Lateral pressure equalisation as a principle for designing support surfaces to prevent deep tissue pressure ulcers

• Published in: PloS one 2020-01, Vol.15 (1), p.e0227064-e0227064
• Main Authors: Boyle, Colin J, Carpanen, Diagarajen, Pandelani, Thanyani, Higgins, Claire A, Masen, Marc A, Masouros, Spyros D
• Format: Article
• Language: English
• Subjects: Bioengineering; Biology and Life Sciences; Biomechanical Phenomena; Buttocks; Data collection; Decubitus ulcer; Deformation; Deformation effects; Deformation mechanisms; Equipment Design; Finite element method; Humans; Information sharing; Injuries; Lateral pressure; Mechanical engineering; Medicine and Health Sciences; Pelvis; Physical Sciences; Pressure; Pressure Ulcer - prevention & control; Pressure ulcers; Soft tissues; Software industry; Stress; Therapy, Soft Tissue - methods; Tissues; Ulcers
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0227064

When immobile or neuropathic patients are supported by beds or chairs, their soft tissues undergo deformations that can cause pressure ulcers. Current support surfaces that redistribute under-body pressures at vulnerable body sites have not succeeded in reducing pressure ulcer prevalence. Here we show that adding a supporting lateral pressure can counter-act the deformations induced by under-body pressure, and that this 'pressure equalisation' approach is a more effective way to reduce ulcer-inducing deformations than current approaches based on redistributing under-body pressure. A finite element model of the seated pelvis predicts that applying a lateral pressure to the soft tissue reduces peak von Mises stress in the deep tissue by a factor of 2.4 relative to a standard cushion (from 113 kPa to 47 kPa)-a greater effect than that achieved by using a more conformable cushion, which reduced von Mises stress to 75 kPa. Combining both a conformable cushion and lateral pressure reduced peak von Mises stresses to 25 kPa. The ratio of peak lateral pressure to peak under-body pressure was shown to regulate deep tissue stress better than under-body pressure alone. By optimising the magnitude and position of lateral pressure, tissue deformations can be reduced to that induced when suspended in a fluid. Our results explain the lack of efficacy in current support surfaces and suggest a new approach to designing and evaluating support surfaces: ensuring sufficient lateral pressure is applied to counter-act under-body pressure.