Hydraulic properties of the Hemopump HP31: a study of the downstream pressure distribution

The Hemopump was commercialized as an useful tool for the left ventricle assistance. Bioengineers and clinicians showed great interest to develop applications and to analyze its hydraulic behaviour; in this work an application for axial pump in different conditions is presented. A study of the spatial pressure distribution generated by the impeller of the Hemopump is investigated in highly accurate steady-flow conditions. The experimental set up adopted for this study consists in a plexiglass test pipe (simulating an aortic conduit of 22-mm diameter) and allows the sampling of the pressure at the outlet of the pump in 16 points spaced 1/2 diameter each other. Keeping fixed the constant head at the inlet of the Hemopump and varying the constant head at its outlet, i.e. afterloads, in 11 step levels, it was possible to draw the characteristic flow curves versus delivered pressure for all the seven speed levels. A pressure range of about 35-130 mmHg and a flow range of about 0.7-3.7 l/min was experimented. The results show that the flow delivered by the Hempopump is fully developed after 5 pressure taps (about 55 mm), with no further varying along the test chamber. These data could be used to optimize the setting up of clinical experimental procedures.