Numerical model of deep venous thrombosis detection using venous occlusionstrain gauge plethysmography

Strain gauge plethysmography (SGP) is a non-invasive method used in the det ection of deep venous thrombosis (DVT). The technique is based on the measu rement of calf volume changes in response to venous occlusion by a thigh cu ff, the volume changes reflecting the rates of arterial inflow and venous o utflow A numerical model of the blood circulation within the limb and the r esponse of this to a SGP test has been derived, based on treating the diffe rent parts of the circulatory system in the leg as resistance and capacitan ce elements. The simulation results were compared with clinical studies and support the ability of SGP to defect nonocclusive clots of more than 50-60 % of the lumen, as well detecting calf vein occlusion. The non-linear behav iour of the venous compliance with intra-luminal pressure appears to be a p articularly important factor within the model. In addition, increases in ve nous tone due to post-operative venospasm were shown to be a potential sour ce of false positive results.