Pressure ulcers: evidence and uncertainty

Most dangerous 6 words in English language: “We’ve always done it this way”

David Barton (@Bartontd), Associate Professor of Nursing at Swansea University, threw this into the debate on Tuesday evening, joining me, WeNurses founder Teresa Chinn (@WeNurses @AgencyNurse) and many others for a #WeNurses tweet chat on pressure ulcer risk assessment. We were asking, is it time for a new way, time to ditch the Waterlows and Bradens, given the lack of evidence of benefit of such tools?

Why change practice?

A Cochrane review was updated early this year and showed that there is no reliable evidence that using these tools reduces the incidence of pressure ulcers. I blogged about it here and nurses on Twitter started questioning their continued use, engaging in lively discussion in this #WeNurses tweetchat, back in March, with some considering trying to make changes, perhaps experimenting with assessing risk using clinical judgement alone. We agreed to revisit this topic later in the year, to see whether anything had changed. In April, NICE appeared to make this easier in a new clinical guideline on pressure ulcers. The Cochrane review was one of seven informing the new guidance, on all aspects of pressure area prevention and management. In it, NICE states that the use of a validated scale should be considered to support clinical judgement but that risk may be assessed ‘with or without a validated risk assessment tool’.

Can we risk dropping the risk assessment tool?

questioning nurse
There remains much uncertainty about the effectiveness of interventions to prevent and treat pressure ulcers

Yet there were lots of concerns raised in our second tweet chat and a reluctance to give up something which is seen to add weight to applications for equipment, to offer reassurance (to staff), to help with audit and to demonstrate that nurses are assessing risk. Of course, it also remains a requirement in many places. So here we have the complexities of evidence meeting practice.

Teresa Chinn reflected on the point she and her colleagues arrived at, after discussing  the evidence. She said it was important to have looked at their practice in the context of the evidence; that it helped bring into focus the reasons why they use Waterlow and gave them more confidence in their clinical judgement. Would she ditch the tool? Not until she has more information.

This is a reminder that, more often than not, the best available evidence has limitations which make for continued uncertainty about the benefits and harms of an intervention. But it’s important to know what is and isn’t known and for ‘best practice’ to take this into account. With this in mind, here’s a round-up of Cochrane evidence on some cornerstones of pressure ulcer prevention and management:  support surfaces, repositioning and nutrition.

Support surfaces


A Cochrane review found that:

  • high-specification foam mattresses reduce the incidence of pressure ulcers in people at risk
  • the relative merits of alternating pressure and constant low pressure devices are unclear
  • alternating pressure mattresses may be more cost-effective than alternating pressure overlays in a UK context (high quality evidence)
  • pressure-relieving overlays on the operating table reduce pressure ulcer incidence, though foam overlays were found to cause adverse skin changes
  • medical grade sheepskins reduce the incidence of pressure ulcers
There’s evidence that a high-specification mattress is better than a ‘standard’ one

Things to consider:

Some of the trials were at high risk of bias, which reduces our confidence in the findings. Also, the ‘standard’ mattress was often not clearly defined and varies between settings and over time. This makes it difficult to interpret the trial results. Given this variation, UK-based trials were analysed together and when this was done the advantage of the high-specification foam was maintained. The NICE guideline advocates the use of high-specification foam mattresses as a preventive measure.


A Cochrane review found that there is no conclusive evidence about the superiority of any support surface for treating pressure ulcers. There were many problems with both design and reporting of the trials and the reviewers highlight the need for rigorous studies to improve the evidence base before any clear conclusions can be drawn.


Repositioning is a key element of pressure ulcer prevention and treatment. It’s widely recommended in practice and has a sound theoretical base. So what can the evidence tell us about it?


A new Cochrane review on repositioning to prevent pressure injury was published in the same month as the new NICE guidance. The review highlighted a need for more robust evaluations, as the current evidence base is weak.* Specifically there is:

  • no good evidence of an effect of repositioning frequency
  • no good evidence of a reduction in pressure ulcers with the 30º tilt compared with the 90º tilt
  • no good evidence whether repositioning 3 hourly using the 30º tilt is less costly in terms of nursing time compared with 6 hourly using the 90º tilt

The NICE guideline recommends encouraging adults to ‘change their position frequently and at least every 6 hours’, increasing to every 4 hours for those assessed as being at high risk of developing a pressure ulcer. No specific angle is advocated.


A Cochrane review on the effect of repositioning on healing rates of pressure ulcers found…nothing. Despite looking for both randomized and non-randomized controlled trials, the reviewers found none that met the inclusion criteria. They note that international best practice advocates the use of repositioning as a key element of managing pressure ulcers yet we have no evidence to show whether this is effective.

So the use of repositioning in both preventing and treating pressure ulcers remains based on theory and experience rather than evidence. It’s important not to confuse a lack of evidence of effectiveness with evidence of no effectiveness. What we have here is not a clear demonstration that this doesn’t work but  uncertainty about whether it does and the effects of different angles and frequencies.

 Nutritional interventions

A Cochrane review on the effects of enteral or parenteral nutrition on the prevention and treatment of pressure ulcers, which measured the incidence of new ulcers, ulcer healing or changes in pressure ulcer severity, was updated this year. More trials were added but the evidence base is poor, with many trials being small and at high risk of bias. The studies were conducted in hospitals and nursing homes, comparing a variety of nutritional supplements with a ‘standard’ hospital diet, so its applicability to community settings, where nutritional supplements may more often be used, is questionable. There was such a lot of variation between studies that no meta-analysis could be undertaken.

The authors concluded: “There is currently no clear evidence of a benefit associated with nutritional interventions for either the prevention or treatment of pressure ulcers.”

The NICE guideline states that in adults whose nutritional status is adequate, nutritional supplements should not be offered specifically to prevent or treat a pressure ulcer. It recommends offering supplements to those who are found to have a nutritional deficiency, after assessment by a dietician or other competent professional.

 Where does this leave us?

vintage nurse talking on the phone
“Shall we talk about this on Twitter?”

There’s plenty more Cochrane evidence on other aspects of pressure ulcer management, which I’d like to return to in future blogs, but these basics of pressure ulcer prevention and management seem like a good place to start. We’re largely in a state of continued uncertainty in these areas, though with some evidence to guide the choice of mattresses.

So now it’s over to you. What do those of you in clinical practice think about all this? There were many thoughts flying around the Twittersphere during our tweetchat and if you missed it you can catch up with that here. You can also find my previous blog, on the risk assessment review, here and in that you’ll see some of the initial thoughts nurses shared with me on Twitter. Pressure ulcers are immensely costly, to the patient first and foremost, but also in terms of our health budgets and time to care. The vast majority are avoidable. We’ve got to #stopthepressure and get this right.

Do share your thoughts, here or on Twitter, where I tweet as @ukcochranecentr and @SarahChapman30.

Find out more

You might also like to visit NHS England’s Stop The Pressure campaign and the RCN’s This Is Nursing site, where special blogs are being published throughout the month in support of the campaign, including this particularly helpful blog in which the RCN and NICE team up to tell us about the new guidance and how it can be applied to practice. This evening Caroline Lecko (@celecko) Patient Safety Lead Nursing Directorate NHS England guest hosts another #WeNurses tweetchat, on pressure ulcer prevention. If you miss it, you’ll find the chat archived on that page.

*The addition of five studies to the Cochrane Review on repositioning for pressure injury prevention, in June 2020, has not changed the conclusions.


Moore ZEH, Patton D. Risk assessment tools for the prevention of pressure ulcers. Cochrane Database of Systematic Reviews 2014, Issue 2. Art. No.: CD006471. DOI: 10.1002/14651858.CD006471.pub4.

National Clinical Guideline Centre, National Institute for Health and Care Excellence (commissioner). Pressure ulcer management: the prevention and management of pressure ulcers in primary and secondary care. London: National Institute for Health and Care Excellence; 2014 (NICE CG179). [Issued April 2014]. Available from URL:

McInnes E, Jammali-Blasi A, Bell-Syer SEM, Dumville JC, Middleton V, Cullum N. Support surfaces for pressure ulcer prevention. Cochrane Database of Systematic Reviews 2015, Issue 9. Art. No.: CD001735. DOI: 10.1002/14651858.CD001735.pub5.

Gillespie  BM, Walker  RM, Latimer  SL, Thalib  L, Whitty  JA, McInnes  E, Chaboyer  WP. Repositioning for pressure injury prevention in adults. Cochrane Database of Systematic Reviews 2020, Issue 6. Art. No.: CD009958. DOI: 10.1002/14651858.CD009958.pub3.

Moore ZEH, Cowman S. Repositioning for treating pressure ulcers. Cochrane Database of Systematic Reviews 2015, Issue 1. Art. No.: CD006898. DOI: 10.1002/14651858.CD006898.pub4.

Langer G, Fink A. Nutritional interventions for preventing and treating pressure ulcers. Cochrane Database of Systematic Reviews 2014, Issue 6. Art. No.: CD003216. DOI: 10.1002/14651858.CD003216.pub2.


Page last updated 04 June 2020


Pressure ulcers: evidence and uncertainty by Sarah Chapman

is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International

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