[Theoretical bases of a cardio-synchronised jet injection system into the vena cava]

Aim of this paper is to present a procedure aimed at raising the flow rate in the vena cava. To this purpose some fluid is injected at high speed in the vessel, accelerating the flow and dragging the stagnating flow upstream the catheter. In order to raise the efficiency of the system and to avoid damage to heart valves, the injection is synchronised with the diastole. A prototype of an injection system has been designed and built, in order to reach these goals. The injection times are controlled by the electrocardiogram track of the patient, in such a way that the maximum flow rate occurs when the tricuspid valve is open. A "dragging effect" index, that is the ratio between overall flow rate induced by any injection (injected flux plus dragged flux) and injected flux flow rate has been evaluated, both theoretically and experimentally. An experimental model of the lower vena cava has been built and used to measure the velocity profile in the vessel. The dragging effect at the confluence between the two iliac and the vena cava has been verified. By making the catheter sections smaller and/or raising the feeding pressure it is possible to have the injection of small volumes at high speed, capable of moving the blood in the vena cava with a minor contribution of external fluid, thus reducing risks of volume overload and overdiluition of blood.