Clients at high risk of developing pressure ulcers may benefit from an alternating pressure mattress or other high-tech pressure redistributing system (Consortium for Spinal Cord Medicine,2000; RCN, 2000). Alternating pressure devices generate alternating high and low interface pressures between the body and support surface (bed), usually by alternate inflation and deflation of air-filled cell. These devices are available as mattress overlays, and single or multi-later mattress replacements. The systematic review conducted by Cullum et al.(2004) indicates the relative merits of higher-tech constant low pressure and alternating pressure for prevention are unclear