摘要：normal characteristics of venous blood flow and im- plications of abnormal venous hemodynamics are much less understood than arterial vascular (dys)functionality. This is mainly due to limitations of methods to study the venous system, especially when they are performed in clinical conditions. Methods to study body venous tone have been re- viewed by Pang (2000): they include mean circula- tory filling pressure technique, constant CO reservoir technique, plethysmography, blood-pool scintigra- phy, linear variable differential transformer tech- nique and intravascular ultrasound. recently, duplex sonography has been reported to be a simple, non- invasive and easily-accessible method to study venous hemodynamics, especially in pregnant women (Karabulut et al., 2003; bateman et al., 2004; roobottom et al., 1995; Gyselaers et al., 2009/1; Gyselaers et al., 2009/2).
