Air-fluidized beds and their ability to distribute interface pressures generated between the subject and the bed surface.

Pressures were measured under five anatomical sites prone to pressures sores for ten subjects, supine and sitting on two different air-fluidized beds. The beds were the Clinitron (trademark, SSI) and the Fluidair Plus (trademark, KCI Mediscus). Mean supine pressures were less than 4 kPa under four sites. The average supine buttock pressure was 2.65 kPa. This increased to 3.71 kPa upon sitting up, though pressures did not rise above the accepted capillary closing pressure, on either bed. Low interface pressures at these sites were due to good moulding between subject and bed. Heel pressures averaging 7.08 kPa, were a factor of 2.67 times greater than buttock pressure, and were higher than expected considering the depth the heels sunk to in both beds. This exceeded the accepted capillary closing pressure and was attributed to covering sheets preventing true floatation at the heels.