Adaptive flow calculation for a mechanical circulatory support device

1 . A method of determining flow through a circulatory support device, the method comprising:

receiving a motor current signal measured from a motor of the circulatory support device during operation;

determining within a time window of the motor current signal, a measured motor current value at which flow through the circulatory support device is maximum;

determining an offset value based, at least in part, on the measured motor current value;

determining based, at least in part, on the received motor current signal, whether an abnormal condition has occurred;

adjusting the motor current signal measured from the motor based, at least in part, on the offset value and the determination of whether an abnormal condition has occurred to produce an adjusted motor current signal; and

determining the flow through the circulatory support device based, at least in part, on the adjusted motor current signal.

2 . The method of claim 1 , wherein the measured motor current value is a maximum motor current value or a minimum motor current value within the time window.

3 . The method of claim 2 , wherein the measured motor current value is the minimum motor current value within the time window.

4 . The method of claim 1 , wherein a length of the time window is between one and four seconds.

5 . The method of claim 1 , wherein determining the offset value is further based, at least in part, on a speed of the motor.

6 . The method of claim 5 , further comprising:

storing, on at least one storage device, data relating flow values to motor current values for each of a plurality of motor speeds, and

wherein determining the offset value comprises:

determining based, at least in part, on the stored data, an expected motor current value associated with a maximum flow at the speed of the motor; and

determining the offset value as a difference between the motor current value and the expected motor current value.

7 . The method of claim 6 , wherein adjusting the motor current signal comprises adding the offset value to the motor current signal to produce the adjusted motor current signal.

8 . The method of claim 6 , wherein determining the flow through the circulatory support device comprises:

determining the flow further based, at least in part, on the stored data relating flow values to motor current values at the speed of the motor.

9 . The method of claim 1 , wherein adjusting the motor current signal based, at least in part, on the offset value and the determination of whether an abnormal condition has occurred to produce an adjusted motor current signal comprises using an offset value of zero when it is determined that an abnormal condition has occurred.

10 . The method of claim 9 , wherein determining whether an abnormal condition has occurred comprises determining whether the circulatory support device is in a suction state or a decoupling state.

11 . The method of claim 1 , further comprising:

storing previously determined offset values in a buffer; and

storing the determined offset value in the buffer.

12 . The method of claim 11 , wherein the each of the previously determined offset values in the buffer is a scaled offset value scaled based on a speed of the motor at the time when the offset value was determined, and

wherein storing the determined offset value in the buffer comprises:

scaling the determined offset value based on the speed of the motor; and

storing the scaled determined offset value in the buffer.

13 . The method of claim 11 , wherein adjusting the motor current signal comprises adjusting the motor current signal based, at least in part, on a median value of the previously determined offset values in the buffer.

14 . The method of claim 13 , wherein adjusting the motor current signal comprises:

transforming the median value based on a present speed of the motor; and

adjusting the motor current signal based on the transformed median value.

15 . The method of claim 11 , further comprising:

storing the determined offset value in the buffer only when it is determined that an abnormal condition has not occurred.

16 . The method of claim 1 , further comprising:

filtering the received motor current signal, and

wherein adjusting the motor current signal comprises adjusting the filtered motor current signal.

17 . The method of claim 1 , further comprising:

displaying on at least one graphical user interface, an indication of the determined flow through the circulatory support device.

18 . The method of claim 1 , further comprising displaying on at least one graphical user interface, a numerical value of the determined flow and/or a graphical value indicating the determined flow.

19 . A circulatory support device, comprising:

a rotor;

a motor configured to drive rotation of the rotor at one or more speeds; and

at least one controller configured to:

receive a motor current signal measured from the motor;

determine within a time window of the motor current signal, a measured motor current value at which flow through the circulatory support device is maximum;

determine an offset value based, at least in part, on the measured motor current value;

determine based, at least in part, on the received motor current signal, whether an abnormal condition has occurred;

adjust the motor current signal measured from the motor based, at least in part, on the offset value and the determination of whether an abnormal condition has occurred to produce an adjusted motor current signal; and

determine the flow through the circulatory support device based, at least in part, on the adjusted motor current signal.

20 . A controller for a circulatory support device, the controller comprising:

at least one hardware processor configured to:

receive a motor current signal measured from a motor of the circulatory support device;

determine within a time window of the motor current signal, a measured motor current value at which flow through the circulatory support device is maximum;

determine an offset value based, at least in part, on the measured motor current value;

determine based, at least in part, on the received motor current signal, whether an abnormal condition has occurred;

adjust the motor current signal measured from the motor based, at least in part, on the offset value and the determination of whether an abnormal condition has occurred to produce an adjusted motor current signal; and

determine the flow through the circulatory support device based, at least in part, on the adjusted motor current signal.