A decision analytic Markov model, with a one-day cycle length, was used to simulate a cohort of patients with an average age of 63 years, who were undergoing scheduled surgical procedures lasting 90 minutes or more, in the supine or lithotomy position. The time horizon was one year. The authors stated that a health care payer perspective was adopted.
The clinical and effectiveness data were from systematic reviews, pressure ulcer surveys, a large cohort study of home care patients, and literature searches. The main effectiveness measure was the reduction in relative risk of pressure ulcers, which was from five randomised controlled trials, identified by two systematic reviews.
Monetary benefit and utility valuations:
The health utility estimates were from published studies, all of which used the Health Utilities Index.
Measure of benefit:
The measure of benefit was quality-adjusted life-days (QALDs) gained.
The direct costs included those of the operating table overlays (the unit price was amortised over its average life span, and the average number of surgical procedures); hospital stay (ward care, pharmacy, overheads, and capital depreciation); and home care (nursing, personal support, dietary services, social work, and physical and occupational therapy). The costs of the mattresses were from the manufacturer. All other costs were from published studies. They were expressed in 2009 Canadian dollars (CAD) after adjusting for power parity, with CAD 1 equal to 0.84 US dollars.
Analysis of uncertainty:
One-way sensitivity analyses were performed by varying each of the key model inputs over its plausible range. A probabilistic sensitivity analysis was undertaken by sampling 10,000 random values from the assigned input distributions.