“How did an ineffective and costly intervention become routine care in the NHS [UK National Health Service]?” Ian Chetter, MBChB, chair of surgery at Hull York Medical School, University of Hull in Hull, England, posed at the 39th European Society for Vascular Surgery (ESVS) annual meeting in Istanbul, Turkey (Sept. 23–26), following a presentation highlighting the SWHSI-2 trial results.
SWHSI-2—data from which were first shared at the 2024 Vascular Society of Great Britain and Ireland (VSGBI) Annual Scientific Meeting and recently published in The Lancet— suggested that negative pressure wound therapy (NPWT) should not be first-line treatment for open surgical wounds.
“Negative pressure doesn’t seem to have any benefit whatsoever.” This was Chetter’s key conclusion to be drawn from the “long-awaited” results of the SWHSI-2 trial in his initial presentation of the results at the VSGBI 2024 VSASM meeting. For Chetter, the data underscore the severity of the clinical issue at hand, highlight a pressing need for research aimed at accelerating wound healing, and raise questions around how this technology—commonly used in the NHS—was accepted into clinical practice without the robust evidence to back it.
Providing context to the trial at the UK meeting, co-investigator Catherine Arundel, MD, from York Trials Unit at the University of York in York, England, first noted the “common” nature of secondary wounds healing by secondary intention (SWHSI) and the “prolonged and complex” nature of their healing. Arundel also underlined the costly nature of treatment, “particularly considering that the use of complex, expensive treatments such as [NPWT] has been and continues to be increasing.”
Against this backdrop, SWHSI-2 was initiated by Chetter, Arundel and colleagues and funded by National Institute for Health and Care Research funding. This was a pragmatic, multicenter, two-arm, parallel-group randomized controlled trial designed to assess NPWT versus usual care in patients with open surgical wounds. The primary outcome was wound healing and time to wound healing. Across 28 UK sites, 686 patients were enrolled, with 349 allocated to the negative pressure intervention group and 337 to usual care.
Chetter then provided an overview of patient characteristics, noting that 75% of the trial cohort were men, the majority of whom were white and had diabetes. He added that 90% of patients were vascular patients. “Although we tried to recruit across the different surgical specialties,” said Chetter, “this ended up being a vascular surgical, diabetic foot wound trial.” Regarding wound characteristics, Chetter shared that the wounds included in the trial were large—26cm2 on average—with the majority on either the foot or the leg.
Sharing the results of SWHSI-2 for the first time at VSASM 2024, Chetter reported that 42% of patients had unhealed wounds at 12 months, a result which “shocked” him. “Importantly,” he continued,” there was no difference in the number of healed wounds between patients randomised to negative pressure or usual care.”
Chetter added that the median time to wound healing was 187 days (NPWT)/195 (standard dressings), or six months, and that there was no difference between negative pressure and usual care. “There’s no evidence that negative pressure accelerates healing in these patients,” the presenter told the VSASM audience, going on to state that the primary result was consistent throughout various subgroup analyses.
The researchers also looked at secondary outcomes, finding high rates of hospital readmission, reoperation, and wound infection, as well as a high number of patients receiving antibiotics for their surgical wound infections, with no statistically significant difference between the two groups. “Negative pressure doesn’t reduce wound infection, doesn’t reduce your risk of reoperation, and doesn’t reduce your risk of requiring antibiotics,” Chetter said.
Furthermore, on the topic of secondary outcomes, Chetter underlined that 10% of patients ended up with an amputation and 10% of patients died.
Quality of life was also measured. “With both treatments,” Chetter reported, “the scores improved—so wound healing improved, and pain improved with both treatments over time—but there’s no statistically significant difference between the two groups. So, negative pressure doesn’t improve wound pain and doesn’t improve your quality of life related to the wound.”
Finally, Arundel shared the results of a cost-effectiveness analysis. “Within the trial,” she summarized, “we can say that negative pressure was more costly, but not more effective than usual care.”
The researchers also considered the longer-term cost-effectiveness of negative pressure, employing a decision analytic model that allowed the team to use both evidence from the trial and external evidence. “There are very small gains in quality-adjusted life years over a longer-term model,” Arundel shared with VSASM. “There were lower healthcare costs for negative pressure compared to usual care, but higher intervention costs, and the incremental costs are therefore higher for negative pressure, but not significantly.”
“There was no gain in terms of quality of life, and no real gain in terms of cost either,” Arundel concluded at this point during the dedicated SWHSI-2 trial session.
‘A chronic, disabling problem’
Following the presentation of these first-time results, Chetter shared his key take-home messages.
“These wounds are a chronic, disabling problem,” the presenter stressed, citing again the proportion of wounds in the trial that did not heal being “much higher” than he expected and the length of time it took for those wounds that did heal being “much longer” than anticipated.
Chetter continued that the indications for negative pressure are “minimal”. It “doesn’t accelerate healing, doesn’t improve your quality of life, and doesn’t reduce those secondary outcome measures that we looked at,” he listed. In addition, the presenter reiterated that negative pressure does not reduce a patient’s chance of their wound getting an infection, does not reduce their chance of needing another operation or being readmitted to hospital, and does not reduce their chance of needing antibiotics. Chetter also referenced again the “scary” amputation and mortality rates of 10% among the patients included in the trial.
Here, Chetter queried how the SWHSI-2 findings might impact his clinical decision-making moving forward. “If I was faced with a patient […] and I could predict that that patient would be in the 40% that didn’t heal or be in the 10% that ended up with an amputation, anyway, would we together— me and the patient—make a different decision about how we manage that foot problem?” he asked.
Closing his presentation, Chetter restated the severity of the problem at the centre of the SWHSI-2 trial. “These wounds are horrendous,” he stressed. “They severely affect our patients.” As a result, Chetter’s forward-looking message was clear: “We need to continue research to try and find a way to accelerate wound healing. Patients are desperate to get these wounds to heal and the quicker we can help them heal these wounds, the better.”
Chetter also highlighted the fact that the data raise wider questions about evidence-based practice. “I think we need to contemplate how technology gets into the NHS,” he posited, citing that NPWT is “widely used” and “widely advocated for” in the UK.
“It was kind of putting the cart before the horse,” the presenter analogized, detailing that NPWT was accepted into UK practice without “robust” clinical and cost-effectiveness data being available.
Initial reactions
Before opening the floor to questions, session co-chair Matt Brown, MD, from King’s College London, London, commented on the significance of the SWHSI-2 results for vascular practice: “This is incredibly important, to debunk some of these things we do routinely because we think they work.”
Subsequently, one audience member asked for Chetter’s advice to encourage units who might rely on their positive experiences regarding negative pressure to change their practice based on the SWHSI-2 data.
“My answer is: the data’s there,” Chetter replied. “It’s a level-one, high-quality trial—the best evidence you can get. Why would you go against that?”
Manj Gohel, MD, from Cambridge University Hospitals NHS Foundation Trust in Cambridge, England, praised the “incredible achievement” of Chetter, Arundel and colleagues in completing the trial. “This is why we do randomized trials—to challenge those dogmas,” he remarked, adding that the results were “going to take a while to sink in.”
Gohel went on to ask whether there are any subgroups in which there is still a role for negative pressure. Chetter replied in the affirmative, with the caveat that there are far fewer than previously thought. One example he mentioned was as a wound management strategy. “Save the money,” was Chetter’s main piece of advice here. “Spend it on something more useful, like more nurses, more research nurses, to get that research delivery problem sorted out.”
Will SWHSI-2 change practice?
At ESVS 2025, where Chetter presented the SWHSI-2 findings during the Janet Powell session on late-breaking news in clinical trials, a question from Ian Loftus, MD, from St George’s University Hospitals NHS Foundation Trust in London, England, probed whether the results will translate into clinical practice. Loftus cited anecdotal evidence that he has not seen a reduction in the use of NPWT at his center in the months following Chetter and Arundel’s initial presentation of the findings in November 2024.
Chetter noted that the SWHSI-2 team has ongoing plans to disseminate the results of the trial widely, and subsequently to conduct a survey to assess their real-world impact. He also shared that the team plans to look at Hospital Episode Statistics (HES) data to see whether NPWT prescriptions are falling.
