PRESSURE ULCERS: BACK TO BASICS – THE FUNDAMENTAL PRINCIPLES
Eighth EPUAP Open Meeting, Aberdeen Conference Centre, Scotland, 5–7 May 2005
Selected Abstracts (continued)

INTERFACE PRESSURE OR TISSUE PERFUSION MEASUREMENTS?
Goossens R.H.M.1, Van Veelen, M.A.1 and Rithalia S.V.S.2
(1) Delft University of Technology, Faculty of Industrial Design, Department of Applied Ergonomics and Design, Landbergstraat 15, 2628 CE Delft, The Netherlands.
(2) University of Salford, School of Health Care Professions, United Kingdom.

Introduction
The parameter of the maximum interface pressure (IP) is still often used to evaluate different mattresses. This parameter is used because it is thought to highly correlate with blood perfusion in the tissue. Since most (42%) of the pressure ulcers among their high-risk patients occurred on the heels, the heel is an interesting part on the body to test this correlation between IP and blood perfusion.

The aim of the study is to investigate the performance of three alternating pressure mattresses, using both interface pressure and laser Doppler perfusion measurements. This work is performed under laboratory conditions with healthy volunteers.

Methods
Three alternating pressure mattress commercially available on the market were used. They included Duo Care Plus (Doove Medical, The Netherlands), Proficare (KCI Medical, United Kingdom) and AUTOlogic200 (Huntleigh Healthcare, United Kingdom).

Each mattress was set up according to the manufacturers instructions and covered with a cotton sheet. Each subject rested upon the mattress for at least two cycles or until a stable trace was seen; between each test the subject was instructed to ambulate for at least five minutes to counter the effect of muscle relaxation. The full methodology has been previously described (1). Interface pressure measurements on the heel were conducted with the Oxford Pressure Monitor (OPM, Talley Group Ltd, Hants, UK). Laser Doppler perfusion measurements were performed using the Vasamedics Laserflo BPM2 Laser Doppler instrument with the Softflo 90mm probe (Vasamedics Inc, MN, USA). The interface pressure probe was placed under the right heel and the laser Doppler perfusion probe placed under the left heel, whilst ensuring that both heels were located along the centre of the same cell. The measurements were performed under laboratory conditions on eleven able-bodied adult volunteers of which six were males and five females (23.9 s.d. 2.1 years, weights 65.6 s.d. 12.4 kg, heights 1.76 s.d. 0.84 m, Body mass index BMI 21.0 ± 2.4 kg/cm2).

For each mattress the mean maximum and minimum IP and mean area under the perfusion curve were measured. Statistical analysis is performed by means of the Mann Whitney U-test using SPSS 10.0, with a level of significance a = 0.05.

Results
• There was no significant difference in maximum interface pressure (IP) for the three mattresses.
• The AUTOlogic gave a statistically significant enhanced perfusion per cycle when compared to other two mattresses (Duo Care Plus, p = 0.03 or Proficare, p = 0.01)

Summary
A test on the heels of eleven healthy subjects was performed using three APAMs that were based upon similar technologies, that is, alternately inflating and deflating the mattress. The test showed that there was no significant difference in maximum or peak interface pressure for the three mattresses. The AUTOlogic gave a statistically significant enhanced perfusion per cycle when compared to other two mattresses (Duo Care Plus, p = 0.03 or Proficare, p = 0.01) Literature Rithalia SVS, Russell L. Evaluation of alternating pressure air mattresses using a time based pressure threshold technique and laser Doppler micro-vascular perfusion measurements on the heel. 6th European Pressure Ulcer Advisory Panel Open Meeting, Budapest, Hungary, 18–21 September 2002.

EFFECT OF A NEW PRESSURE ULCER PREVENTIVE DRESSING ON SHEAR FORCE REDUCTION
G. Nakagami1, C. Konya2, A. Kitagawa1, E. Tadaka1, M.
Urasaki1 and H. Sanada1
(1) Division of Health Sciences and Nursing, Graduate School of Medicine, The University of Tokyo, Japan.
(2) School of Health Sciences, Faculty of Medicine, Kanazawa University, Japan.

Introduction
Shear force, in addition to pressure, is one of the main causes of pressure ulcer development. To reduce the shear force near bony prominences, application of a transparent film dressing is recommended by the AHCPR clinical practice guidelines. However, the coefficient of kinetic friction of the film dressing is so high that it can be easily peeled off, leading to wrinkle formation. This makes it difficult to determine its efficacy as a pressure ulcer preventive agent. We developed a new hydrocolloid dressing (PPD–02) for pressure ulcer prevention in cooperation with ALCARE Corporation in Japan. A 76.6% reduction in touch area was achieved by including multifilament nylon fiber in the external layer in a reticular pattern. The purpose of the present study was to compare the shear force with application of PPD-02 and that with film dressings in a clinical setting.

Methods
This study was a quasi-experimentally designed crossover clinical trial. Participants were thirty elderly patients (5 males, 25 females; mean age: 86.4 ± 8.0) hospitalized in a geriatrics hospital in Japan; all had a Braden score of under 14 (mean: 10.1 ± 1.1). Informed consent was obtained from all patients. A shear force and pressure sensor (Predia, Molten Corporation, Japan) including a strain gauge and oval airbag-type pressure sensor was attached to the heel using double-sided tape. The target dressing was then applied over the sensor and on the opposite heel then both heels were placed on a block board covered by a sheet. Shear force was measured at 0.2-second intervals while the sheet was manually pulled at a velocity of around 5cm per second. Shear force was determined by averaging the stable shear force lasting for two seconds. The pressure of the heel was measured just before pulling the sheet.

Results
The mean pressure with the PPD–02 and film dressing was 70.7 ± 16.5 and 70.2 ± 15.2mmHg, respectively (not statistically significant; p = 0.4198, paired t-test), and the shear force produced during pulling of the sheet was 2.2 ± 1.4 and 11.7 ± 5.8N, respectively (statistically significant; p < 0.001, Wilcoxon signed-rank test).

Summary
The results indicate the necessity for pressure ulcer dressings to be designed with a slippery external surface. We showed that PPD–02 could reduce shear force compared to film dressings, suggesting that this new dressing is beneficial in pressure ulcer prevention.

THE EFFECTS OF APPLIED DRESSINGS ON SHEAR STRESS IN THE UPPER AND SUBCUTANEOUS LAYERS OF THE SKIN
Takehiko Ohura1, Makoto Takahashi2, Kaoru Nishide3, Yutaka Chiba4 and Norihiko Ohura5
(1) Kohjinkai, Pressure Ulcer and Wound Healing Institute.
(2) Hokkaido University Graduate School Department of Engineering. (3) Smith & Nephew KK, Wound Management Division, (4) Molten Co. (5) Saitama Medical University Department of Plastic Surgery.

Objective
The purpose of this study was to investigate how shear stress is affected by the dressing surface after application, its effect on the skin and subcutaneous tissues, and the evaluation of preventative measures using a pigskin model.

Method
A basic measuring apparatus, friction tester (RTE–1210, Orpemtec), was used and covered with cotton and a 1kg weight of metal beads was put in a trapezoid shaped frame and moved by pulling at a rate of 5cm/30sec. Shear stress in the upper layer of the pigskin was then measured (as Upper Layer) and the pressure and shear in the lower layer of the pigskin (as Subcutaneous). In the pigskin model, the 0.875 cm/sq shear sensor, mog10 sensor (Molten Co.) was implanted and the pressure and shear stress were measured at the same time with a Predia Mini Sensor (Molten Co.) applied on the plate subcutaneously. The 0.5cm thickness of the sensor represented the bony prominence.

Results
In the control (no dressing, pig skin only), the Subcutaneous shear stress was about 0.47N and the Upper Layer shear stress was greater at about 1.34N. When the shear stress at the Upper Layer and Subcutaneous Layer was increased from zero the Subcutaneous pressure was also increased from about 7mmHg to about 16.5mmHg. When Subcutaneous
shear stress was stable at about 0.3N, then Subcutaneous pressure became stable at about 12mmHg. When various dressings were applied, the shear stress on the Upper and Subcutaneous layers and the pressure were all decreased more than the value of the Control but the degree of decrease was variable between dressings. The peak value of the Upper Layer shear stress in the Control was about 1.34N whereas the lowest value in the various dressing groups was about 0.4N which is about 1/3 of the Control value. In the Subcutaneous shear stress, the Control value was about 0.47N whereas the lowest value in the dressing groups was about 0.15N which is also 1/3 of the Control value. The dressings used in this study were polyurethane foam, hydropolymer, polyurethane film and hydrocolloids, however, it appears that the friction coefficient at the surface and the material quality, hardness and the adhesive method will all have an effect.

Conclusions
1. In dressings that are used clinically for the prevention of pressure ulcers we have now found clear evidence that decreasing shear stress will produce a preventative effect.
2. It is assumed that the friction coefficient in the skin surface and the degree of flexibility in the dressing itself will work effectively against shear stress although the relationship is not a simple one as demonstrated in the dressings used for this experiment.
3. Where dressings are applied to the skin covering a bony prominence, the maximum pressure during movement will be 1.5–2.0 times higher than the static pressure.

A PILOT STUDY OF A NEW METHOD FOR MEASURING THE CO-EFFICIENT OF FRICTION BETWEEN THE SKIN AND MATERIALS
Clarke-O’Neill S, Cottenden A, Fader M

Introduction
Pressure, shear and friction are considered to be the key extrinsic risk factors involved in tissue damage. Hydrated skin has a higher co-efficient of friction than dry skin, and is more susceptible to abrasion damage (Sivamani et al, 2003, Zimmerer et al, 1986). Current methods for measuring friction use a probe that is pressed against the skin at a known ‘normal’ force, it is then possible to measure the skin’s frictional resistance to the movement of the probe (Sivamani et al, 2003). However, whilst these methods are suitable for examining the effect of hydration or topical preparations on the skin, they do no allow insight into the interaction between the skin and materials worn close to the skin e.g., clothing or continence products. This paper describes the development of a new method for measuring the levels of friction on skin, incorporating strips of material, in order to measure the interaction between materials and the skin.

Methods
A laboratory-based quasi-experimental design was used. A Miniature Tensile Tester (Diastron Ltd) connected to a PC, was adapted to include a custom-built armrest. This equipment was designed to pull strips of absorbent continence pad material across the volar forearm of volunteers in order to measure the friction between the material and the skin, this has been termed ‘stick and slip’ friction. For this study the equipment was set to a pull the material for 60mm at a maximum force of 1000gmf, at a rate of 150mm/min. A sample of five young (range 31–44yrs) and five senior (range 67–85yrs) female volunteers visited the department on three occasions and had three repeat measurements taken on their lower forearm, 75mm from the wrist crease on both dry and wetted skin. Skin was wetted using a standard reproducible method developed at UCL, and all experiments were carried out in an environmentally controlled room with a temperature of 23°C and a relative humidity (RH) of 50%.

Results
The maximum force for wet skin was calculated for each measurement, this represents the point at which the material being pulled across the skin stops sticking and slips relative to the skin. For two volunteers (one young, one senior) the exact value of the maximum force for some measurements were unknown as they exceeded the maximum force of the programme. The intra-subject reliability (test-retest) together with inter-subject variability were calculated for the measurements on dry and wet skin from each of the ten volunteers, the inter-subject variability ranged from 6.8–35.2%. There were large significant differences in mean force between dry and wet skin, shown in the histogram below, (P = < .001, CI 646.16-825.24). There were no differences in mean force between wet and dry skin of the younger and senior volunteers. The amount of distortion of the skin as the material was pulled across, at maximum force before the point of ‘slip’ was also measured. Observation of forearm skin suggested that senior skin tended to be more flaccid and there was a trend for the skin to be extended for greater distances in the senior volunteers than the younger volunteers however, the differences were not statistically significant.

Summary
The preliminary results show that there are important differences in mean force for wet and dry skin, wet skin was subjected to higher friction and could be at increased risk of damage. Although it is not possible to quantify a level at which damage to the skin may occur, this large difference is likely to have clinical significance for individuals who have wet pad materials in contact with their skin. The trend for the skin of senior volunteers to distort for greater distances than younger skin merits further investigation, it is likely that there was insufficient data in this study to find an association. Similarly there did appear to be a trend for higher mean forces for wet skin, in senior volunteers, that requires further study. Refinement of the method is needed to improve reliability but it appears promising for measuring clinical friction co-efficients with materials.

ALTERNATING PRESSURE AIR MATTRESSES (AP-AM) VS. CONTINUOUS LOW PRESSURE AIR MATTRESS (CLP AM): IS THERE A CLINICAL DIFFERENCE IN THE PREVENTION OF PRESSURE ULCERS IN A HOSPITAL SETTING?
Andrea Cavicchioli1, RN and Gianna Carella2, MD
(1) Tissue Viability Nurse, Az. USL Modena, Italy
(2) Qeriatrician, 1st. Ger. “C . Golgi”, Abbiategrasso, Italy

Introduction
There is limited evidence available to support which type of air mattress has the best clinical performance, Alternating Pressure Air Mattress (AP-AM) versus a Continuous Low Pressure Air Mattress (CLP-AM) for patients at risk for developing pressure ulcers. We conducted a pilot study to quantify what clinical difference we could assess in the incidence of pressure ulcers in acute and post-acute care settings.

Methods
For this pilot we adopt a mattress, DUO 2® (Hill-Rom®) that is able to work in two different operational modes: Alternating Pressure or Continuous Low Pressure.

1. We randomised the two arms of the trial adopting an envelope randomization scheme where the Braden pressure ulcer risk score was obtained and if the Mobility or Activity levels were three or less, and did not have more than one stage-one pressure ulcer, they were given an envelope for study randomisation.

2. If patient’s were found to be candidates for study, the Team opened the envelope and set the mattress to operate in compliance with the instructions (AP or CLP). At that time, the patient’s initials, along with the patient’s specific pressure ulcer risk data, and current pressure ulcer status was obtained.

3. Patients were excluded if 1) the patient was found to not be at risk, or the patient with a Braden subscale Activity or Mobility greater than 3, or 2) the patient had more than one pressure sore at study entry or the patient’s pressure sore was found to be stage II (EPUAP scale) or greater.

After two weeks the ward team call the external trained observer. They set the mattress in the pMax position. In this manner it is impossible for the observer to understand the working condition of the mattress. The observer then assesses the patient’s current Braden score and the presence or absence and stage of pressure sores.

Results
At present (Jan 2005) we have enrolled 56 patients in three hospitals. The units were principally internal or long-termcare. Sometimes the patients were transferred between two units, without any disruption of the mattress regimen. Normal pressure ulcer prevention protocols were in place across all units studied. To date, 12 males and 34 females have been enrolled.

We have zero incidence of new pressure sores in both arms of the study. Four patients at the beginning of the observation period had a single stage-one lesion. Three of these concluded the study and one died before the end of it. Of the three, two healed during the two weeks of the study and the last maintained the same ulcer status. We did not observe any clinical differences in the mattress performance (CLP or AP) for the two-week study observation period.

Summary
We have started a pilot of a RCT to evaluate the performance of a mattress (DUO 2® Hill-Rom) that is able to work both as an AP-AM or a CLP-AM. The current results are equal with zero incidence of pressure sores in both the operational
modes.

NUTRITIONAL ASPECTS IN PRESSURE ULCER CARE
J.M.G.A. Schols, MD, PhD
Tilburg University and Maastricht University, The Netherlands J.M.G.A.Schols@uvt.nl

In this presentation some relevant aspects regarding nutrition in PU-care are presented. Attention is focused on the importance of nutritional assessment and nutritional intervention in patients with PU, of which a lot often are in a bad nutritional shape. Nutrition deserves a transparent place in PU-prevention and treatment guidelines. To facilitate this EPUAP itself recently has developed Nutritional Guidelines for Pressure Ulcer Prevention mid Treatment. These guidelines have been translated in at least seven languages and can be downloaded from the EPUAP website: www.epuap.org/guidelines/index.html.

Of course, these guidelines now have to be implemented broadly to achieve a better quality of care for PU patients. In the latter part of the presentation some important implementation hazards are discussed with special attention for the cost effectiveness of nutritional therapy.