Learning the Language: Terms for Beds & Support Surfaces
On Jan. 29, 2007, the National Pressure Ulcer Advisory Panel (NPUAP) issued revised definitions for support surfaces. Use the following glossary of terms to use as a handy reference. The terms are also available for download at www.npuap.org.

active support surface

A powered support surface with the capability to change its load distribution properties, with or without applied load.

air

A low density fluid with minimal resistance to flow.

air fluidized

A feature of a support surface that provides pressure redistribution via a fluid-like medium created by forcing air through beads as characterized by immersion and envelopment.

alternating pressure

A feature of a support surface that provides pressure redistribution via cyclic changes in loading and unloading as characterized by frequency, duration, amplitude and rate of change parameters.

cell/bladder

A means of encapsulating a support medium.

closed cell foam

A non-permeable structure in which there is a barrier between cells, preventing gases or liquids from passing through the foam.

coefficient of friction

A measurement of the amount of friction existing between two surfaces.

elastic foam

A type of porous polymer material that conforms in proportion to the applied weight. Air enters and exits the foam cells more rapidly, due to greater density. (non-memory)

elastomer

Any material that can be repeatedly stretched to at least twice its original length; upon release the stretch will return to approximately its original length.

envelopment

The ability of a support surface to conform, so to fit or mold around irregularities in the body.

fatigue

The reduced capacity of a surface or its components to perform as specified. This change may be the result of intended or unintended use and/or prolonged exposure to chemical, thermal or physical forces.

friction (frictional force)

The resistance to motion in a parallel direction relative to the common boundary of two surfaces.

force

A push-pull vector with magnitude (quantity) and direction (pressure, shear) that is capable of maintaining or altering the position of a body.

gel

A semisolid system consisting of a network of solid aggregates, colloidal dispersions or polymers which may exhibit elastic properties. Can range from a hard gel to a soft gel.

immersion

Depth of penetration (sinking) into a support surface.

integrated bed system

A bed frame and support surface that are combined into a single unit whereby the surface is unable to function separately.

lateral rotation

A feature of a support surface that provides rotation about a longitudinal axis as characterized by degree of patient turn, duration and frequency.

life expectancy

The defined period of time during which a product is able to effectively fulfill its designated purpose.

low air loss

A feature of a support surface that provides a flow of air to assist in managing the heat and humidity (microclimate) of the skin.

mattress

A support surface designed to be placed directly on the existing bed frame.

mechanical load

Force distribution acting on a surface.

multi-zoned surface

A surface in which different segments can have different pressure redistribution capabilities.

non-powered

Any support surface not requiring or using external sources of energy for operation.

open cell foam

A permeable structure in which there is no barrier between cells and gases or liquids can pass through the foam.

overlay

An additional support surface designed to be placed directly on top of an existing surface.

pad

A cushion-like mass of soft material used for comfort, protection or positioning.

powered

Any support surface requiring or using external sources of energy to operate. (Energy=D/C or A/C)

pressure

The force per unit area exerted perpendicular to the plane of interest.

pressure redistribution

The ability of a support surface to distribute load over the contact areas of the human body. This term replaces prior terminology of pressure reduction and pressure relief surfaces.

pressure reduction

This term is no longer used to describe classes of support surfaces. The term is pressure redistribution.

pressure relief

This term is no longer used to describe classes of support surfaces. The term is pressure redistribution.

reactive support surface

A powered or non-powered support surface with the capability to change its load distribution properties only in response to applied load.

shear (shear stress)

The force per unit area exerted parallel to the plane of interest.

shear strain

Distortion or deformation of tissue as a result of shear stress.

solid

A substance that does not flow perceptibly under stress. Under ordinary conditions retains its size and shape.

support surface

A specialized device for pressure redistribution designed for management of tissue loads, micro-climate, and/or other therapeutic functions (i.e. any mattresses, integrated bed system, mattress replacement, overlay, or seat cushion or seat cushion overlay).

viscoelastic foam

A type of porous polymer material that conforms in proportion to the applied weight. The air exits and enters the foam cells slowly, which allows the material to respond slower than a standard elastic foam (memory foam).

viscous fluid

A fluid with a relatively high resistance to flow of the fluid.

water

A moderate density fluid with moderate resistance to flow.

zone

A segment with a single pressure redistribution capability.