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Methods and devices are described for monitoring reservoir fluid in an implantable infusion pump. Such methods and devices can be used when the infusion pump has a temperature-dependent component. For example, a method of monitoring reservoir fluid can include obtaining measurements from the reservo

Methods and devices are described for monitoring reservoir fluid in an implantable infusion pump. Such methods and devices can be used when the infusion pump has a temperature-dependent component. For example, a method of monitoring reservoir fluid can include obtaining measurements from the reservoir that include corresponding data related to the amount of fluid and temperature in the reservoir. A pair of measurements can be used to monitor the fluid level, or flow rate out of, the reservoir when the corresponding temperatures of the measurements are within a temperature tolerance value. In such an instance, a measured amount difference can be calculated based on the fluid amounts corresponding to the pair of measurements. Other variations of fluid monitoring methods, and implantable infusion pump systems that can perform fluid monitoring, are also described.

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What is claimed is: 1. A method of monitoring fluid in a reservoir of an implantable infusion pump, comprising: a) obtaining a plurality of measurements from the reservoir, each measurement including corresponding data related to a fluid amount and a temperature; b) selecting a first measurement an

What is claimed is: 1. A method of monitoring fluid in a reservoir of an implantable infusion pump, comprising: a) obtaining a plurality of measurements from the reservoir, each measurement including corresponding data related to a fluid amount and a temperature; b) selecting a first measurement and a second measurement from the plurality of measurements such that a temperature difference based at least in part on temperatures corresponding with the first and second measurements is less than a temperature tolerance value; and c) calculating a measured amount difference based at least in part on fluid amounts corresponding with the first and second measurements. 2. The method of claim 1, wherein the step of obtaining the plurality of measurements includes: obtaining a first plurality of measurements, and obtaining a second plurality of measurements after the first plurality, and further wherein the step of selecting the first and second measurements includes selecting the first measurement from the first plurality and the second measurement from the second plurality. 3. The method of claim 2, wherein the step of selecting the first and second measurements includes: selecting a first candidate measurement from the first plurality, selecting a second candidate measurement from the second plurality, and replacing at least one of the first candidate measurement and the second candidate measurement if a temperature difference based at least in part on temperatures corresponding with the first and second candidate measurements is greater than the temperature tolerance value. 4. The method of claim 3, wherein each measurement of the plurality of measurements includes corresponding data related to a time, and further wherein the steps of selecting and replacing candidate measurements depends at least in part on the time corresponding with at least one candidate measurement. 5. The method of claim 3, wherein the step of replacing is repeated until the temperature difference is less than the temperature tolerance value. 6. The method of claim 1, further comprising: d) obtaining at least one additional measurement from the reservoir, each measurement including corresponding data related to the fluid amount and the temperature; e) selecting two measurements such that a temperature difference based at least in part on temperatures corresponding with the two measurements is less than the temperature tolerance value, at least one of the two measurements selected from the at least one additional measurement; and f) calculating a new measured amount difference based at least in part on the fluid amounts corresponding with the two measurements. 7. The method of claim 6, wherein steps d), e), and f) are repeated at least once during operation of the infusion pump. 8. A method of monitoring fluid flow from a reservoir of an implantable infusion pump, comprising: a) obtaining a plurality of measurements from the reservoir, each measurement including corresponding data related to a fluid amount, a temperature, and a time; b) selecting a first measurement and a second measurement from the plurality of measurements such that a temperature difference based at least in part on temperatures corresponding with the first and second measurements is less than a temperature tolerance value; c) calculating a measured amount difference based at least in part on fluid amounts corresponding with the first and second measurements. d) calculating a time difference based at least in part on times corresponding with the first and second measurements; and e) comparing the measured amount difference with a controlled amount difference, the controlled amount difference based at least in part on the time difference and operation of the implantable infusion pump to deliver fluid from the reservoir. 9. The method of claim 8, wherein the step of comparing the measured amount difference with the controlled amount difference is performed by comparing a measured flow rate with a controlled flow rate, the measured flow rate depending at least in part on the measured amount difference and the controlled flow rate depending at least in part on the controlled amount difference. 10. The method of claim 8, wherein the step of comparing includes determining a leakage in the implantable infusion pump when the measured amount difference exceeds the controlled amount difference by more than a leakage tolerance amount. 11. The method of claim 10, wherein the leakage tolerance amount is based at least in part on an accuracy of a level sensor used to identify an amount of fluid in the reservoir. 12. The method of claim 8, wherein the step of comparing includes determining a blockage in the implantable infusion pump when the controlled amount difference exceeds the measured amount difference by more than a blockage tolerance amount. 13. The method of claim 12, wherein the blockage tolerance amount is based at least in part on an accuracy of a level sensor used to identify an amount of fluid in the reservoir. 14. The method of claim 8, wherein the step of obtaining the plurality of measurements includes using a temperature-dependent level sensor to identify fluid amounts. 15. The method of claim 14, wherein the step of using the temperature dependent level sensor includes measuring an inductance of a coil coupled to the reservoir. 16. The method of claim 8, wherein the controlled amount difference is based at least in part on control electronics of the implantable infusion pump. 17. The method of claim 16, wherein the controlled amount difference is based at least in part on signals sent between the control electronics and a valve used to control flow from the reservoir. 18. The method of claim 16, wherein the step of obtaining the plurality of measurements includes sending a signal between the control electronics and a sensor to determine the fluid amount in the reservoir. 19. A control system for an implantable infusion pump, comprising: a measurement history module for storing a plurality of measurements, each measurement including corresponding data related to a temperature, a measured amount, and a time associated with measurements from the reservoir; and at least one processor electrically coupled to the measurement history module, the at least one processor configured to (i) select two measurements from the measurement history module such that a temperature difference based at least on temperatures corresponding with the two measurements is less than a temperature tolerance value, and (ii) calculate a measured amount difference based at least in part on measured amounts corresponding with the two measurements. 20. The control system of claim 19, wherein the measurement history module is in communication with a temperature-dependent level sensor for determining amounts of fluid in the reservoir. 21. The control system of claim 20, wherein the temperature-dependent level sensor includes an inductance-varying coil for determining the amounts of fluid in the reservoir. 22. The control system of claim 19, wherein the control system is embedded as a portion of the implantable infusion pump. 23. The control system of claim 19, further comprising: an operating history module for storing operating history data used to regulate flow from a reservoir of the infusion pump; wherein the at least one processor is electrically coupled to the operating history module, and further configured to (iii) calculate a time difference based at least in part on times corresponding with the two measurements, (iv) calculate a controlled amount difference based on the operating history and the time difference, and (v) compare the measured amount difference and the controlled amount difference. 24. The control system of claim 23, wherein the operating history module is a valve history module for storing operating history data of a valve. 25. The control system of claim 24, wherein the valve history module is configured to store operating history data that includes a total amount of time that the valve is disposed in at least one of an open position and a closed position over a selected period of time. 26. The control system of claim 23, wherein the at least one processor is configured to trigger a leakage signal when the measured amount difference exceeds the controlled amount difference by more than a leakage tolerance amount. 27. The control system of claim 23, wherein the at least one processor is configured to trigger a blockage signal when the controlled amount difference exceeds the measured amount difference by more than a blockage tolerance amount. 28. The control system of claim 23, wherein the at least one processor also calculates (vi) a measured flow rate based at least in part on the measured amount difference, and (vii) a controlled flow rate based at least in part on the controlled difference amount, the at least one processor configured to compare the measured amount difference and the controlled amount difference by comparing the measured flow rate and the controlled flow rate. 29. The control system of claim 19, wherein the measurement history module and the at least one processor are each portions of a single microprocessor.