This method is a non-invasive examination procedure which measures the venous blood flow in the lower legs using infrared light to evaluate the function of venous valves and the effectiveness of venous muscle pump. It is a special mode of Photo-Plethysmography (PPG) and, therefore, sometimes also named D-PPG. In case of LRR venous blood volume changes in the skin are measured which reflect the venous blood flow in the deeper veins because the deep veins are connected with the surface veins via perforating veins.
The examination procedure includes two phases: At the beginning an exercise test must be made which is also called tip-toe-test or muscle pump test. During this exercise the muscle pump in the lower legs is activated to empty the veins what is the pre-condition to measure the refilling of the veins afterwards. In a second phase of the procedure the change of the venous blood volume during the refilling of the veins is recorded and analysed.
In case of healthy venous valves a venous reflow is not possible so that the veins are filled by the arterial inflow only. If in the result of pathological changes, such as varicose veins, the functioning of the venous valves is insufficient then the described regular process is superimposed by a venous reflow so that the previously pumped out blood flows back. In the result the refilling of the veins is accelerated so that the refilling time becomes shorter whereby the higher the level of insufficiency of venous valves the shorter the refilling time. Therefore, the refilling time corresponds with the severity of venous insufficiency.
LRR is a very simple and fast test and, therefore, very suitable as screening examination to evaluate the function of venous valves whereby measurements can be taken also through medical stockings. It allows an early recognition of pathological changes so that an early therapy can slow down the development of the disease.
|T0||Refilling Time||time period necessary to refill the veins after exercise test normal values are > 25 s|
|V0||Volume Displacement||relative blood volume pumped out during exercise|