Injection device

Abstract

Injection monitoring circuitry is provided for coupling to part of an injection device having a syringe and a plunger rod. The injection monitoring circuitry has an input to receive force measurement data from a force sensor, the force measurement data includes a plurality of timestamped force measurements of force applied by a user to the injection device when an injection is administered to an injection site. Processing circuitry is provided to determine from the force measurement data when an end of injection has been reached, the end of injection corresponding to the plunger rod having reached an end position in a distal portion of the barrel of the syringe during administration of the injection by the user. Machine readable instructions and an injection monitoring method are also provided.

What is claimed is: 
     
         1 . A plunger rod comprising:
 a stopper engaging element configured to couple to a stopper in a syringe barrel;   a switch configured to determine whether the stopper engaging element is coupled to the stopper; and   a processor in electrical communication with the switch,   wherein the switch is further configured to activate the processor in response to the determination that the stopper engaging element is coupled to the stopper.   
     
     
         2 . The plunger rod of  claim 1 , further comprising at least one force sensor configured to detect a force applied to the plunger rod. 
     
     
         3 . The plunger rod of  claim 2 , further comprising:
 a proximal head; and   a printed circuit board in the proximal head,   wherein the at least one force sensor, the processor, and the switch are on the printed circuit board.   
     
     
         4 . The plunger rod of  claim 3 , wherein the at least one force sensor comprises a plurality of forced sensors that are spaced apart on the printed circuit board. 
     
     
         5 . The plunger rod of  claim 1 , wherein the processor is in a sleep state before the switch activates the processor. 
     
     
         6 . The plunger rod of  claim 1 , wherein the switch is configured to activate the processor by changing a power level of the processor. 
     
     
         7 . The plunger rod of  claim 1 , wherein the switch is configured to determine that the stopper engaging element is coupled to the stopper by determining that the stopper engaging element is sufficiently close to the stopper. 
     
     
         8 . The plunger rod of  claim 1 , wherein the switch is a Hall-effect sensor. 
     
     
         9 . The plunger rod of  claim 1 , wherein the switch is a magnetometer, a reed switch, an inductive switch, a capacitive switch, a light sensing switch, a radar switch, or a contacting mechanical switch. 
     
     
         10 . The plunger rod of  claim 1 , wherein the stopper engaging element comprises magnetic material and the stopper comprises magnetic material. 
     
     
         11 . The plunger rod of  claim 1 , further comprising a conductive rod extending axially along the plunger rod to electrically connect the stopper engaging element and the switch. 
     
     
         12 . A syringe comprising:
 a syringe barrel;   a stopper in the syringe barrel; and   the plunger rod of  claim 1 , wherein the plunger rod is configured to couple to the stopper.   
     
     
         13 . A system comprising:
 a syringe comprising a stopper;   the plunger rod of  claim 1 ; and   an external device in wireless communication with the plunger rod.   
     
     
         14 . The system of  claim 13 , wherein the plunger rod further comprises an antenna configured to wireless communicate with the external device. 
     
     
         15 . A method of monitoring an injection performed by an injection device, the injection device comprising a plunger rod and a syringe, the method comprising:
 receiving, from a force sensor of the plunger rod, a plurality of timestamped force measurements applied to the plunger rod while the injection is being administered;   determining, based on the timestamped force measurements, and using a machine learning algorithm, that the injection is successful, wherein the machine learning algorithm is trained on a labelled data set of successful injection events and unsuccessful injection events; and   generating, in response to determining that the injection is successful, an end of injection indication.   
     
     
         16 . The method of  claim 15 , wherein determining that the injection is successful comprises determining that an intended dose of a medicament is completely delivered. 
     
     
         17 . The method of  claim 15 , further comprising determining, based on the timestamped force measurements, and using a state machine, a possible injection start time and a possible injection end time. 
     
     
         18 . The method of  claim 17 , wherein the state machine:
 determines the possible injection start time based on a first predetermined number of time steps after a first threshold force in the timestamped force measurements is detected; and   determines the possible injection end time based on a second number of time-steps before a second threshold force in the timestamped force measurements is detected.   
     
     
         19 . The method of  claim 17 , wherein determining that the injection is successful is based on timestamped force measurements between the possible injection start time and the possible injection end time. 
     
     
         20 . The method of  claim 15 , wherein determining that the injection is successful further comprises analyzing at least one feature of the plurality of timestamped force measurements, the at least one feature being at least one of an injection duration, a mean magnitude of the plurality of timestamped force measurements, a standard deviation of the plurality of timestamped force measurements, a skew of the plurality of timestamped force measurements, a kurtosis of the plurality of timestamped force measurements, a maximum value of the plurality of timestamped force measurements, a minimum value of the plurality of timestamped force measurements, a 25 th  percentile value of the plurality of timestamped force measurements, and a 75 th  percentile value of the plurality of timestamped force measurements.