Aronovitch 1999.

Study characteristics
Methods	Study objective: "... to determine the efficacy and safety of the experimental system (study group), in comparison with conventional management (control group), for the prevention of pressure ulcers in the operative and postoperative settings" Study design: randomised controlled trial Study grouping: parallel group Duration of follow‐up: 7 days Number of arms: 2 Single centre or multi‐site: single centre Study start date and end date: March 1997 to February 1998 Setting: tertiary care facility (operating theatre and wards)
Participants	Baseline characteristics Inclusion criteria: "18 years of age or older undergoing a scheduled surgery with general anesthesia for at least 4 hours (actual operative time of 3 hours or more)" Exclusion criteria: patients "participated in a clinical trial within 30 days of the baseline visit ... or had a pressure ulcer at the baseline visit" Sex (M:F): 79:31 in experimental system; 77:27 in conventional management Age (years): mean 63.5 (SD 11.9) in experimental system; 64.7 (11.8) in conventional management Baseline skin status: Modified Knoll scale score ‐ on average less than 4 (range 0 to 13; a score of 12 or higher = at risk of pressure ulcer development) in both groups; and those with pressure ulcers at baseline excluded Group difference: no difference Total number of participants: 217 patients Unit of analysis: individuals Unit of randomisation (per patient): groups of individuals by weeks
Interventions	Intervention characteristics Experimental management Description of interventions: "using the MicroPulse System (MicroPulse, Inc., Portage, Mich) both during then after surgery ... comprised of a thin multi‐segmented pad with more than 2,500 small air‐cells enclosed in a fluid‐proof cover. The air‐cells are arranged in rows so the patient is supported by 50% of the cells (the inflated cells) at any given time ... the cells are deflated ... a cycle time of less than 5 minutes ... until discharge from the hospital or for a maximum of 7 days post‐surgery" NPUAP S3I classification: powered, alternating pressure (active) air surface Co‐interventions: not described Number of participants randomised: n = 112 Number of participants analysed: not described Conventional management Description of interventions: "the use of an Action Pad (Action Products, inc, Hagerstown, Md) in the operating room on top of a standard operating room pad, and a Pressure Guard II hospital replacement mattress (Span‐America Medical Systems, Inc., Spartanburg, SC) on the hospital bed" (Aronovitch 1999); for operating table, Action Pad (Action Products) consisting of AKTON® Viscoelastic polymer that looks and feels like a gel (www.actionproducts.com/media/files/Action_Support_Surface_Brochure.pdf); a series of PressureGuard products identified from Span‐America product catalogue (www.spanamerica.com/product-catalog-new.php) and the catalogue states "... every PressureGuard model combines the effectiveness of an air flotation system with the unmatched stability and safety of a multi‐component engineered foam shell" NPUAP S3I classification: non‐powered, reactive gel surface; non‐powered, reactive foam surface; applied sequentially Co‐interventions: not described Number of participants randomised: n = 105 Number of participants analysed: not described
Outcomes	Proportion of participants developing a new pressure ulcer Outcome type: binary Time points: within 7 days Reporting: partially reported Measurement method (e.g. scale, self‐reporting): using the recommendations of both the NPUAP and the Wound, Ostomy, and Continence Nurses Society (WOCN) Definition (including ulcer stage): the occurrence of a pressure ulcer of any stage at any time within 7 days of surgery Dropouts: not described Notes (e.g. other results reported): data on stages of ulcers available. Experimental system: one individual (not considered to be related to the study device); conventional management: 7 individuals (8.75%), one with three ulcers, two with two ulcers, and four with one ulcer (P < 0.005 between groups) Time to pressure ulcer development Reporting: not reported Support‐surface‐associated patient comfort Reporting: not reported All reported adverse events using allocated support surfaces Reporting: not reported Health‐related quality of life (HRQOL) Reporting: not reported Cost‐effectiveness Reporting: not reported Outcomes that are not considered in this review but reported in trials: No further outcome
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Randomization was performed by week rather than by patient to decrease protocol error." Comment: unclear risk of bias because the methods were not clear
Allocation concealment (selection bias)	Unclear risk	Comment: no information provided
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Outcome group: primary outcome Comment: no information provided
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Outcome group: primary outcome Quote: "Patients were examined following surgery and daily for pressure ulcers, including number, stage (I‐IV), size (area), location, and appearance." Comment: insufficient information to permit judgement of low or high risk of bias.
Incomplete outcome data (attrition bias) All outcomes	High risk	Outcome group: primary outcome Quote: "Seven patients (8.75%) in the control group developed a total of 11 pressure ulcers ..." Comment: high risk of bias because 7 (8.75%) in control group implied 80 of 105 individuals were considered in data analysis, meaning a large proportion of missing data in the control group alone. However, the number of available cases in experimental group is not given.
Selective reporting (reporting bias)	Low risk	Comment: the study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified.
Other bias	Low risk	Comment: the study appears to be free of other sources of bias.