Background: One of the recommended treatments for disorders associated with the\nlower extremity venous insufficiency is the application of external mechanical compression.\nCompression stockings and elastic bandages are widely used for the purpose\nof compression therapy and are usually designed to exert a specified value or range\nof compression on the leg. However, the leg deforms under external compression,\nwhich can lead to undesirable variations in the amount of compression applied by the\ncompression bandages. In this paper, the use of an active compression bandage (ACB),\nwhose compression can be regulated through an electrical signal, is investigated. The\nACB is based on the use of dielectric elastomer actuators. This paper specifically investigates,\nvia both analytical and non-linear numerical simulations, the potential pressure\nthe ACB can apply when the compliancy of the human leg is taken into account. The\nwork underpins the need to account for the compressibility of the leg when designing\ncompression garments for lower extremity venous insufficiency.\nMethods: A mathematical model is used to simulate the volumetric change of a calf\nwhen compressed. Suitable parameters for this calf model are selected from the literature\nwhere the calf, from ankle to knee, is divided into six different regions. An analytical\nelectromechanical model of the ACB, which considers its compliancy as a function\nof its pre-stretch and electricity applied, is used to predict the ACB�s behavior. Based on\nthese calf and ACB analytical models, a simulation is performed to investigate the interaction\nbetween the ACB and the human calf with and without an electrical stimulus\napplied to the ACB. This simulation is validated by non-linear analysis performed using\na software based on the finite element method (FEM). In all simulations, the ACB�s elastomer\nis stretched to a value in the range between 140 and 220 % of its initial length.\nResults: Using data from the literature, the human calf model, which is examined\nin this work, has different compliancy in its different regions. For example, when a\n28.5 mmHg (3.8 kPa) of external compression is applied to the entire calf, the ankle\nshows a 3.7 % of volume change whereas the knee region undergoes a 2.7 % of volume\nchange. The paper presents the actual pressure in the different regions of the calf\nfor different values of the ACB�s stretch ratio when it is either electrically activated or not activated, and when compliancy of the leg is either considered or not considered.\nFor example, results of the performed simulation show that about 10 % variation in\ncompression in the ankle region is expected when the ACB initially applies 6 kPa and\nthe compressibility of the calf is first considered and then not considered. Such a variation\nreduces to 5 % when the initial pressure applied by the ACB reduced by half.\nConclusions: Comparison with non-linear FEM simulations show that the analytical\nmodels used in this work can closely estimate interaction between an active compression\nbandage and a human calf. In addition, compliancy of the leg should not be\nneglected when either designing a compression band or predicting the compressive\nforce it can exert. The methodology proposed in this work can be extended to other\ntypes of elastic compression bandages and garments for biomedical applications.
Loading....