Reservoir plunger position monitoring and medical device incorporating same

Abstract

Apparatus are provided for infusion devices and related control systems and methods. In one embodiment, an infusion device includes a voided portion adapted to receive a shaft portion that includes a shaft coupled to a plunger of a reservoir. The shaft portion includes a detectable feature, and the infusion device includes a sensing arrangement proximate the voided portion to sense the detectable feature. In some embodiments, a control module is coupled to the sensing arrangement to determine a remaining amount of fluid in the reservoir based at least in part on the sensed position of the detectable feature. In other embodiments, the control module identifies an anomalous condition based at least in part on the sensed position of the detectable feature.

What is claimed is: 
     
         1 . A method of operating an infusion device comprising a housing including a voided portion to receive a shaft portion including a displaceable shaft coupled to a plunger of a reservoir and a sensing arrangement proximate the voided portion to sense a detectable feature on a side of the shaft facing the sensing arrangement, the method comprising:
 monitoring an electrical output signal from the sensing arrangement; and   detecting seating of the reservoir based on the electrical output signal, wherein an electrical characteristic of the sensing arrangement is influenced by the detectable feature.   
     
     
         2 . The method of  claim 1 , the detectable feature comprising a protruding feature, wherein detecting seating of the reservoir comprises determining the electrical output signal is indicative of the protruding feature contacting the sensing arrangement. 
     
     
         3 . The method of  claim 2 , wherein a resistance of the sensing arrangement is influenced by the protruding feature contacting the sensing arrangement. 
     
     
         4 . The method of  claim 3 , wherein the sensing arrangement comprises a resistive sensing arrangement having a variable resistance that is influenced by a position of the protruding feature with respect to the sensing arrangement. 
     
     
         5 . The method of  claim 1 , the sensing arrangement generating the electrical output signal based on a proximity of the detectable feature, wherein detecting seating of the reservoir comprises determining the electrical output signal is indicative of the detectable feature within a threshold distance of the sensing arrangement. 
     
     
         6 . The method of  claim 5 , wherein a capacitance of the sensing arrangement is influenced by the proximity of the detectable feature. 
     
     
         7 . The method of  claim 6 , wherein the sensing arrangement comprises a capacitive sensing arrangement having a variable capacitance that is influenced by a position of the detectable feature with respect to the sensing arrangement. 
     
     
         8 . The method of  claim 5 , wherein an inductance of the sensing arrangement is influenced by the proximity of the detectable feature. 
     
     
         9 . The method of  claim 6 , wherein the sensing arrangement comprises an inductive sensing arrangement having a variable inductance that is influenced by a position of the detectable feature with respect to the sensing arrangement. 
     
     
         10 . The method of  claim 1 , further comprising automatically initiating a priming sequence to initialize positioning of the plunger within the reservoir in response to detecting seating of the reservoir. 
     
     
         11 . The method of  claim 1 , further comprising, after detecting seating, providing indication the reservoir has become unseated when the electrical output signal fails to indicate presence of the reservoir. 
     
     
         12 . The method of  claim 1 , wherein the sensing arrangement comprises an optical sensing arrangement. 
     
     
         13 . The method of  claim 1 , further comprising:
 operating a motor having a rotor coupled to the shaft to displace the shaft in response to rotation of the rotor, displacement of the shaft resulting in displacement of the plunger to deliver fluid from the reservoir;   obtaining a measured shaft position based at least in part on the electrical output signal provided by the sensing arrangement, wherein the electrical output signal corresponds to a position of the detectable feature;   determining a remaining amount of fluid in the reservoir based on the measured shaft position; and   providing a low fluid notification when the remaining amount is less than a threshold value.   
     
     
         14 . The method of  claim 1 , further comprising:
 operating a motor having a rotor coupled to the shaft to displace the shaft in response to rotation of the rotor, displacement of the shaft resulting in displacement of the plunger to deliver fluid from the reservoir;   obtaining a measured shaft position based at least in part on the electrical output signal provided by the sensing arrangement, wherein the electrical output signal corresponds to a position of the detectable feature;   determining an expected shaft position based on an amount of rotation of the rotor; and   identifying an occlusion condition when a difference between the expected shaft position and the measured shaft position exceeds a threshold amount.   
     
     
         15 . The method of  claim 1 , further comprising:
 operating a motor having a rotor coupled to the shaft to displace the shaft in response to rotation of the rotor, displacement of the shaft resulting in displacement of the plunger to deliver fluid from the reservoir;   obtaining a measured shaft position based at least in part on the electrical output signal provided by the sensing arrangement, wherein the electrical output signal corresponds to a position of the detectable feature;   determining an expected shaft position based on an amount of rotation of the rotor; and   identifying a drive system anomaly when a difference between the expected shaft position and the measured shaft position exceeds a threshold amount.   
     
     
         16 . A computer-readable medium having computer-executable instructions stored thereon that, when executed by a control module coupled to the sensing arrangement, cause the control module to perform the method of  claim 1 . 
     
     
         17 . A method of operating an infusion device, the method comprising:
 monitoring an electrical output signal from a sensing arrangement disposed proximate a voided portion of a housing to sense a protruding feature, the voided portion receiving a shaft portion including a displaceable shaft coupled to a plunger of a reservoir and the shaft portion comprising the protruding feature on a side of the shaft, wherein an electrical characteristic of the sensing arrangement is influenced by contact with the protruding feature; and   detecting seating of the reservoir based on the electrical output signal.   
     
     
         18 . The method of  claim 17 , wherein the sensing arrangement comprises a resistive sensing arrangement having a variable resistance that is influenced by a position of the protruding feature with respect to the sensing arrangement. 
     
     
         19 . The method of  claim 17 , further comprising:
 operating a motor having a rotor coupled to the shaft to displace the shaft in response to rotation of the rotor, displacement of the shaft resulting in displacement of the plunger to deliver fluid from the reservoir;   obtaining a measured shaft position based at least in part on the electrical output signal provided by the sensing arrangement, wherein the electrical output signal corresponds to a position of the protruding feature;   determining a remaining amount of fluid in the reservoir based on the measured shaft position; and   providing a low fluid notification when the remaining amount is less than a threshold value.   
     
     
         20 . The method of  claim 17 , further comprising:
 operating a motor having a rotor coupled to the shaft to displace the shaft in response to rotation of the rotor, displacement of the shaft resulting in displacement of the plunger to deliver fluid from the reservoir;   obtaining a measured shaft position based at least in part on the electrical output signal provided by the sensing arrangement, wherein the electrical output signal corresponds to a position of the protruding feature;   determining an expected shaft position based on an amount of rotation of the rotor; and   identifying an occlusion condition when a difference between the expected shaft position and the measured shaft position exceeds a threshold amount.