Abstract: An air mattress for preventing bedridden patients' suffering from bed sores and the like is provided. A mattress assembly is provided comprising a matrix member disposed throughout its interior region for uniformly distributing air to the mattress-patient interface. This matrix member comprises a network of vertical rigid tubes and interconnected horizontal rigid tubes which are configured to uniformly distribute air to the upper mattress surface. Ambient air enters into the bottom end of this plurality of vertical tubes and is then delivered to the upper mattress surface through a plurality of tufted recess surfaces located at the top end of the plurality of vertical tubes. The matrix member is contained within an air mattress portion which is, in turn, configured to be abuttably received by a corresponding peripheral mattress portion. The air mattress portion is secured to the peripheral mattress portion by brace members.