System and method for impedance-based detection of pulmonary edema and reduced respiration using an implantable medical system

• US 7,628,757 B1
• Filed: 05/25/2005
• Issued: 12/08/2009
• Est. Priority Date: 05/25/2005
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Koh, Steve
• Primary Examiner(s): Marmor, II; Charles A
• Assistant Examiner(s): JANG, CHRISTIAN YONGKYUN
• Application Number:
  US11/138,229
• Time in Patent Office: 1,658 Days
• Field of Search: 600/484
• US Class Current: 600/484
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61N 1/3601 of respiratory organs
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance

Abstract

Techniques are provided for detecting pulmonary edema based on a comparison of impedance-based respiratory patterns and impedance-based cardiac patterns, i.e. patterns derived from thoracic impedance signals. In one example, a numerical ratio is calculated between average peak-to-peak amplitudes of the respiratory patterns and average peak-to-peak amplitudes of the cardiac patterns. Pulmonary edema is detected if the amplitude ratio falls below a pulmonary edema detection threshold. Techniques are also provided for controlling operation of an impedance-based reduced respiration detector, i.e. a detector which seeks to detect apnea, hypopnea, or the like, based on analysis of respiratory patterns derived from a thoracic impedance signal. If the numerical ratio falls below a minimum reliability threshold, then the reduced respiration detector is deactivated because episodes of reduced respiration cannot then reliably be derived from an analysis of respiration patterns obtained from the thoracic impedance signals.

Claims

1. A system for use with an implantable medical device for implant within a patient, the system comprising:

a respiratory pattern/cardiac pattern comparison unit operative to determine a comparison value representative of a comparison of impedance-based respiratory patterns and impedance-based cardiac patterns, wherein the respiratory pattern/cardiac pattern comparison unit determines the comparison value by comparing amplitudes of the respiratory and cardiac patterns; and

a pulmonary edema detector operative to detect pulmonary edema based on the comparison value.

2. The system of claim 1 further comprising:

an impedance-based reduced respiration detector operative to detect an episode of reduced respiration; and

a controller operative to selectively activate the impedance-based reduced respiration detector based on the comparison value.

3. A system for use with an implantable medical device for implant within a patient, the system comprising:

means for detecting impedance;

means for detecting cardiac patterns based on thoracic impedance;

means for detecting respiratory patterns based on thoracic impedance;

means for comparing amplitudes of the respiratory patterns and cardiac patterns; and

means for detecting pulmonary edema based on the comparison.

4. The system of claim 3 and further comprising means for delivering therapy in response to detecting pulmonary edema.

5. The system of claim 3 and further comprising means for generating a warning in response to detecting pulmonary edema.