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A clinical evaluation of an alternating-pressure mattress replacement system in hospital and residential care settings
6
Journal of Tissue Viability 2000 Vol 10 No 1
A clinical evaluation of an alternatingpressure mattress replacement system in hospital and residential care settings Lucy Land 1, Debra Evans 1, Amanda Geary2 and Carl Taylor 1 of Central England in Birmingham, Health and Social Care Research Centre, Faculty of Health and Community Care, Edgbaston, Birmingham, and 2 City Hospital NHS Trust, Dudley Road, Birmingham 1University
An observational study was carried out to compare wound healing on alternating-pressure mattress replacement systems (APMRS) and other surfaces in an elderly population in acute and residential care settings. Subjects were assessed for the reduction in their pressure ulcers at approximately two weeks and per day, and a visual analogue scale was used to record the patients' comfort. Seven and ten subjects were allocated to the Nimbus III APMRS (Huntleigh Healthcare Ltd) in the hospital and residential care settings respectively. There was no significant difference in the healing of the subjects' sores in the two areas either at two weeks or per day. Five people were allocated to control surfaces in the hospital setting (mainly APMRS; Pegasus Airwave, Pegasus Egerton) and ten in the residential care setting (mainly alternating-pressure overlays; AlphaXcell, Huntleigh Healthcare Ltd). There was no significant difference in the healing of subjects' sores in the two areas, either at two weeks or per day. The trial APMRS was found to be equally comfortable in either setting, and in both settings the control surfaces were not regarded as significantly different in terms of comfort. These findings, from a small sample, promote discussion about the use of pressure-relieving equipment in settings where there are older people who may be at particular risk from pressure damage and where nursing interventions are less intensive and routine.
Introduction This paper discusses observations made in two acute hospital settings and two residential care homes where pressurerelieving equipment was used in the care of older people with pressure ulcers. The data presented here were collected during a randomized controlled trial, to compare an alternating-pressure mattress replacement system (APMRS; Nimbus III, Huntleigh Healthcare Ltd) with control surfaces used routinely in hospital and residential care settings. The main study and relevant findings are presented in a report by Evans and Land 1 which raised questions about the nature of interventions used in each area and the need for specialist equipment in the independent community sector. In order to investigate these questions further, it was decided to determine whether the characteristics of the subjects, particularly in relation to the setting in which they were cared for, had an effect on the outcome of healing. Studies into ageing and pressure damage indicate that there is a significantly greater risk of older people developing pressure sores as a result of both the ageing process and the Received 25 May 1999; revised 26 July 1999; accepted 17 September 1999
increased likelihood of illness and debility 2•3 . There is a flattening of the dermo-epidermal junction with age, resulting in more fragile tissue, which is less resistant to shearing forces. Diseases that affect wound healing are also more likely to occur in older people and make them more susceptible to tissue breakdown4-6. There is very little information about the incidence of pressure sores on admission to nursing homes, but in the USA, it is estimated that between 20 and 35% of older people have pressure damage on admission to long-term care facilities 7 . Bergstrom and Braden's study of the institutionalized elderly indicated that subjects who developed pressure sores were significantly older than those who remained free of pressure damage 8. In the UK, there has been a blurring of boundaries between health and social care which has produced differences in the type of interventions provided for older people9 . The level of nursing intervention in an acute hospital setting will generally be more intensive than in a residential care setting, and research undertaken in nursing elderly care facilities indicates that the provision of specialist equipment may be of © Tissue Viability Society
Journal of Tissue Viability 2000 Vol 10 No 1 7
particular use where nursing interventions are performed less routinely 8•10. Research emphasis has often been placed upon the ability of pressure-relieving devices to prevent the formation of pressure sores, although some studies to assess wound healing have been performed 11 - 14 . The duration of healing depends upon the depth, area and the anatomical location of the wound. Acute, shallow wounds usually take 7-10 days to heal, but in less optimal conditions take 11-15 days. Whilst small and large wounds heal at similar rates, biopsy wounds may take 2-3 weeks to heal and deep pressure sores about 6-12 weeks 15 . Larger deep wounds will take longer to heal than smaller deep wounds. Of particular relevance to this study is the assertion that wounds that have decreased at least 39% in two weeks of treatment heal faster than wounds that do not demonstrate such a reduction 16 .
Methods This paper explores the assumption that the care setting and nursing interventions affect wound healing in each setting. Ethical approval for the evaluation of the trial APMRS was granted by the local research ethics committee for each hospital, and permission to access the residents of the care homes was given by the group home directorate and the residents' general practitioners. Acute medical and surgical units in two hospitals and two residential care settings participated, and patients were recruited according to strict inclusion criteria (Figure 1). Subjects who met these criteria were approached by the tissue viability research assistant (TVRA) who discussed the study with the subject and, where possible, with their relatives; those willing to participate were provided with a subject information sheet and gave informed consent. Once they were recruited, their demographic details were recorded, together with other general medical and nursing information. The estimated n for an effect size (y) of 0.065 with a= 0.05 and ~ = 0.02, in a two-group mean difference situation, was
Aged 65 years or over
AND A grade 3 pressure sore or above 18
OR A grade 2 pressure sore 18 and at least one of the following problems: • difficult to reposition on bed and unable to tolerate the 30° tilt • unable to move in bed for more than 20 hours in 24 hours • weighs more than 17 stone and is bed-bound • has spent 2 hours or more on an operating table or trolley in the last 7 days • received a spinal anaesthetic
Figure 1 Criteria for inclusion in the study
• Age (years) • Pulse (beats/min) • Respirations (breaths/min) • Temperature CC) • Blood pressure (mmHg) • White blood cell count (per mm 3 ) • Creatinine (mmol/1) • Sodium (mmol/1)
Figure 2 Measures recorded for the modified APACHE III score
30 subjects per group. Consequently, a sample size of 120 subjects, 60 in each setting (acute or continuing care) and 30 in each group (control or experimental) was required. A modified APACHE III score 17 (Figure 2) was generated to assess severity of illness (the full APACHE III score requires the collection of arterial blood, which was deemed inappropriate for the residents of the care home). The use of an APACHE score is somewhat unusual in this type of setting but was used to assess equivalence in health status between subjects in the control and experimental groups. The APACHE score is validated for use in critical care settings where it is used for estimating the likelihood of morbidity and is not limited to clinical diagnosis. It was used here because it is otherwise impossible to estimate the impact of diverse medical diagnoses on wound healing. The score for the complete APACHE assessment is 0-299, but for the eight variables used in this study the possible range of scores was 0-132. The characteristics of the sores were also recorded at baseline by the TVRA, who recorded the wound grade 18, site, size, appearance and the initial product used to dress the wound. Subjects in both areas were randomly allocated to the experimental surface using a randomization sequence determined from a table of random numbers. This sequence was concealed from both the researchers and the tissue viability nurse. Nurses working in each of the trial areas were trained by the manufacturers on the use and care of the trial APMRS, and then subjects were nursed on the surface using manufacturer's guidelines and their established practice for the regular relief of pressure. Wound dressings were performed in each setting according to one of the hospital's protocols. Each wound was assessed approximately twice weekly for appearance, and photographed at routine intervals. The wound was traced using sterile transparent film by the TVRA. The mean surface area of the wound was calculated from three measures using WAND software 19 by two of the research team who remained blind to the surface to which each subject had been allocated. The percentage reduction in wound surface area was compared per day and at approximately two weeks.
8 Journal of Tissue Viability 2000 Vol 10 No 1 The Statistical Package for the Social Sciences was used to analyse the data, and descriptive statistics calculated to summarize the data. Inferential statistics were used, where appropriate, to determine any differences in the data sets, and confidence intervals are presented for key estimates. The patients and residents were also asked to consider the comfort of the surfaces they were allocated to, and using a visual analogue scale, rated their comfort once weekly.
Results Recruitment to the study was not as high as predicted, and it was therefore decided to terminate data gathering at 20 months. In all, seven subjects were recruited to the experimental group in the acute hospital setting and ten to the experimental group in the residential care setting. Table 1 shows that there was a statistically significant difference between the two groups with respect to age, the residents of the care setting being older than those in hospital (P = 0.022). Differences in gender were also demonstrated to be statistically significant, with the residents recruited being exclusively women (P = 0.015). The groups were equivalent with respect to their severity of illness measurement, with no differences in their modified APACHE score. There was also no difference between the two groups using a Waterlow score to assess their risk of pressure damage, with the majority of subjects placed in the very high risk category. Since the sample did not reach its minimum size, a decision was made to perform the analysis on the basis of the sores presented by the subjects. This would have potentially confounded the randomization process so an analysis of the characteristics of the sores was conducted to establish that they were equivalent across all groups. In both hospitals and both residential care homes, there was no statistical difference in the characteristics of the sores from each subject at baseline (Table 2).
Table 1 Subject characteristics (nursed on the trial APMRS)
Characteristic Age (years; median and range) Gender (female:male) Modified APACHE score (median and range) Waterlow score (15+:20+) Number of sores at baseline (median and range)
Table 2 Sore characteristics (subjects nursed on the trial APMRS)
Characteristic
Hospital experimental group (n = 7)
Nursing home experimental group (n = 10)
Grade 2 3 4
7 6 0
16 12 3
0.499a
Site Heel Sacrum Other
5 7 1
9 14 8
0.393a
11:2
28:3
0.623b
Size Small (< 10 cm2): large > 10 cm2)
P value
'7.2 test, bFisher's exact test (statistically significant if P < 0.05) There was no statistically significant difference in the percentage reduction in wound surface area at approximately two weeks between the subjects' sores nursed on the trial APMRS, both in the acute hospital setting and the residential care setting. The subjects nursed on the trial APMRS in hospital whose sores reduced in size by 39% in the first two weeks demonstrated greater expediency in healing. When assessed per day, the same groups did not demonstrate any significant difference in wound healing (Table 3). Comparison of the subjects nursed on the control surfaces demonstrated that the groups were comparable in terms of age, gender, Waterlow score and the number of sores present when included in the study. However, there was a statistically significant difference in the modified APACHE score (P = 0.042), with the residents showing a higher average illness severity score than that of the patients in hospital (Table 4). When analysed, the characteristics of the subjects' sores did not demonstrate any significant differences between groups with respect to grade, site and size (Table 5). There was no significant difference in the healing of wounds between those subjects nursed on control surfaces in the hospital setting and the residential care homes (Table 6). Those nursed on the control surfaces in hospital who experienced a reduction in wound size of 39% at two weeks also demonstrated greater expediency of healing.
Nursing home experimental group (n = 10)
P value
68 (66-91)
84.5 (71-99)
0.022a
3:4
10:0
0.015b
22 (20--35)
29 (20--47)
0.142a
0:7
1:8
l.OOOb
Discussion and limitations
2 (1-3)
3 (1-5)
o.o71a
The results show no difference in wound healing using the trial APMRS in the acute hospital setting and the residential care setting, despite the difference in age between the two groups. Although the residents were significantly older, exclusively female and the level of care they might expect to
Hospital experimental group (n = 7)
aMann-Whitney U test, bFisher's exact test (statistically significant if p < 0.05)
There was no difference in the perceived comfort between the patients ]lild residents nursed on the trial APMRS in either setting (P =0.403). Comparison between patients and residents nursed on control surfaces in each area revealed that all subjects found these products equally comfortable.
Journal of Tissue Viability 2000 Vol10 No 1
9
Table 3 Sore outcomes (subjects nursed on the trial APMRS)
Hospital experimental group (n = 13)
Nursing home experimental group (n = 31)
2.2 (0.7-12.4)
2.7 (0.2-21.0)
0.652
0.2 (0-10)
0.9 (0-22.5)
0.593
Percentage reduction in wound surface area at two weeks 88.9 (0-100) Median and range 65.0 Mean 40.4-89.6 95% confidence intervals
51.3 (0-100) 54.7 37.4-71.9
0.384
Percentage reduction in wound surface area per day 6.7 (0-14.3) Median and range 5.4 Mean 2.8-8.1 95% confidence intervals
2.4 (0-14.3) 4.9 3.1-6.7
0.511
Outcome Initial wound size (cm2, median and range) Wound size at two weeks (cm2 , median and range)
•Mann-Whitney U test (statistically significant if P < 0.05) Table 4 Subject characteristics (nursed on control surfaces)
Characteristics Age (years, median and range Gender (female:male) Modified APACHE score (median and range) Waterlow score (15+:20+) Number of sores at baseline( median and range)
Hospital control group (n = 5)
Nursing home control group (n =10)
P value
78 (65-91)
88.5 (72-94)
0.1243
3:2
9:1
0.242b
23 (17-33)
28 (23-34)
0.042 3
2:3
0:9
0.110b
1 (1-3)
1 (1-5)
0.889•
"Mann-Whitney U test, bFisher's exact test (statistically significant if P< 0.05 Table 5 Sore characteristics (subjects nursed on control surfaces)
Hospital control group
=5)
Nursing home control group (n = 10)
P value
Characteristic
(n
Grade 2 3 4
6 3 0
7 6 7
Site Heel Sacrum Other
2 4 3
5 11 4
0.737b
7:2
17:3
0.633"
Size Small(< 10 cm2): large > 10 cm2)
•Fisher's exact test, bx 2 test (statistically significant if P < 0.05)
receive would be less intensive, the trial APMRS appeared to be as effective in the community setting as in the hospital. However, the sample size is relatively small and replication studies with a larger sample size would give a more accurate picture.
Comparison of the control surfaces between settings is also interesting. Baseline data regarding the two groups indicated that they were equivalent in most respects, although the subjects from the residential care setting had a significantly higher modified APACHE score. The use of the APACHE III score in this study has highlighted the way in which the health status of different people might be gauged, and has been cited as a useful means of comparing subjects in randomized controlled trials 20- 23 . Whilst it might be expected that hospital patients are more acutely ill, the difference in scores could be attributed to the general deterioration of health found amongst an ageing population and supports previous studies into ageing and causes of pressure damage 8. The sample size calculation indicated that a total of 120 subjects should have been recruited and clearly this was not the case. The small sample size was in part due to the high standard of care delivered in order to prevent tissue damage, meaning that very few patients or residents presented with pressure ulcers, and partly due to the nature of the inclusion criteria. The inclusion criteria for this study specified that the sample should be drawn from subjects who exhibited a grade three sore or above or at least a grade two sore and additional significant medical or mobility problems. These criteria almost certainly had an effect on the numbers available for recruitment, but, perhaps more importantly, the high grades of these wounds meant that the management of these wounds was more complex. However, the rationale for the inclusion criteria was based upon the role an alternating-pressure mattress replacement system performs in the clinical area. It should also be noted that, because of the sample size, a type II error might have occurred. The most appropriate outcome measure for this study would have been to evaluate the length of time to complete healing, although data on this are available, they would have needed to have been collected in a more consistent manner for appropriate presentation. The study did not set out to compare specific surfaces against the trial APMRS but to evaluate it against products
10
Journal of Tissue Viability 2000 Vol 10 No 1 Table 6 Sore outcomes (subjects nursed on control surfaces)
Outcome
Hospital control group
(n
Nursing home control group
=9)
(n = 20)
P value
2.4 (0.6-11.5)
2.1 (0.1-37.4)
0.795
1.8 (0-11.6)
1.7 (0-36.4)
0.957
Percentage reduction in wound surface area at two weeks Median and range 29.8 (0-100) Mean 39.2 95% confidence intervals 14.7-63.7
12.1 (0-100) 25.7 9.1-42.3
0.245
Percentage reduction in wound surface area per day Median and range 1.8 (l.l-7.1) Mean 2.9 95% confidence intervals 1.2-4.6
0.9 (0-8.3) 1.9 0.7-3.1
0.511
Initial wound size (cm2, median and range) Wound size at two weeks (cm2, median and range)
aMann-Whitney U test (statistically significant if P < 0.05)
used routinely in each setting. The main control surface used in the hospital setting was an alternative APMRS, whilst in the residential care setting an alternating-pressure overlay was often the only alternative. The results demonstrate that there was no statistical difference in wound healing between the control APMRS and the alternating-pressure overlay when measured at two weeks or per day over the study period. If the care settings, level of intervention and the differences in illness severity are taken into account, it appears that, despite different specifications, both surfaces performed equally well. The use of a visual analogue scale to measure perceived comfort, although subjective, appears to be the only possible method of measuring such a concept, and the finding of no differences across the two experimental and two control groups needs to be viewed in this light.
setting were obviously different, and assuming that the level of interventions in this setting are likely to be less intensive, it does seem that further investigation of specialist pressurerelieving devices in this setting would be useful.
Acknowledgements This study was funded by Huntleigh Healthcare.
Address for correspondence Lucy Land, University of Central England in Birmingham, Health and Social Care Research Centre, Faculty of Health and Community Care, Ravensbury House, Westbourne Road, Edgbaston, Birmingham B 15 3TN.
References
Conclusions The aim of the study was to compare the trial APMRS in different settings using a randomized controlled trial. It was successful in its approach to randomization, and the protocols put in place to control the environment of the research were useful. An obvious limitation of the study was the sample size, which necessitated the analysis of groups of sores rather than subjects. This may have caused problems in demonstrating equivalence, but analysis of sore characteristics showed that there were no statistically significant differences in their baseline measurement. Although there were differences in some of the subjects' characteristics at baseline, there was no difference in the effectiveness of any of the surfaces in either setting. It would be inappropriate, given the small sample size and the type of data analysis, to make particular inferences from the study; however, the results do offer some interesting areas for further investigation. The age and severity of illness in the experimental and control groups in the residential care
2
Evans D, Land L. A clinical evaulation of the Nimbus 3 alternating pressure mattress replacement system. Birmingham: University of Central England in Birmingham, 1999. Bliss MR. Aetiology of pressure sores. Reviews in Clinical
Gerontology 1993; 3: 379-397. 3 Desai H. Ageing and wounds, part 2: healing and old age. Journal ofWound Care 1997; 6: 237-239.
4 Norton D, McLaren R, Exton Smith AN. An investigation of geriatric nursing problems in hospital. Edinburgh: Churchill Livingstone, 1962. 5 Maklebust J, Brockhorst L. Pressure ulcer incidence in high risk patients managed on a special three layered air cushion. Decubitus 1988; 1: 2!h40.
6 Gosnell DJ. An assessment tool to identify pressure sores. Nursing Research 1973; 22: 55-59.
7 Martin BJ, Devine BL, MacDonald JB, Williams J, Higgins P, Norrie J, Ford I. Incidence of pressure sores in geriatric long term hospital care. Journal of Tissue Viability 1995; 5: 83-87. 8 Bergstrom N, Braden B. A prospective study of pressure sore risk among the institutionalised elderly. Journal of the American Geriatrics Society 1992; 40: 747-758.
9 ni Mhaolrunaigh S, Land L, Daniels L, Jesson W. The health care needs of older people in Stockland Green. Birmingham: University of Central England in Birmingham, 1995. 10 Land L. A review of pressure damage prevention strategies. Journal of Advanced Nursing 1995; 22: 329-337.
Journal of Tissue Viability 2000 Vol 10 No 1 11 Andersen KE, Jensen 0, Kvorning SA, Bach E. Decubitus prophylaxis: a prospective trial of an alternating air mattress and a water mattress. Acta Dennatologica (Stockholm) 1982; 63: 227-230. 12 Conine TA, Daeschel D, Lau MS. The role of alternating air and silicone overlays in preventing decubitus ulcers. International Journal of Rehabilitation 1990; 13: 57-65. 13 Bliss MR. Pressure sores in elderly patients: a comparison of seven mattress overlays. Age and Ageing 1995; 24: 297-302. 14 Gebhardt KS, Bliss MR, Winwright PL, Thomas J. Pressure relieving supports in an ICU. Journal ofWound Care 1996; 5: 116-121. 15 Kerstein MD. The scientific basis of wound healing. Advances in Wound Care 1997; 10(3): 30-36. 16 Van Rijswijk L, Polansky M. Predictors of time to healing deep pressure ulcers. Ostomy/Wound Management 1994; 40(8): 40-51. 17 Knaus WA, Wagner DP, Draper EA, Zimmerman JE, Bergner M, Bastos PG, et a!. The Apache III prognostic system risk prediction of hospital mortality for critically ill hospitalised adults. Chest 1991; 100: 1619-1636.
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18 Johnson A. A blueprint for the prevention and management of pressure sores. Care: Science and Practice 1985; 2: 8-13. 19 Plassman P. Measuring wounds - a guide to the use of wound measurement techniques. Journal of Wound Care 1995; 4: 269-272. 20 Russell L. Randomised comparison clinical trial of Pegasus Cairwave mattress and Proactive seating cushion and Huntleigh Nimbus 3 and Aura seating cushion. Burton: Burton Hospitals NHS Trust, 1999. 21 Inman KJ, Sibbald WJ, Rutledge FS, Clark BJ. Clincal utility and cost effectiveness of an air suspension bed in the prevention of pressure ulcers. Journal of the American Medical Association 1993; 269: 1139-1143. 22 Lemeshow S, Le Gall JR. Modelling the severity of illness of ICU patients: a systems update. Journal of the American Medical Association 1994; 272: 1049-1055. 23 Shuster DP. Predicting outcome after ICU admission: the art and science of assessing risk. Chest 1992; 102: 1861-1870.
TISSUE VIABILITY SOCIETY 34TH CONFERENCE East Midlands Conference Centre, Nottingham 4-5 April 2000 Title: IMAGES OF WOUND CARE: RESTORING AND REBUILDING DAMAGED TISSUE Day 1
Day2
Theme: Altered body image
Theme: Treatment options
• Remodelling and reconstruction • Facial & body prosthetics after surgery • Head and neck surgery: the impact on the tissues and patient • Making wounds for a living • Psychological aspects of pressure sore prevention: preventive health behaviours of wheelchair users • Odour and exudate • Free papers
• • • • • • • •
Fungating wounds Difficult woundcare The diagnosis of early pressure sores Treatment possibilities in rheumatoid ulcers Laser treatment in skin defects Recording wounds - documenting woundcare Digital photography Factitious wounds
Fee per day: £50 Members/£65 Non-Members. 'Early Bird' and group booking discounts. Please contact for further information the Tissue Viability Society, Glanville Centre, Salisbury District Hospital, Salisbury SP2 8BJ, tel: 01722 336262 ext 4057
Journal of Tissue Viability 2000 Vol 10 No 1
A clinical evaluation of an alternatingpressure mattress replacement system in hospital and residential care settings Lucy Land 1, Debra Evans 1, Amanda Geary2 and Carl Taylor 1 of Central England in Birmingham, Health and Social Care Research Centre, Faculty of Health and Community Care, Edgbaston, Birmingham, and 2 City Hospital NHS Trust, Dudley Road, Birmingham 1University
An observational study was carried out to compare wound healing on alternating-pressure mattress replacement systems (APMRS) and other surfaces in an elderly population in acute and residential care settings. Subjects were assessed for the reduction in their pressure ulcers at approximately two weeks and per day, and a visual analogue scale was used to record the patients' comfort. Seven and ten subjects were allocated to the Nimbus III APMRS (Huntleigh Healthcare Ltd) in the hospital and residential care settings respectively. There was no significant difference in the healing of the subjects' sores in the two areas either at two weeks or per day. Five people were allocated to control surfaces in the hospital setting (mainly APMRS; Pegasus Airwave, Pegasus Egerton) and ten in the residential care setting (mainly alternating-pressure overlays; AlphaXcell, Huntleigh Healthcare Ltd). There was no significant difference in the healing of subjects' sores in the two areas, either at two weeks or per day. The trial APMRS was found to be equally comfortable in either setting, and in both settings the control surfaces were not regarded as significantly different in terms of comfort. These findings, from a small sample, promote discussion about the use of pressure-relieving equipment in settings where there are older people who may be at particular risk from pressure damage and where nursing interventions are less intensive and routine.
Introduction This paper discusses observations made in two acute hospital settings and two residential care homes where pressurerelieving equipment was used in the care of older people with pressure ulcers. The data presented here were collected during a randomized controlled trial, to compare an alternating-pressure mattress replacement system (APMRS; Nimbus III, Huntleigh Healthcare Ltd) with control surfaces used routinely in hospital and residential care settings. The main study and relevant findings are presented in a report by Evans and Land 1 which raised questions about the nature of interventions used in each area and the need for specialist equipment in the independent community sector. In order to investigate these questions further, it was decided to determine whether the characteristics of the subjects, particularly in relation to the setting in which they were cared for, had an effect on the outcome of healing. Studies into ageing and pressure damage indicate that there is a significantly greater risk of older people developing pressure sores as a result of both the ageing process and the Received 25 May 1999; revised 26 July 1999; accepted 17 September 1999
increased likelihood of illness and debility 2•3 . There is a flattening of the dermo-epidermal junction with age, resulting in more fragile tissue, which is less resistant to shearing forces. Diseases that affect wound healing are also more likely to occur in older people and make them more susceptible to tissue breakdown4-6. There is very little information about the incidence of pressure sores on admission to nursing homes, but in the USA, it is estimated that between 20 and 35% of older people have pressure damage on admission to long-term care facilities 7 . Bergstrom and Braden's study of the institutionalized elderly indicated that subjects who developed pressure sores were significantly older than those who remained free of pressure damage 8. In the UK, there has been a blurring of boundaries between health and social care which has produced differences in the type of interventions provided for older people9 . The level of nursing intervention in an acute hospital setting will generally be more intensive than in a residential care setting, and research undertaken in nursing elderly care facilities indicates that the provision of specialist equipment may be of © Tissue Viability Society
Journal of Tissue Viability 2000 Vol 10 No 1 7
particular use where nursing interventions are performed less routinely 8•10. Research emphasis has often been placed upon the ability of pressure-relieving devices to prevent the formation of pressure sores, although some studies to assess wound healing have been performed 11 - 14 . The duration of healing depends upon the depth, area and the anatomical location of the wound. Acute, shallow wounds usually take 7-10 days to heal, but in less optimal conditions take 11-15 days. Whilst small and large wounds heal at similar rates, biopsy wounds may take 2-3 weeks to heal and deep pressure sores about 6-12 weeks 15 . Larger deep wounds will take longer to heal than smaller deep wounds. Of particular relevance to this study is the assertion that wounds that have decreased at least 39% in two weeks of treatment heal faster than wounds that do not demonstrate such a reduction 16 .
Methods This paper explores the assumption that the care setting and nursing interventions affect wound healing in each setting. Ethical approval for the evaluation of the trial APMRS was granted by the local research ethics committee for each hospital, and permission to access the residents of the care homes was given by the group home directorate and the residents' general practitioners. Acute medical and surgical units in two hospitals and two residential care settings participated, and patients were recruited according to strict inclusion criteria (Figure 1). Subjects who met these criteria were approached by the tissue viability research assistant (TVRA) who discussed the study with the subject and, where possible, with their relatives; those willing to participate were provided with a subject information sheet and gave informed consent. Once they were recruited, their demographic details were recorded, together with other general medical and nursing information. The estimated n for an effect size (y) of 0.065 with a= 0.05 and ~ = 0.02, in a two-group mean difference situation, was
Aged 65 years or over
AND A grade 3 pressure sore or above 18
OR A grade 2 pressure sore 18 and at least one of the following problems: • difficult to reposition on bed and unable to tolerate the 30° tilt • unable to move in bed for more than 20 hours in 24 hours • weighs more than 17 stone and is bed-bound • has spent 2 hours or more on an operating table or trolley in the last 7 days • received a spinal anaesthetic
Figure 1 Criteria for inclusion in the study
• Age (years) • Pulse (beats/min) • Respirations (breaths/min) • Temperature CC) • Blood pressure (mmHg) • White blood cell count (per mm 3 ) • Creatinine (mmol/1) • Sodium (mmol/1)
Figure 2 Measures recorded for the modified APACHE III score
30 subjects per group. Consequently, a sample size of 120 subjects, 60 in each setting (acute or continuing care) and 30 in each group (control or experimental) was required. A modified APACHE III score 17 (Figure 2) was generated to assess severity of illness (the full APACHE III score requires the collection of arterial blood, which was deemed inappropriate for the residents of the care home). The use of an APACHE score is somewhat unusual in this type of setting but was used to assess equivalence in health status between subjects in the control and experimental groups. The APACHE score is validated for use in critical care settings where it is used for estimating the likelihood of morbidity and is not limited to clinical diagnosis. It was used here because it is otherwise impossible to estimate the impact of diverse medical diagnoses on wound healing. The score for the complete APACHE assessment is 0-299, but for the eight variables used in this study the possible range of scores was 0-132. The characteristics of the sores were also recorded at baseline by the TVRA, who recorded the wound grade 18, site, size, appearance and the initial product used to dress the wound. Subjects in both areas were randomly allocated to the experimental surface using a randomization sequence determined from a table of random numbers. This sequence was concealed from both the researchers and the tissue viability nurse. Nurses working in each of the trial areas were trained by the manufacturers on the use and care of the trial APMRS, and then subjects were nursed on the surface using manufacturer's guidelines and their established practice for the regular relief of pressure. Wound dressings were performed in each setting according to one of the hospital's protocols. Each wound was assessed approximately twice weekly for appearance, and photographed at routine intervals. The wound was traced using sterile transparent film by the TVRA. The mean surface area of the wound was calculated from three measures using WAND software 19 by two of the research team who remained blind to the surface to which each subject had been allocated. The percentage reduction in wound surface area was compared per day and at approximately two weeks.
8 Journal of Tissue Viability 2000 Vol 10 No 1 The Statistical Package for the Social Sciences was used to analyse the data, and descriptive statistics calculated to summarize the data. Inferential statistics were used, where appropriate, to determine any differences in the data sets, and confidence intervals are presented for key estimates. The patients and residents were also asked to consider the comfort of the surfaces they were allocated to, and using a visual analogue scale, rated their comfort once weekly.
Results Recruitment to the study was not as high as predicted, and it was therefore decided to terminate data gathering at 20 months. In all, seven subjects were recruited to the experimental group in the acute hospital setting and ten to the experimental group in the residential care setting. Table 1 shows that there was a statistically significant difference between the two groups with respect to age, the residents of the care setting being older than those in hospital (P = 0.022). Differences in gender were also demonstrated to be statistically significant, with the residents recruited being exclusively women (P = 0.015). The groups were equivalent with respect to their severity of illness measurement, with no differences in their modified APACHE score. There was also no difference between the two groups using a Waterlow score to assess their risk of pressure damage, with the majority of subjects placed in the very high risk category. Since the sample did not reach its minimum size, a decision was made to perform the analysis on the basis of the sores presented by the subjects. This would have potentially confounded the randomization process so an analysis of the characteristics of the sores was conducted to establish that they were equivalent across all groups. In both hospitals and both residential care homes, there was no statistical difference in the characteristics of the sores from each subject at baseline (Table 2).
Table 1 Subject characteristics (nursed on the trial APMRS)
Characteristic Age (years; median and range) Gender (female:male) Modified APACHE score (median and range) Waterlow score (15+:20+) Number of sores at baseline (median and range)
Table 2 Sore characteristics (subjects nursed on the trial APMRS)
Characteristic
Hospital experimental group (n = 7)
Nursing home experimental group (n = 10)
Grade 2 3 4
7 6 0
16 12 3
0.499a
Site Heel Sacrum Other
5 7 1
9 14 8
0.393a
11:2
28:3
0.623b
Size Small (< 10 cm2): large > 10 cm2)
P value
'7.2 test, bFisher's exact test (statistically significant if P < 0.05) There was no statistically significant difference in the percentage reduction in wound surface area at approximately two weeks between the subjects' sores nursed on the trial APMRS, both in the acute hospital setting and the residential care setting. The subjects nursed on the trial APMRS in hospital whose sores reduced in size by 39% in the first two weeks demonstrated greater expediency in healing. When assessed per day, the same groups did not demonstrate any significant difference in wound healing (Table 3). Comparison of the subjects nursed on the control surfaces demonstrated that the groups were comparable in terms of age, gender, Waterlow score and the number of sores present when included in the study. However, there was a statistically significant difference in the modified APACHE score (P = 0.042), with the residents showing a higher average illness severity score than that of the patients in hospital (Table 4). When analysed, the characteristics of the subjects' sores did not demonstrate any significant differences between groups with respect to grade, site and size (Table 5). There was no significant difference in the healing of wounds between those subjects nursed on control surfaces in the hospital setting and the residential care homes (Table 6). Those nursed on the control surfaces in hospital who experienced a reduction in wound size of 39% at two weeks also demonstrated greater expediency of healing.
Nursing home experimental group (n = 10)
P value
68 (66-91)
84.5 (71-99)
0.022a
3:4
10:0
0.015b
22 (20--35)
29 (20--47)
0.142a
0:7
1:8
l.OOOb
Discussion and limitations
2 (1-3)
3 (1-5)
o.o71a
The results show no difference in wound healing using the trial APMRS in the acute hospital setting and the residential care setting, despite the difference in age between the two groups. Although the residents were significantly older, exclusively female and the level of care they might expect to
Hospital experimental group (n = 7)
aMann-Whitney U test, bFisher's exact test (statistically significant if p < 0.05)
There was no difference in the perceived comfort between the patients ]lild residents nursed on the trial APMRS in either setting (P =0.403). Comparison between patients and residents nursed on control surfaces in each area revealed that all subjects found these products equally comfortable.
Journal of Tissue Viability 2000 Vol10 No 1
9
Table 3 Sore outcomes (subjects nursed on the trial APMRS)
Hospital experimental group (n = 13)
Nursing home experimental group (n = 31)
2.2 (0.7-12.4)
2.7 (0.2-21.0)
0.652
0.2 (0-10)
0.9 (0-22.5)
0.593
Percentage reduction in wound surface area at two weeks 88.9 (0-100) Median and range 65.0 Mean 40.4-89.6 95% confidence intervals
51.3 (0-100) 54.7 37.4-71.9
0.384
Percentage reduction in wound surface area per day 6.7 (0-14.3) Median and range 5.4 Mean 2.8-8.1 95% confidence intervals
2.4 (0-14.3) 4.9 3.1-6.7
0.511
Outcome Initial wound size (cm2, median and range) Wound size at two weeks (cm2 , median and range)
•Mann-Whitney U test (statistically significant if P < 0.05) Table 4 Subject characteristics (nursed on control surfaces)
Characteristics Age (years, median and range Gender (female:male) Modified APACHE score (median and range) Waterlow score (15+:20+) Number of sores at baseline( median and range)
Hospital control group (n = 5)
Nursing home control group (n =10)
P value
78 (65-91)
88.5 (72-94)
0.1243
3:2
9:1
0.242b
23 (17-33)
28 (23-34)
0.042 3
2:3
0:9
0.110b
1 (1-3)
1 (1-5)
0.889•
"Mann-Whitney U test, bFisher's exact test (statistically significant if P< 0.05 Table 5 Sore characteristics (subjects nursed on control surfaces)
Hospital control group
=5)
Nursing home control group (n = 10)
P value
Characteristic
(n
Grade 2 3 4
6 3 0
7 6 7
Site Heel Sacrum Other
2 4 3
5 11 4
0.737b
7:2
17:3
0.633"
Size Small(< 10 cm2): large > 10 cm2)
•Fisher's exact test, bx 2 test (statistically significant if P < 0.05)
receive would be less intensive, the trial APMRS appeared to be as effective in the community setting as in the hospital. However, the sample size is relatively small and replication studies with a larger sample size would give a more accurate picture.
Comparison of the control surfaces between settings is also interesting. Baseline data regarding the two groups indicated that they were equivalent in most respects, although the subjects from the residential care setting had a significantly higher modified APACHE score. The use of the APACHE III score in this study has highlighted the way in which the health status of different people might be gauged, and has been cited as a useful means of comparing subjects in randomized controlled trials 20- 23 . Whilst it might be expected that hospital patients are more acutely ill, the difference in scores could be attributed to the general deterioration of health found amongst an ageing population and supports previous studies into ageing and causes of pressure damage 8. The sample size calculation indicated that a total of 120 subjects should have been recruited and clearly this was not the case. The small sample size was in part due to the high standard of care delivered in order to prevent tissue damage, meaning that very few patients or residents presented with pressure ulcers, and partly due to the nature of the inclusion criteria. The inclusion criteria for this study specified that the sample should be drawn from subjects who exhibited a grade three sore or above or at least a grade two sore and additional significant medical or mobility problems. These criteria almost certainly had an effect on the numbers available for recruitment, but, perhaps more importantly, the high grades of these wounds meant that the management of these wounds was more complex. However, the rationale for the inclusion criteria was based upon the role an alternating-pressure mattress replacement system performs in the clinical area. It should also be noted that, because of the sample size, a type II error might have occurred. The most appropriate outcome measure for this study would have been to evaluate the length of time to complete healing, although data on this are available, they would have needed to have been collected in a more consistent manner for appropriate presentation. The study did not set out to compare specific surfaces against the trial APMRS but to evaluate it against products
10
Journal of Tissue Viability 2000 Vol 10 No 1 Table 6 Sore outcomes (subjects nursed on control surfaces)
Outcome
Hospital control group
(n
Nursing home control group
=9)
(n = 20)
P value
2.4 (0.6-11.5)
2.1 (0.1-37.4)
0.795
1.8 (0-11.6)
1.7 (0-36.4)
0.957
Percentage reduction in wound surface area at two weeks Median and range 29.8 (0-100) Mean 39.2 95% confidence intervals 14.7-63.7
12.1 (0-100) 25.7 9.1-42.3
0.245
Percentage reduction in wound surface area per day Median and range 1.8 (l.l-7.1) Mean 2.9 95% confidence intervals 1.2-4.6
0.9 (0-8.3) 1.9 0.7-3.1
0.511
Initial wound size (cm2, median and range) Wound size at two weeks (cm2, median and range)
aMann-Whitney U test (statistically significant if P < 0.05)
used routinely in each setting. The main control surface used in the hospital setting was an alternative APMRS, whilst in the residential care setting an alternating-pressure overlay was often the only alternative. The results demonstrate that there was no statistical difference in wound healing between the control APMRS and the alternating-pressure overlay when measured at two weeks or per day over the study period. If the care settings, level of intervention and the differences in illness severity are taken into account, it appears that, despite different specifications, both surfaces performed equally well. The use of a visual analogue scale to measure perceived comfort, although subjective, appears to be the only possible method of measuring such a concept, and the finding of no differences across the two experimental and two control groups needs to be viewed in this light.
setting were obviously different, and assuming that the level of interventions in this setting are likely to be less intensive, it does seem that further investigation of specialist pressurerelieving devices in this setting would be useful.
Acknowledgements This study was funded by Huntleigh Healthcare.
Address for correspondence Lucy Land, University of Central England in Birmingham, Health and Social Care Research Centre, Faculty of Health and Community Care, Ravensbury House, Westbourne Road, Edgbaston, Birmingham B 15 3TN.
References
Conclusions The aim of the study was to compare the trial APMRS in different settings using a randomized controlled trial. It was successful in its approach to randomization, and the protocols put in place to control the environment of the research were useful. An obvious limitation of the study was the sample size, which necessitated the analysis of groups of sores rather than subjects. This may have caused problems in demonstrating equivalence, but analysis of sore characteristics showed that there were no statistically significant differences in their baseline measurement. Although there were differences in some of the subjects' characteristics at baseline, there was no difference in the effectiveness of any of the surfaces in either setting. It would be inappropriate, given the small sample size and the type of data analysis, to make particular inferences from the study; however, the results do offer some interesting areas for further investigation. The age and severity of illness in the experimental and control groups in the residential care
2
Evans D, Land L. A clinical evaulation of the Nimbus 3 alternating pressure mattress replacement system. Birmingham: University of Central England in Birmingham, 1999. Bliss MR. Aetiology of pressure sores. Reviews in Clinical
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18 Johnson A. A blueprint for the prevention and management of pressure sores. Care: Science and Practice 1985; 2: 8-13. 19 Plassman P. Measuring wounds - a guide to the use of wound measurement techniques. Journal of Wound Care 1995; 4: 269-272. 20 Russell L. Randomised comparison clinical trial of Pegasus Cairwave mattress and Proactive seating cushion and Huntleigh Nimbus 3 and Aura seating cushion. Burton: Burton Hospitals NHS Trust, 1999. 21 Inman KJ, Sibbald WJ, Rutledge FS, Clark BJ. Clincal utility and cost effectiveness of an air suspension bed in the prevention of pressure ulcers. Journal of the American Medical Association 1993; 269: 1139-1143. 22 Lemeshow S, Le Gall JR. Modelling the severity of illness of ICU patients: a systems update. Journal of the American Medical Association 1994; 272: 1049-1055. 23 Shuster DP. Predicting outcome after ICU admission: the art and science of assessing risk. Chest 1992; 102: 1861-1870.
TISSUE VIABILITY SOCIETY 34TH CONFERENCE East Midlands Conference Centre, Nottingham 4-5 April 2000 Title: IMAGES OF WOUND CARE: RESTORING AND REBUILDING DAMAGED TISSUE Day 1
Day2
Theme: Altered body image
Theme: Treatment options
• Remodelling and reconstruction • Facial & body prosthetics after surgery • Head and neck surgery: the impact on the tissues and patient • Making wounds for a living • Psychological aspects of pressure sore prevention: preventive health behaviours of wheelchair users • Odour and exudate • Free papers
• • • • • • • •
Fungating wounds Difficult woundcare The diagnosis of early pressure sores Treatment possibilities in rheumatoid ulcers Laser treatment in skin defects Recording wounds - documenting woundcare Digital photography Factitious wounds
Fee per day: £50 Members/£65 Non-Members. 'Early Bird' and group booking discounts. Please contact for further information the Tissue Viability Society, Glanville Centre, Salisbury District Hospital, Salisbury SP2 8BJ, tel: 01722 336262 ext 4057