Calibration of impedance monitoring of respiratory volumes using thoracic D.C. impedance
First Claim
1. A system comprising:
- a medical device, including;
an implantable trans-thoracic impedance measurement circuit to provide a trans-thoracic impedance signal of a subject; and
a controller coupled to the trans-thoracic impedance circuit, the controller configured to;
store a reference baseline value of a DC component of a trans-thoracic impedance;
measure a more recent value of the DC component of a trans-thoracic impedance different from the reference baseline value;
adjust a breathing volume calibration factor using the reference baseline value and the more recent measured value of a DC component of a trans-thoracic impedance, wherein the breathing volume calibration factor translates a measure of impedance to a measure of breathing volume, and wherein the adjusted breathing volume calibration factor includes a ratio of a reference DC trans-thoracic impedance to a more recent measured value of the DC trans-thoracic impedance;
extract a respiration signal from the trans-thoracic impedance signal, the respiration signal including a respiration amplitude; and
compute a breathing volume of the subject using the respiration amplitude scaled by the adjusted breathing volume calibration factor.
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Accused Products
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
19 Claims
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1. A system comprising:
a medical device, including; an implantable trans-thoracic impedance measurement circuit to provide a trans-thoracic impedance signal of a subject; and a controller coupled to the trans-thoracic impedance circuit, the controller configured to; store a reference baseline value of a DC component of a trans-thoracic impedance; measure a more recent value of the DC component of a trans-thoracic impedance different from the reference baseline value; adjust a breathing volume calibration factor using the reference baseline value and the more recent measured value of a DC component of a trans-thoracic impedance, wherein the breathing volume calibration factor translates a measure of impedance to a measure of breathing volume, and wherein the adjusted breathing volume calibration factor includes a ratio of a reference DC trans-thoracic impedance to a more recent measured value of the DC trans-thoracic impedance; extract a respiration signal from the trans-thoracic impedance signal, the respiration signal including a respiration amplitude; and compute a breathing volume of the subject using the respiration amplitude scaled by the adjusted breathing volume calibration factor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A system comprising:
a medical device, including; an implantable trans-thoracic impedance measurement circuit to provide a trans-thoracic impedance signal of a subject, the measurement circuit including an adjustable test current circuit; and a controller coupled to the trans-thoracic impedance circuit, the controller operable to; store a reference baseline value of a DC component of a trans-thoracic impedance; measure a more recent value of the DC component of a trans-thoracic impedance different from the reference baseline value; adjust a test current value until the measured value of the DC component of a trans-thoracic impedance is substantially the same as the reference baseline DC voltage value; extract a respiration signal from the trans-thoracic impedance signal, the respiration signal including a respiration amplitude; and compute a breathing volume of the subject. - View Dependent Claims (14, 15, 16, 17, 18, 19)
Specification