A relatively shallow mattress for a bed which has three integral parts: an inner bladder, an outer bladder and a mattress cover. The inner bladder is formed from a rectangular top and bottom side welded together along the edges. The top side contains a valve. The outer bladder is effectively a safety...http://www.google.de/patents/US5109559?utm_source=gb-gplus-sharePatent US5109559 - Flotation mattress pad having a cover with pad retaining straps
