort. Comorbidities, surgical techniques, and clinical results were all covered by the data. Based on their wound infections, patients were divided into two groups: those with exclusively anaerobic NSTIs and those with different bacterial groups (such as polymicrobial and aerobic). Multiple regression, χ2 analysis, and analysis of variance (ANOVA) were among the analytical methods used. Results: One hundred twelve patients with NSTI who had received NPWT comprised the study cohort. Sixteen of these patients (14.3%) had NSTIs that were exclusively anaerobic, whereas the remaining 96 (85.7%) had NSTIs that were mixed aerobic, facultative, or polymicrobial. Between the two groups, there was no difference in the initial wound size. Patients with anaerobic NSTI who underwent NPWT showed a statistically significant increase in the number of debridements (3 [interquartile range {IQR},1-9] vs. 2 [IQR, 1-4]; p = 0.012) and an increased 100-day re-admission rate (37.5% vs. 12.5%; p = 0.012) when compared with patients with non-anaerobic NSTI. The 100-day re-admission rate increased three-fold in NPWT-treated anaerobic NSTIs, according to a logistic regression analysis (odds ratio [OR], 3.63; 95% confidence interval [CI], 1.06-12.44; p = 0.04). Conclusions: In contrast to patients with other bacterial strains, our data show that patients with NSTI treated with NPWT who only have anaerobic bacterial infections have a larger number of debridements and are much more likely to require re-admission within 100 days. We call for additional prospective studies to be conducted to identify additional risk factors and consider alternate treatment options for individuals with exclusively anaerobic NSTIs in light of these findings.

The influence of negative pressure wound therapy on bacterial and fungal growth

BACKGROUND

The use of negative pressure wound therapy (NPWT) in superinfected wounds is controversial. The mechanism of action is unclear, but recent studies have shown lower atmospheric oxygen levels within the dressing. Therefore, different oxygen-favoring bacteria and fungi might benefit or face impaired thriving conditions. The aim of this in vitro study is to investigate the influence of NPWT on bacterial and fungal growth.

METHODS

Salmonella enterica subsp. enterica serovar Typhimurium, Pseudomonas aeruginosa and Candida albicans strains were cultured on concentrated agars and attached to a standard NPWT-device. After 48 hours, colonies were separately harvested from the agar and foam. Optical density (OD) was obtained in order to estimate bacterial loads.

RESULTS

For all tested microorganisms, no overall significant differences were found compared to controls. Subanalysis showed lower OD levels from the agar beneath the foam in the NPWT-group.

CONCLUSION

NPWT removed bacteria and fungi from the wound surface but accumulation is found within the foam. The use of NPWT showed no influence on bacterial or fungal growth selection. With superinfected wounds, the use of NPWT should thoroughly be evaluated as toxins and virulence factors may not fully be evacuated.

Negative-Pressure Wound Therapy: What We Know and What We Need to Know

Negative-pressure wound therapy (NPWT) promotes wound healing by applying negative pressure to the wound surface. A quarter of a century after its introduction, NPWT has been used in various clinical conditions, although molecular biological evidence is insufficient due to delay in basic research. Here, we have summarized the history of NPWT, its mechanism of action, what is currently known about it, and what is expected to be known in the future. Particularly, attention has shifted from the four main mechanisms of NPWT to the accompanying secondary effects, such as effects on various cells, bacteria, and surgical wounds. This chapter will help the reader to understand the current status and shortcomings of NPWT-related research, which could aid in the development of basic research and, eventually, clinical use with stronger scientific evidence.

Novel cell culture system for monitoring cells during continuous and variable negative-pressure wound therapy

BACKGROUND

Although the clinical efficacy of negative-pressure wound therapy (NPWT) is well known, many of its molecular biological mechanisms remain unresolved, mainly due to the difficulty and paucity of relevant in vitro studies. We attempted to develop an in vitro cell culture system capable of real-time monitoring of cells during NPWT treatment.

MATERIALS AND METHODS

A novel negative-pressure cell culture system was developed by combining an inverted microscope, a stage-top incubator, a sealed metal chamber for cell culture, and an NPWT treatment device. Human keratinocytes, PSVK-1, were divided into ambient pressure (AP), continuous negative-pressure (NPc), and intermittent negative-pressure (NPi) groups and cultured for 24 h with scratch assay using our real-time monitoring system and device. Pressure inside the device, medium evaporation rate, and the residual wound area were compared across the groups.

RESULTS

Pressure in the device was maintained at almost the same value as set in all groups. Medium evaporation rate was significantly higher in the NPi group than in the other two groups; however, it had negligible effect on cell culture. Residual wound area after 9 h evaluated by the scratch assay was significantly smaller in the NPc and NPi groups than in the AP group.

CONCLUSION

We developed a negative-pressure cell culture device that enables negative-pressure cell culture under conditions similar to those used in clinical practice and is able to monitor cells under NPWT. Further experiments using this device would provide high-quality molecular biological evidence for NPWT.

The local physiological effects of a single-use topical negative pressure device in healthy volunteers: the PICO-1 study

OBJECTIVE

This study aimed to investigate the effects of a single-use negative pressure wound therapy (sNPWT) device on tissue perfusion, oxygenation and pressure in the intact skin of healthy volunteers.

METHOD

Healthy volunteers wore a PICO sNPWT device (Smith+Nephew, UK) on their right medial calf for one week. Perfusion, tissue oxygenation and tissue pressure were recorded in superficial and deep tissues over a period of seven days. At the baseline visit, measurements were recorded before and after dressing application without activation. Macrovascular flow and transduced needle pressure measures were recorded at 0 minutes, 30 minutes and 60 minutes after device activation. Superficial tissue perfusion and both oxygenation measures were recorded continuously over the hour following activation. All outcome measures were repeated at 24 hours and again after seven days, both with the dressing and following dressing removal.

RESULTS

The device was associated with a measurable increase in perfusion of the limb in 12 healthy volunteers. Superficial tissue oxygenation adjacent to the dressing was reduced during wear, while deeper tissue demonstrated an increase in oxygenation levels. Superficial skin perfusion was observed to differ between skin overlying muscle and that overlying bone. Pressure in tissue underneath the dressing pad was increased throughout dressing wear and returned to baseline levels on dressing removal.

CONCLUSION

sNPWT produced measurable changes in local physiology in healthy volunteers with intact skin, despite the absence of a wound. Effects may differ according to anatomical site and the composition of underlying tissues. Other factors that promote healing were not explored in this study.

DECLARATION OF INTEREST

This study was funded by Smith+Nephew investigator-initiated grant IIS 684. The funder had no input into study design, conduct, analysis, manuscript preparation or dissemination. The authors have no conflicts of interest to declare.

Topical negative pressure wound therapy enhances the local tissue perfusion - A pilot study

BACKGROUND

Topical negative pressure wound therapy (TNPWT) is a regularly used method in modern wound treatment with a growing and diverse potential for clinical use. So far positive effects on microcirculation have been observed and examined, although precise statements on the underlying mechanism appear unsatisfying.

OBJECTIVE

The aim of our study was to extend the understanding of the effect of TNPWT on tissue perfusion and determine the time frame and the extent to which the tissue perfusion changes due to TNPWT.

MATERIAL AND METHODS

TNPWT was applied to the anterior thighs of 40 healthy individuals for 30 min, respectively. Before and up to 90 min after the application, measurements of the amount of regional haemoglobin (rHb), capillary venous oxygen saturation (sO2), blood flow (flow) and velocity were conducted with spectrophotometry (combining white light spectrometry and laser Doppler spectroscopy) within two different depths/skin layers. A superficial measuring probe for depths up to 3 mm and a deep measuring probe for up to 7 mm were used.

RESULTS

All parameters show significant changes after the intervention compared to baseline measurements. The greater effect was seen superficially. The superficially measured rHb, sO2 and flow showed a significant increase and stayed above the baseline at the end of the protocol. Whereas deeply measured, the rHb initially showed a decrease. The flow and sO2 showed a significant increase up to 60 min after the intervention.

CONCLUSION

The application of TNPWT on healthy tissue shows an increase in capillary-venous oxygen saturation and haemoglobin concentration of at least 90 min after intervention. A possible use in clinical practice for preconditioning to enhance wound healing for high-risk patients to develop wound healing disorder, requires further studies to investigate the actual duration of the effect.

Minimizing treatment complexity of combat-related soft tissue injuries using a dedicated tension relief system and negative pressure therapy augmented by high-dose in situ antibiotic therapy and oxygen delivery: a retrospective study

BACKGROUND

Following combat-related, extensive soft tissue injury from gunshot wounds or blasts, prolonged duration from injury to full wound closure is associated with infection, increased morbidity and mortality, failure to mobilize, poor functional outcome and increased cost. The purpose of this study was to evaluate a novel treatment enabling early primary closure of combat wounds.

METHODS

This was a retrospective study of 10 soldiers and civilians with extensive combat-related soft tissue limb injuries (5 gunshot wounds, 5 blasts) treated using the TopClosure^® Tension Relief System (TRS) with simultaneous administration of regulated oxygen-enriched and irrigation negative pressure-assisted wound therapy (ROINPT) via the Vcare α^® device.

RESULTS

Nine patients were treated during the acute phase of injury and one was treated following removal of a flap due to deep infection 20 years after injury and flap reconstruction. Two patients had upper limb injury and the rest lower limb injury. With the aid of the TRS and/or ROINPT, immediate primary closure during reconstruction was achieved in 6 patients and delayed primary closure in three. Only one patient required a skin graft to close a small area of the wound after most of the wound had been closed by delayed primary closure. Wound closure was achieved within 0-37 days (median: 12.5 days, interquartile range: 2.75-19.75) from injury.

CONCLUSIONS

The TRS is a novel device for effective, early skin stretching and secure wound closure through the application of stress relaxation and mechanical creep, achieving primary closure of large defects using a simplified surgical technique and reducing the need for closure using skin grafts and flaps and the use of tissue expanders. Delivering supplemental oxygen to the wound by ROINPT reverses the reduced oxygen levels inherent in conventional negative pressure-assisted wound therapy, mitigating anaerobic contamination and reducing infection. Irrigation may accelerate the evacuation of infectious material from the wound and provide a novel method for antibiotic administration. The combination of TRS and ROINPT devices allow for early primary closure with improved functionality of combat-related limb injuries.

Analysis of Rinsing Fluid during Negative Pressure Wound Therapy with Instillation: A Potential Monitoring Tool in Acute and Chronic Wound Treatment. A Pilot Study

Background: During negative pressure wound therapy (NPWT), open wounds are draped with a nontransparent sponge, making daily wound evaluation impossible. Sometimes, late or undetected bacterial infections and postoperative bleeding result in repetitive surgery, thus prolonging inpatient time. With the introduction of additional fluid instillation (NPWTi), the wound surface is rinsed, and bacteria, proteins and biomarkers are flushed into a collecting canister, which is later discarded. Methods: The aim of this pilot study was to analyze rinsing fluid samples (0.9% sodium chloride) from the NPWTi device in patients with acute and chronic wounds. In 31 consecutive patients a standardized laboratory analysis was performed to evaluate cellular composition and potassium, phosphate, lactate dehydrooxygenase, pH and total protein levels. Results: While there was an increase in the total cellular amount and the number of polymorphonuclear cells, the number of red blood cells (RBC) decreased after surgery. Potassium and pH showed no significant changes in the first three postoperative days, whereas total protein showed an undulant and partially significant course. Conclusion: We were able to quantify cellular metabolites by analyzing the rinsing fluid of NPWTi. We propose the analysis of this material as a novel and potentially promising tool to monitor wound status without removal of the dressing. The establishment of reference values might help to improve the NPWTi therapy.

Improvised vacuum assisted closure dressing for enterocutenous fistula, a case report

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Enterocutaneous fistula is a postoperative complication is 75–80% of the cases that results in metabolic complications.

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Management of this complication is difficult, necessitating delayed surgery with associated high morbidity and significant mortality.

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Vacuum-assisted closure (VAC) dressing has been shown to decrease the healing time of chronic wounds and achieves a 64% spontaneous enterocutaneous fistula closure rate.

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We improvised VAC dressing using simple materials for proximal enterocutaneous fistula.

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Spontaneous closure was achieved on day 32.

Introduction

Management of enterocutaneous fistula is challenging with high morbidities and mortalities despite the recent advances in surgical technique. The bad outcomes are a result of associated metabolic complications. Vacuum-assisted closure dressing for the management of enterocutaneous fistula is a relatively new technique with benefit as a bridge to definitive surgery or definitive management in achieving spontaneous closure at a shorter time. In the current report, we share our experience of improvising vacuum-assisted closure dressing for managing postoperative enterocutaneous fistula and achieving spontaneous closure

Presentation of case

We describe a case of a 56-year-old male from Tanzanian with a postoperative discharge of intestinal contents from the wound. He was diagnosed to have a proximal enterocutaneous fistula. After sepsis control and achieving hemodynamic stability, the enterocutaneous fistula was managed with parenteral nutrition, proton pump inhibitors, anti-cathartics, and somatostatin analogs. Endoscopic therapies and fibrin sealants are other described nonoperative interventions for enterocutaneous fistula. The unavailability of these modalities limited us. Vacuum-assisted closure dressing was improvised using gauze pieces, feeding tube, and Op-site dressings at a pressure of −30 mmHg. We achieved spontaneous closure of the proximal enterocutaneous fistula in 32 days.

Discussion

The time to closure was within the range of 12–90 described for conventional vacuum assisted closure dressing, and there were no complications. Close monitoring of improvised VAC dressings is required as the risks are unknown; however, given the known complications of conventional VAC dressing, a risk of hemorrhage and creation of entero-atmospheric fistula exists.

Conclusion

Improvised VAC dressing for ECF is potentially an acceptable option with promising outcomes in low-resource settings.

Integration of microbubbles with biomaterials in tissue engineering for pharmaceutical purposes

Tissue engineering with the aid of biomaterials is a novel and promising knowledge aiming at improving human life expectancy. Besides, microbubbles are increasingly employed in biomedical applications due to their capability as a reservoir of therapeutic agents and oxygen molecules. In the present study, Microbubbles as the backbone of the research are produced as one of the potent devices in tissue engineering approaches, including drug delivery, wound healing, 3D printing, and scaffolding. It was shown that microbubbles are capable of promoting oxygen penetration and boosting the wound healing process by supplying adequate oxygen. Microbubbles also demonstrated their strength and potency in advancing drug delivery systems by reinforcing mass transfer phenomena. Furthermore, microbubbles developed the mechanical and biological characteristics of engineered scaffolds by manipulating the pores. Increasing cell survival, the biological activity of cells, angiogenesis, cell migration, and also nutrient diffusion into the inner layers of the scaffold were other achievements by microbubbles. In conclusion, the interest of biomedical communities in simultaneous usage of microbubbles and biomaterials under tissue engineering approaches experiences remarkable growth in Pharmaceutical studies.