Suction detection methods and devices

Abstract

A method of detecting a suction condition during operation of a rotary blood pump with an inlet connected to a ventricle of the heart of a patient, an outlet connected to an artery of the patient, a rotor, and a control circuit configured maintain the rotor at a set rotational speed. The method includes measuring the rotational speed of the rotor at a plurality of times during each of a plurality of speed measurement intervals. A speed range is determined between a minimum measured speed and a maximum measured speed during each of the plurality of speed measurement intervals. At least one additional parameter relating to the operation of the blood pump is derived. A suction detection signal is generated if both at least one determined speed range is above a speed range limit and the at least one additional parameter is indicative of a suction condition.

What is claimed is: 
     
         1 . A method of detecting a suction condition during operation of a rotary blood pump with an inlet connected to a ventricle of a heart of a patient, an outlet connected to an artery of the patient, and a control circuit configured to maintain a rotor of the rotary blood pump at a set rotational speed, comprising:
 (a) monitoring a flow rate of blood through the pump; and   (b) determining a duty parameter representing a proportion of a time during one or more cardiac cycles of the patient's heart when the flow rate is above a crossover flow rate; and   (c) generating a suction detect signal based at least in part on the duty parameter.   
     
     
         2 . The method of  claim 1 , wherein generating the suction detect signal includes comparing the duty parameter in one or more cardiac cycles with a duty limit corresponding to a set proportion of the time during the one or more cardiac cycles and generating the suction detect signal based at least in part on the comparison. 
     
     
         3 . The method of  claim 2 , further comprising the step of generating the suction detect signal if the duty parameter in one or more cardiac cycles represents a proportion above the set proportion. 
     
     
         4 . The method of  claim 3 , wherein generating the suction detect signal is performed if the duty parameter in a single cardiac cycle represents a proportion above the set proportion. 
     
     
         5 . The method of  claim 4 , further comprising deriving at least one additional parameter relating to operation of the blood pump, generating at least one additional signal if the at least one additional parameter is indicative of a suction condition, and altering operation of the blood pump if both the duty cycle signal and the at least one additional signal are generated. 
     
     
         6 . The method of  claim 5 , wherein deriving at least one additional parameter includes measuring a speed of the pump at a plurality of times during one or more speed measurement intervals at least partially encompassing the one or more cardiac cycles and determining a speed range between a minimum measured speed and a maximum measured speed during each speed measurement interval. 
     
     
         7 . The method of  claim 5 , wherein generating at least one additional signal is performed by generating a speed range signal if the speed range exceeds a range limit, and wherein the suction detect signal is generated if both the speed range signal and the duty signal are both generated. 
     
     
         8 . The method of  claim 1 , further comprising determining an average flow rate, and wherein the crossover flow rate is a function of the average flow rate. 
     
     
         9 . The method of  claim 8 , wherein the crossover flow rate is equal to the average flow rate. 
     
     
         10 . The method of  claim 9 , further comprising altering operation of the blood pump responsive to the suction detect signal.