Exploring the risk factors for pressure ulcer development in vulnerable seated patients and interventions involving self-repositioning to minimise risk
Lesley Stockton, PhD, PGCHE, BSc, DipOT, is lecturer; Maria Flynn,PhD, MSc, PGCHE, BSc, RGN, is senior lecturer; both at Schoolof Health Sciences,Universityof Liverpool.
Stockton, L., Flynn, M. (2009) Sitting and pressure ulcers 1: risk factors, self-repositioning and other interventions. Nursing Times; 105: 24: early online publication.
This is the first in a two-part unit on continuous unrelieved sitting and its role in pressure ulcer development. The unit highlights points from new Tissue Viability Society (2009) guidelines. This part examines risk factors and interventions involving self-repositioning in vulnerable patients.
Keywords: Sitting, Pressure ulcers, Pressure ulcer prevention, Repositioning
- This article has been double-blind peer reviewed
It is widely acknowledged that many pressure ulcers are preventable, yet they remain a global problem.
There are huge international costs associated with their management and treatment, and costs in the UK reach an estimated £1.4bn–£2.1bn annually (Bennet et al, 2004; Clark, 2004). Consequently, preventing pressure ulcers would enable valuable healthcare resources to be redirected as well as protecting patients’ quality of life.
The intrinsic physiological factors of pressure ulcer formation are well documented. Acute illness, immobility, altered consciousness, use of analgesics, lack of sensation, nutritional status, and status of local perfusion are all cited in their development (Bliss, 1993; Dinsdale, 1974).
It is generally accepted that in vulnerable people, the external effects of unrelieved localised pressure, shear forces and friction will result in tissue damage (Rithalia and Gonsalkorale, 1998; Brienza et al, 1996).
Key pressure ulcer development sites when recumbent are the back of the head, scapulae, elbows, sacrum and heels when supine, and over the ear, shoulder, greater trochanter, medial and lateral condyle and malleolus when lying on the side.
During sitting, Trumble (1930) estimated that as much as 75% of body weight is taken through just 8% of body surface area, with peak pressures predominantly taken through the ischial tuberosities, which have the lowest point of contact with a seat.
People who are immobile often sit in one chair for many hours throughout the day. In the community, wheelchair users spend up to 18 hours a day in a wheelchair (Stockton and Parker, 2002). Many are subject to sustained unrelieved pressures due to their lack of pressure-relieving movement.
In the vulnerable inpatient population, Gebhardt and Bliss (1994) found that older orthopaedic patients had an increased risk of pressure ulcer development when sitting for just over two hours.
If patients have a poor sitting position and regimen, thensustained shear and pressure forces cause tissue deformation, ischaemia and hypoxia, interfering with blood flow and lymphatic drainage, resulting in a necrotic deep tissue injury (DTI).
The ischii are the most common sites for this type of wound, with extensive internal damage occurring near the curvature of the bones before visible signs of damage appear on the skin surface.
DTIs can take months or even years to heal as they have high infection rates and can even be fatal. Often surgical intervention is needed to close the wound, and there is a high potential for recurrence at the depleted and weakened tissues at the healed site.
Although the ischial tuberosities are the prime sites for pressure ulcer development in seated people, other potential sites with sustained contact with the chair are: the sacrum; greater trochanter; popliteal fossa (at the back of the knee); bony prominences of the spine; and scapula (see Figs 1 and 2).
Heels are also at risk of pressure ulcer development due to poor sitting position caused by an unsuitable chair, as they can take intense pressures if being used as an anchor to prevent people from sliding out of their seat.
Less frequently, other sites such as elbows, medial aspect of the knees and the genitals may be affected in some people with severe postural difficulties.
During the course of a day, a healthy mobile person will sit on several seats and adopt different positions and different seating. Whichever postural positions are used, healthy people will not normally suffer long-term damage to their muscles or skeletal system as they are not subject to unrelieved pressure.
However, this is not the case for vulnerable people who need to spend large parts of every day in a sitting position. For them, inadequate seating adjustments leading to poor sitting positions, such as pelvic obliquity (see Fig 3) can increase their vulnerability to pressure ulcers, increase spasm, spasticity and pain. It can also result in fixed postural deformities such as scoliosis of the spine.
There are important preventative principles in relation to positioning people who spend substantial periods of time in a chair or wheelchair. These should take into account postural alignment and supporting the feet to minimise the damaging effects of pressure and shear forces when sitting.
Specific consideration of the design and dimensions of a chair when seating patients will help in their postural maintenance and function. This should include the height, depth and width of the seat, the backrest height and angle, and the height and style of the armrests.
A patient’s sitting posture is primarily determined by the position of the pelvis in the chair, as the spine alters its position accordingly to enable the head to be held upright, and the upper and lower limbs are subsequently aligned.
A posterior pelvic tilt will result in the patient being ‘slumped’ in the chair, so that the bony sacrum takes the pressure, with horizontal shear forces arising because of this poor sitting position. The thin tissue is both compressed and deformed over the sacrum, in effect being both pulled and squeezed at the bony prominence, resulting in an elongated shear pressure ulcer.
A slumped sitting position is an all-too familiar sight on wards and in the community and routinely occurs when the seat is too deep (long), or too high for patients, who assume this position so their feet can reach the floor to support them.
Specific attention should also be given to patients’ level of activity to maintain their optimal occupational performance, so their chair and sitting position enables rather than disables them.
For example, when people feel unstable due to inadequate seating, they are less likely to risk moving in the seat to reach a drink on the ward table. In the community, they are less likely to bend forward in a wheelchair to load a washing machine or to do pressure-relieving movements.
Current advice is that self-repositioning pressure-relief movement should be carried out by a seated person every 15–30 minutes (NHS Choices, 2008). There is little readily available advice on how long this pressure-relief movement or ‘off-load’ of tissues should be maintained. One small research study indicated that up to three minutes and 30 seconds may be needed each time to raise tissue oxygenation to unloaded levels in some wheelchair users (Coggrave and Rose, 2003).
When continuously sitting, several types of self-repositioning and off-loading movements can be done by patients themselves or with nurses’ or carers’ help (Stockton and Rithalia, 2008; Henderson et al, 1994). Each type of movement requires different personal skill and physical ability that nurses need to be aware of. These movements are:
Lift-off: in this type of movement, the seated person pushes up from the armrest of the chair to take the buttocks completely off the support surface. For wheelchair users unable to support any of their weight through their legs, their entire lifted body weight is taken through their arms as they push upwards, locking the elbows.
This lift requires good upper-body strength and therefore tends to be done by younger, active wheelchair users. Those who can perform this movement when young may need to rethink their approach as they age and experience joint degeneration, or develop median nerve problems due to continuous wheelchair propulsion.
Stand: this should be done routinely if patients are able to do so. Those who can bear weight should be encouraged to stand for a short period, ensuring necessary support and help is provided.
To prepare to stand, patients could be encouraged to make small movements to the edge of the seat, put heels back slightly and push to stand using the armrests.
It is important that the design and dimensions of the seat do not obstruct the action of safely rising from the chair, as seen when patients struggle to rise when armrest heights are not at the correct height, or the seat is too deep, or with obstructive chair-frame designs that make it difficult for them to pull the heels back slightly.
Before encouraging someone to stand up from a wheelchair, ensure the brakes are on and that the footplates are moved to each side.
Roll: the seated person moves from side to side, lifting each buttock completely from the cushion to encourage tissue reperfusion at the lifted side.
The height and position of the armrests are important for carrying out this movement safely. If they are too low, patients will need to lean downwards to gain support while rolling, and they may become unstable in their seat.
Although this movement does not need as much strength as the lift, it does require patients to have good trunk control to gauge the movement and control their return to a midline seated position.
However, this level of trunk control is not always possible in those with degenerative neurological conditions, and the movement may result in painful muscle spasticity in some people.
Forward lean: in this type of movement, the seated person leans forward while seated, moving the chest towards the knees. This movement does not take the buttocks off the support surface but it helps to reduce the peak pressures taken through the ischial tuberosities.
To perform this movement, patients need to have some trunk control.
The forward movement can cause difficulties with incontinence if the bladder is full, and difficulties with breathing in some people, or even autonomic dysreflexia in those with spinal cord injury.
Current pressure ulcer prevention guidelines limit clinical direction on seating to four points. They advise that seating assessment for aids and equipment should be carried out by trained assessors with specific specialist knowledge and expertise, such as physiotherapists or occupational therapists (NICE, 2005).
However, waiting for specialist advice can lead to lengthy delays, so nurses who have daily contact with patients on wards or in the community have an important role in preventing pressure ulcer development in vulnerable people who have to spend long periods of time in chairs.
An awareness of the potential risks of pressure ulcer development, together with knowledge on the principles of good seating, can provide nurses with key information to support and educate patients and carers.
For more information on preventing and managing pressure ulcers in seated patients, see the Tissue Viability Society (2009) guidelines and Clark (2009).
- Part 2, to be published next week, examines patient posture and techniques to prevent pressure ulcers
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