EUROPEAN PRESSURE ULCER ADVISORY PANEL

UTILISATION OF EVIDENCE BASED MEDICINE WITH REFERENCE TO THE PREVENTION AND TREATMENT OF PRESSURE SORES

Professor David Sackett,
Centre of Evidence Based Medicine,
Nuffield Department of Medicine,
Level 5, John Radcliffe Hospital,
Headington, Oxford.

COMPARISON OF FOUR ALTERNATING PRESSURE AIR MATTRESSES USING A TIME BASED PRESSURE THRESHOLD TECHNIQUE AND CONTINUOUS MEASUREMENTS OF TRANSCUTANEOUS GASES.

Dr S Rithalia,
University of Salford

and

Dr M Gonsalkorale,
Ladywell Hospital,
Salford,
Manchester, M6 6PU.

INTRODUCTION
Since the action of an alternating pressure air mattress (APAM) is time varying, it is important that any pressure relieving 'performance' indicator takes a this factor into account. We have developed a computerised system which continuously measures the air pressure (AP), interface pressure (IP), pressure-time cycle characteristics, tanscutaneous oxygen (tcPo2) carbon dioxide (tcPCo2) tension data. The software, developed using a graphically-orientated programming tool, expresses pressure relief (PR) as a percentage of the cycle. This allows like-for-like comparisons to be made choosing any arbitrary common multiple of the cycle times (for example, one hour requires five 12-minute cycles or six 10-minute cycles).

MATERIALS AND METHODS
The present study evaluated four different commercially available APAMs. These included three AlphXcell, the Astec 345, the Biwave Plus and the PPS 2000). Eleven healthy adult volunteers (7 males, 4 females) participated in the study. Their ages, weights and heights ranged from 21 to 55 (mean + SD, 31.1 + 10.3) years, 62 to 99 kg (71.6 + 0.10) m respectively. Measurements of interface pressure and transcutaneous gas tensions were carried out under the sacrum when each subject was lying supine on the mattress. For pressure relief (PR) calculations as a percentage of the cycle the IP thresholds were set at 30, 20 and 10 mm HG. Data were expressed as the mean + standard deviation (mean + SD).

RESULTS
The time intervals calculated over 60 minutes when IP remained below three arbitrarily chosen thresholds of 30, 20 and 10 mm Hg were: 56, 43 and 29 minutes for the AlphXcell; 54, 39 and 26 for Astec; 35, 29 and 23 minutes for Biwave; 33, 19 and 8 minutes for PPS mattress. The Area under the tcPO2 and tcPCO2 curves (oxygen debt and carbon dioxide surplus) in arbitrary units were: 688 and 133 for the AlphaXcell; 509 and 139 for Astec; 810 and 151 for Biwave 859 and 208 for PPS mattress. There was no significant difference in the performance characteristics of the AlphaXcell and the Astec. The PPS mattress gave consistently higher peak interface pressures, oxygen debt and carbon dioxide surplus indicating comparatively poor performance in all cases.

DISCUSSION
The results of this investigation indicated that all the APAMs included in the study are capable of providing very low or near zero interface pressures at the sacrum as long as the inflated cells can support the body weight. For optimum pressure relief an alternating pressure mattress must be correctly inflated. The inflation pressure should be directly proportional to the patient's weight and surface area in contact with the support surface. Apart from better pressure relief characteristics, there are many other parameters which should be considered before making choice of a support surface for a patient. These include comfort, stability, cost, durability, ease of use and maintenance. Ultimately, the effectiveness of these devices can only be fully demonstrated by controlled clinical trials. 

RISK ASSESSMENT TOOLS IN THE PREVENTION OF PRESSURE ULCERS

Jeen R E Haalboom and Frik Ruskens,
Department of Internal Medicine and of Clinical Epidemiology,
University Hospital Utrecht,
The Netherlands.

INTRODUCTION
Preventative measures cost money. It is economically important to use preventative measures only in patients at risk and if possible not in patients with no risk. This is also true in the prevention of pressure ulcers. Especially the use of special mattresses and beds is expensive and the development of 'risk scores' is worth while. None of the frequently used 'risk scores' is satisfactorily validated. Especially the individual values of the items used in the scores are not known. We performed a case control study in which eventually 107 patients were included, 65 patients with pressure ulcers (all stages included; depts of internal medicine, neurology and surgery) and 42 controls with the same age and medical diagnosis, investigated were the scales of Norton, Gosnell, Knoll, Waterlow, Braden, Douglas and the Dutch Consensus Score (CBO, in 1985 especially designed for use in the Netherlands, based on Norton, but with the adding of parameters of neurology, feeding, use of medication). All scales were evaluated by means of logistic univariate analysis. The individual items of each score were analysed by means of multiple logistic regression analysis and finally the three best scoring items were investigated if they were a new risk score.

RESULTS
1. Results of univariate analysis on risk scores:

Results of Multivariate analysis of three top-scoring items of all score lists:

Item                         p-value              Odds ratio              95% c.i.

Incontinence           0,002                   4,644                 1,798-11,99

Neurology               0,062                   2,365                 0,956-5,849

Nutrit. cond.            0,048                   2,587                 1,007-6,645

CONCLUSION
Of all risk scores only the Norton, Douglas and CBO score predict patients at risk correctly. The use of the other scores implicates the use of preventative measures in patient not really at risk. In the three correct scores only incontinence for urine and/or faeces, the neurological status (spinal cord lesions, hemiplegia, coma) and the nutritional status (bad condition, cachexia) are responsible for the outcome of the whole list. This implicates that a new risk score, only consisting of these three items, is enough to predict the development of pressure ulcers. Since this investigation was performed in a university hospital with more severely ill patients it is necessary that the investigations are repeated on a larger scale in other types of health care institutions.

The prevention Fund of the Ministry of Health (the Netherlands) has given a grant to perform this study in 25,000 patients admitted in the next two years.