Advanced thoracic fluid monitoring capability with impedance

• US 20070156061A1
• Filed: 12/30/2005
• Published: 07/05/2007
• Est. Priority Date: 12/30/2005
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Hess, Michael
• Granted Patent: US 8,442,627 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• 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: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36535 controlled by body position or posture

Abstract

Advanced thoracic fluid monitoring capabilities using impedance are disclosed. An implantable medical device used for detection of changes in impedance in a patient can have means for measuring impedances of the patient in a supine position and in an upright position. Impedance differences can be generated which correspond to a diurnal delta value showing impedance differences between the supine and upright positions.

Claims

1. An implantable medical device for detection of changes in impedance in a patient, comprising:

means for measuring impedances corresponding to a supine patient position and for measuring impedances corresponding to an upright patient position;

means for generating a diurnal delta corresponding to the impedance differences between the supine and upright patient positions.

2. An implantable medical device according to claim 1, wherein the upright patient position is a period of time when the patient is likely in an upright position, and the supine patient position is a period of time when the patient is likely in a supine position.

3. An implantable medical device according to claim 1, wherein the upright and supine patient positions are the detected position of the patient based on sensor inputs.

4. An implantable medical device according to claim 1, wherein an alarm is initiated if the delta increases as compared to deltas generated in the past.

5. An implantable medical device according to claim 1, wherein an alarm is initiated if the delta decreases over a predetermined amount of time.

6. An implantable medical device according to claim 1, wherein the delta is the difference between the nighttime and daytime period average impedances.

7. An implantable medical device according to claim 1, wherein the delta is the difference between the nighttime and daytime short-term average impedances.

8. An implantable medical device according to claim 1, wherein the delta is the difference between the nighttime and daytime long-term average impedances.

9. An implantable medical device according to claim 1, wherein the delta is the difference between the nighttime and daytime integral differences, the integral differences being the integral of the difference between baseline impedances and period average impedances.

10. An implantable medical device, comprising:

a plurality of electrodes;

an output circuit outputting a plurality of output pulse signals along a vector formed by two electrodes of the plurality of electrodes;

a measurement circuit generating a corresponding plurality of measurement signals in response to the plurality of output pulse signals; and

a microprocessor determining a plurality of impedances in response to the plurality of output pulse signals and the plurality of measurement signals corresponding to a nighttime period and a daytime period, and generating a diurnal delta value that is a differential value of the impedances measured during the daytime period and the nighttime period.

11. An implantable medical device according to claim 10, further comprising a position detector for detection of a supine position in a patient.

12. An implantable medical device according to claim 10, further comprising a position detector for detection of an upright position in a patient.

13. A computer-readable medium programmed with instructions for performing a method in an implantable medical device, the medium comprising instructions for causing a programmable processor to:

measure impedances of a patient in a supine position;

measure impedances of the patient in an upright position; and

generate a diurnal delta corresponding to impedance differences between the supine and upright positions.

14. A medium according to claim 13, further comprising instructions to reset certain impedance data after receipt of a reset input.

15. A medium according to claim 13, wherein an alarm is initiated if the supine position impedance measurements drop below a threshold.

16. A medium according to claim 13, wherein an alarm is initiated if the upright position impedance measurements drop below a threshold.

17. A medium according to claim 13, further comprising instructions to detect when the patient is in the supine position.

18. A medium according to claim 13, further comprising instructions to wait a predetermined time limit before measuring impedances when the patient is first detected in the supine position.

19. A medium according to claim 13, further comprising instructions to determine whether the diurnal delta values are increasing or decreasing over time.

20. A medium according to claim 13, further comprising instructions to determine whether a predetermined time limit has elapsed during which the delta value was increasing or decreasing.