Apparatus and methods of bioelectrical impedance analysis of blood flow
First Claim
1. Apparatus for computing a metric corresponding to a patient'"'"'s cardiac output, the apparatus comprising:
- a bioelectrical impedance recorder;
a tube having a proximal portion, and a distal portion;
an expandable member disposed on the distal portion;
three orthogonal pairs of sense electrodes disposed on the expandable member and electrically coupled to the bioelectrical impedance recorder;
a current electrode for injecting a current into the patient'"'"'s thorax; and
a ground electrode;
wherein the three orthogonal pairs of sense electrodes generate signals corresponding to the bioelectrical impedance of blood flow through the aorta and the signals are provided to the bioelectrical impedance recorder.
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Abstract
Apparatus and methods are provided for monitoring cardiac output using bioelectrical impedance techniques in which three orthogonal pairs of sense electrodes are placed in the trachea or esophagus in the vicinity of the aorta, while an excitation current is injected into the intervening tissue mass via a current electrode, so that bioelectrical impedance measurements based on the voltage drop sensed by the sense electrodes reflect voltage changes induced primarily by blood flow dynamics. Methods are provided for computing cardiac output from bioelectrical impedance values using a multi-parameter algorithm derived using stepwise multiple linear regression or other optimization techniques. Apparatus and methods are also provided so that the measured cardiac output may be used to control administration of intravenous fluids or medication to an organism or to optimize a heart rate controlled by a pacemaker.
159 Citations
43 Claims
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1. Apparatus for computing a metric corresponding to a patient'"'"'s cardiac output, the apparatus comprising:
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a bioelectrical impedance recorder;
a tube having a proximal portion, and a distal portion;
an expandable member disposed on the distal portion;
three orthogonal pairs of sense electrodes disposed on the expandable member and electrically coupled to the bioelectrical impedance recorder;
a current electrode for injecting a current into the patient'"'"'s thorax; and
a ground electrode;
wherein the three orthogonal pairs of sense electrodes generate signals corresponding to the bioelectrical impedance of blood flow through the aorta and the signals are provided to the bioelectrical impedance recorder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of measuring the cardiac output of an organism comprising steps of:
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positioning three orthogonal pairs of sense electrodes within the organism in the vicinity of the aorta;
injecting a current into the thorax of the organism through a current electrode;
applying a voltage between the current electrode and a ground electrode so that a current flows through the tissues of the organism disposed between the current electrode and the ground electrode; and
detecting voltages developed across the three orthogonal pairs of sense electrodes caused by the current flowing in the tissues of the organism, the voltages varying in accordance with changes in the bioelectrical impedance of the tissues. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
providing a fluid administration system for injecting a fluid intravenously into the organism'"'"'s vascular system; and
periodically actuating the fluid administration system responsive to the detected voltage developed across the three orthogonal pairs of sense electrodes.
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30. The method as defined in claim 21 further comprising steps of:
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providing a drug administration system for injecting a medication intravenously into the organism'"'"'s vascular system; and
periodically actuating the drug administration system responsive to the detected voltage developed across the three orthogonal pairs of sense electrodes.
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31. The method as defined in claim 21 further comprising steps of:
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providing a pacemaker electrically coupled to the heart of the organism to control heart rate; and
adjusting the heart rate responsive to voltage developed across the three orthogonal pairs of sense electrodes to optimize cardiac output.
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32. The method as defined in claim 31 wherein the step of adjusting the heart rate comprises a step of lowering the heart rate to obtain either a predetermined minimum heart rate or until the cardiac output is measured to be decreasing.
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33. Apparatus for detecting a three-dimensional bioimpedance field in the vicinity of a patient'"'"'s aorta, the apparatus comprising:
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a tube having a proximal portion, and a distal portion;
an expandable member disposed on the distal portion;
three orthogonal pairs of sense electrodes disposed on the expandable member;
a current electrode for injecting a current into the patient'"'"'s thorax; and
a ground electrode;
wherein the three orthogonal pairs of sense electrodes generate signals corresponding to the bioelectrical impedance of blood flow through the aorta. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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Specification