Challenges in characterising a wool knit component of a textile-based compression intervention

Wool knits in the form of bandages, stockings, and/or next-to-skin layers, are used in compression interventions and are normally in direct contact with human skin. The structure of compression products is complex: they are typically multi-layered, overlapped, stretched and applied to a three-dimensional curved surface part of the body. In the case of compression to the lower limb, different sites along the limb differ in shape and also physiologically (e.g. differences in sensible and insensible water/vapour release under different environmental conditions). Thus, measuring fabric properties relevant to wearer thermophysiological responses is challenging but essential. The purpose of this investigation was to refine methods for measuring these textiles properties which influence end-user acceptability and use of compression devices. Key performance properties in question included thermal and water vapour resistance, water vapour and air permeability. Fabrics were examined in relaxed form and also in arrangements simulating use: that is, fabric extension during use was measured in the length and width directions for three different locations on a lower leg manikin. Specimens in these locations were cut, stretched, and fitted to a pre-prepared frame simulating arrangement during use. Results for relaxed and extended arrangements were examined. The performance properties of the fabrics were affected by extension of that fabric. Standard methods used to measure the physiological responses do not adequately reflect use and thus affect clarity of interpretation of the performance of a complex compression device which includes a wool knit layer