Pneumatic wheelchair cushion

A generally rectangular pneumatic wheelchair cushion system comprising an air cushion with five adjoining lateral tubes, said lateral tubes comprising a right greater trochanter tube, a right ischial tuberosity tube, a coccyx tube, a left ischial tuberosity tube and a left greater trochanter tube, and one adjoining transverse tube for cushioning the user's thighs, said transverse tube comprising a femur tube, said tubes pneumatically interconnected with restricted passageways, one of which passageways interconnects the coccyx tube and the femur tube, such that pressure on one or more of the tubes is transmitted between the coccyx tube and femur tube and to the other tubes, and a control module with means for controlling an inflation pressure in the air cushion within an upper and a lower set point, said control module pneumatically connected to the air cushion, said right and left greater trochanter tubes being larger in cross-section than the right and left ischial tuberosity and coccyx tubes so that the air cushion is concave when viewed from above.