Use of support surface in preventing the pressure ulcers

What is the support surface?

The support surface is a particular pressure redistribution device that helps in controlling the tissue loads, microclimate, and therapeutic activities. It circulates the pressure exerted on the tissues that were in contact with the surface. The support surface picks up the weight of the patient while lying or sitting. The redistribution of pressure is important because it helps in relieving the pressure as well as enabling the blood flow again. If pressure is not relieved then the flow of blood will be reduced and that will damage the skin and soft tissue causing pressure ulcers. 

What parameters should be considered while evaluating the characteristics of the support surface?

Nine parameters should be considered while evaluating the characteristics of support surfaces for the patient with a wound. And these are:

• Pressure redistribution
• Reputation of product
• Moisture control
• Temperature control
• Fail safety
• Control of infection
• Fail safety
• Control of friction (between patient and product)
• Flammability
• Life expectancy

Biomechanics of soft tissue:

There are macromolecules in human soft tissue, and these are muscles, fat, skin, ligaments, tendon, arteries, and nerves.  These macromolecules are secreted by fibroblast making the extracellular matrix in most connective tissue. There are two types of macromolecules that create the matrix.

1. Polysaccharide chain

2. Fibrous protein

Characteristics of support surface:

1. Pressure distribution:

Pressure distribution is the potential of the support surface to spread the load over the contact areas of the human body. The pressure, as well as shear force, will also reduce.

2. Immersion:

The depth of penetration and sinking into the surface is referred to as immersion. It allows the pressure to cover the surrounding area rather than directly over a bony prominence. 

In a fluid-filled support surface, the immersion depends on the thickness and flexibility of the cover. 

The immersion depends on stiffness and thickness in elastic and viscoelastic support surfaces.

3. Envelopment:

Envelopment is the capacity of the support surface to reconcile or to mould around the irregularities in the body. The irregularties are creases in clothing, bedding, seat covers, and protrusions of the bony prominence.

4. Pressure gradient:

The word gradient means difference, so it is also called pressure differential. The pressure gradient is the change or difference of pressure over a distance. In the device, the pressure gradient is calculated as a change in millimeters of mercury (mm Hg) per square cm or square inch. 

It is the pressure gradient that flows the tissue fluid component from the area containing high pressure towards the area containing low pressure. 

5. The reduction of friction and shear:

We can also use shear in reference to shear stress or shear strain. Shear stress is the application of force that is tangential over an area of tissue. It can induce deformation.

The friction is the resistive force applied to the motion of two surfaces that are in contact. Friction prevents the support surfaces as well as tissues from sliding.

6. Temperature control:

The metabolic and oxygen consumption increases with the higher ambient temperature. The skin temperature raises with repetitive loading. The temperature rise also increases blood perfusion and stiffness. As the stiffness increases, there will be a decrease in deformation. 

7. Control of moisture:

The moisture has a role in developing a pressure ulcer and thus damage the skin. The moisture will increase with the rise of friction along with sweating. The moisture can also increase with the increase of bacterial load when alkaline sources of moisture neutralize the skin's natural acid layer.  

Which material and components are used in the supportive system?

The materials include:

• Foam
• Gel
• Gel pads
• Viscous fluid 
• Fluid-filled bladders
• Elastomers

1. FOAM:

The foam can be an elastic or viscoelastic build-up of open or closed cells. In open-cell foam, there is no barrier between the cells and is permeable allowing gases or liquids to pass through. There is a barrier present between the cells of closed-cell foam making it non-permeable. Thus, the gases and liquids do not flow through them. 

2. ELASTIC FOAM: 

The elastic foam is resilient and returns to its normal shape or thickness when the load is removed. It is the build-up of porous polymer material conforming in proportion to applied weight. 

3. VISCOELASTIC FOAM: 

Viscoelastic foam is one of the special types of open-cell foam. It compresses under load similar to elastic foam but there are some unique qualities in it. Sometimes it is also called memory foam because it can contour to the body and diminish the elastic response over time.  There is a variety of stiffness in viscoelastic foam so that it can allow the immersion same as elastic foam. The viscoelastic foam might be sensitive to temperature and becomes softer if exposed near to human body temperature. The average rise in temperature for viscoelastic foam is 5F allowing the body to sink deeper into the foam. Along with that, it also increases contact area and decreases the interface pressure. The viscoelastic foam should be chosen for both seating and mattress application based on the patient's unique demand. 

4. FLUID-FILLED BLADDERS & COMPARTMENTS: 

The fluid-filled bladders and compartments allow a high level of immersion and enable the body to sink beneath the surface. It consists of chambers that are filled with air, water, or other viscous fluid materials .i.e. silicon elastomer, silicone, polyvinyl. The chambers may be small or large. The surface adapts to bony prominence due to the transmission of pressure to the neighboring locations. Thus expanding the surface pressure distribution area and reducing the interface pressure.  

What are the features of supporting surfaces?

The features include:

• Air-fluidized
• Low air loss
• Alternating pressure
• Lateral rotation products

1. Air Fluidized:

The mattress of a bed is filled with tiny glass or ceramic spheres .i.e. silicon beads encased in polyester or Gore-Tex sheeting that is suspended by a continuous flow of warm air. To reduce the pressure. it uses fluid technology through the principle of immersion while simultaneously reducing the shear and permitting the highest degree of immersion. The pressurized warm air in these products is generally warmed to a temperature level of 82.4 °F to 95°F. These beds are effective in managing the body fluid and useful in preventing bacteriologic contamination. 

2. Low air loss:

The air pump circulates a continuous flow of air through the device. It consists of series-connected air-filled compartments. Based on the need of an individual, we can adjust the inflation pressure. We can also have an option of alternating or pulsating low air loss systems that will incorporate the feature of alternating pressure surfaces. The patient will lie on a loose-fitting, waterproof cover which will be placed over the air cushions. The waterproof covers are smooth with a low coefficient of friction to reduce shear and also allow air as well as water vapor penetration. 

3. Alternating Pressure Support Surfaces:

The alternating pressure support surfaces have an air-filled chamber and that is arranged lengthwise, interdigitated, or in various other patterns. The air is periodically pumped into the chambers to inflate or deflate the chambers. The alternating-pressure devices distribute the pressure by changing the body weight to a different surface contact area, rather than increasing the surface area for distribution through immersion and envelopment. It can also raise the interface pressure in that location during the inflating phase. To maintain the correct level of inflation, we must take care.

4. Lateral Rotation: 

This feature of a support surface help in moving the patient in a regular pattern around a longitudinal axis. In lateral rotation, the patients are positioned in a way so the lung can be higher than the other to prevent pneumonia. We can also use these devices in pulmonary therapy.