A mattress (550) is provided having a generally planar upwardly-facing patient surface (552). The mattress (550) includes a stepped downwardly-facing bottom surface (586) having a perimetral portion (580) extending downwardly from the patient surface (552) a first depth and a central projection (576) extending downwardly from the patient surface (552) a second depth greater than the first depth. The mattress (550) also includes head, seat, thigh, and foot portions (558, 560, 562, 564), at least one of which is inflatable.
