The pressure mapping system
The system output is displayed numerically and visually as color-coded maps of pressure distribution. Examples are shown: a “good” pressure map (Fig. 16.2), not requiring intervention, and a “poor” pressure map (Fig. 16.3), requiring adaptation of the seating system.
Example of a good pressure map. There are no areas of excessively high interface pressure, and a good spread of pressure across the seating surface
Example of a “poor” pressure map. There are areas of high interface pressure over the buttocks (ischial tuberosities) (A) and sacrum (B) and an uneven spread of interface pressure across the seating surface
Pressure mapping arrays for clinical use have evolved from the early 1990s, and with advances in technology have become increasingly reliable. Designed as an objective method to measure interface pressure, they complement pen-and-paper pressure ulcer risk assessment tools, such as the Braden Scale (Bergstrom et al. 1987).
The purpose of interface pressure mapping is to assist with the risk assessment of pressure ulcers and to educate clients, caregivers , and health-care professionals in pressure ulcer prevention and management.
Candidates for Pressure Mapping
Pressure mapping can be used with children or adults at risk of pressure ulceration, particularly those with reduced mobility, poor nutrition, lack of sensation , and acute or chronic illness . Examples are people who are sitting in a wheelchair or chair for most of the daytime.
Pressure ulcers remain a common problem. An extensive European survey, involving 25 hospitals, showed a prevalence rate of 18.1 %, with the most frequently affected areas being the sacrum and heels (Vanderwee et al. 2007). The cost of pressure ulcers is immense, both to the client in terms of pain and decreased quality of life, and to health-care resources in terms of financial expenditure.
Pressure mapping systems are portable and can be used in hospitals, clinics, community settings, and clients’ homes.
The Role of the Occupational Therapist in Applying the Intervention
The role of the occupational therapist (OT) is to complete the assessment process of pressure mapping. The aim is to adapt the most appropriate wheelchair or seat cushion, and to educate clients and caregivers regarding pressure ulcer prevention and management. This process has been outlined by the International Standards Organization (ISO) protocol (ISO 2013) and is summarized as follows:
Clients are initially positioned on a firm surface, such as a mat table, with the pressure-sensing mat placed between the buttocks and the seating surface. This identifies weight-bearing areas, postural abnormalities, and bony prominences. The latter should be confirmed by palpation.
Clients are pressure mapped on their own seating surface.
The adjustable parts of the wheelchair are checked, e.g., to ensure the footplates are at the correct height.
Clients are positioned on a small number of alternative cushions in turn, selected on the basis of client needs, e.g., risk level, posture, stability, and continence.
The pressure maps are recorded after a period of sitting time, at a consistent time point between 5 and 8 min (Stinson et al. 2002; Crawford et al. 2005a; Davis and Sprigle 2008; ISO 2013) on each seating surface.
The OT visually ranks the maps from best to worst pressure distribution. Good pressure distribution is characterized by an even spread of pressure, including good femoral loading and no areas of excessively high pressure (Stinson et al. 2003; Fig. 16.2). Cushions showing poor pressure distribution (Fig. 16.3) for an individual are eliminated (Sprigle 2000).
Optimal cushion selection is based on pressure maps in combination with other factors including the client’s comfort, cushion maintenance, transfers, posture, and stability (Sprigle 2000).
The OT uses the results of pressure maps to educate clients, caregivers , and health professionals. This education includes teaching clients to regularly shift weight from the buttocks and explaining what good postural alignment entails.
The pressure mapping system is used to assist clinicians and clients in eliminating unsuitable seating surfaces.
The results of a pressure mapping assessment demonstrate (1) sitting areas of high interface pressure, such as over the ischial tuberosities and (2) postural abnormalities, such as pelvic obliquity/rotation. The OT uses the pressure mapping results to compare seating surfaces. This procedure determines the optimal sitting surfaces for each client (Crawford et al. 2005b; Sprigle 2000) and can be used to guide adjustment of seating cushions. Pressure maps (Figs. 16.2 and 16.3) provide immediate biofeedback to clients, caregivers, and health professionals, visually demonstrating the effect of an optimal sitting posture and cushion on lowering interface pressures and thus reducing pressure ulcer risk for an individual (Fig. 16.4).
The role of pressure mapping systems in cushion selection
The intervention includes sessions where the clients are educated on the optimal sitting position. Biofeedback is provided to the clients through visualizing pressure maps of their usual sitting position. Here, the OT demonstrates the benefits of shifting weight from the buttocks, and the effect of poor posture or incorrect placement of cushions. The client is informed about the importance of adjusting other components of the seating systems, such as the use or adjustment of wheelchair footplates and the use of tilt and recline functions (Stein et al. 2006). The pressure mapping system also permits optimal cushion settings for high-risk clients, for example air-filled cushions or cushions with accessories.
How the Intervention Eases Impairments, Activity Limitations, and Participation Restrictions
Pressure mapping systems provide valuable information regarding maintenance of skin integrity (International Classification of Functioning, Disability, and Health (ICF) code b810–b849). They provide biofeedback on pelvic alignment (ICF b7201) and on the effects of changing and maintaining body position (ICF d410–d429), hence assisting clinicians in the overall management and prevention of pressure ulcers .
The link between high interface pressure, as measured with pressure mapping systems, and pressure ulcer incidence has been demonstrated in randomized controlled trials . Interface pressures were significantly higher (p < 0.01) for participants who developed pressure ulcers than for those who did not (Brienza et al. 2001; Conine et al. 1994).