Table 1

       A common language is the first thing that is needed for effective communication. Until now, there has not been a set of definitions for the words and terms that are commonly used with support surfaces. In the absence of agreed-upon definitions, any one term or word has developed many definitions. For example, answer this multiple choice question: What is low-air-loss?

a) any surface that plugs into the wall
b) any surface that has laser holes and an air blower
c) a surface that blows air across the patient’s skin
d) a surface that has laser holes, a vapor-permeable cover, and an air blower source to directly or indirectly dissipate heat and moisture from the patient/mattress interface.¹

       The correct answer is “d,” but the other simple definitions and misconceptions persist. The result of this lack of clear definitions is confusion among manufacturers, distributors, dealers, clinicians, and end users. It can also result in a product being misrepresented as having a certain effect on the skin and tissue by virtue of its name, when in actuality it does not have that effect at all. The consequences are mixed messages from manufacturers and eventual confusion for purchasers.
       Further, there is no way for anyone to know if a support surface truly does what its manufacturer claims it does or what its name or sales literature implies it can do. How does the customer know if the low-air-loss mattress truly affects moisture on the skin? How does he or she know if the alternating pressure in the air cylinders is sufficient to affect the tissues?
       In 2002, the National Pressure Ulcer Advisory Panel (NPUAP) began the Support Surfaces Standards Initiative (S3I). The three goals of S3I, as stated by NPUAP are “to coordinate the development of a uniform terminology and test methods and reporting standards for support surfaces. The guidelines will provide an objective means for evaluating and comparing support surface characteristics. Test methods and reporting standards will improve the process of selection and procurement. Clinicians, patients, and other users would benefit from having product information and test data presented in a consistent manner. In essence, standards will empower consumers. Standards will also serve as a product development guide for manufacturers and enhance quality assurance in the manufacturing process.”
       As a first step in fulfilling its mission, S3I published its final set of Terms and Definitions in the fall of 2006. These were written and approved by S3I after several years of work by dedicated clinicians, researchers, and manufacturers. As often as possible, definitions were based on extensive research through literature searches and involved many meetings and discussions in person, online, and via telephone conferences. The results were put out for public comment in the fall of 2005 and then refined by comments received in the public comment period. The final set of Terms and Definitions can be found on the NPUAP website at www.npuap.org. The work of S3I continues with the development of test methods and reporting standards.

The Difference Between Pressure Relief and Reduction

       The definitions for pressure relief and pressure reduction have morphed many times over the years, and the S31 initiative replaced them with the term “redistribution.” The Department of Health and Human Services (HHS)’s Agency for Health Care Policy and Research (AHCPR) defines pressure reduction as reduction of interface pressure, not necessarily below the level required to close capillaries (ie, capillary-closing pressure).² Pressure relief is defined as reduction of interface pressure below capillary-closing pressure. These two definitions depend on capillary-closing pressure, which is defined as 32 mm Hg. Therefore, these two definitions depend on the veracity of 32 mm Hg. This is, however, a poor measurement to use as an absolute. Consider the following facts:

1. In 1930, Landis determined that the capillary-closing pressure of the adult human venule was 6–18 mm Hg, with an average of 12, and the capillary-closing pressure of the adult human arteriole was 21–48, with an average of 32.³ So the variance in capillary-closing pressure at this microscopic level is 6–48 mm Hg; it is not an absolute 32.
2. The only way we can determine capillary-closing pressure for an individual is through invasive techniques.
3. Many erroneously believe that interface pressure mapping can be equated to capillary-closing pressure. Although it is noninvasive and objective, interface pressure mapping does not capture capillary-closing pressure. Interface pressures are read between the support surface and the patient’s skin, while capillary-closing pressure is read at the microscopic level. Therefore, a numerical value on a pressure map—whether it is above, below, or at 32 mm Hg—does not equate to pressure values at the capillary level.
4. When pressure mapping is used, one subject may yield interface pressures below 32 mm Hg, while another subject on that same mattress will record interface pressures above 32 mm Hg. This can be due to bony prominences, body weight distribution, weight in relation to height, and many other factors. So does that make this mattress fit into reduction or relief? The definitions are impossible to apply when subjects vary so widely in their pressure readings. This applies to nearly all support surface products on the market.

       In clinical practice, pressure reduction has come to mean mattresses that are normally used for the prevention of pressure ulcers. These are generally static or nonpowered mattresses, such as foam mattresses. In home care, these mattresses are often referred to as “Group 1” mattresses because most of the basic mattresses used for prevention fall into that category under Medicare.
       Pressure relief has come to refer to mattresses that are normally used during the treatment of existing pressure ulcers. These are generally powered mattresses, such as alternating- pressure, low-air-loss, and lateral-rotation surfaces. A small group of nonpowered mattresses that are also commonly used during treatment also fall into this “relief” or treatment category. In home care, treatment mattresses are often referred to as “Group 2” mattresses, the name of the Medicare category.

Active and Reactive Surfaces

       Federal Tag 314 (Tag F314) refers to pressure redistribution devices and subdivides them into “static” and “dynamic” devices or surfaces. The NPUAP definitions do not use the terms static and dynamic, as these do not refer to the effect on the patient but to the use of electricity to power the surface. Some powered surfaces simply equalize pressure, while others, such as alternating-pressure and low-air-loss surfaces, do much more than that. Therefore, the terms static and dynamic do not help to clarify support surfaces.
       The S3I Terms and Definitions include definitions⁴ for “active” and “reactive” surfaces as follows:
       Active: A powered support surface with the capability to change its load distribution properties, with or without applied load.
       Reactive: A powered or nonpowered support surface with the capability to change its load distribution properties only in response to applied load.
       An active surface, such as alternating-pressure or lateral-rotation, has motion or activity within the support surface, whether or not someone is lying on the surface; the cylinders alternately inflate and deflate, and in many surfaces this motion is visible.

Figure 1

The PressureGuard® APM2 active surface has air cylinders and firm foam edges for patient support.

Comparatively, a reactive surface, whether powered or not, does not exhibit any motion until a person lies on the surface. Then, imposed pressures are equalized or redistributed by movement in the support material (eg, air, gel, foam, viscoelastic foam, etc.).
       Some powered or dynamic surfaces are reactive, such as those that equalize pressures when someone lies on them. Other powered or dynamic surfaces are active, such as the alternating-pressure or lateral-rotation mattresses as described above. Active and reactive, although not as intuitive as static and dynamic, give a much clearer view of how the surface will actually affect the patient. They are, therefore, more helpful to both the purchaser and the patient.

Powered Versus Nonpowered

       Although many studies have been done, their results are inconsistent and conflicting. Cullum et al⁵ published a systematic review in 2004. Their goal was to determine “to what extent do pressure-relieving cushions, beds, mattress overlays, and mattress replacements reduce the incidence of pressure ulcers compared with standard support surfaces,” and “how effective are different pressure-relieving surfaces in preventing pressure ulcers compared to one another.” They did an extensive search of the literature and included only randomized controlled trials that assessed the effectiveness of support surfaces in preventing pressure ulcers. Their only conclusion was that higher-specification foam surface alternatives to the standard hospital mattress can reduce the incidence of pressure ulcers in persons at risk. The relative merits of alternating-pressure and constant-low-pressure surfaces in preventing pressure ulcers were unclear.
       Reddy et al⁶ published a systematic review in 2006, examining interventions to prevent pressure ulcers. Their perusal of available literature yielded 59 randomized controlled trials that were categorized by mobility, nutrition, or skin health. Of the 59 trials, 48 addressed the role of support surfaces in pressure ulcer prevention. In general, the authors criticized the quality of the studies, which calls into question the quality of the results. They found that specialized foam and specialized sheepskin overlays were the only surfaces that were consistently superior to standard hospital mattresses in reducing pressure ulcer incidence. The 14 randomized controlled trials that compared dynamic and static support surfaces in preventing pressure ulcers yielded conflicting results. The authors concluded that support surfaces—along with repositioning the patient, optimizing nutritional status, and moisturizing sacral skin—represent an appropriate strategy to prevent pressure ulcers.

Figure 2

An illustration of the benefits of a firm foam edge to help prevent falls and entrapment when the patient sits on the edge of the support surface.

       While studies are conflicting, recognized clinical guidelines for the prevention and management of pressure ulcers include the use of static or pressure-equalizing (ie, reactive) support surfaces for prevention and dynamic (ie, active) support surfaces for prevention for the patients at highest risk as well as for treatment of existing pressure ulcers.^2,7,8 A patient with a pressure ulcer has a limited number of positions to lie on if he or she is to keep pressure off of an ulcer. Therefore, if the ulcer is not touching the support surface, the support surface may be working more to prevent breakdown on the remaining weight-bearing body surfaces rather than directly affecting the ulcer.

The Value of Pressure Mapping

       Pressure mapping is useful only to help determine the best product for a particular patient by mapping that subject on comparative surfaces. A single pressure map of one patient is not helpful for indicating the distribution of pressure of all patients who use that surface. Patients vary widely in body type, height and weight, presence of contractures, bony prominences, weight distribution, etc. Each of these has a large effect on the resulting pressure map. Just as each person is unique, so each pressure map is unique and cannot be used to generalize across all body types.
       In a fairly extensive discussion of pressure mapping, Rithalia⁹ concludes that “[Interface pressure mapping] does not provide sufficient information to fully describe the loading at the particular point on the body surface and cannot be used in isolation to infer internal stresses and strains in the tissue.”
       Different pressure mapping systems by different manufacturers give different results, even on the same subject and the same surface. It is comparable to different scales yielding different weight measurements on the same person.
In attempting to use pressure mapping to develop international test standards, researchers found that pressure maps are impossible to replicate with consistency across different laboratories and different mapping systems, even when the same surrogate model is used.¹⁰ This inconsistency makes it impossible to compare pressure maps of different persons on different systems, as is often done with support surfaces. A clinician will ask manufacturers for “pressure mapping on your product.” But unless the maps were done on the same person in the same setting with the same device, they are not comparable, so there is no information to be gained from them. Dr. Stephen Sprigle, Director of the Center for Assistive Technology and Environmental Access, says the clinician should not “sweat a single value, and…[pressure mapping] is a much better tool to rule out…surfaces than to prescribe them.”¹⁰
       You may be asking yourself, “What other features should I look for?” See Table 1 for a list of some of the many features that decision makers look for.
       Many facilities have developed evaluation tools to gather input from clinicians, patients, and housekeeping staff. These tools make the decision more objective and often pull information from the participants that they would not have thought to give. They are also available from many of the manufacturers and distributors.

The Importance of Fall Prevention

       Every facility should be concerned about preventing falls. The Centers for Disease Control and Prevention (CDC) National Center for Injury Prevention and Control publication “Falls in Nursing Homes” details this prevalent hazard concisely and convincingly through an extensive literature search.¹¹ Among the findings:
• Each year, a 100-bed nursing home reports 100–200 falls.¹²
• About 1,800 persons living in American nursing homes die each year from falls.¹³
• About 10–20% of resident falls cause serious injury; 2–6% cause fracture.¹³
       Whenever a nursing home invests in equipment, it makes sense to choose products that will enhance patient care as well as reduce risk of injury. Thapa et al¹⁴ reported that 35% of fall injuries occur among residents who cannot walk and that these were more likely to involve equipment and occur while seated or during transferring from a chair/bed level. The authors conclude that “increasing the safety of transferring and of equipment are appropriate targets for interventions.”
       The majority of specialty support surfaces on the market have edges that collapse when a patient sits or lies on those edges. Choosing support surface equipment with firm edges that will not collapse during edge-of-bed sitting or during a transfer can help to decrease the falls that often result in injury and death.
       You have many choices in support surfaces. Armed with the proper terminology, a list of desired product features, and an evaluation tool to gather opinions and outcomes from an in-house trial of product samples, you can make an informed decision for this major capital expense and integral part of patient care.

References

1. Fleck CA. Support Surfaces: Criteria and Selection. In: Krasner DL, Rodeheaver GT, Sibbald RG, eds. Chronic Wound Care: a Clinical Sourcebook for Healthcare Professionals. 3rd ed. Wayne, Pa: HMP Communications; 2001:666.
2. Bennett MA, Carlson CE, Bergstrom N, et al. Clinical Practice Guideline Number 15: Treatment of Pressure Ulcers in Adults. US Department of Health and Human Services. Agency for Health Care Policy and Research; 1994. AHCPR Publication 95-0653.
3. Landis EM. Micro-injection studies of capillary blood pressure in human skin. Heart. 1930;15:209–228.
4. National Pressure Ulcer Advisory Panel Support Surface Standards Initiative (S3I). Terms and definitions related to support surfaces. Available at: www.npuap.org/pdf/ NPUAP_S3I?TD.pdf. Accessed February 22, 2007.
5. Cullum N, McInnes E, Bell-Syer SE, Legood R. Support surfaces for pressure ulcer prevention. Cochrane Database Syst Rev. 2004;(3);CD001735. Review.
6. Reddy M, Gill SS, Rochon PA. Preventing pressure ulcers: a systematic review. JAMA. 2006;296(8):974–984.
7. The American Medical Directors Association (AMDA). AMDA’s Clinical Practice Guidelines for Pressure Ulcers. Columbia, Md: American Medical Directors Association. 2004.
8. Ratliff C, Bryant D. Guideline for prevention and management of pressure ulcers. Glenview, Ill: Wound, Ostomy, and Continence Nurses Society; 2003.
9. Rithalia S, Kenney L. The art and science of evaluating patient support surfaces. Available at www.worldwidewounds.com/2001/september/Rithalia-and-Kenney/Evaluating-Support-Surfaces.html. Accessed February 22, 2007.
10. Bury E. Navigating the pressure gradient: mapping technology helps clinicians assess and teach. Mobility Management. 2006;5(11):14–24.
11. The Centers for Disease Control and Prevention (CDC) National Center for Injury Prevention and Control. Falls in nursing homes. Available at www.cdc.gov/ncipc/factsheets/nursing.htm. Accessed February 22, 2006.
12. Rubenstein LZ. Preventing falls in the nursing home. JAMA. 1997;278(7):595–596.
13. Rubenstein LZ, Robbins AS, Schulman BL, Rosado J, Osterweil D, Josephson KR. Falls and instability in the eldrly. J Am Geriatr Soc. 1988;36(3):266–278.
14. Thapa PB, Brockman KG, Gideon P, Fought RL, Ray WA. Injurious falls in nonambulatory nursing home residents: a comparative study of circumstances, incidence and risk factors. J Am Geriatr Soc. 1996;44(3):273–278.