 This study investigates the function of the femoral vein, proximal valve, and its relationship to the respiratory cycle and heartbeat. The results show that the valve works when the patient is breathing or when their heartbeat is synchronized with the respiration. This suggests that the valve is affected by the kinetic energy of the blood flow in the heart rather than the potential energy of the vascular wall deformations. This article was authored by R. Kolinin, Isuchkov, G. Puchkova, and others.