Calibration of impedance monitoring of respiratory volumes using thoracic D.C. impedance
First Claim
1. A method comprising:
- detecting a change in direct current (DC) trans-thoracic impedance;
adjusting a breathing volume calibration factor in accordance with the change in DC trans-thoracic impedance, wherein the breathing volume calibration factor translates a measure of impedance to a measure of breathing volume, and the adjusted breathing volume calibration factor includes a ratio of a reference DC trans-thoracic impedance to a more recently measured value of the DC trans-thoracic impedance; and
measuring breathing volume of a patient using the implantable medical device, the medical device adjusting the measured breathing volume using the breathing volume calibration factor.
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Abstract
A system includes an implantable medical device that includes a trans-thoracic impedance measurement circuit providing a trans-thoracic impedance signal of a subject. A controller is coupled to the trans-thoracic impedance circuit. The controller extracts a respiration signal from the trans-thoracic impedance signal, measures a breathing volume of the subject using the amplitude of the respiration signal and a breathing volume calibration factor, computes an adjusted breathing volume calibration factor using a reference baseline value of the trans-thoracic impedance and a measured baseline value of the trans-thoracic impedance, and computes a calibrated breathing volume using the adjusted breathing volume calibration factor.
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Citations
22 Claims
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1. A method comprising:
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detecting a change in direct current (DC) trans-thoracic impedance; adjusting a breathing volume calibration factor in accordance with the change in DC trans-thoracic impedance, wherein the breathing volume calibration factor translates a measure of impedance to a measure of breathing volume, and the adjusted breathing volume calibration factor includes a ratio of a reference DC trans-thoracic impedance to a more recently measured value of the DC trans-thoracic impedance; and measuring breathing volume of a patient using the implantable medical device, the medical device adjusting the measured breathing volume using the breathing volume calibration factor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method comprising:
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measuring a direct current (DC) component of a trans-thoracic impedance signal of a subject using an implantable medical device; adjusting a breathing volume calibration factor using a reference baseline value of the DC component of the trans-thoracic impedance and a measured change from the reference baseline value of the DC component of the trans-thoracic impedance, wherein the breathing volume calibration factor translates a measure of impedance to a measure of breathing volume, and the adjusted breathing volume calibration factor includes a ratio of a reference DC trans-thoracic impedance to a more recently measured value of the DC component of the trans-thoracic impedance; extracting a respiration signal from the trans-thoracic impedance signal, the respiration signal including the DC component of the trans-thoracic impedance that is modulated by a breathing of the subject, the respiration signal including an amplitude; and computing, using the implantable medical device, a breathing volume of the subject using the amplitude of the respiration signal and a breathing volume calibration factor. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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Specification