Product POINTERS

Prediction, prevention of heel pressure ulcers

By Liza G. Ovington, PhD, CWS
President
Ovington & Associates
Ft. Lauderdale, FL

The treatment of pressure ulcers is an enormous health care expenditure in terms of time and money. Strategies and products for pressure ulcer prevention abound, but evidence of efficacy is rare.

One of the most difficult anatomical areas to be addressed by preventive products is the heel, which is the second most common site of pressure ulcer formation after the sacrum.

Literature shows that the incidence (or number of new cases occurring over a specific time period) of heel pressure ulcers ranges from 19% to 32% of a given population. Prevalence (or number of cases at a specific point in time) of heel pressure ulcers has been documented in four National Pressure Ulcer Prevalence Surveys conducted in 1989, 1991, 1993, and 1995.1

The heel is the only anatomical site to show an increase in pressure ulcer prevalence each year (except for a slight decrease in 1995). Prevalence of pressure ulcers in other anatomical sites either remained constant or declined over the course of the surveys. The 1995 survey involved 265 acute care hospitals and 39,874 patients.

Little has been published about the etiology of pressure ulcers on the heels, with more attention given to prevention. A 1997 study tackled the issue of predicting heel pressure ulcers by examining potential contributing factors.2

The researchers undertook a comprehensive review of the literature and multidisciplinary discussion to identify more than 150 potential contributing factors. They then carried out a prospective, descriptive cohort study to examine these factors.

The study, which took place in a 280-bed regional hospital, recruited patients from four nursing units that had been shown to have a high prevalence of heel pressure ulcers based on a 1993 survey. Of 432 patients admitted to these units, 209 were enrolled in the study. Reasons for patients not being enrolled were usually related to a transfer from the unit or a short length of stay. Multidisciplinary teams performed chart reviews, collected demographics, and performed assessments of the heels during the course of the study. Of the 209 patients enrolled in the study, 56 (26.8%) developed pressure ulcers on the heel(s).

Data variables between patients who developed heel ulcers and patients who did not were compared and statistically analyzed. The more than 150 potential contributing factors were reduced to fewer than 20 significant factors. Of these, the team eliminated those that related more to prevention than to prediction and those not readily available for use in a predictive tool.

A second prospective descriptive cohort study was then undertaken to validate factors identified in the prior study. Another 291 patients were enrolled. Of the 291 enrolled, 63 (21.7%) developed heel pressure ulcers. Specific variables found to be significantly different (and therefore potentially predictive) between patients who developed ulcers and those who did not are listed below:

• age;

• length of stay;

• admitted with pressure ulcer;

• incontinence;

• limb weakness;

• absent popliteal and posterior tibial pulses;

• circulatory problems of the lower extremities;

• diagnosis of congestive heart failure;

• total Braden risk assessment score;

• Braden subscale scores in moisture and friction/ shear.

The team then attempted to devise a predictive tool for the risk of developing a heel ulcer based on these variables. However, they found that no combination of variables gave a higher specificity and sensitivity than the overall Braden Scale. The study concluded that while the Braden Scale may not be perfect, it remains the best available tool for predicting pressure ulcers on the heel.

It may be advisable to pay particular attention to the subscores in moisture and friction/shear with regard to heel ulcers. It is surprising that incontinence and Braden moisture scores were found to be significant in heel ulcer development because many assume that these factors affect the sacral area as opposed to the heels. The study authors posit that there may be physical factors that predispose a patient for incontinence that also affect heel ulcer formation.

The heels are difficult to address in terms of pressure relief for a number of reasons. The heel is a very small area and therefore subject to very high interface pressures as it rests on a surface. Patients often rotate their legs or hips to one side or another and may dislodge or interfere with a positioning device. Patients with fractures of the hip or lower extremity are especially susceptible to heel pressure ulcers, and it is thought that pain and immobility are significant contributors. Hospital sheets may be tucked in tightly, providing little room for the foot at the bottom of the bed.

It has been shown that while a variety of support surfaces (overlays and mattresses) address pressure reduction in the pelvic area, few if any adequately address pressure reduction in the area of the heels. If specialty products designed to address the heel are not properly fitted, they may create pressure in other places on the lower extremity.

Several studies suggest that the appropriate use of a standard hospital head pillow positioned beneath the legs such that the heels are suspended off the bed surface is more effective than many specialty products.3,4,5 Literature also shows that certain practices thought to aid in prevention of heel ulcers may actually contribute to their development.

Use of a latex glove filled with 260 ml of water to cushion heels was shown to generate interface pressures that were higher than if the heel was simply allowed to rest on the bed. Interface pressure between the heel and the water-filled glove in 40 patients averaged 144.6 mm Hg, while interface pressures between the heel and the bed averaged 126.5 mm Hg.6

The most effective strategy is to suspend the heel completely rather than to cushion it. The bottom line for prevention of heel pressure ulcers lies not with any one product but with assessment of risk, ongoing assessment of the heels, and diligence regarding positioning of the patient.

References

1. Barczak CA, Barnett RI, Childs EJ, Bosley LM. Fourth national pressure ulcer survey. Advances in Wound Care 1997; 10:8-26.

2. Tourtual DM, Gill RD, Talati K, et al. Predictors of hospital acquired heel pressure ulcers. Ostomy Wound Management 1997; 43:24-28, 30, 32-34 passim.

3. Tymec AC, Vollman K, Pieper B. A comparison of two pressure-relieving devices on the prevention of heel pressure ulcers. Advances in Wound Care 1997; 10:39-44.

4. De Keyser G, Dejaeger H, De Meyst H, Evers G. Pressure reducing effects of heel protectors. Advances in Wound Care 1994; 4:30-32.

5. Smith I. Two heel aids. Nursing Times 1984; 80:35-39.

6. Williams C. Using water filled gloves for pressure relief on heels. Journal of Wound Care 1993; 2:345-348.