Control systems for rotary blood pumps

Abstract

The present invention generally relates to a control system for a rotary blood pump adapted to move blood in a patient. The control system comprises a means for measuring and varying the speed of the pump and a means for measuring the pulsatility index of a patient, and the control system is adapted to maintain the pulsatility index at or near a predetermined value by varying the speed of the pump. The pulsatility index is derived from the amplitude of the actual pump speed over a predetermined time period. Optionally, also, the control system can calculate the second derivative of instantaneous speed of the rotary blood pump and use the calculation of the second derivative of instantaneous speed to detect a suction event, and help prevent it.

1 . A control system for a rotary blood pump adapted to move blood in a patient, said control system comprising a means for measuring and varying the speed of said pump and a means for measuring the pulsatility index of a patient, said control system adapted to maintain said pulsatility index at or near a predetermined value by varying the speed of said pump, and wherein said pulsatility index is derived from the amplitude of the actual pump speed over a predetermined time period.  
     
     
         2 . The control system as defined in  claim 1 , wherein said predetermined time period is about 40 milliseconds.  
     
     
         3 . The control system as defined in  claim 2 , wherein said predetermined value is between 20 to 45 units.  
     
     
         4 . The control system as defined in  claim 1 , wherein said control system calculates the second derivative of instantaneous speed of the rotary blood pump and uses the calculation of the second derivative of instantaneous speed detect a suction event.  
     
     
         5 . The control system as defined in  claim 1 , said control system determines imminence of a suction event based on said stroke work.  
     
     
         6 . The control system as defined in  claim 1 , wherein said target speed is pulsed in cooperation with the heart.  
     
     
         7 . The control system as defined in  claim 1 , wherein said control system includes a selective mode that minimises target pump speed to achieve forward blood flow through both the pump and aortic valve, whilst avoiding retrograde flow.  
     
     
         8 . The control system as defined in  claim 7 , wherein said selective mode sets target speed at about 1250 rpm.  
     
     
         9 . The control system as defined in  claim 1 , wherein said control system calculates or detects left ventricular pressure with respect to time.  
     
     
         10 . The control system as defined in  claim 1 , wherein said control system uses said pulsatility index to derive preload.  
     
     
         11 . The control system as defined in  claim 10 , wherein said control system maintains said preload within a predetermined range by adjusting target speed.  
     
     
         12 . The control system as defined in  claim 11 , wherein said control system mimics starling curve responses of a natural heart.  
     
     
         13 . The control system as defined in  claim 12 , wherein said control system uses preload to mimic starling curve responses of a natural heart.  
     
     
         14 . A control system for use with rotary blood pumps, wherein the control system includes a selective mode that minimises target pump speed to achieve forward blood flow through both the pump and aortic valve, whilst avoiding retrograde flow.