Pressure Mapping

After 8 months at home, Mr. A.H. has lost weight and is experiencing muscle atrophy, especially in his buttocks and lower extremities; as a result, he now has increased boney prominences. Mr. A.H. continues to worry about redeveloping a wound at his coccyx and has started to develop red areas under both of his ischial tuberosities. He is wondering if his wheelchair cushion could be causing some of this redness, and whether he should be using the power tilt option on his power wheelchair more frequently for pressure relief. Mr. A.H. has booked a reassessment of his wheelchair seating prescription with his occupational therapist to determine if modifying his positioning would reduce his risk of skin issues.
Q32. What is pressure mapping?
1. Pressure mapping systems measure interface pressure between the user and the support surface.
2. Pressure is defined as force over area. Interface pressure is defined as the pressure that occurs at the interface between the body and the support surface.

Figure 10. Areas where bones are close to the surface (called "bony prominences") and areas that are under the most pressure are at greatest risk for developing pressure sores. Source: Copyright © 2010 by University of Washington/MSKTC.

Q33. Describe the various factors that can confound results obtained from a pressure mapping assessment.
1. Other contributing factors (extrinsic: skin moisture, friction, shear; and intrinsic: nutrition, age, arterial pressure) influence relationship between interface pressure and pressure ulcer incidence.
2. Subject variability, such as body weight, muscle tone, body fat content and skeletal frame size influences interface pressure.
3. Time.
4. Material properties of the pressure transducer, soft tissue and the support surface may cause variability in data output.
5. No standard methodological guidelines exist for pressure measurement.
Q34. Are results from pressure mapping studies in able-bodied populations or in seniors applicable to persons with SCI?
1. Data generated from pressure mapping studies on non-disabled subjects should not be generalized to the SCI population, as there are significant pressure differences between the 2 groups.
2. Typical areas of high pressure for the SCI population are ischial tuberosities (IT) especially if there is asymmetry in the IT loading and the sacrum or coccyx.
3. Data generated from pressure mapping studies on seniors should not be generalized to the SCI population.
For more information please see: Pressure Mapping