Analyte sensor
Systems and methods of use for continuous analyte measurement of a host's vascular system are provided. In some embodiments, a continuous glucose measurement system includes a vascular access device, a sensor and sensor electronics, the system being configured for insertion into communication with a host's circulatory system.
1. A system for monitoring a glucose concentration, the system comprising:
a transcutaneous glucose sensor comprising:
an ex vivo portion configured to remain outside of a body of a host; and
an in vivo portion configured to be inserted into the body of the host, wherein the in vivo portion comprises:
an electrode; and
a membrane disposed over at least a portion of the electrode, wherein the membrane comprises at least one enzyme;
wherein the transcutaneous glucose sensor is configured to generate a signal, wherein the magnitude of the signal depends upon a glucose concentration existing at the in vivo portion of the transcutaneous glucose sensor inserted into the body of the host; and
electronics configured to operably connect to the transcutaneous glucose sensor, wherein the electronics comprises a memory, wherein the memory stores information associated with a profile wherein the profile is based at least in part on a priori information related to expected sensitivity changes associated with a length of time the in vivo portion of the transcutaneous glucose sensor has been inserted into the body of the host.
2. The system of claim 1 , wherein the electronics is configured to determine a glucose concentration value based at least in part on the information associated with the profile.
3. The system of claim 2 wherein the electronics is configured to determine the glucose concentration value solely using information obtained prior to insertion of the in vivo portion of the transcutaneous glucose sensor into the body of the host.
4. The system of claim 2 , wherein the electronics is configured to use a conversion function to determine the glucose concentration value.
5. The system of claim 4 , wherein the conversion function is based at least in part on a predictive relationship between in vitro sensitivity and in vivo sensitivity.
6. The system of claim 2 wherein the electronics is configured to use a calibration factor to determine the glucose concentration value.
7. The system of claim 2 , further comprising a temperature sensor for providing a temperature measurement, wherein the glucose concentration value is derived at least in part from the temperature measurement from the temperature sensor.
8. The system of claim 1 , wherein the profile accounts for a break-in of the transcutaneous glucose sensor after the in vivo portion of the transcutaneous glucose sensor has been inserted into the body of the host.
9. The system of claim 1 , wherein the electronics comprises sensor electronics.
10. The system of claim 1 , wherein the electronics comprises receiver electronics.
11. The system of claim 1 , wherein the electronics comprises sensor electronics and receiver electronics.
12. The system of claim 1 , wherein the expected sensitivity changes are associated at least in part with a change in one or more physical properties of an environment surrounding the in vivo portion of the transcutaneous glucose sensor within the body of the host.
13. The system of claim 1 wherein the profile has a first slope associated with a first time and a second slope associated with a second time, wherein the first time is different from the second time, wherein the first slope is different from the second slope.
14. A method of monitoring a glucose concentration, the method comprising:
beginning a sensor session associated with use of a transcutaneous glucose sensor, wherein the transcutaneous glucose sensor comprises:
an ex vivo portion configured to remain outside of a body of a host; and
an in vivo portion configured to be inserted within the body of the host, wherein the in vivo portion comprises:
an electrode; and
a membrane disposed over at least a portion of the electrode, wherein the membrane comprises at least one enzyme;
generating sensor data at least in part from a signal received from the in vivo portion of the transcutaneous glucose sensor; and
calibrating the sensor data based at least in part on a priori information, wherein the a priori information comprises a profile associated with a drift in a sensitivity of the in vivo portion of the transcutaneous glucose sensor over time.
15. The method of claim 14 , wherein the a priori information is based at least in part on expected sensitivity changes associated with a length of time the transcutaneous glucose sensor has been inserted within the body of the host.
16. The method of claim 14 , wherein the calibrating comprises applying a conversion function based at least in part on a predictive relationship between in vitro sensitivity and in vivo sensitivity.
17. The method of claim 14 ; wherein the calibrating comprises applying a calibration factor based at least in part on a predictive relationship between in vitro sensitivity and in vivo sensitivity.
18. The method of claim of claim 14 , wherein the calibrating is performed without a need for a reference analyte value obtained after insertion of in vivo portion of the transcutaneous glucose sensor into the body of the host.
19. The method of claim 14 , wherein the membrane comprises a plurality of different membrane layers.
20. The method of claim 14 , wherein the drift in the sensitivity is associated at least in part with a change in one or more physical properties of an environment surrounding the in vivo portion of the transcutaneous glucose sensor within the body of the host.
21. The method of claim 14 wherein the profile accounts for break-in of the transcutaneous glucose sensor.
22. The method of claim 14 wherein the profile has a first slope associated with a first time and a second slope associated with a second time, wherein the first time is different from the second time, wherein the first slope is different from the second slope.
23. A method for monitoring a glucose concentration, the method comprising:
beginning a sensor session associated with use of a transcutaneous glucose sensor, wherein the transcutaneous glucose sensor comprises:
an ex vivo portion configured to remain outside of a body of a host; and
an in vivo portion configured to be inserted within the body of the host;
generating sensor data derived at least in part from the transcutaneous glucose sensor;
determining a glucose concentration value based at least in part on the sensor data and information associated with a drift profile, wherein the drift profile is associated with a shift over time in measurement characteristic of the transcutaneous glucose sensor to the glucose concentration within the body of the host resulting from the in vivo portion of the transcutaneous glucose sensor being within the body of the host for a period of time; and
displaying the glucose concentration value.
24. The method of claim 23 wherein the in vivo portion of the transcutaneous glucose sensor comprises a substantially planar configuration.
25. The method of claim 23 wherein the drift profile accounts for a break-in of the transcutaneous glucose sensor after the in vivo portion of the transcutaneous glucose sensor has been inserted into the body of the host.
26. The method of claim 23 wherein the drift profile accounts for a change in sensitivity over time of the in vivo portion of the transcutaneous glucose sensor to the glucose concentration within the body of the host.
27. The method of claim 23 wherein the drift profile accounts for a change in baseline over time associated with the in vivo portion of the transcutaneous glucose sensor.
28. The method of claim 23 wherein the drift profile accounts for a change in baseline over time associated with the in vivo portion of the transcutaneous glucose sensor and a change in sensitivity over time of the in vivo portion of the transcutaneous glucose sensor to the glucose concentration within the body of the host.
29. The method of claim 23 wherein the shift over time is an elapsed time measured from the beginning of the sensor session.
30. The method of claim 23 wherein the shift over time is associated at least in part with a change in one or more physical properties of an environment surrounding the in vivo portion of the transcutaneous glucose sensor within the body of the host.
31. The method of claim 30 wherein the one or more physical properties of the environment surrounding the in vivo portion of the transcutaneous glucose sensor within the body of the host is associated with at least one of: trauma, wound healing, blockage of a surface of the transcutaneous glucose sensor, inflammation, blood clotting, or biofouling.
32. The method of claim 23 wherein the shift over time is associated at least in part with a physical property of the transcutaneous glucose sensor, wherein the physical property corresponds to a membrane of the in vivo portion of the transcutaneous glucose sensor.
33. The method of claim 23 wherein the shift over time is an elapsed time measured from the insertion of the in vivo portion of the transcutaneous glucose sensor within the body of the host.
34. The method of claim 23 wherein the drift profile has a first slope associated with a first time and a second slope associated with a second time, wherein the first time is different from the second time, wherein the first slope is different from the second slope.
35. A sensor system comprising:
a transcutaneous glucose sensor comprising:
an ex vivo portion configured to remain outside of a body of a host; and
an in vivo portion configured to be implanted within the body of the host, wherein the in vivo portion comprises:
an electrode; and
a membrane disposed over at least a portion of the electrode, wherein the membrane comprises at least one enzyme;
wherein the transcutaneous glucose sensor generates a signal associated with a glucose concentration within the body of the host; and
electronics configured to receive the signal from the transcutaneous glucose sensor, wherein the electronics comprises a memory, wherein the memory stores information associated with an expected change over time in a relationship between the signal and the glucose concentration within the body of the host, wherein the electronics is configured to generate a glucose concentration value based at least in part on the signal and the information associated with the expected change over time in the relationship.
36. The sensor system of claim 35 wherein the change over time in the relationship is associated at least in part with a change in one or more physical properties of an environment surrounding the in vivo portion of the transcutaneous glucose sensor within the body of the host.
37. The sensor system of claim 36 , wherein the one or more physical properties of the environment surrounding the in vivo portion of the transcutaneous glucose sensor within the body of the host include trauma, wound healing, blockage of a surface of the transcutaneous glucose sensor, inflammation, blood clotting, or biofouling.
38. The sensor system of claim 35 wherein the change over time in the relationship is associated with the implantation of the in vivo portion of the transcutaneous glucose sensor within the body of the host.
39. The sensor system of claim 35 wherein the change over time in the relationship is over an elapsed time measured from a beginning of a sensor session after implantation of the in vivo portion of the transcutaneous glucose sensor within the body of the host.
40. The sensor system of claim 35 wherein the change over time in the relationship is over an elapsed time measured from the implantation of the in vivo portion of the transcutaneous glucose sensor within the body of the host.
41. The sensor system of claim 35 wherein the change over time in the relationship is associated at least in part with a physical property of the transcutaneous glucose sensor, wherein the physical property of the transcutaneous glucose sensor corresponds to membrane of the in vivo portion of the transcutaneous glucose sensor.
42. A method for monitoring a glucose concentration, the method comprising:
beginning a sensor session associated with use of a transcutaneous glucose sensor, wherein the transcutaneous glucose sensor comprises:
an ex vivo portion configured to remain outside of a body of a host; and
an in vivo portion configured to be inserted within the body of the host;
wherein the transcutaneous glucose sensor is configured to generate a signal;
calibrating the transcutaneous glucose sensor by applying a priori information, wherein the a priori information comprises an expected relationship between the signal and a glucose concentration existing within the body of the host, wherein the relationship changes as a function of time;
generating a glucose concentration value based at least in part on the calibrating; and
displaying the glucose concentration value.
43. The method of claim 42 wherein the time the relationship changes is an elapsed time measured from the beginning of the sensor session.
44. The method of claim 42 wherein the relationship changes as a function of time is associated at least in part with a change in one or more physical properties of an environment surrounding the in vivo portion of the transcutaneous glucose sensor within the body of the host.
45. The method of claim 44 wherein the one or more physical properties of the environment surrounding the in vivo portion of the transcutaneous glucose sensor within the body of the host include trauma, wound healing, blockage of a surface of the transcutaneous glucose sensor, inflammation, blood clotting, or biofouling.
46. The method of claim 42 wherein the relationship changes as a function of time is associated at least in part with a physical property of the transcutaneous glucose sensor, wherein the physical property of the transcutaneous glucose sensor corresponds to a membrane of the in vivo portion of the transcutaneous glucose sensor.