SHEAR-STRESS MEASURED ON BEDS AND WHEELCHAIRS

Local shear is understood to be one of the principal risk factors for the development of pressure sores. There is a need for a small deforma ble sensor that can measure the shear force between skin and deformabl e materials without disturbing the shear phenomenon. In the present st udy a new shear sensor is introduced with a contact area of 4.05 cm(2) . A series of validation experiments was performed with ten healthy yo ung subjects. It was demonstrated that with a forward-tilted seat, the sum of the local shear forces between skin and sensormat is equal to the resultant shear force measured with a force plate. This result ser ves as a validation of the new sensor. The shear values recorded are 4 .8 kPa in the longitudinal direction and 8.5 kPa in the transversal di rection while sitting in a wheelchair, and 5.6 kPa in the longitudinal direction and 3.1 kPa in the transversal direction on a mattress of a hospital bed, while in sitting position in bed.