Pressure relieving devices for treating heel pressure ulcers
Abstract
This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:
To conduct a systematic review of all randomised controlled trials (RCTs) of support surface interventions for treating pressure ulcers of the heel.
This will be used to answer the following question:
What are the relative effects of pressure‐relieving interventions used to treat heel pressure ulcers?
Background
Description of the condition
Aetiology of pressure ulcers
Pressure ulcers (also known as pressure sores, decubitus ulcers and bed sores) are areas of localized damage to the skin and underlying tissue, believed to be caused by pressure, shear or friction (Allman 1997). They usually occur over bony prominences, such as the heel, where there is little soft tissue, in particular subcutaneous fat, to provide mobility and padding. Animal studies show the severity of tissue damage to be proportional to the time and intensity of the pressure (Kosiak 1959). This has also been shown to apply to humans, by Reswick and Rogers (Reswick 1976) in their study of spinal injured patients.
Size of the problem
Pressure ulcers present a major burden of sickness and are likely to reduce the quality of life for patients and their carers. The financial costs to the NHS are also substantial. In the UK, the cost of preventing and treating pressure ulcers in a 600‐bedded large general hospital was estimated at between £600,000 and £3 million per year (Clark 1994). Most published data on prevalence and incidence of pressure ulcers come from hospital populations. In the UK, pressure ulcer prevalence ranges from 5 to 32% and incidence from 2 to 29% (Kaltenthaler 2001).
The majority of pressure ulcers are found on the lower body or feet. Although the sacral or buttock region is still the most common body site (Dealey 1991) the heels are frequently reported as a common location (Dealey 1991a). In the UK most NHS Trusts collect data on the prevalence and incidence of pressure ulcers. Prevalence surveys of pressure ulcers in the Leeds Teaching Hospitals Trust support the hypothesis that the proportion of ulcers on the heels may be increasing (see Appendix 1).
Heel pressure ulcers
Heel ulcers appear to have been mostly neglected in the research literature. The evidence behind many interventions commonly used as treatment strategies (for example nutritional support) to address intrinsic factors contributing to the development of pressure ulcers has been extrapolated from studies of prevention. This evidence is sparse and of generally poor quality and there is insufficient evidence to demonstrate the effectiveness of nutritional supplements in prevention, and particularly treatment, of pressure ulcers (Langer 2003). The use of local pressure relief through support surfaces has been studied as a preventative intervention (Cullum 2004). The continued use of support surfaces, even when a pressure ulcer has occurred, is advocated to prevent further damage. Diabetic foot ulcers are wounds which occur anywhere on the feet; they may occur on the heel and be pressure related. There are two Cochrane systematic reviews on preventing and treating diabetic foot ulcers but these do not define foot ulcer and so may include pressure ulcers (Spencer 2000; Valk 2001). Neither of the reviews looked at heel ulcers as a subgroup. Since heel ulcers may represent a distinct clinical entity, in terms of risk and responses to treatment, they are worthy of specific scrutiny.
The feet are physiologically distinct from other body sites for the following reasons:
1. They are designed for weight bearing, with thickened dermis on the sole of the foot. This means that the skin has a relatively high number of collagen and elastic fibres to allow extensibility and elasticity and Pacinian corpuscles to identify pressure (Thoolen 2000) compared to skin found on most other areas of the body.
2. The circulation to the lower limbs can become compromised due to arterial diseases such as atherosclerosis. Although associated with increasing age (Vogt 1992), poor circulation is seen in younger people particularly in association with risk factors such as smoking, diabetes and hypertension (Vogt 1992). The internal capillary pressures reduce and if subjected to external pressure are not able to respond appropriately to prevent occlusion (Kannell 1973).
3. Neuropathy (reduced or altered sensation) has been identified as a risk factor for ulceration in the feet of people with diabetes (McNeeley 1995). Neuropathy is also known to be associated with other diseases such as stroke, pernicious anaemia, spina bifida and multiple sclerosis although its precise prevalence is unknown (Neale 1981). Although no published papers have been identified so far, data collected during a study on pain in leg ulcers (Briggs 2003) has shown that many elderly people have some degree of neuropathy of the lower limbs. The presence of neuropathy may result in a person being unaware of pressure and, therefore, not responding to it (Raney 1989).
4. Oedema is the presence of excess extracellular fluid which causes localised swelling. It is associated with peripheral vascular disease, the effects of gravity on a dependant limb and other physiological changes (Ciocon 1993). The presence of oedema compromises tissue perfusion and removal of waste products (Ryan 1969). Also, the weight of the extra fluid in the feet is likely to result in normal resting pressures being exceeded; which may have an impact on tissue tolerance of pressure.
5. The absence of sebaceous glands on the sole of the foot results in a lack of lubrication of the skin; this may increase the likelihood of friction damage.
6. The superficial fascia is dense over the heel and contains loci of fat in facial pockets. Although this provides added protection from pressure, the effect of exceeding normal tissue tolerance has not been identified. This is likely to affect the response to pressure.
The presence of arterial disease and neuropathy may have an impact on the tolerance of the heel in terms of the extent and duration of applied pressure. Clearly these pathologies are less likely to influence other pressure sites such as the sacrum or ischial tuberosities (parts of the pelvis prone to pressure ulcers). The review of heel pressure ulcers as a separate entity is, therefore, a worthy study.
Description of the intervention
Once a heel pressure ulcer has occurred, treatment is concerned with reducing exposure of the heel to pressure and the management of the wound. The management of the wound is outside the scope of this review.
Reducing the extent and duration of applied pressure is achieved by changing a person's position, using equipment which provides an overall reduced pressure or alternating periods of low and high pressure or both. Pressure‐reducing supports can be for the whole body, for example mattresses, or specific to the body site as with foot protectors and booties. Most interventions are designed for pressure ulcer prevention; however, if an ulcer has occurred it is necessary to reduce the risks of further tissue breakdown.
Devices that reduce the magnitude of the applied pressure are thought to work by distributing body weight over a larger surface area, by conforming to the shape of the body generally or the heel specifically. These are known as constant low pressure devices (CLP). They vary in their construction, for example foam, gel, sheepskin, an air filled or water filled device. Devices which reduce the duration of pressure use a system of air‐filled cells (AP) which alternate between high and low pressure by inflation and deflation of alternate cells. Other devices remove pressure from the body site at risk, for example by supporting the foot or calf in a splint, using a foot trough or pillow that leaves the heel with no surface contact.
Objectives
To conduct a systematic review of all randomised controlled trials (RCTs) of support surface interventions for treating pressure ulcers of the heel.
This will be used to answer the following question:
What are the relative effects of pressure‐relieving interventions used to treat heel pressure ulcers?
Methods
Criteria for considering studies for this review
Types of studies
All randomised controlled trials (RCTs) which compare the effectiveness of pressure‐relieving devices on heel pressure ulcer healing.
RCTs which compare effects of pressure relief for diabetic foot ulcers specifically will be included if heel ulcers can be separately identified.
Controlled clinical trials (CCTs) will be included in the absence of RCTs.
Types of participants
All patients with existing heel pressure ulcers in any care setting. A heel pressure ulcer can be defined as localized damage to the skin and underlying tissue, believed to be caused by pressure, shear or friction, over the external aspect of the calcaneum (the bone at the back of the foot) extending from the plantar surface to below the Achilles tendon.
Types of interventions
Pressure relieving or reducing aids are usually used in combination with wound care to improve healing of a pressure ulcer. Pressure‐relieving aids include the following.
Mattresses:
foam overlays;
foam mattress replacements;
alternating air‐filled overlays;
alternating air‐filled mattress replacements;
air overlays;
air‐fluidised bead beds.
Heel‐specific aids:
air‐filled booties;
foam foot protectors;
gel foot protectors;
pillows and other aids positioned under the legs to relieve pressure;
splints or other medical devices;
sheepskin.
Eligible comparisons will be any of the interventions listed above compared with each other, no intervention or standard care as defined by the trial.
Types of outcome measures
Primary outcomes
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Proportion of wounds healed within a defined time period
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Time to complete healing
Secondary outcomes
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Costs of treatments
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Total costs of interventions where given
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Patient comfort
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Ease of use
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Health‐related quality of life
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Adverse events associated with the intervention
Search methods for identification of studies
Electronic searches
Trials to be considered for this review will be sought from the Cochrane Wounds Specialised Register and the Cochrane Central Register of Controlled Trials (CENTRAL). A search strategy will be developed using the following key words, which will include free text and MeSH terms: decubitus ulcer, pressure sore, pressure ulcer, bed sore, heel ulcer, bed*, mattress*, pressure relie*, overlay*, foot ulcer.
The Cochrane Wounds Group Specialised Register has been compiled through searching the major databases including MEDLINE, CINAHL and EMBASE and is regularly updated through searching the Cochrane Central Register of Controlled Trials, handsearching of wound care journals and relevant conference proceedings. The following search strategy will be used:
#1. BEDS single term (MeSH)
#2. (bed or beds or bedding)
#3. mattress*
#4. (cushion* and (foot or feet))
#5. (foam or foams or cutfoam)
#6. overlay*
#7. (pad or pads or padding)
#8. (gel near pressure)
#9. (gels near pressure)
#10. (pressure near relie*)
#11. (pressure near device*)
#12. (pressure near reduction)
#13. (pressure near reducing)
#14. (pressure near redistribution*)
#15. silicore
#16. ((low next pressure) and support*)
#17. ((low next pressure) and device*)
#18. (constant near pressure)
#19. (alternat* near pressure)
#20. (air near suspension*)
#21. (water near suspension*)
#22. (heel near protector*)
#23. sheepskin*
#24. (foot next waffle)
#25. (air next bag*)
#26. (elevation near device*)
#27. (static next air)
#28. shoe*
#29. footwear*
#30. (callus near remov*)
#31. hosiery
#32. orthoses
#33. orthosis
#34. (orthotic near device*)
#35. (orthotic near therap*)
#36. (foot near pressure)
#37. (foot near protect*)
#38. (feet near pressure)
#39. (feet near protect*)
#40. (heel near pressure)
#41. (heel near protect*)
#42. (contact and cast*)
#43. (walking near cast*)
#44. (boot near pressure)
#45. (boots near pressure)
#46. (booties near pressure)
#47. (glove* near water)
#48. (heel near lift)
#49. (heel near float*)
#50. (heel near suspension*)
#51. (heel near elevat*)
#52. (splint* near heel)
#53. (trough near leg*)
#54. (trough near foot)
#55. (trough near feet)
#56. (trough near heel)
#57. (glove* and heel)
#58. (foot near device*)
#59. (feet near device*)
#60. (heel near device*)
#61. pillow*
#62. (#1 or #2 or #3 or #4 or #5 or #6 or #7 or #8 or #9 or #10 or #11 or #12 or #13 or #14 or #15 or #16 or #17 or #18 or #19 or #20 or #21 or #22 or #23 or #24 or #25 or #26 or #27 or #28 or #29 or #30 or #31 or #32 or #33 or #34 or #35 or #36 or #37 or #38 or #39 or #40 or #41 or #42 or #43 or #44 or #45 or #46 or #47 or #48 or #49 or #50 or #51 or #52 or #53 or #54 or #55 or #56 or #57 or #58 or #59 or #60 or #61)
#63. DECUBITUS ULCER explode all trees (MeSH)
#64. (decubitus near ulcer*)
#65. (bed near ulcer*)
#66. (pressure near ulcer*)
#67. (pressure near sore*)
#68. (bed near sore*)
#69. (#63 or #64 or #65 or #66 or #67 or #68)
#70. (#62 and #69)
#71. (heel or foot or feet)
#72. (#70 and #71)
There will be no restriction on date of publication, language of publication, or publication status (published or unpublished work). Studies and articles cited in articles identified will be checked for eligibility.
Searching other resources
Experts in the field will be contacted and asked if they have been involved in any further studies or are aware of recent or ongoing studies on the treatment of heel pressure ulcers. Manufacturers of pressure‐relieving equipment, wound dressings, topical therapies and debriding agents will be contacted for studies which include heel pressure ulcers.
The following journals will be searched by hand, from 1996 to present:
Phlebology; Diabetic Foot
These journals are not currently indexed in MEDLINE or handsearched by the Cochrane Wounds Group.
Data collection and analysis
Selection of studies
Both review authors will separately examine the titles and abstracts of trials generated by the search to identify those with potential relevance. Disagreements will be resolved by consensus or by reference to a Review Group Editor, when necessary. With the full text of these articles, two review authors will independently assess each study for inclusion according to the selection criteria.
References identified from searches will be entered into a bibliographic software package (Reference Manager).
Data extraction and management
Details of eligible trials will be extracted and summarised using a data extraction sheet. The following data will be extracted:
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patient inclusion and exclusion criteria;
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care setting;
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baseline variables, for example age, sex, diagnosis, co‐morbidity, baseline risk, details of existing ulcers;
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description of interventions;
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numbers of patients ‐ both randomised and analysed;
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description of any co‐interventions;
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follow‐up period;
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results;
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outcome measures;
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adverse events;
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use of intention‐to‐treat analysis;
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trialists' conclusions.
Attempts will be made to obtain any missing data by contacting the study authors. Data from studies that have been published more than once will be included only once, however, where trials are published more than once then the data extraction process will utilise all available sources to facilitate the retrieval of the maximum amount of trial data possible. Data extraction will be undertaken by two review authors independently. Disagreement will be resolved by consensus or by reference to a Review Group Editor, when necessary.
Assessment of risk of bias in included studies
The validity of the studies will be assessed to detect potential sources of bias from the study design. Assessment will include:
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use of clear inclusion and exclusion criteria;
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extent of allocation concealment at the point of randomisation;
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method of generation of the randomisation sequence;
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baseline comparability of treatment groups for important variables;
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use of intention‐to‐treat analysis ‐ whether participants were analysed in the groups to which
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they were originally randomised;
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length of follow up and extent of loss to follow up;
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evidence of blinded outcome assessment.
Assessment of heterogeneity
We will estimate the extent of heterogeneity between study results using the I2 statistic (Higgins 2003). This examines the percentage of total variation across studies due to heterogeneity rather than to chance. Values of I2 over 75% indicate a high level of heterogeneity. In the presence of statistical heterogeneity we will use a random‐effects model for pooling. Where there is no statistical heterogeneity or where I2 is less than 75%, we will apply a fixed‐effect model.
Data synthesis
A narrative summary of results will be presented. The method of synthesising the studies will depend upon the quality, design and heterogeneity of studies identified. If the clinical characteristics, methodology, outcome measures or statistical tests are too variable it may be inappropriate to perform a meta‐analysis. Results will be presented with 95% confidence intervals. Estimates for dichotomous outcomes will be reported as relative risks and mean difference will be used for continuous outcomes.
Subgroup analysis and investigation of heterogeneity
Subgroup analyses will be undertaken, when appropriate, to assess whether the presence of a wound in a specific condition, for example in a diabetic has any effect on treatment. Subgroup analysis will also be done according to grade of ulcer; it is known that the reliability of pressure ulcer diagnosis and classification is particularly poor with Grade 1 pressure ulcers (Nixon 2005)
