* Ergonomical pump equipped with security functions controlled by audible and visual alarms system. * Maintenance free and silent compressor. * A secured knob enables to set the patient weight. * The compressor is equipped with a pressure sensor and regulates the pressures relief according to the patients weight. * It operates: - in alternating mode: for prevention and help for treatment, - in low pressure static mode: constant low pressure reduction if the alternating is not required, - in nursing mode for nursing procedures with automatic return in alternating mode after 30 min. * The MODENA mattress (supplied with its cover) fits directly on the bed base. * The mattress is composed of two independant air layers. Lower part: three individual cells which always operate in static mode. Upper part: 24 tubes which are welded to each other by groups of 8 and operate in static or alternating mode.