Pressure RElieving Support SUrfaces: a Randomised Evaluation 2 (PRESSURE 2)

Design: The trial is a multicentre, open, randomised, double triangular group sequential, parallel group trial, with two planned interim analyses. Consenting high risk patients will be randomised to receive either HSF or APM in conjunction with an electric profiling bed. The sequential design addresses methodological issues and provides an efficient design through the possibility of early stopping (Appendix 1). Both mattresses are in widespread use: the design allows ruling out futility of the trial and inferiority of either mattress. PU incidence rates cannot be estimated accurately for the HSF and the maximum sample size estimate is based on the detection of the smallest relevant difference of 5% (clinical opinion): If the difference is greater than 5% then the trial may have sufficient power for stopping early having demonstrated superiority (or inferiority) of the APM; if there is no difference then the trial is likely to stop early for futility. As an early primary endpoint is to be used this is an efficient design. Health technologies being assessed: Patients will be randomised to receive either HSF or APM mattresses as used by the participating centre. APMs will be limited to the main mattress suppliers at each centre. An operational definition of an APM will include minimum and maximum values for cell height, cycle time and cycle frequency. The intervention period is to trial completion, withdrawal or death. Trial completion is defined as: discharge from hospital OR 60 days from randomisation OR no longer at high risk (normal skin on all pressure area sites AND improved mobility and activity) whichever is soonest. Measurement of costs & outcomes: Outcomes will be assessed by a trained research nurse until discharge/trial completion - twice weekly from randomisation to day 30 and once weekly from 31 to 60 days, with a final follow-up at 30 days post discharge/trial completion at either home or hospital. At each visit skin outcomes will be clinically assessed on the key anatomical sites of PU development. EQ-5D, SF12 and PU-QoL will be researcher administered and health care resource utilisation will be abstracted from hospital records and a short researcher administered questionnaire. Unit costs will be obtained from national sources such as the NHS Reference costs, PSSRU Unit costs of health and social care and British National Formulary. Setting: hospital in-patient services Target Population: Inclusion criteria: acute admission patients; aged 18 years or over; admitted to vascular, orthopaedic, surgery, medical or elderly care ward; has an expected length of stay of 5 days or above; bedfast/ chairfast and completely immobile/very limited mobility OR have a pre-existing Category 1 PU; provide written informed consent/witnessed verbal consent/consultee agreement and; are expected to be able to comply with follow-up schedule. Exclusion criteria: previously participated in the trial; have a current or previous Category 3 or above pressure ulcer; planned admission to ICU; sleep at night in a chair and; patient weight is lower or higher than weight limits for HSF and APMs. Primary outcome measure: Time to developing a new Category 2 or above PUs to 30 days post trial completion or withdrawal/death. Sample size: This is a group sequential trial. Patient numbers, timescales and costs are a maximum and are likely to be lower depending on the results of the interim analyses. A maximum of 588 events, corresponding to 2954 patients, are required for the study to have 90% power for detecting a difference of 5% in the incidence of Category 2 or above PUs between APM and HSF, assuming an incidence rate of 18% on APM and 23% on HSF (corresponding to a hazard ratio of 0.759), 2-sided significance level of 5%, and accounting for 6% loss to follow-up.