A patient support (10, 14) includes a source of pressurized air (64), a bladder (30), a valve (66) in fluid communication with the source of pressurized air (64) and to the bladder (30), a pressure sensor (28) in fluid communication with the bladder (30), and a controller (26) responsive to a pressure signal from the pressure sensor (28). The controller (26) may determine a rate of change of pressure within the bladder (30) and may store historical pressure data.
