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. 2021 May 6;2021(5):CD013621. doi: 10.1002/14651858.CD013621.pub2

Nixon 2019.

Study characteristics
Methods Study objective: to compare clinical and cost‐effectiveness of 2 mattress types: alternating pressure mattresses (APMs) or high specification foam (HSF)
Study design: randomised controlled trial (double triangular group sequential design)
Study grouping: parallel group
Duration of follow‐up: maximum treatment phase of 60 days; 30 days post‐treatment
Number of arms: two
Single centre or multi‐sites: multi‐sites
Study start date and end date: August 2013 to November 2016
Setting: 42 UK secondary/community inpatient facilities
Participants Baseline characteristics
Inclusion criteria: inpatient with evidence of acute illness; ≥ 18 years; expected stay ≥ 5 days; expected to comply with follow‐up; on electric profiling bed‐frame; high pressure ulcer risk due to at least 1 of following: Braden activity score 1/2 and mobility score 1/2; category 1 ulcers; localised skin pain on a healthy/altered/category 1 pressure area
Exclusion criteria: had previously participated; current/previous ulcer category ≥ 3; planned intensive care unit (ICU) admission; unable to receive intervention; out of mattress weight limits (< 45 kg or > 180 kg); ethically inappropriate (e.g. thought to be in the last few days of their life).
Sex (M:F): 907:1119 overall; 462:553 in APM; 445:566 in HSF
Age (years): median 81 (range 21 to 105) overall; mean 77.8 (SD 13.42) in APM; 78.2 (12.87) in HSF
Baseline skin status: overall 78 with a Braden score > 18 (not at risk) in APM and 69 in HSF; 937 with a score ≤ 18 (at risk) in APM; 942 in HSF. At risk and allowed to have category 1 ulcers.
Group difference: no difference
Total number of participants: n = 2029
Unit of analysis: individuals
Unit of randomisation (per patient): individuals
Interventions Intervention characteristics
Alternating pressure air mattress (APM)

  • Description of interventions: fully automatic; some may have dual therapy; for example, the mattress comprises a combination of alternating pressure or low‐air‐loss. The trial will include only those participants nursed on the alternating pressure mode of action, with a 7.5 to 30 minute cycle time.

  • NPIAP S3I classification: powered, alternating pressure (active) air surface

  • Co‐interventions: not reported

  • Number of participants randomised: n = 1017

  • Number of participants analysed: n = 1016


High‐specification foam mattress (HSF)

  • Description of interventions: be a high‐density foam, viscoelastic (memory) foam or a combination of both, and can be castellated (for ventilation and profiling). Have a cover with the following characteristics: removable, minimum two‐way stretch, vapour permeable and covered zips as defined in BS 3379.36. Be a replacement mattresses with a minimum depth of 150–200 mm

  • NPIAP S3I classification: non‐powered, reactive foam surface

  • Co‐interventions: not reported

  • Number of participants randomised: n = 1013

  • Number of participants analysed: n = 1013
Outcomes Proportion of participants developing a new pressure ulcer

  • Outcome type: binary

  • Time points: 90 days

  • Reporting: partially reported

  • Measurement method (e.g. scale, self‐reporting): classified using the 2009 NPIAP/EPUAP system

  • Definition (including ulcer stage): incidence of pressure ulcer (PU) category ≥ 2 from randomisation to 30 days from the end of the treatment phase (maximum of 90 days)

  • Dropouts: intention‐to‐treat (ITT) analysis but 1 participant excluded from alternating pressure mattress due to the person's previous inclusion/randomisation

  • Notes (e.g. other results reported): primary time point (90 days): 70 of 1016 (6.9%) in alternating pressure air mattress; 90 of 1013 (8.9%) in high‐specification foam mattress. Data from randomisation to end of treatment (60 days): 53 of 1016 (5.2) in alternating pressure air mattress; 79 of 1013 (7.8%) in high‐specification foam mattress. Seconday endpoint (incidence of a new PU category ≥ 1 by 90 days): 160 of 1016 in alternating pressure air mattress; 190 of 1013 in high‐specification foam mattress. Seconday endpoint (incidence of a new PU category ≥ 3 by 90 days): 14 of 1016 vs 18 of 1013


Time to pressure ulcer incidence

  • Outcome type: time‐to‐event

  • Time points: maximum 90 days

  • Reporting: partially reported

  • Measurement method (e.g. scale, self‐reporting): classified using the 2009 NPIAP/EPUAP system

  • Definition (including ulcer stage): time to developing a new PU category ≥ 2 from randomisation to 30 days from the end of the treatment phase (maximum of 90 days)

  • Dropouts: ITT analysis but 1 participant excluded from alternating pressure mattress due to the person's previous inclusion/randomisation.

  • Notes (e.g. other results reported): primary time point (90 days): median time to first new ulcer 18 days (range 2 to 86) in alternating pressure air mattress; 12 (2 to 94) in high‐specification foam mattress; adjusted analysis Fine and Gray model HR 0.76 (95% CI 0.56 to 1.04, exact P = 0.0890). Data within 60 days: Fine and Gray model HR 0.66 (95% CI 0.46 to 0.93; exact P = 0.0176). Seconday endpoint (incidence of a new PU category ≥ 1 by 90 days): Fine and Gray model HR 0.83 (95% CI 0.67 to 1.02; exact P 0.0733). Seconday endpoint (incidence of a new PU category ≥3 by 90 days): HR 0.81 (95% CI 0.40 to 1.62); exact P 0.5530. Univariate survival analysis curves presented in Fig 2.


Support‐surface‐associated patient comfort

  • Reporting: not reported


All reported adverse events

  • Outcome type: binary

  • Time points: 90 days

  • Reporting: partially reported

  • Measurement method (e.g. scale, self‐reporting):

  • Definition (including ulcer stage):

  • Dropouts: ITT analysis but 1 participant excluded from alternating pressure mattress due to the person's previous inclusion/randomisation

  • Notes (e.g. other results reported): no safety concerns indicated for either mattress. No related and unexpected serious adverse events in either group. Expected adverse events/serious adverse events: 163 of 1017 in APM and 167 of 1013 in HSFM. The proportion of deaths (APM 82/1017, 8.1% vs. HSFM 84/1013, 8.3%), re‐admission rates (APM 82/1017, 8.1% vs. HSFM 62/1013, 6.1%) and fall rates (APM 152/1017, 14.9% vs. HSFM 159/1013, 15.7%) similar between arms


Health‐related quality of life (HRQOL)

  • Outcome type: binary

  • Time points: 90 days

  • Reporting: partially reported

  • Measurement method (e.g. scale, self‐reporting): HRQOL assessed using the EQ‐5D‐5L and quality‐adjusted life‐years (QALY) calculated based on EQ‐5D‐5L using an equation QALY = {[(EQ5DBaseline + EQ5Dweek1) × t]/ 2 + [(EQ5Dweek1 + EQ5Dweek3) × t]/ 2 + [(EQ5Dweek3 + EQ5DEndpoint) × t)]/2}. Sensitivity analysis performed with HRQOL measure of PU‐QoL‐UI. The utility values of the EQ‐5D‐5L and PU‐QoL‐UI have a scale of negative 1 to 1, with 1 representing perfect health, 0 representing death, and − 1 representing worse than death.

  • Definition (including ulcer stage): mean estimated QALYs

  • Dropouts: 267 participants (APM arm, n = 118; HSFM arm, n = 149) completed the EQ‐5D‐5L at all 4 time points, and 233 had completed the PU‐QoL‐UI at all 4 time points (APM arm, n = 107; HSFM arm, n = 126)

  • Notes (e.g. other results reported): 90‐day EQ‐5D‐5L: mean 0.52 (SD 0.21) in APM, 0.52 (0.22) in HSF; P = 0.49. Mean QALYs higher in alternating pressure air mattress 0.128 (95% 0.126 to 0.130) than high‐specification foam mattress 0.127 (0.124 to 0.129); P = 0.47. 90‐day PU‐QoL‐UI: mean 0.69 (SD 0.13) in APM, 0.69 (0.13) in HSF; P = 0.28


Cost‐effectiveness

  • Outcome type: binary

  • Time points: 90 days

  • Reporting: partially reported

  • Measurement method (e.g. scale, self‐reporting): an ITT analysis used quality‐adjusted life‐years (QALYs) as the main outcome and adopted the perspective of the UK National Health Service (NHS) and Personal Social Services (PSS). The NICE £20,000 per QALY gained threshold was used to determine cost‐effectiveness. Utility values were derived from the EQ‐5D‐5L, and costs were estimated using the UK tariff. Costs and outcomes were adjusted for baseline imbalances. Sampling uncertainty was determined via a probabilistic sensitivity analysis (PSA) using a non‐parametric bootstrap.

  • Definition (including ulcer stage): the incremental cost per QALY gained; within‐trial analyses using QALYs derived from the EQ‐5D‐5L

  • Dropouts: ITT analysis

  • Notes (e.g. other results reported): adjusted for baseline costs and QALYs, deterministic analysis suggests the mean total costs of APM and HSFM are GBP 4,533 and GBP 4,646, respectively, with mean QALYs of 0.128 and 0.127, respectively. Incremental cost‐effectiveness ratio (ICER) = GBP –136,171; net‐monetary benefit (NMB) = GBP –2077; probabilistic analysis shows mean total costs of APM and HSFM are GBP 4,533 and GBP 4,646, respectively, and mean QALYs are 0.128 and 0.127, respectively. ICER = –101,699 and NMB = –2114. Estimates indicate that APM has a 99% probability of being cost‐effective at a threshold of GBP 20,000 (APMs dominate HSFM, as APM has lower costs and higher QALY values). Lifetime decision‐analytic model developed for lifetime cost‐effectiveness analysis but data not extracted for this review. Finding is: APM to be cost‐effective over both the short and the long term.


Outcomes that are not considered in this review but reported in trials:

  • Time to healing of all pre‐existing category 2 ulcers

  • Mattress compliance
Notes  
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk Quote: "Participants were randomised centrally (24 h automated telephone system, ensuring allocation concealment) on a 1:1 basis using minimisation (with random element) and minimisation factors: centre, PU status, type of facility, and type of consent"
Comment: low risk of bias because of the use of a proper randomisation method.
Allocation concealment (selection bias) Low risk Quote: "Participants were randomised centrally (24 h automated telephone system, ensuring allocation concealment) on a 1:1 basis using minimisation (with random element) and minimisation factors: centre, PU status, type of facility, and type of consent"
Comment: low risk of bias because allocation is properly concealed.
Blinding of participants and personnel (performance bias)
All outcomes High risk Quote: "Blinding of the research and clinical staff or patients was not possible due to the appearance of the mattresses"
Comment: high risk of bias because non‐blinding is clearly stated.
Blinding of outcome assessment (detection bias)
All outcomes Low risk Quote: "Assessment of risk of bias of the primary endpoint was done with central blind review of photographs and a 10% sample of patients who had skin assessments by a practitioner blinded to previous assessments was performed"
Comment: low risk of bias because attempts were made to mask outcome assessment.
Incomplete outcome data (attrition bias)
All outcomes Low risk Quote: "All participants recruited were included using Intention‐To‐Treat (ITT) and analysed by randomised allocation"
Comment: low risk of bias because ITT analysis was performed.
Selective reporting (reporting bias) Low risk Comment: the study protocol is available and it is clear that the published reports include all outcomes, including those that were pre‐specified.
Other bias Low risk Comment: the study appears to be free of other sources of bias.