ADAPTATIONS TO OPTIVOL ALERT ALGORITHM

• US 20080024293A1
• Filed: 12/07/2006
• Published: 01/31/2008
• Est. Priority Date: 07/28/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Stylos, Lee
• Granted Patent: US 8,700,143 B2
• Time in Patent Office: Days
• US Class Current: 340/532
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/07 Endoradiosondes
• CPC Class Codes: A61B 5/076 Permanent implantations telemetry using implanted circuitry A61B5/0031; implanted stimulators for therapy A61N1/3605, A61N1/362, A61N1/372
• CPC Class Codes: A61B 5/4869 Determining body composition
• CPC Class Codes: A61B 5/4878 Evaluating oedema
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/37258 Alerting the patient
• CPC Class Codes: G16H 10/60 for patient-specific data, e.g. for electronic patient records
• CPC Class Codes: G16H 10/65 stored on portable record carriers, e.g. on smartcards, RFID tags or CD
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

Adaptations to the OptiVol™ alert algorithm are disclosed which may reduce the number of false positive alerts while retaining the desired sensitivity. Some embodiments monitor fluid levels in patients. Some embodiments reset a cumulative index when a short-term impedance value is greater than a baseline impedance value minus a predetermined positive hysteresis value.

Claims

1. A computer-readable medium programmed with instructions for performing a method of monitoring for abnormally high or abnormally low fluid levels, the medium comprising instructions for causing a programmable processor to:

intermittently receive a measured physiological parameter value related to a patient'"'"'s fluid level;

calculate a short-term representative value and an associated long-term representative value of the measured physiological parameter values after receipt of one or more of the measured physiological parameter values;

compare each short-term representative value and the associated long-term representative value to determine if the short-term representative value indicates normal fluid levels, the short-term representative value indicating normal fluid levels when, depending on whether monitoring for abnormally high fluid levels or abnormally low fluid levels, predeterminately one of (a) the short-term representative value is greater than the long-term representative value minus a first predetermined hysteresis value or (b) the short-term representative value is less than the long-term representative value plus a second predetermined hysteresis value;

cumulatively sum a difference between the short-term representative value and the associated long-term representative value when the short-term representative value does not indicate normal fluid levels; and

reset the cumulative sum when the short-term representative value indicates normal fluid levels.

2. The medium of claim 1, wherein the short-term representative value indicates normal fluid levels only when the short-term representative value is greater than the long-term representative value minus the first predetermined hysteresis value.

3. The medium of claim 1, wherein the short-term representative value indicates normal fluid levels only when the short-term representative value is less than the long-term representative value plus the second predetermined hysteresis value.

4. The medium of claim 1, wherein the short-term representative value comprises a short-term average value and the long-term representative value comprises a long-term average value.

5. The medium of claim 1, wherein the medium is housed in a type of implantable medical device, and the second or first predetermined hysteresis value is based on the type of implantable medical device.

6. The medium of claim 1, wherein the measured physiological parameter values comprise measured impedance values.

7. The medium of claim 6, further comprising instructions for causing a programmable processor to calculate an initial long-term representative impedance value, wherein the second or first predetermined hysteresis value is a percentage of the initial long-term impedance value.

8. The medium of claim 6, wherein the measured impedance values comprise measured transthoracic impedance values.

9. The medium of claim 1, further comprising instructions for causing a programmable processor to notify the patient of possible abnormal fluid levels when the cumulative sum exceeds a predetermined threshold value.

10. The medium of claim 9, further comprising instructions for causing a programmable processor to perform a subsequent cycle of the method and to modify one or more steps in the subsequent cycle when the cumulative sum exceeds the predetermined threshold value.

11. The medium of claim 9, further comprising instructions for causing a programmable processor to initiate therapy to the patient or to modify therapy being provided to the patient when the cumulative sum exceeds the predetermined threshold value.

12. The medium of claim 9, wherein notifying the patient of possible abnormal fluid levels includes one or more of (a) sounding an audible alarm, (b) vibrating, (c) causing stimulation, and (d) communicating to an external medical device.

13. An implantable medical device, comprising:

(a) a hermetically-sealed enclosure carrying an enclosure electrode;

(b) a lead functionally coupled to the enclosure at its proximal end, the lead carrying a lead electrode at its distal end; and

(c) circuitry housed within the enclosure, the circuitry being configured to;

(i) intermittently receive a measured physiological parameter value related to a patient'"'"'s fluid level, the physiological parameter value being taken from the patient via the enclosure electrode and the lead electrode;

(ii) calculate a short-term representative value and an associated long-term representative value of the measured physiological parameter values after receipt of one or more of the measured physiological parameter values;

(iii) compare each short-term representative value and the associated long-term representative value to determine if the short-term representative value indicates normal fluid levels, the short-term representative value indicating normal fluid levels when, depending on whether monitoring for abnormally high fluid levels or abnormally low fluid levels, predeterminately one of (a) the short-term representative value is greater than the long-term representative value minus a first predetermined hysteresis value or (b) the short-term representative value is less than the long-term representative value plus a second predetermined hysteresis value;

(iv) cumulatively sum a difference between the long-term representative value and the short-term representative value when the short-term representative value does not indicate normal fluid levels; and

(v) reset the cumulative sum when the short-term representative value indicates normal fluid levels.

14. The implantable medical device of claim 13, wherein the enclosure has a size, and the first or second predetermined hysteresis value is based on the size of the enclosure.

15. The implantable medical device of claim 13, wherein the short-term representative value indicates normal fluid levels only when the short-term representative value is greater than the long-term representative value minus the first predetermined hysteresis value.

16. The implantable medical device of claim 13, wherein the intermittently received measured physiological parameter values have a degree of variation from day to day, and wherein the first or second predetermined hysteresis value is based on the degree of variation.

17. The implantable medical device of claim 13, wherein the intermittently received measured physiological parameter values comprise transthoracic impedance values.

18. A computer-readable medium programmed with instructions for performing a method of monitoring for abnormally high fluid levels, the medium comprising instructions for causing a programmable processor to:

intermittently receive a measured transthoracic impedance value;

calculate a short-term representative value and an associated long-term representative value of the measured transthoracic impedance values after receipt of one or more of the measured transthoracic impedance values;

compare each short-term representative value and the associated long-term representative value to determine if the short-term representative value indicates normal fluid levels, the short-term representative value indicating normal fluid levels when the short-term representative value is greater than the long-term representative value minus a high-fluid predetermined hysteresis value;

cumulatively sum a difference between the long-term representative value and the short-term representative value when the short-term representative value does not indicate normal fluid levels; and

reset the cumulative sum when the short-term representative value indicates normal fluid levels.

19. The medium of claim 18, further comprising instructions for causing a programmable processor to notify the patient of possible abnormal fluid levels when the cumulative sum exceeds a predetermined threshold value, notifying the patient of possible abnormal fluid levels including one or more of (a) sounding an audible alarm, (b) vibrating, (c) causing stimulation, and (d) communicating to an external medical device.

20. The medium of claim 18, further comprising instructions for causing a programmable processor to initiate therapy to the patient or to modify therapy being provided to the patient when the cumulative sum exceeds the predetermined threshold value.