Validation of a test setup for measuring compression load under elements of multilayer bandages: an in vitro study

Aim . To develop and validate a test setup for measuring the load under compression elements (CE) of multilayer bandages composed of materials with different stiffness. Materials and methods . Prototypes of multilayer bandages were fabricated in the laboratory by combining three types of CEs (foam polymer and dense nonwoven viscose material) with three types of fixing fabrics (FF) based on polyester and viscose/polyester. The test setup consisted of an upper-limb model made of rigid plastic covered with artificial skin and a block with two strain‑gauge sensors that recorded the load in gram-force (gf) under the CE area and in a control zone without a CE at an external pressure of 40 mmHg. For each CE–FF combination, 10 repeated measurements were performed in two regions of the sample (60 values per sensor per group), and the data were analysed using nonparametric statistical tests. Results . The load under the CE differed significantly between groups ( p < 0.001) and depended on the type and stiffness of the material: the median load under type 3 CE with the highest stiffness was 259.4 (252.6; 263.3) gf, whereas under type 1 CE with the lowest stiffness it was 149.9 (145.1; 171.9) gf. Type 2 CE produced intermediate values of 241.7 (206.4; 259.3) gf. Testing of the FFs also showed statistically significant differences in pressure in the absence of a CE ( p < 0.001): the highest load was recorded under type 2 FF (viscose/polyester) at 141.0 (140.2; 142.1) gf, and the lowest under type 1 FF made of polyester with higher surface density at 14.5 (14.3; 15.6) gf; type 3 FF provided an intermediate level of 65.7 (64.9; 69.3) gf. Conclusion . The developed in vitro setup shows high sensitivity to differences in CE stiffness and FF properties and can be used as a screening tool for quantitative comparative assessment of multilayer bandage prototypes with locally differentiated compression areas prior to in vivo studies.