American Academy of Nursing
“A multi-layer pressure redistribution surface was found to be statistically significant in reducing pressure ulcer incidence when compared with the “Standard” OR table pad.”

Lummus AC.
Study of a Multi-Layer Pressure Relief Pad in the Operating Room (OR)
University of Tennessee Health Science Center

That pressure ulcers may occur within a 1 to 4 hour timeframe, well within the range of current surgical procedures*
* Baron S, MacFarlane G. Reducing Pressure Ulcer Risk In The Operating Room. White Paper. 2009. Allen Medical Systems, D-770444-A2