Left atrial pressure-based criteria for monitoring intrathoracic impedance

• US 7,774,055 B1
• Filed: 11/07/2005
• Issued: 08/10/2010
• Est. Priority Date: 11/07/2005
• Status: Expired due to Fees

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories)
• Inventors: Min, Xiaoyi
• Primary Examiner(s): Casler; Brian
• Assistant Examiner(s): CHAO, ELMER M
• Application Number:
  US11/269,390
• Time in Patent Office: 1,737 Days
• Field of Search: 607/17, 607/18, 607/28, 607/9, 600/547, 600/300, 600/481, 600/484, 600/529
• US Class Current: 600/547
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0538 invasively, e.g. using a catheter
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/145 Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissuemeasuring of blood pressure or blood flow A61B5/02; non-radiation detecting or locating of foreign bodies in blood A61B5/06
• CPC Class Codes: A61B 5/4878 Evaluating oedema
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61B 7/00 Instruments for auscultation
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

An exemplary method includes providing left atrial pressure information, based at least in part on the information, determining a weight and, based at least in part on the weight, determining a threshold for use in intrathoracic impedance monitoring. Such an exemplary method may include comparing an intrathoracic impedance to the threshold, comparing an intrathoracic impedance change to the threshold, or comparing a product of intrathoracic impedance and time to the threshold. Various exemplary methods, devices, systems, etc., are disclosed.

Claims

1. A method comprising:

determining a left atrial pressure of a patient;

based at least in part on the left atrial pressure, determining a weight, the weight associated with a particular phase of pulmonary edema;

based at least in part on the weight, determining a threshold for use in intrathoracic impedance monitoring of the patient wherein the intrathoracic impedance monitoring provides evidence of lung fluid;

comparing an intrathoracic impedance, a change in intrathoracic impedance or a product of intrathoracic impedance and time to the threshold; and

implementing control logic of a module, operable in conjunction with a processor, to decide, based on the comparing, whether to trigger a pulmonary edema phase alarm for the patient.

2. The method of claim 1 wherein the intrathoracic impedance comprises, in part, an intracardiac impedance.

3. The method of claim 1 wherein the product has units of ohms-days.

4. The method of claim 1 wherein the threshold pertains to a pulmonary edema onset phase occurring in a period of less than one day.

5. The method of claim 1 wherein the threshold pertains to a pulmonary edema phase occurring over a period of more than one day.

6. The method of claim 1 wherein the threshold pertains to a pulmonary edema fibrosis-related phase associated with an increase in dry lung weight.

7. The method of claim 1 wherein the threshold pertains to a pulmonary edema phase associated with an increase in left atrial pressure.

8. The method of claim 1 wherein comparing comprises comparing an intrathoracic impedance or a change in intrathoracic impedance to the threshold, and the threshold comprises a percentage decrease in intrathoracic impedance from a base value or baseline.

9. The method of claim 1 wherein the determining determines a weight associated with an onset phase of pulmonary edema if the patient does not exhibit pulmonary edema.

10. The method of claim 1 wherein the determining determines a weight associated with a post-onset fluid accumulation phase of pulmonary edema if the patient does exhibit pulmonary edema.

11. An implantable device comprising:

a processor;

an impedance measuring circuit operably connected to the processor to acquire intrathoracic impedance as evidence of lung fluid; and

control logic operable in conjunction with the processor configured to acquire or determine a weight associated with a particular phase of pulmonary edema based at least in part on left atrial pressure, to calculate a threshold based at least in part on the weight, to compare the threshold to one or more of an intrathoracic impedance, a change in intrathoracic impedance, and a product of intrathoracic impedance and time, and to trigger a pulmonary edema phase alarm or call for other action based on a comparison performed by the control logic operable to compare.

12. The implantable device of claim 11 wherein the impedance measuring circuit is operative to further measure intracardiac impedance.

13. An implantable device comprising:

means for determining a left atrial pressure;

means for determining a threshold associated with a particular phase of pulmonary edema, for use in intrathoracic impedance monitoring, based at least in part on the left atrial pressure;

means for monitoring intrathoracic impedance as evidence of lung fluid;

means for comparing an intrathoracic impedance, a change in intrathoracic impedance or a product of intrathoracic impedance and time to the threshold; and

means for triggering a pulmonary edema phase alarm or calling for other action based on a comparison performed by the means for comparing.

14. The implantable device of claim 13 wherein the means for determining a threshold comprises means for determining a value pertaining to a pulmonary edema onset phase occurring in a period of less than one day.

15. The implantable device of claim 13 wherein the means for determining a threshold comprises means for determining a value pertaining to a pulmonary edema phase occurring over a period of more than one day.