Abstract
Pressure sores are a major problem world-wide, affecting over 5% of all hospital inpatients, and countless others in the community at large. Many different types of specialised beds, mattresses, chairs, cushions, and pads (known collectively as ‘patient support systems’) are sold as pressure-sore prevention equipment, but no consensus exists as to their respective efficacies. The aim of this study is to develop a repeatable and reliable method for their evaluation. An anthropometric articulated phantom has been designed which can be precisely and repeatably applied to a patient support system. The weight of the phantom can be adjusted to represent 3 different percentiles of the population, and can be applied in the flat supine position, or sitting with the torso inclined at 45 or 80 A rotary facial laser-scanner was specially adapted to scan the bottoms of a group of elderly volunteers in order to derive a standard bottom shape. Equipment was designed to measure the rheological properties of the soft tissues overlying the posterior pelvis, and silicone rubbers were formulated to reproduce these properties in the standard bottom. The phantom was instrumented to measure interface pressure distribution under the bottom, pressures inside the soft tissues on the bony prominences, interface pressure on the heels, and normal and shear distortion of the soft tissues. A series of tests were conducted on a range of support systems using both the phantom and live volunteer subjects. Interface pressure maps indicate that the phantom represents a realistic physiological loading condition on all surfaces, but with the benefit of greatly enhanced repeatability. Distortion and shear measurements prove to be highly selective in ranking support surfaces.