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Part 3. Prevention strategies

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VOL: 98, ISSUE: 13, PAGE NO: 37

Krzysztof S. Gebhardt, PhD, RGN, is clinical nurse specialist, pressure ulcer prevention, St George's Healthcare NHS Trust, London

SPONSORED BY THE TIELLE RANGE

Krzysztof S. Gebhardt, PhD, RGN, is clinical nurse specialist, pressure ulcer prevention, St George's Healthcare NHS Trust, London

Revision

As discussed in part 1 of this series (Gebhardt, 2002a), when soft tissues are distorted by pressure and shear in a fixed manner for a prolonged period of time, tissue ischaemia develops. If the distortion persists for long enough, tissue death and necrosis will occur.

The healthy body has mechanisms to protect it against distortion damage. These involve sensing tissue distortion and ischaemia; initiating reflex and voluntary postural changes to relieve pressure and shear, and circulatory adaptations that increase blood flow in distorted tissue to minimise circulatory depletion. After the tissues have been restored to their natural shape, a period of increased blood flow occurs (reactive hyperaemia) to restore the tissues rapidly to their resting state.

These mechanisms can fail for a number of reasons (Box 1). In the case of such patients, pressure ulcers will develop unless effective strategies are in place to prevent their occurrence. When a patient requires care, it is considered good practice initially to make an informal assessment to determine whether there is a risk of pressure ulceration. If there is, a formal assessment should be undertaken. An appropriate risk-assessment tool can be used for this process but the tool should not replace clinical judgement.

Some patients are acutely susceptible to pressure ulcers for a limited period (for example, following trauma or during severe illness), and may completely recover their protective mechanisms. Others are chronically susceptible, for example because of a congenital problem such as spina bifida, or a permanent change in their physical state such as spinal injury. However, an acute episode may leave some chronic damage, and a chronic susceptibility may become very acute owing to an intercurrent illness such as an infection.

As discussed in Part 2 (Gebhardt, 2002b), patients considered to be acutely at risk of pressure ulcers should be provided with an effective pressure-relieving support surface, such as an alternating-pressure air mattress. They should not be left sitting in a chair for more than two hours at a time.

It is considered good practice (although not supported by strong research evidence) to implement a repositioning schedule to minimise intense or prolonged pressure and shear, and provide seating that gives good support. Any interventions that improve a patient's general condition and hasten recovery, such as improved nutrition, effective therapy and good hygiene, are also likely to reduce the period the patient will be at risk.

Why do ulcers still occur?

The NHS has made a significant investment in pressure-ulcer prevention equipment, education and services, and in raising their profile over the past 15 years (Department of Health, 1992; NHSME, 1998). However, there seems to be little reduction in their incidence. This is perhaps the most significant current debate, since it questions the very basis of modern approaches to the problem. There are a number of possible explanations, some of which are outlined below, and it is likely they all play a part.

Over the years, the patient population in hospitals (where the majority of incidence and prevalence data comes from) has become sicker and the length of stay has reduced. This would suggest that at any one time the population contains higher numbers of patients who are acutely ill and so at greater risk of pressure ulcers than, say, 15 years ago.

Much of the effort in pressure-ulcer prevention has been pumped into the provision of equipment. However, this alone is unlikely to reduce incidence. The equipment must be effective, in good working condition, set up appropriately, used for the right patients and at the right time. There is evidence that it is rare for all these criteria to be met (Clark and Cullum, 1992).

Although there is limited documentary evidence to support this, many clinicians who worked in the 1960s and 1970s believe that, while the overall number of pressure ulcers has remained about the same, the number of deep and multiple ulcers has been reduced. In other words, the number of patients affected has remained static but the average amount of damage to each patient has fallen.

Despite evidence of their damaging effects, educational efforts and national guidance, high-risk activities continue. This is particularly pertinent to the practice of sitting patients in chairs for prolonged periods which, although there is no evidence of benefit, continues to be done.

The issue of pressure-ulcer prevention has, lip service aside, a low priority for most clinicians. Pressure-area care is often left until other medical and administrative procedures have been completed. This means that acutely ill patients frequently wait for hours or days to be assessed, to receive pressure-relieving equipment and be put on it, precisely when their need for active intervention is greatest. In the community, waiting times for pressure-relieving equipment can be weeks or even months.

This delay probably arises because of the prevalent belief that pressure ulcers are a 'nursing problem' (Kulkarni and Philbin, 1993) and thus accorded less status than 'medical problems'. This is compounded by the lack of precision in identifying susceptible patients. Since most people identified as being in an 'at risk' group are not actually susceptible, clinicians soon learn that ignoring potential risk rarely leads to actual damage.

Pressure-relieving mattresses

The relative effectiveness of various pressure-relieving devices remains the subject of much debate. A range of devices has been found to be effective in reducing the incidence of pressure ulcers in orthopaedic patients (Box 2).

Low air-loss beds (Inman et al, 1993) and static air mattresses (Takala et al, 1996) have been found to be effective in critical care. In this and other specialties (elderly, medical, orthopaedic, critical care) most evidence is available for the effectiveness of alternating pressure air mattresses (APAMs) (Bliss, 1995; Gebhardt, 1994; Andersen et al, 1982; Bliss et al, 1966). However APAMs less than 10cm deep when inflated appear to be less effective (Conine et al, 1990; Daeschel and Conine, 1985; Sideranko et al, 1992). Those that frequently break down mechanically also have limited usefulness (Stapleton, 1986; Exton-Smith et al, 1982).

Cushions

Although heavily marketed, there is scant evidence to suggest pressure-relieving/reducing cushions are effective in preventing ulcers in acutely ill patients. Best evidence at present suggests that such patients should restrict chair sitting to less than two hours at a time, until their general condition improves (National Institute for Clinical Excellence, 2001).

When patients are seated, it is important to ensure that the chair is of appropriate dimensions to promote good posture. Cushions that promote poor posture and interfere with mobilisation probably cause more harm than good. However, they are probably useful for wheelchair users and those at chronic risk of pressure ulcers who spend prolonged periods in chairs. Nevertheless, cushions should be supplied only after a full and holistic assessment by appropriately trained staff.

The 30° tilt

Perhaps first described by Guttmann (1976), the 30° tilt has been extensively promoted since about 1995 as an effective strategy for pressure-ulcer prevention. Rather than being turned on their side, patients are tilted to 30° and supported in that position with pillows (Preston, 1988). This is supposed to lead to better pressure distribution by keeping patients off their bony prominences, thereby reducing risk of pressure ulcers.

Apart from some anecdotal evidence in spinally injured (Guttmann, 1976) and young disabled patients (Preston, 1988), this practice is supported almost entirely by laboratory studies that show favourable pressure distributions and blood flow in some anatomical positions (Colin et al, 1994).

However, there is little or no clinical evidence that the 30° tilt is effective and safe and, indeed, practicable other than for patients who are completely immobilised. On the contrary, an audit carried out in Japan (Sanada, 2000) showed around 100% increase in pressure-ulcer incidence after the introduction of 30° tilting. It seems wise, therefore, to avoid promotion of this strategy until it can be properly evaluated through controlled studies, as it may not only be useless but actually harmful.

Risk-assessment scales

It is generally recommended that assessment should be assisted by the use of a risk-assessment scale. These have a number of advantages, including the fact that they provide documented evidence of what was considered when the assessment was made and are a useful aide-mémoire to guide the clinician in their thought processes.

The main disadvantage is that they can be used in a ritualistic manner to determine care, especially if based on assumed risk levels that, in fact, have no real meaning (Scott, 2000; Whitfield et al, 2000). This can lead to patients being either denied the necessary care or being given unnecessary care. Current guidance, therefore, stresses that scales should be an aid to clinical judgement not a substitute (NICE, 2001).

There has been extensive debate about the relative advantages of the many available scales. However, there is no research evidence to suggest that the use of any one scale brings better clinical outcomes (such as reduced incidence) than another (Effective Health Care, 1995).

The perfect scale would effectively reduce pressure-ulcer incidence - for example, by guiding preventive interventions consistently to at-risk patients. Scales should not only be appropriate for the patient group/specialty but also acceptable to the clinicians using them and have good inter-rater reliability, the meaning of which should be understood clearly by the whole health-care team.

Grading of pressure ulcers

As with risk assessment scales, there are numerous systems for grading pressure ulcers, most related to the anatomical depth of the ulcer (EPUAP, 1999). Grading pressure ulcers has been found to be a useful tool in pressure ulcer research, a useful surrogate measurement of severity of damage. In general, the higher the grade, the worse the damage.

However, the value of grading has been questioned. The clinical aims of grading are to convey information on the condition accurately to other clinicians in an unambiguous way and provide objective documentation. But which is worse: a small grade 4 pressure ulcer on an ankle or an extensive grade 2 ulcer on the buttocks? The latter is likely to take longer to heal, cause the patient more disability and discomfort and have greater cost implications for the NHS. Yet, if one were to be provided with just the grade, one would probably assume the opposite.

Because a simple grading system does not convey essential information such as location, dimensions, amount of exudate, tissue types present, odour and so on, attempts have been made to develop grading tools that encompass some of these factors (Reid and Morrison, 1994).

However, it has been found that the more complex the tool the lower the inter-rater reliability seems to be and hence accuracy (Healey, 1995), which is the other prerequisite for effective communication. Where health-care institution policy/guidelines expect all wounds to be documented (usually by wound chart), it could be argued that grading pressure ulcers is an unnecessary and potentially misleading duplication from a clinical perspective.

Pressure ulcers are also graded for audit purposes, with prevalence or incidence being presented broken down by ulcer grade. But it could be argued that most current grading systems deliver a level of detail too great for the needs of assessing the problem at macro level.

It has been known since the first pressure-ulcer prevalence surveys that the recording of tissue damage that has not yet broken the skin (for example, persistent erythema - grade 1 in most grading systems) is so unreliable as to make the data useless (Barbenel et al, 1977). In any case, since red patches that resolve with time cause little or no distress or disability to the patient and do not affect health-care resources, the value of recording this data is questionable.

Where there is actual broken skin, the wounds could be described usefully as either cutaneous (shallow) or subcutaneous (deep). The rationale for this is that there are likely to be large differences in healing times, types of dressing used and impact on scarring/loss of function for the two types of wound. The finer distinctions made by most grading systems, while of anatomical interest, are unlikely to augment the macro picture concerned with practical management.

Research gaps

There can be little doubt that the biggest deficit in our knowledge of pressure-area care is a fundamental gap in our understanding of basic physiology. Since life first came out of the supporting medium of the saline water of the sea on to dry land, with the air offering minimal support, organisms had to develop defence mechanisms against catastrophic soft-tissue distortion. We know little or nothing about how these work in the healthy human body. We do not know which sensory organs receive information on tissue distortion and pressure ischaemia, how it is conveyed to the central nervous system, where and how it is processed, and how muscular and circulatory responses are coordinated to restore homeostasis.

Without this understanding, we cannot identify people in whom some aspects of the system are failing, or have failed, who are therefore susceptible to pressure damage. It makes it impossible to target prevention exclusively at those at risk. Rather, we use an expensive scattergun approach, with poorly defined at-risk populations targeted for prevention.

Only a small percentage of those populations are in fact susceptible. Conversely, some people who are vulnerable but do not fit into a recognised at-risk group develop pressure ulcers because their status cannot be identified. This approach, although the only one possible given the current state of knowledge, not only wastes resources but also fails to target all those at risk.

Guidance

The guidance most applicable to the UK is the RCN's Clinical Practice Guideline: Pressure ulcer risk assessment and prevention (2000), which was endorsed by NICE last year. A further set of NICE guidelines on the use of pressure-relieving/reducing equipment is expected this year.

The Department of Health (2001) has also issued a set of benchmarks related to pressure-ulcer prevention as part of its Essence of Care initiative. These have been discussed extensively in the literature (Scanlon and Whitfield, 2002).

New solutions

Perhaps the most exciting development in pressure-ulcer prevention has been the work described by Rosenberg (2000). His Pressure Sore Prevention System (PSPS) uses biofeedback.

The patient support (cushion or mattress) contains elastic chambers connected to small balloons attached to healthy sensitive skin of a paraplegic or quadriplegic patient. For example, when a paraplegic patient is seated on an PSPS cushion, the pressure exerted by the buttocks on the supporting elastic chambers of the cushion is mimicked by small balloons attached to the patient's upper arm, which exert a small but annoying pressure. The pressure is relieved only by altering the position of the buttocks.

In a small, placebo-controlled trial Rosenberg found that use of the system increased repositioning movements significantly in seated paraplegics and a bedbound patient. The non-placebo patients - after a short period of habituation - appeared unaware of the functioning of the system. Most believed it had either broken down or that they were in the placebo group. They did, however, often complain of unusual tiredness after some hours of use, suggesting that the amount of repositioning observed with PSPS was greater than that to which they were accustomed.

Conclusion

There seems little doubt - but not much documentary evidence - to suggest that investment of resources in pressure-ulcer prevention over the past 15 years or so has had some benefits. It has resulted, if not in a reduction in overall incidence of ulcers, at least in reducing the incidence of large and devastating ulcers that were familiar to geriatricians 20 years ago. Equally, pressure ulcers are no longer one of the leading causes of early death in paraplegic patients as they were until the 1950s.

There is general consensus that all patients should be assessed. If deemed at risk, they should be provided with pressure-relieving/reducing equipment and, where appropriate, education on avoidance of high-risk activities. Today many, if not most, health-care organisations have the resources and structures to satisfy these requirements.

Nevertheless, the incidence of pressure ulcers remains unacceptably high. I believe that further progress will be made only if there is a substantial shift in our understanding of the body's defence mechanisms against pressure damage.

We must also develop an accurate method of predicting which patients are susceptible rather than, as at present, guessing who might belong to one of the rather nebulously defined at-risk groups. Only then will it be possible to target resources effectively, carry out reliable randomly controlled studies of the effectiveness of equipment and so on, and begin to overcome the inertia that, all too frequently, leads to tissue damage that can devastate lives.

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