Support Surfaces. Special beds, mattresses, mattress overlays, or seat cushions that reduce or relieve pressure while sitting or lying.

1) Air-Flotation Bed. Generic descriptor for low-air-loss beds and air-fluidized beds.

2) Air-Fluidized Bed. Class of support surfaces that uses a high rate of air flow to fluidize fine particulate material (such as sand) to produce a support medium that has characteristics similar to a liquid.

3) Alternating-Air Mattress or Overlay. Mattress or overlay with interconnecting air cells that cyclically inflate and deflate to produce alternating high and low pressure intervals. Cells with larger depth and diameter produce greater pressure relief over the body.

4) Donut-Type Device. A rigid, ring-shaped device created to relieve pressure on the sitting surface. This device is not recommended, because even though pressure is relieved in the tissue over the center of the ring, pressure in tissue resting on the ring causes vascular congestion and may impede circulation to the tissues.

5) Dynamic Device (or Dynamic Support Surface). Pressure-reducing device designed to change its support characteristics in a cyclical fashion. Examples include alternating-air mattresses and mechanical seats that change shape and redistribute pressure.

6) Foam Mattress Overlay. Thick foam slab with a textured surface designed to be placed on top of the standard hospital mattress to reduce pressure by enveloping the body. Its effectiveness is influenced by its thickness, density, and stiffness. Needs to be at least 4" thick to be effective.

7) Low-Air-Loss Bed. A series of interconnected woven fabric air pillows that allow some air to escape through the support surface. The pillows can be variably inflated to adjust the level of pressure relief.

8) Mattress Replacement System. Mattress with pressure-reducing or pressure-relieving features that can be placed on an existing bed frame.

9) Overlay. General term used to describe support surfaces placed on top of a standard hospital mattress.

10) Static Air Mattress. A vinyl mattress overlay composed of interconnected air cells that are inflated with a blower before use. The shifting of air among the cells distributes pressure uniformly over the support area to create a flotation effect.

11) Static Device (or Static Support Surface). Pressure-reducing device designed to provide support characteristics that remain constant - i.e., do not cycle in time. Examples include foam overlays, cushions, and water mattresses.

12) Static Water Mattress. A vinyl mattress or overlay composed of interconnected compartments that are filled with water to distribute pressure uniformly over the support surface to create a flotation effect.