E.E. Kunst

Dynamic pumping performance of the Hemopump - a small intraventricular blood pump

We studied the pumping characteristics of the Hemopump®, a commercially availabe miniature intraventricular blood pump for temporary support of failing hearts. The Hemopump® is an axial flow pump of which the characteristics can be described by turbomachine theory. Experiments with water and a mock circulation verified that the pumping characteristics of the Hemopump®, in terms of both pressure head and flow as a function of rotational speed, very well can be described by a first order differential equation. The influence of blood with its non-Newtonian character is being investigated

Dynamic pumping characteristics of the Hemopump

While pumping blood with the Hemopump® in sheep, the ability of predicting the instantaneous pump flow from the pressure difference over the pump system and pump parameters was investigated. For rotational speed n between 300 and 475 revolutions per second (rps), maximum pump flow QO(n) at zero pressure difference, internal pump resistance R(n), and inertia parameter Lc were found to be suitable parameters for Hemopump® characterization. The instantaneous pump flow could be estimated with an accuracy of approximately 1.0 [ml/s]. The values of the pump source parameters (± sd) were: (the figures in parentheses represent earlier reported values found while pumping water) Lc was a constant of 21.4 ± 6.4 [Pa·s2/ml] (in water: 10.8). QO(n) is linearly related to rotational speed n according to: QO(n) = Qo(ncen) + CQ(n - ncen), with QO(ncen) = 49.4 ± 4.5 [ml/s] (in water: 60.3), CQ = 142 ± 22.4 [10−3 ml] (in water: 146), and ncen = 387.5 [rps]. R(n) is linearly related to rotational speed n according to: R(n) = R(ncen) + CR(n - ncen), with R(ncen) = 556 ± 124 [Pa·s/ml] (in water: 502) and CR = 1.47 ± 0.83 [Pa·s2/ml] (in water: 1.67).