Skip navigation

Pressure Sores: Five reviews & an RCT

Pressure sores are a big problem, with a prevalence of 5 to 9% and more than 70% occurring in patients over 70 years. They are often blamed (falsely) on poor nursing care, but are best seen as a potentially preventable complication of acute immobility illness. Prevention involves a variety of issues, including assessment of risk, appropriateness of care, and the effectiveness of special equipment.

Bandolier became interested in pressure sores after reading an excellent randomised study of a pressure reducing mattress in Lancet earlier this year; other studies were sought by searching the literature, with little result. We did find a number of good reviews looking at pressure reducing systems and other facets of pressure sores.

While well written and thorough, they all made the same depressing point - that there are few if any well conducted randomised controlled trials of effectiveness in this area. A survey of 48 products sold for pressure sore prevention revealed that only two had been subjected to RCTs to confirm their effectiveness [1].

Bandolier is well aware that few companies making medical equipment (rather than drugs) can produce evidence of effectiveness when asked to do so. Even so, with the financial costs of pressure sore treatment estimated as high as £755 million a year in the UK [2], with concomitant stress on patients, staff, beds and budgets, the professions might have made a greater contribution. This is not just a hospital problem: with more patients being nursed by carers at home, the expertise, techniques and equipment for pressure sore prevention and management need also to be available in the community. The issue needs central co-ordination with a district wide strategy, as suggested by a King's Fund report of 1990.

Right now, neither purchasers nor providers of health care have much to go on, other than standard good practice. That includes guidelines such as turning acutely ill bedridden patients every two hours, a practice developed during the war because that was how long it took the staff to turn all the patients in a ward! There are no effectiveness data for turning two-hourly.

In order, therefore, to try to increase interest in the subject of pressure sores, we report below on one excellent RCT and five relatively recent well written and useful reviews of different areas of this problem.

Epidemiology and current management concepts



This review [1] is from Young & Dobrzanski from Bradford. It covers epidemiology and mechanisms of formation of sores, together with sections on prevention and management.

Cost



Pressure sores are expensive. Estimates of the total cost to the NHS range from £150 million in 1982 to £750 million now [2]. A full thickness sacral sore extends hospital stay by over 25 weeks at a cost of £26,000. This includes all the extra staffing, drugs and dressings as well as hospital overheads. The costs of lost opportunity are even greater - for each sacral pressure sore which is prevented it is possible to undertake 16 total hip replacements. This emphasises the need for prevention.

Incidence & Prevalence



The idea that sores develop only in long-stay geriatric patients is far from the truth. Most pressure sores are to be found in acute hospital wards, though this is hardly well documented. A survey in the `60s showed that the incidence of sores after admission to a geriatric unit was 24%, with the majority occurring in the first two weeks after admission.

Prevalence rates between 5.3% and 8.8% have been recorded in large studies of hospital and community patients. About 70% occur in those aged over 70 years, though some younger groups such as cerebral palsy and spinal cord lesions also have high prevalence, as do patients with fractured neck of femur. In the latter group, about two-thirds develop pressure sores, especially on the heels.

Mortality



The relative mortality of those with pressure sores has been reported to be five times higher than those without sores. Audit has shown pressure sores to be a primary cause of death in as many as 6% of patients admitted to geriatric wards and a major contributing factor in a further 6%. Pressure sores do not figure highly as a cause of death on death certificates, and so the problem may be seriously underestimated from such sources.

Prevention



The article gives brief descriptions of systems which have been shown to have effectiveness in prevention, but goes into few details.

Management



A whole range of treatments including airwave and polystyrene bead systems is reviewed, each briefly. The depressing repetition that none of the treatments has evidence of effectiveness is topped off by a description of the use of chlorinated solutions. "Despite widespread use for over 70 years on all types of dirty wounds, it is not clear if these solutions actually work........It is important to appreciate that chlorinated solutions kill healthy cells. If ulcer improvement occurs it may be despite their use rather than because of it."

Pressure ulcers and the elderly



447 papers (1980-1990) were found via MEDLINE [3]. Forty four made it into the review, which was focused on the elderly.

There are good sections on prevention strategies and treatment and management, though again the main theme is the lack of good clinical studies of effectiveness. This review is useful mainly for the references, and the tantalising hints from some of the reports that the right strategy can crack the problem. These include a Swiss report that a combination of soft bedding support and regular turning could reduce the incidence of pressure sores to near zero and the effects of intensive educational programmes.

Nutrition and pressure sores



Another American nurse, Rosalind Breslow, has researched the literature from 1943 to 1989 concerning nutritional status and dietary intake of patients with pressure sores [4]. Few of the studies she reviewed were blind, none randomised, many were retrospective evaluations from notes, and most studied small numbers of patients. The review has a limited number of references (20) and has three main and well recognised conclusions.

Proteins



There is a strong association between protein-calorie malnutrition and pressure sores. Low serum total proteins, albumin and haemoglobin as well as low lymphocyte counts have been shown to be associated with higher rates of pressure sore formation in a number of studies. In one survey of 634 hospital patients, for each 10 g/L reduction in serum albumin there was a three-fold increase in the chance of having a pressure sore.

A number of studies indicated that increased nutrition intake of protein and calories improved the healing rate of pressure sores.

Ascorbic acid



Ascorbic acid is necessary for the formation of hydroxyproline from proline; hydroxyproline is an essential constituent of collagen. In a prospective double-blind study of ascorbic acid (1 gram per day) in 20 patients, the 10 who received placebo had reduction in pressure sore area of 43% over one month. The ten who received ascorbic acid had much higher tissue levels, and had a reduction in pressure sore area of 84% (p<0.005).

Zinc



While serum zinc is apparently lower in patients with pressure sores, dietary supplementation with zinc has not been shown to be effective in aiding healing in any study.

Review of pressure reduction device studies



A third American nurse, Judith Hedrick-Thompson, has reviewed five studies on devices which reduce pressure [5] and should therefore aid in prevention of pressure sores. Capillary blood flow pressure ranges between 22 and 32 mm Hg; when external pressure is above this, blood flow is obstructed and circulation reduced, setting the stage for pressure sores. Pressure reduction devices should spread the pressure between the patient and the bed and avoid pressures above 35 mm Hg, especially at sacrum, trochanters and heels.

All five studies reviewed looked at healthy volunteers and measured interface pressures with a variety of devices. The products were those found in the United States, and the results are not entirely applicable in the UK, but the figure below aggregates data from the review to give an idea of the results found with different types of products.

Over a number of studies, each of which used up to 15 volunteers, standard hospital beds produced average interface pressures at the sacrum of 32 mm Hg, with much higher interface pressures at trochanters and heels. Foam (either 2 or 4 inches thick) did reduce the pressures somewhat, but not significantly below 32 mm Hg at any site. Only the air loss beds and mattresses produced interface pressures significantly below the critical level at sacrum (18 mm Hg) and trochanter (26 mm Hg). Several devices were intermediate between foam and air loss beds.

This is relatively simple science, easily performed in non-invasive ways with volunteer subjects and which can provide good indicative information that devices intended for pressure sore prevention are likely to be effective. With a very large number of such devices available, this area is crying out for a "Which?" type of survey even before randomised controlled trials for effectiveness are begun.

Overview of RCTs of alternating pressure supports



This review [6] by Mary Bliss and Janice Thomas from London is one of a series which appeared last year. The first part [7] highlighted the importance of referring to clinical randomised controlled trials when making purchasing decisions regarding pressure-relieving mattresses, and should be a well thumbed reprint on the desks of people making purchasing decisions.

Bliss & Thomas [6] examined five randomised controlled trials of the benefits of different types of alternating pressure mattresses. They came up with four key points:-

  • Large-cell alternating pressure mattresses are more effective than small-cell mattresses in preventing pressure sores.
  • Mattresses must be sufficiently robust not to break down in use.
  • Clinical trials are often faulty and therefore need to be read carefully.
  • Control regimens must be fully described.

This review is useful, not because it gives any indication of what to purchase in what circumstance, but Bliss & Thomas do point out clearly the faults in the studies (including one of their own) which makes it easier to design studies which are useful for purchasers.

A third article in the series deals with trials concerned with low pressure supports.

RCT of pressure decreasing mattresses



This RCT compared the Comfortex DeCube mattress with a standard hospital mattress used in The Netherlands [8]. The DeCube mattress uses a special surface covering; small cubes of the mattress under bony protuberances of the patient can be removed to reduce pressure locally.

The study was carried out in 44 patients with femoral-neck fractures (mean age 85 years) who have a high risk of developing pressure sores. Patients were randomised to one type of mattress; the study was not blind.

Patients were examined one and two weeks after surgery, and the presence and grade of sores on the sacrum, trochanters, shoulders, heels and elsewhere were noted independently by two physicians.

The distribution of maximum pressure sore gradings differed significantly at one and two weeks (p <0.01). Of patients nursed on the DeCube mattress, 25% had clinically relevant sores (grade 2 or more) at one week and 24% at two weeks. Figures for the standard mattress were 64% and 68% respectively.

The occurrence of pressure scores with high grades was much more frequent in patients nursed on the standard mattress than in those nursed on the DeCube mattress.

This was a well conducted study which showed clearly the benefits in pressure sore reduction accruing from the use of one product. It is an example of the type of information needed by purchasers and providers of health care.

The future



A number of district health authorities are now tackling pressure sores in a co-ordinated manner using local guidelines. It is, however, undeniable that guidelines are likely to be based on inadequate information due to the lack of RCTs.

In the absence of adequate effectiveness information, purchasing the cheapest product would seem to make sense. Manufacturers should urgently seek to conduct studies of effectiveness for their products.

References:



  1. JB Young ,S Dobrzanski. Pressure sores: epidemiological and current management concepts. Drugs & Ageing 1992 2: 42-57.
  2. P West, J Priestley. Money under the mattress. Health Service Journal 1994, 14 April, 20-22.
  3. M Krainski. Pressure Ulcers and the Elderly: A Review of the Literature, 1980-1990. Ostomy/Wound Management 1992 38: 22-37.
  4. R Breslow. Nutritional Status and Dietary Intake of Patients with Pressure Ulcers: Review of the Research Literature 1943 to 1989. Decubitus 1991 4: 16-21.
  5. JK Hedrick-Thompson. A review of Pressure Reduction Device Studies. Journal of Vascular Nursing 1992 X: 3-5.
  6. MR Bliss, JM Thomas. An investigative approach: An overview of randomised controlled trials of alternating pressure supports. Professional Nurse 1993 8: 437-44.
  7. MR Bliss, JM Thomas. Clinical trials with budgetary implications: establishing randomised trials of pressure-relieving equipment. Professional Nurse 1993 8: 292-6.
  8. A Hofman, RH Geelkerken, J Wille, JJ Hamming, J Hermans, PJ Breslau. Pressure sores and pressure-decreasing mattresses: controlled clinical trial. Lancet 1994 343: 568-71.



next story in this issue