Preventing pressure sores in elderly patients: a comparison of seven mattress overlays

Age and Ageing, July, 1995 by M.R. Bliss

Introduction

Pressure relieving supports are now widely used in hospitals and nursing homes, but with little proof of their efficacy [1]. This study was part of a general, randomized controlled trial to compare the efficacy, practicability and cost of alternating pressure (AP) and constant low pressure (CLP) supports for preventing pressure sores in hospital [2]. The aim of this section of the trial was to identify inexpensive and, if possible, non-mechanical CLP overlays effective for patients at long-term risk in continuing-care wards for elderly people.

Method

The study began in Ward 1 (mixed sex) and extended to Wards 2 (female), 3 (female) and 4 (mixed) over two and a half years. Each had one G/E and three or four D/A grade nurses normally on day duty. Medical care was provided by a clinical assistant and one consultant. Almost all the patients were nonambulant, about 90% were demented and 100% incontinent.

Beds: The beds were King's Fund type [3] with Vaperm mattresses. Originally designed to provide pressure relief for spinal injury patients [4] but also used as a general purpose hospital mattress, the Vaperm contains four ventilated layers of foam of decreasing density from 60 kg/[m.sup.3] on the base to 35kg/[m.sup.3] on the surface [5] enclosed in inner and outer covers respectively of two-way-stretch Terry towelling and Platilon (elastic, waterproof, vapour permeable polyurethane sheeting).

Subjects: Patients liable to pressure sores are normally identified by means of prediction scores [6] based on, for example, medical condition, nutrition, mobility and incontinence. However, many chronically disabled patients may have `at risk' scores and yet be well and unlikely to develop sores. We therefore accepted as potential subjects only those who already had superficial breaks in the skin of the pressure areas (Grade 2-3 sores) [7] indicating definite susceptibility. Patients with superficial sores > 5 cm and discoloured areas >2cm diameter were not included as our aim was primarily a study of prevention not healing.

For patients thus identified, their nurses were asked for permission for them to be entered into the trial. With this agreement, the patient was randomly allocated to an experimental overlay by the researcher writing the names of all those available at the time on slips of paper which were folded and offered to the nurse to choose one blind. The designated overlay was then placed on the bed. Patients whom the nurses did not wish to be entered for the trial were left to their care, but they had to agree beforehand that patients accepted into the trial would be given the chosen overlay.

Overlays: Initially, the trial was confined to CLP overlays. The first patients were randomized to either a prototype `Groove' or Spenco mattress. The Groove was a contoured 10-cm thick foam overlay with a 60-cm wide longitudinal gutter in the upper two thirds bevelled to a depth of 8 cm in the centre and with 145 cm wide 4 cm deep longitudinal gutters in the lower third designed to relieve pressure in the pelvic/heel areas respectively. It was enclosed in an adherent polyurethane-coated woven nylon cover. The Spenco was a one-piece cotton hollow-core fibrefill with horizontal cushions protected by a detachable Platilon cover. As the early results suggested a modest benefit of the foam compared with the fibre overlay, the study was expanded to include two marketed slit-foam overlays. The Modular Propad was an 8.5 cm thick foam pad with the upper surface moulded into air-ducted, rounded horizontal blocks, 4 x 5 cm in the sacral and 2 x 5 cm in the head/heels area, with a Platilon cover. The Preventix was a 16-cm thick mat of 8-cm square foam modules of different densities inserted into a flexible PVC frame which allowed their projection to be varied according to the weight/shape of the patient thus providing a variably soft, contoured, slit surface to optimize pressure distribution. It was enclosed in a loose-fitted, waterproof, vapour-permeable, two-way-stretch polyurethane-coated fabric cover with a ventilated base. Another one-piece fibrefill, the Surgicgoods Hollowcore Mattress Pad, with horizontal cushions and one cotton and one waterproofed surface; and a water overlay, the Ardo Watersoft, consisting of three 4-cm deep, partly-filled water cushions with stabilizing baffles, were also introduced.

Finally, we included an AP mattress, the Large Cell Ripplebed. Although the aim of this study had been to identify effective static overlays and avoid the need for mechanical supports, when it appeared that none was likely to provide the degree of protection required, we decided that they should be compared with the Large Cell Ripplebed. Its cost was similar, and despite its well known disadvantages, a motor requiring frequent servicing, noise and poor tube connections [8], the nurses who had used it for many years had found it practical and thought it was effective. It consisted of 14 horizontal cells 10 cm in diameter in the centre, connected in two alternating series powered by a small pump which caused them to inflate and deflate reciprocally underneath the patient every 10 minutes, thus continually changing the supporting points of pressure. It was fitted with a loose cover. As the Ripplebed was one of the main pressure-relieving supports used in the hospital, unlimited numbers were available but in order to reduce bias the nurses were not told which of the current supports were being randomized and at least one low-pressure overlay was always included (Figure 1).