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).