DYNAMIC PUMPING CHARACTERISTICS OF THE HEMOPUMP(R)

While pumping blood with the Hemopump(R) in sheep, the ability of pred icting the instantaneous pump flow from the pressure difference over t he pump system and pump parameters was investigated. For rotational sp eed n between 300 and 475 revolutions per second (rps), maximum pump f low Q(o)(n) at zero pressure difference, internal pump resistance R(n) , and inertia parameter L(c) were found to be suitable parameters for Hemopump(R) characterization The instantaneous pump flow could be esti mated with an accuracy of approximately 1.0 [ml/s]. The values of the pump source parameters (+/- sd) were: (the figures in parentheses repr esent earlier reported values found while pumping wafer) L(c) was a co nstant of 21.4 +/- 6.4 [Pa.s(2)/ml] (in water: 10.8). Q(O)(n) is linea rly related to rotational speed n according to: Q(O)(n) = Q(O)(n(cen)) + C-Q(n - n(cen)), with Q(o)(n(cen)) = 49.4 +/- 4.5 [ml/s] (in water 60.3), C-Q = 142 +/- 22.4 [10(-3) ml] (in water: 146), and n(cen) = 38 7.5 [rps]. R(n) is linearly related to rotational speed n according to : R(n) = R(n(cen)) + C-R(n - n(cen)), with R(n(cen)) = 556 +/- 124 [Pa . s/ml] (in water: 502) and C-R = 1.47 +/- 0.83 [Pa. s(2)/ml] (in wate r: 1.67).