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ABSTRACT: This paper presents a validated model of calf compression with an external pressure cuff as used for deep vein thrombosis. Magnetic resonance (MR) images of calf geometry were used to generate subject-specific finite-element (FE) models of the calf cross section. Ultrasound images of deep vessel collapse obtained through a water-filled cuff were used to validate model behavior. Calf/cuff pressure interface measurements were applied to the FE model and the resulting tissue deformation was compared with MR image in normal volunteers (three females, four males, age range 20-55) using two distinct cuffs. MR observations and the model results showed good qualitative agreement. A similar reduction in cross-sectional area of the posterior tibial veins was obtained under both symmetric compression (89%) and asymmetric compression (81%), but greater compression of the anterior tibial veins was achieved with symmetric compression. The need to account for the effective compressibility of the calf tissue suggests that external measurements of the calf tissue deformation will not accurately predict deep vessel collapse. These results have implications for the modification of venous haemodynamics by such systems and could help to improve cuff design.
IEEE Transactions on Biomedical Engineering 03/2009; · 2.28 Impact Factor
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ABSTRACT: This paper presents a validated model of calf compression with an external pressure cuff as used for deep vein thrombosis. Magnetic resonance (MR) images of calf geometry were used to generate subject-specific finite-element (FE) models of the calf cross section. Ultrasound images of deep vessel collapse obtained through a water-filled cuff were used to validate model behavior. Calf/cuff pressure interface measurements were applied to the FE model and the resulting tissue deformation was compared with MR image in normal volunteers (three females, four males, age range 20-55) using two distinct cuffs. MR observations and the model results showed good qualitative agreement. A similar reduction in cross-sectional area of the posterior tibial veins was obtained under both symmetric compression (89%) and asymmetric compression (81%), but greater compression of the anterior tibial veins was achieved with symmetric compression. The need to account for the effective compressibility of the calf tissue suggests that external measurements of the calf tissue deformation will not accurately predict deep vessel collapse. These results have implications for the modification of venous haemodynamics by such systems and could help to improve cuff design.
IEEE transactions on bio-medical engineering 03/2009; 56(2):273-80. · 2.15 Impact Factor
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ABSTRACT: Intermittent pneumatic compression (IPC) is widely used for deep vein thrombosis (DVT) prophylaxis. The technique involves periodic inflation of a compression cuff around a limb, which acts to simulate the muscle pump mechanism, encouraging venous blood flow. However, there is uncertainty regarding the relationship between compression, vascular effects and clinical outcomes. This study investigates calf compression provided by four IPC cuffs with different air bladder configurations. Interface pressure between the cuff and the skin surface is measured and magnetic resonance (MR) images are obtained showing the calf cross section before and during compression. The data will be used to inform numerical simulations of IPC, leading to increased understanding of the implications of cuff design in relation to IPC and DVT prophylaxis.
Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE; 09/2007
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ABSTRACT: The intermittent compression of the calf with an external pressure cuff for the prevention of deep vein thrombosis (DVT) is a well established treatment for surgical patients. The exact mechanisms by which DVT is prevented are poorly understood. This study presents a finite element model of calf cross section, based on MR images of calf geometry, to examine the variation in calf deformation during compression with four different cuff types. Cuff pressure distribution is modelled using interface pressures obtained in a volunteer study. The model has been validated against gross calf deformation obtained from MR images of the compressed calf. This validation has illustrated the importance of out-of-plane boundary conditions, material properties and the variation in cuff loading in the axial direction. In the future this model may have merit in determining optimum pressure loading regimes for intermittent pneumatic compression (IPC) cuff design.
Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE; 09/2007
