Comparing alternating pressure mattresses and high-specification foam mattresses to prevent pressure ulcers in high-risk patients: the PRESSURE 2 RCT.

Background: Pressure ulcers (PUs) are a burden to patients, carers and health-care providers. Specialist mattresses minimise the intensity and duration of pressure on vulnerable skin sites in at-risk patients.

Primary Objective: Time to developing a new PU of category ≥ 2 in patients using an alternating pressure mattress (APM) compared with a high-specification foam mattress (HSFM).

Design: A multicentre, Phase III, open, prospective, planned as an adaptive double-triangular group sequential, parallel-group, randomised controlled trial with an a priori sample size of 2954 participants. Randomisation used minimisation (incorporating a random element).

Setting: The trial was set in 42 secondary and community inpatient facilities in the UK.

Participants: Adult inpatients with evidence of acute illness and at a high risk of PU development.

Interventions And Follow-up: APM or HSFM - the treatment phase lasted a maximum of 60 days; the final 30 days were post-treatment follow-up.

Main Outcome Measures: Time to event.

Results: From August 2013 to November 2016, 2029 participants were randomised to receive either APM ( = 1016) or HSFM ( = 1013). Primary end point - 30-day final follow-up: of the 2029 participants in the intention-to-treat population, 160 (7.9%) developed a new PU of category ≥ 2. There was insufficient evidence of a difference between groups for time to new PU of category ≥ 2 [Fine and Gray model HR 0.76, 95% confidence interval (CI) 0.56 to 1.04; exact -value of 0.0890 and 2% absolute difference]. Treatment phase sensitivity analysis: 132 (6.5%) participants developed a new PU of category ≥ 2 between randomisation and end of treatment phase. There was a statistically significant difference in the treatment phase time-to-event sensitivity analysis (Fine and Gray model HR 0.66, 95% CI 0.46 to 0.93;  = 0.0176 and 2.6% absolute difference). Secondary end points - 30-day final follow-up: new PUs of category ≥ 1 developed in 350 (17.2%) participants, with no evidence of a difference between mattress groups in time to PU development, (Fine and Gray model HR 0.83, 95% CI 0.67 to 1.02; -value = 0.0733 and absolute difference 3.1%). New PUs of category ≥ 3 developed in 32 (1.6%) participants with insufficient evidence of a difference between mattress groups in time to PU development (Fine and Gray model HR 0.81, 95% CI 0.40 to 1.62;  = 0.5530 and absolute difference 0.4%). Of the 145 pre-existing PUs of category 2, 89 (61.4%) healed - there was insufficient evidence of a difference in time to healing (Fine and Gray model HR 1.12, 95% CI 0.74 to 1.68;  = 0.6122 and absolute difference 2.9%). Health economics - the within-trial and long-term analysis showed APM to be cost-effective compared with HSFM; however, the difference in costs models are small and the quality-adjusted life-year gains are very small. There were no safety concerns. Blinded photography substudy - the reliability of central blinded review compared with clinical assessment for PUs of category ≥ 2 was 'very good' (kappa statistic 0.82, prevalence- and bias-adjusted kappa 0.82). Quality-of-life substudy - the Pressure Ulcer Quality of Life - Prevention (PU-QoL-P) instrument meets the established criteria for reliability, construct validity and responsiveness.

Limitations: A lower than anticipated event rate.

Conclusions: In acutely ill inpatients who are bedfast/chairfast and/or have a category 1 PU and/or localised skin pain, APMs confer a small treatment phase benefit that is diminished over time. Overall, the APM patient compliance, very low PU incidence rate observed and small differences between mattresses indicate the need for improved indicators for targeting of APMs and individualised decision-making. Decisions should take into account skin status, patient preferences (movement ability and rehabilitation needs) and the presence of factors that may be potentially modifiable through APM allocation, including being completely immobile, having nutritional deficits, lacking capacity and/or having altered skin/category 1 PU.

Future Work: Explore the relationship between mental capacity, levels of independent movement, repositioning and PU development. Explore 'what works for whom and in what circumstances'.

Trial Registration: Current Controlled Trials ISRCTN01151335.

Funding: This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in ; Vol. 23, No. 52. See the NIHR Journals Library website for further project information.