Special support surfaces

The use of special support surfaces attempts to reduce the pressure at the contacting skin surface to a level below capillary occlusion pressure. In most cases, it is sufficient to use postural changes to minimise the time the support surface contacts with any one area of skin.

Factors suggesting need for special support surfaces

• Patients with severely restricted mobility due to external traction or cardiorespiratory instability cannot be turned frequently, if at all.

• Patients with decreased skin integrity, e.g. burns, pressure sores already present, chronic corticosteroid use, diabetes mellitus.

• Patients on vasoactive drug infusions and/or poor tissue perfusion.

Types of special support surface

Air mattress

This either replaces or is placed on top of a standard hospital bed mattress.

Although providing minimum reduction in contact pressure, they

should be considered as minimum support for patients with any of the

above factors.

Low air loss bed

These purpose-built, pressure-relieving beds allow easier patient mobility than other support surfaces. Contact pressure may still be higher than capillary occlusion pressure so positioning is still required. Patients who are haemodynamically unstable should usually be managed on a low air loss bed, particularly if receiving vasoconstrictor drugs. The presence of pressure sores with intact skin is an indication for a low air loss bed. Rotational low air loss beds allow automated lateral rotation at variable time intervals to facilitate chest drainage. These may also be useful where manual positioning is impractical.

Air fluidised bed

This is the only support surface that consistently lowers contact pressure to below capillary occlusion pressure. Consequently, most benefit is seen in patients with severe cardiorespiratory instability who cannot be turned, and those with pressure sores and broken skin. The additional ability to control temperature of the immediate environment is advantageous in hypothermic patients and those with large surface area burns. Any exudate from the skin is adsorbed into the silicone beads on which the patient floats. This drying effect is particularly useful in major burns (although it must be taken into account for fluid replacement therapy). The air fluidised bed also has a role in pain relief.

Rotation therapy

Rotation therapy beds continuously change the pressure with the contacting surface by lateral turning to each side. This reduces shear and minimizes pain and discomfort associated with manual turning.