A support cushion comprising a first air tight support portion 14 comprising first and second chambers 16 and 18 linked such that air can flow between them a second air tight support 22 portion comprising a further chamber wherein external pressure on the first chamber 16 of the first support portion results in air flow between it and the second chamber 18 but no flow between it and the further chamber. The chambers may have air retention means 26 in them which can be sponge or polyurethane foam. Indents 30 may be provided in this to support a users Ischia and coccyx. Valves may be used to control air flow into the chambers and may operate without a pump. The device is designed for use on a wheelchair to help prevent pressure sores.
