Methods and apparatuses for detecting occlusions in an ambulatory infusion pump
An improved pump, reservoir and reservoir piston are provided for controlled delivery of fluids. A motor is operably coupled to a drive member, such as a drive screw, which is adapted to advance a plunger slide in response to operation of the motor. The plunger slide is removably coupled to the piston. Methods, systems, and articles of manufacture for automatically detecting an occlusion in a medication infusion pump are provided. The electrical current to an infusion pump may be measured. Based on measurements of one or more variables, and/or multiple measurements of a single variable, such as force, the infusion pump detects whether there is an occlusion in the system. The methods of detecting occlusions may be dynamic.
1. A method of detecting an occlusion in an infusion pump having a drive mechanism that includes a motor and one or more drive train components for infusing fluid into a body of a user, the method comprising:
during delivery of a current pulse of infusion fluid, periodically measuring the amount of force that is applied to a drive train component to obtain a series of measurements;
determining a peak value of the series of measurements;
selecting a second value within the series of measurements later than the peak value;
calculating a difference between the peak value and the second value;
incrementing a counter when the difference exceeds a threshold value;
restarting the counter when the difference is below the threshold value; and
declaring an occlusion has occurred when the counter exceeds an occlusion-detection count.
2. A method of detecting an occlusion in an infusion pump having a drive mechanism that includes a motor and one or more drive train components for infusing fluid into a body of a user, the method comprising:
during delivery of a current pulse of infusion fluid, periodically measuring the amount of force that is applied to a drive train component to obtain a series of measurements;
determining a peak value of the series of measurements;
selecting a second value within the series of measurements later than the peak value;
calculating a current difference between the peak value and the second value;
retrieving a previous difference between a previous peak value and a previous second value later than the previous peak value calculated based on measurements of applied force during delivery of a previous pulse of infusion fluid;
calculating an average difference using the previous difference and the current difference; and
declaring an occlusion has occurred if the average difference exceeds a threshold value.
3. The method of claim 2 , wherein the calculating an average difference further includes using a second previous difference calculated based on measurements of applied force during delivery of a second previous pulse of infusion fluid.
4. The method of claim 3 , wherein the average difference is calculated based on measurements of applied force during delivery of three consecutive pulses of infusion fluid.
5. A method of detecting an occlusion in an infusion pump having a drive mechanism that includes a motor and one or more drive train components for infusing fluid into a body of a user, the method comprising:
during delivery of a current pulse of infusion fluid, periodically measuring the amount of force that is applied to a drive train component to obtain a series of measurements;
determining a peak value of the series of measurements;
selecting a second value within the series of measurements later than the peak value;
measuring the amount of applied force before the delivery of the current pulse of infusion fluid to obtain a third value;
calculating a first difference between the peak value and the second value;
calculating a second difference between the third value and the peak value; and
determining whether an occlusion has occurred by comparing the second difference between the third value and the peak value to the first difference between the peak value and the second value.
6. The method of claim 5 , wherein the comparing the second difference to the first difference includes calculating the first difference as a percentage of the second difference, and wherein the method further comprises declaring an occlusion has occurred if the percentage is below a threshold value.
7. A method of detecting an occlusion in an infusion pump having a drive mechanism that includes a motor and one or more drive train components for infusing fluid into a body of a user, the method comprising:
during delivery of a current pulse of infusion fluid, periodically measuring the amount of force that is applied to a drive train component to obtain a series of measurements;
determining a peak value of the series of measurements;
selecting a second value within the series of measurements later than the peak value;
selecting a third value within the series of measurements later than the peak value;
calculating a slope of a line using the second and third values; and
determining whether an occlusion has occurred by comparing the slope to a threshold value.
8. The method of claim 7 , further including declaring an occlusion has occurred if the slope exceeds the threshold value.
9. The method of claim 7 , wherein the determining whether an occlusion has occurred is based upon a comparison of the slope to a predetermined percentage of the threshold value.
10. The method of claim 7 , wherein the threshold value is predetermined for the infusion pump.
11. A method of detecting an occlusion in an infusion pump having a drive mechanism that includes a motor and one or more drive train components for infusing fluid into a body of a user, the method comprising:
during delivery of a current pulse of infusion fluid, periodically measuring the amount of force that is applied to a drive train component to obtain a series of measurements;
determining a peak value of the series of measurements;
selecting a second value within the series of measurements later than the peak value;
calculating a current difference between the peak value and the second value; and
declaring an occlusion has occurred if the current difference exceeds a threshold value,
wherein the threshold value is dynamically updated based on measurements of applied force during delivery of at least one previous pulse of infusion fluid before the delivery of the current pulse of infusion fluid.
12. The method of claim 11 , further comprising:
retrieving a first previous difference between a first previous peak value and a first previous second value later than the first previous peak value calculated based on measurements of applied force during delivery of a first previous pulse of infusion fluid;
retrieving a second previous difference between a second previous peak value and a second previous second value later than the second previous peak value calculated based on measurements of applied force during delivery of a second previous pulse of infusion fluid; and
calculating an average difference using the first previous difference and the second previous difference,
wherein the threshold value is the average difference.
13. The method of claim 12 , wherein the calculating an average difference further includes using a third previous difference calculated based on measurements of applied force during delivery of a third previous pulse of infusion fluid.
14. The method of claim 13 , wherein the average difference is calculated based on measurements of applied force during delivery of three consecutive pulses of infusion fluid.
15. The method of claim 13 , wherein the average difference is calculated based on measurements of applied force during delivery of three consecutive pulses of infusion fluid that are at least three pulses prior to the delivery of the current pulse of infusion fluid.