A passive magnetically and hydrodynamically suspended rotary blood pump

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Medical Devices

Background:

• Conventional rotary blood pumps often rely on mechanical bearings or active magnetic systems requiring sensors and power.
• Existing hydromagnetic bearing pumps necessitate extremely small, precise rotor-housing gaps, limiting their use in disposable applications.
• There is a need for rotary blood pump designs with larger manufacturing tolerances for disposable pump heads.

Purpose of the Study:

• To design and evaluate a rotary blood pump utilizing passive magnetic bearings with significantly larger rotor-housing gaps.
• To optimize rotor geometry for reduced shear stress and assess pump performance across various operating conditions.
• To compare the blood damage potential of the novel pump design against a commercial device.

Main Methods:

• A novel pump design with passive magnetic bearings and a rotor-housing gap up to 0.5 mm was developed.
• Numerical simulations were used to optimize rotor geometry for low shear stress.
• An experimental test stand evaluated pressure-flow relationships, vibration, and hemolysis using a viscosity-adjusted fluid and three rotor geometries.

Main Results:

• Stable pump operation was achieved with total gap widths between 0.3 and 0.7 mm, supporting flows of 0-10 L/min and afterloads up to 230 mm Hg.
• Optimal performance occurred with rotors on a fluid pillow (50-250 µm outer gap) and a substantial inner gap (up to 500 µm).
• Hemolysis levels (NIH = 0.0029 ± 0.0012 g/100 L) were lower than the Biomedicus BP-80 (NIH = 0.0033 ± 0.0011 g/100 L).

Conclusions:

• Rotary blood pumps with passive hydromagnetic bearings and large rotor-housing gaps are feasible.
• Pump performance is sensitive to magnetic drive unit positioning, rotational speed, and gap settings.
• Further research is needed to optimize the magnetic drive and assess its robustness against external forces.