Thoracic impedance detection with blood resistivity compensation
First Claim
1. A method comprising:
- detecting a thoracic impedance signal of a thorax of a subject;
detecting a blood resistivity signal by sensing between at least two intravascular or intracardiac electrodes disposed in the same chamber of the heart or the same blood vessel; and
using a signal processing circuit, extracting physiological information from the thoracic impedance signal, the extracting physiological information including using the blood resistivity signal to reduce or eliminate an effect of a change in blood resistivity on the physiological information.
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Abstract
This document discusses, among other things, a cardiac rhythm management device or other implantable medical device that uses thoracic impedance to determine how much fluid is present in the thorax, such as for detecting or predicting congestive heart failure, pulmonary edema, pleural effusion, hypotension, or the like. The thoracic fluid amount determined from the thoracic impedance is compensated for changes in blood resistivity, which may result from changes in hematocrit level or other factors. The blood-resistivity-compensated thoracic fluid amount can be stored in the device or transmitted to an external device for storage or display. The blood-resistivity-compensated thoracic fluid amount can also be used to adjust a cardiac pacing, cardiac resynchronization, or other cardiac rhythm management or other therapy to the patient. This document also discusses applications of the devices and methods for predicting or indicating anemia.
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Citations
20 Claims
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1. A method comprising:
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detecting a thoracic impedance signal of a thorax of a subject; detecting a blood resistivity signal by sensing between at least two intravascular or intracardiac electrodes disposed in the same chamber of the heart or the same blood vessel; and using a signal processing circuit, extracting physiological information from the thoracic impedance signal, the extracting physiological information including using the blood resistivity signal to reduce or eliminate an effect of a change in blood resistivity on the physiological information. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A system comprising:
an implantable medical device including; a thoracic impedance measurement circuit configured to provide a thoracic impedance signal; a blood resistivity measurement circuit configured to provide a blood resistivity signal sensed between at least two intravascular or intracardiac electrodes disposed in the same chamber of the heart or the same blood vessel; and a controller coupled to the blood resistivity measurement circuit, the controller configured to extract physiological information from the thoracic impedance signal, the controller configured to use the blood resistivity signal to reduce or eliminate an effect of a change in blood resistivity on the physiological information. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A system comprising:
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means for detecting a thoracic impedance signal of a thorax of a subject; means for detecting a blood resistivity signal sensed between at least two intravascular or intracardiac electrodes disposed in the same chamber of the heart or the same blood vessel; and means for extracting physiological information from the thoracic impedance signal using the blood resistivity signal to reduce or eliminate an effect of a change in blood resistivity on the physiological information. - View Dependent Claims (20)
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Specification