Method for controlling a blood pump
A blood pump is temporarily operated at a low rotational speed lying below a design rotational speed. This involves a risk of thrombogenesis since flow detachments may occur at blades of an impeller of the rotary blood pump. For eliminating deposits at said impeller, the rotational speed of said pump is temporarily increased to the design rotational speed. Alternatively, said pump alternately operates at said design rotational speed and a low rotational speed, and this pulsed operation is synchronized with the heart rate.
1. A method of operating a rotary blood pump comprising:
providing a rotary blood pump having an impeller shaped such that blood flow over said impeller is detachment free and swirl free at an elevated rotational speed of at least 30,000 rpm to thereby eliminate thrombogenesis on said impeller;
operating said pump at a lower rotational speed of about 10,000 rpm at which speed thrombogenesis may occur; and
intermittently operating said pump at said elevated rotational speed to eliminate any such thrombogenesis on said impeller.
2. The method according to claim 1 , wherein the rotational speed of the blood pump is increased from its lower rotational speed to said elevated rotational speed at a rate of acceleration of more than 3,000 s− 2 .
3. The method according to claim 1 , wherein the rotational speed of the blood pump is decelerated from said elevated rotational speed to said lower rotational speed by a natural slowdown without supply of braking energy.
4. The method according to claim 3 , wherein the rate of deceleration exceeds 3,000 s− 2 .
5. The method according to claim 1 , wherein intermittent operation of said blood pump at said elevated rotational speed defines periodic pulses (I) with a pulse period at least five times longer than a width of the pulse (I).
6. The method according to claim 1 , wherein the blood pump is driven by an electric motor drawing a current in order to maintain a preselected operating frequency, further comprising measuring said current, determining from any variation thereof a frequency of a superimposed pumping, and synchronizing the operation of the blood pump with the superimposed pumping function.
7. An intracardiac blood pump comprising an electric motor connected to a controller via a catheter, and an impeller driven by said motor, wherein said impeller is shaped such that while thrombogenesis may occur at a lower rotational speed of about 10,000 rpm, blood flow over said impeller is detachment free and swirl free at an elevated rotational speed of at least 30,000 rpm at which thrombogenesis forming on said impeller is eliminated, wherein said controller varies a rotational speed of said pump between said elevated rotational speed and said lower rotational speed.
8. The intracardiac blood pump of claim 7 , further comprising a sensor for measuring current drawn by said electric motor, wherein said electric motor draws a current in order to maintain a preselected operating frequency and the controller varies the rotational speed of said pump between the elevated rotational speed and the lower rotational speed as a function of signals supplied by said sensor.