Adaptations to optivol alert algorithm

• US 8,700,143 B2
• Filed: 12/07/2006
• Issued: 04/15/2014
• Est. Priority Date: 07/28/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Stylos, Lee
• Primary Examiner(s): SZMAL, BRIAN SCOTT
• Application Number:
  US11/567,835
• Publication Number:
  US 20080024293A1
• Time in Patent Office: 2,686 Days
• Field of Search: 600/547, 600/300, 600/485, 600/506, 600/508, 600/510, 607/6, 607/17
• US Class Current: 600/547
• 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 method of monitoring for abnormally high fluid levels by an implantable medical device, comprising:

the device intermittently measuring a physiological parameter value related to a patient'"'"'s fluid level;

the device calculating 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;

the device comparing each short-term representative value and the associated long-term representative value to determine if the short-term representative value indicates abnormal fluid levels, wherein abnormally high fluid levels are indicated responsive to the short-term representative value not being greater than the long-term representative value minus a first predetermined hysteresis value and abnormally low fluid levels indicated responsive to the short-term representative value not being less than the long-term representative value plus a second predetermined hysteresis value;

the device cumulatively adding a difference between the short-term representative value and the associated long-term representative value responsive to the short-term representative value not indicating normal fluid levels;

the device resetting the cumulative sum responsive to the short-term representative value indicating normal fluid levels; and

the device generating a notification in response to the cumulative sum exceeding a predetermined threshold value.

2. The method of claim 1, wherein the short-term representative value indicates normal fluid levels only responsive to the short-term representative value being greater than the long-term representative value minus the first predetermined hysteresis value and the short-term representative value is less than the long-term representative value plus the second predetermined hysteresis value.

3. The method 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.

4. The method of claim 1, wherein the second or first predetermined hysteresis value is based on a physical characteristic of the implantable medical device.

5. The method of claim 4, wherein the physical characteristic includes the size of the implantable medical device.

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

7. The method of claim 6, wherein the measured impedance values comprise measured transthoracic impedance values.

8. The method of claim 1, further comprising initiating therapy to the patient or modifying therapy being provided to the patient responsive to the cumulative sum exceeding the predetermined threshold value.

9. The method of claim 1, 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.

10. An implantable medical device, comprising:

a hermetically-sealed enclosure carrying an enclosure electrode;

a lead including an electrode and having a proximal end and a distal end, the proximal end being functionally coupled to the enclosure; and

circuitry housed within the enclosure, the circuitry being configured to;

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;

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 abnormal fluid levels, wherein abnormally high fluid levels are indicated responsive to the short-term representative value not being greater than the long-term representative value minus a first predetermined hysteresis value and abnormally low fluid levels are indicated responsive to the short-term representative value not being less than the long-term representative value plus a second predetermined hysteresis value;

cumulatively sum a difference between the long-term representative value and the short-term representative value responsive to the short-term representative value not indicating normal fluid levels; and

reset the cumulative sum responsive to the short-term representative value indicating normal fluid levels.

11. The implantable medical device of claim 10, wherein the enclosure has a size, and the first or second predetermined hysteresis value is based on the size of the enclosure.

12. The implantable medical device of claim 10, wherein the short-term representative value indicates normal fluid levels only responsive to the short-term representative value being greater than the long-term representative value minus the first predetermined hysteresis value and the short-term representative value is less than the long-term representative value plus the second predetermined hysteresis value.

13. The implantable medical device of claim 10, 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.

14. The implantable medical device of claim 10, wherein the intermittently received measured physiological parameter values comprise transthoracic impedance values.

15. A method of monitoring for abnormally high fluid levels by an implantable medical device, comprising:

the device intermittently measuring a transthoracic impedance value;

the device calculating 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;

the device comparing 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 responsive to the short-term representative value being greater than the long-term representative value minus a high-fluid predetermined hysteresis value and the short-term representative value being less than the long-term representative value plus the second predetermined hysteresis value;

the device cumulatively adding a difference between the long-term representative value and the short-term representative value responsive to the short-term representative value not being indicative of normal fluid levels;

the device resetting the cumulative sum responsive to the short-term representative value indicating normal fluid levels; and

the device generating a notification in response to the cumulative sum exceeding a predetermined threshold value.

16. The method of claim 15, 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.

17. The method of claim 15, further comprising initiating therapy to the patient or modifying therapy being provided to the patient responsive to the cumulative sum exceeding the predetermined threshold value.