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Considerations and Problems in the Development of the Mini‐Spindle Pump
Author(s) -
Hager J.,
Koller J.,
Gschnitzer F.,
Fitz A.,
Klima G.,
Brandstaetter F.
Publication year - 1995
Publication title -
artificial organs
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.684
H-Index - 76
eISSN - 1525-1594
pISSN - 0160-564X
DOI - 10.1111/j.1525-1594.1995.tb02398.x
Subject(s) - engineering , computer science
The premise for the development of the mini‐spindle pump, planned as an implantable device for assisted circulation, was to transport 4 L of water/min in mock circulation with a speed of 12–15,000 rpm against an afterload of 90 mm Hg. After calculations, the resulting first prototype had a spindle rotor with 3 threads (outer diameter, 18 mm; inner diameter, 6.2 mm; length, 45 mm) in a U‐shaped housing, driven by an electric motor with a cooling system. In mock circulation, this pump moved 7.8 L of water/min at 18,000 rpm. To avoid animal experiments, its influence on the blood was tested in a Maxima oxygenator. The device circulated 4.2 L of blood/min with the same speed. Because of its high traumatic he‐molysis rate (>250 mg% of free hemoglobin after 7 h of pumping), the rotor was modified, first without effect at 2.5 threads and then at 4 threads. In addition, in this third prototype, the flow direction was reversed. This prototype was more effective (4.3 L of blood/min at 12,000 rpm in the oxygenator) and the hemolysis rate, after a pumping duration of 8 h, could only be reduced to 180 mg% of free hemoglobin. As a result, a fourth prototype was developed (i.e., the U‐shape of the housing was abandoned). This device functioned better than the third prototype (4.5 L of blood/min at 12,000 rpm in the oxygenator), but the blood trauma increased (220 mg% of free hemoglobin after 7 h of pumping). To find out if the oxygenator may be responsible for the hemolysis problem, the 16th prototype of the large spindle pump was tested in the oxygenator. The result was expected, the level of free plasma hemoglobin was high again (190 mg%). To verify the function of the third and the fourth prototype of the mini‐spindle pump, 4 animal experiments were performed. Under normal cardiac conditions, the devices emptied the left ventricle up to 70% with a speed between 10,500 and 11,200 rpm, moving about 6 L of blood/min (afterload between 65 and 90 mm Hg). The hemolysis rates were between 32 and 90 mg% of free hemoglobin in the plasma.