Sensitivity and specificity of pulmonary edema detection when using transthoracic impedance

• US 9,089,275 B2
• Filed: 05/11/2005
• Issued: 07/28/2015
• Est. Priority Date: 05/11/2005
• Status: Active Grant

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Stahmann, Jeffrey E., Hatlestad, John, Hartley, Jesse W.
• Primary Examiner(s): HINDENBURG, MAX F
• Application Number:
  US11/126,723
• Publication Number:
  US 20060293609A1
• Time in Patent Office: 3,730 Days
• Field of Search: 600/546, 600/547, 600/528, 600/508, 600/536, 607/17
• US Class Current: 1/1
• 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 5/4869 Determining body composition
• CPC Class Codes: A61M 2230/40 Respiratory characteristics
• CPC Class Codes: A61M 2230/65 Impedance, e.g. conductivity, capacity
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/37282 characterised by communication with experts in remote locations using a network

Abstract

This patent document discusses, among other things, systems, devices, and methods for enhancing detection of pulmonary edema using, in addition to thoracic impedance, one or a combination of: physiologic information about a subject, at least one statistical parameter, a user-programmable detection level, at least one parameter associated with a previous pulmonary edema event, and patient symptom information about the subject. In one example, a (base) thoracic impedance threshold is modified to an adjusted thoracic impedance threshold. The adjusted thoracic impedance threshold provides an increased sensitivity of pulmonary edema detection as compared to the base thoracic impedance threshold. In another example, an alert is provided to a subject, a caregiver, or other user based on a pulmonary edema indication determined by the present systems, devices, and methods. In a further example, a therapy (provided to the subject) is adjusted or initiated in response to the pulmonary edema indication.

Claims

1. A system comprising:

an implantable thoracic impedance measurement circuit, adapted to sense a plurality of thoracic impedance signal values from a subject;

a processor, coupled with the thoracic impedance measurement circuit to accept the plurality of thoracic impedance signal values; and

a statistical analysis module adapted to compute a mean and a standard deviation of the plurality of thoracic impedance signal values,

wherein the processor is adapted to extract from the thoracic impedance signal values one or more thoracic impedance signal values that fall within a boundary that is specified at less than or equal to a standard deviation from the mean thoracic impedance and to use the extracted thoracic impedance signal values to determine a pulmonary edema indication.

2. The system as recited in claim 1, wherein the processor determines the pulmonary edema indication, indicating at least some degree of pulmonary edema to be present, when the one or more thoracic impedance signal values within a variability of one standard deviation of the mean thoracic impedance numerically decrease below a thoracic impedance threshold.

3. The system as recited in claim 1, further comprising a frequency selective filter circuit coupled to the thoracic impedance measurement circuit,

wherein the frequency selective filter circuit is adapted to extract from each sensed thoracic impedance signal value a near-DC thoracic impedance signal value, the near-DC thoracic impedance signal value between 0 Hz to about 0.05 Hz, inclusive, and

wherein the processor is adapted to determine the pulmonary edema indication using, at least in part, one or more near-DC thoracic impedance signal values within a variability of one standard deviation of a mean near-DC thoracic impedance computed by the statistical analysis module.

4. The system as recited in claim 1, further comprising:

a posture sensor adapted to sense a posture signal; and

a posture compensation module, coupled with the posture sensor,

wherein the posture compensation module is adapted to compute a posture-compensated thoracic impedance signal value from each thoracic impedance signal value using the posture signal, and

wherein the processor is adapted to determine the pulmonary edema indication using, at least in part, one or more posture-compensated thoracic impedance signal values within a variability of one standard deviation of a mean posture-compensated thoracic impedance computed by the statistical analysis module.

5. The system as recited in claim 1, further comprising:

a blood impedance measurement circuit, adapted to sense a blood impedance signal from the subject; and

a blood impedance correction module, coupled with the blood impedance measurement circuit,

wherein the blood impedance correction module is adapted to extract from each thoracic impedance signal value a blood resistivity-influenced component using the blood impedance signal, and

wherein the processor is adapted to determine the pulmonary edema indication using, at least in part, a one or more blood resistivity-compensated thoracic impedance signal values within a variability of one standard deviation of a mean blood resistivity-compensated thoracic impedance computed by the statistical analysis module.

6. The system as recited in claim 1, further comprising a memory storage device adapted to store a history of the plurality of thoracic impedance signal values and the computed mean and standard deviation of the plurality of thoracic impedance signal values.

7. The system as recited in claim 1, further comprising a therapy control module coupled to the processor,

wherein the therapy control module is adapted to adjust or initiate one or more therapies based, at least in part, on the pulmonary edema indication, and

wherein the one or more therapies are selected from a therapy group consisting essentially of:

cardiac rhythm management therapy, dietary therapy, and breathing assistance therapy.

8. The system as recited in claim 1, further comprising a parameter collection device coupled with the processor,

wherein the parameter collection device is adapted to sense or receive physiologic information about the subject, the physiologic information selected from a physiologic information group consisting essentially of:

at least one heart sound, at least one lung sound, a respiratory pattern, a weight, a neurohormone level, a creatinine level, and a heart wall motion, and

wherein the processor is adapted to determine the pulmonary edema indication using, at least in part, the physiologic information.

19. The system as recited in claim 1, wherein the implantable thoracic impedance measurement circuit includes an intracardiac leadwire having a distal portion adapted for intravascular introduction into a heart of the subject.

23. The system as recited in claim 2, wherein the processor includes a threshold adjustment module adapted to adjust the thoracic impedance threshold using a variance, computed by the statistical analysis module, of the plurality of thoracic impedance signal values to increase the sensitivity of a pulmonary edema indication determination.

9. A system comprising:

a memory storage device, adapted to store at least one previous parameter associated with a first pulmonary edema episode occurring in the past, the at least one previous parameter selected from a previous parameter group consisting essentially of;

a previous thoracic impedance, a previous physiologic parameter, a previous environmental parameter, a previous compliance parameter, and a previous patient symptom parameter;

a parameter collection device, adapted to sense or receive at least one present parameter about a subject, the at least one present parameter not associated with the first pulmonary edema episode and selected from a present parameter group consisting essentially of;

a present physiologic parameter, a present environmental parameter, a present compliance parameter, and a present patient symptom parameter;

an implantable thoracic impedance measurement circuit, adapted to sense a present thoracic impedance signal value from the subject; and

a processor, coupled with the memory storage device to accept the at least one previous parameter, coupled with the parameter collection device to accept the at least one present parameter, and coupled with the thoracic impedance measurement circuit to accept the present thoracic impedance signal value,

wherein the processor is adapted to determine an indication of a presently developing second pulmonary edema episode, distinct from the first pulmonary edema episode, using a combination of;

the at least one previous parameter, the at least one present parameter, and the present thoracic impedance signal value.

10. The system as recited in claim 9, wherein the processor determines the indication of the second pulmonary edema episode when the present thoracic impedance signal value numerically decreases below a thoracic impedance threshold, and

wherein the processor includes a threshold adjustment module adapted to adjust the thoracic impedance threshold using, at least in part, the at least one previous parameter and the at least one present parameter.

11. The system as recited in claim 9, wherein the parameter collection device includes one or more of:

an implantable sensor, an external sensor, an Internet connection, and an external user interface,

wherein the Internet connection is communicatively coupled to an electronic medical database, and

wherein the external user interface includes a user input device.

12. The system as recited in claim 9, further comprising a frequency selective filter circuit adapted to extract from the present thoracic impedance signal value a near-DC thoracic impedance signal value, the near-DC thoracic impedance signal value between 0 Hz to about 0.05 Hz, inclusive, and

wherein the processor is adapted to determine the indication of the second pulmonary edema episode using, at least in part, the near-DC thoracic impedance signal value.

13. The system as recited in claim 9, further comprising:

a blood impedance measurement circuit, adapted to sense a blood impedance signal from the subject; and

a blood impedance correction module coupled with the blood impedance measurement circuit,

wherein the blood impedance correction module is adapted to extract from the present thoracic impedance signal value a blood resistivity-influenced component using the blood impedance signal, and

wherein the processor is adapted to determine the indication of the second pulmonary edema episode using, at least in part, a blood resistivity-compensated thoracic impedance signal value.

14. The system as recited in claim 9, further comprising:

a posture sensor adapted to sense a posture signal; and

a posture compensation module coupled with the posture sensor, adapted to compute a posture-compensated thoracic impedance signal value from the present thoracic impedance signal value using the posture signal,

wherein the processor is adapted to determine the indication of the second pulmonary edema episode using, at least in part, the posture-compensated thoracic impedance signal value.

15. The system as recited in claim 9, further comprising means for storing a history of the at least one present parameter and the thoracic impedance signal value.

16. The system as recited in claim 9, further comprising a therapy control module coupled to the processor,

wherein the therapy control module is adapted to adjust or initiate one or more therapies based, at least in part, on the indication of the second pulmonary edema episode, and

wherein the one or more therapies are selected from a therapy group consisting essentially of:

cardiac rhythm management therapy, dietary therapy, and breathing assistance therapy.

20. The system as recited in claim 9, wherein the implantable thoracic impedance measurement circuit is implantable, at least in part, intravascularly within a heart of the subject.

21. The system as recited in claim 11, wherein the parameter collection device includes an external user interface having a user input device adapted to receive the at least one present parameter selected from the present parameter group.

22. The system as recited in claim 9, wherein the at least one previous parameter is obtained from a medical history of at least one different subject from which the at least one present parameter is obtained.

17. A system comprising:

an implantable thoracic impedance measurement circuit, adapted to sense a plurality of thoracic impedance signal values from a subject;

a frequency selective filter circuit coupled to the thoracic impedance measurement circuit, the frequency selective filter circuit adapted to extract from each thoracic impedance signal value a near-DC thoracic impedance signal value, the near-DC thoracic impedance signal value between 0 Hz to about 0.05 Hz, inclusive;

a processor, coupled with the frequency selective filter circuit to accept a plurality of near-DC thoracic impedance signal values;

a statistical analysis module adapted to compute a mean and a standard deviation of the plurality of near-DC thoracic impedance signal values;

a memory storage device adapted to store a history of the plurality of near-DC thoracic impedance signal values and the computed mean and standard deviation of the plurality of near-DC thoracic impedance signal values, the processor adapted to extract from the thoracic impedance signal values one or more thoracic impedance signal values that fall within a boundary that is specified relative to the mean thoracic impedance and to use the extracted thoracic impedance signal values to determine a pulmonary edema indication; and

a therapy control module coupled to the processor, the therapy control module adapted to adjust or initiate one or more therapies selected from a therapy group consisting essentially of cardiac rhythm management therapy, dietary therapy, and breathing assistance therapy based, at least in part, on the pulmonary edema indication.

18. A system comprising:

a memory storage device, adapted to store at least one previous parameter associated with a first pulmonary edema episode occurring in the past, the at least one previous parameter selected from a previous parameter group consisting essentially of a previous thoracic impedance, a previous physiologic parameter, a previous environmental parameter, a previous compliance parameter, and a previous patient symptom parameter;

a parameter collection device, adapted to sense or receive at least one present parameter about a subject, the at least one present parameter not associated with the first pulmonary edema episode and selected from a present parameter group consisting essentially of a present physiologic parameter, a present environmental parameter, a present compliance parameter, and a present patient symptom parameter;

an implantable thoracic impedance measurement circuit, adapted to sense a present thoracic impedance signal value from the subject;

a processor, coupled with the memory storage device to accept the at least one previous parameter, coupled with the parameter collection device to accept the at least one present parameter, and coupled with the thoracic impedance measurement circuit to accept the present thoracic impedance signal value, the processor adapted to determine an indication of a presently developing second pulmonary edema episode, distinct from the first pulmonary edema episode, using one or a combination of the at least one previous parameter, the at least one present parameter, and the present thoracic impedance signal value; and

a therapy control module coupled to the processor, the therapy control module adapted to adjust or initiate one or more therapies selected from a therapy group consisting essentially of cardiac rhythm management therapy, dietary therapy, and breathing assistance therapy based, at least in part, on the indication of the second pulmonary edema episode,

wherein the processor determines the indication of the second pulmonary edema episode when the present thoracic impedance signal value is less than a thoracic impedance threshold, the thoracic impedance threshold adjusted using, at least in part, the at least one previous parameter and the at least one present parameter.