Apparatus and method for determining cardiac output in a living subject

A method of measuring the cardiac output of a living subject, comprising:

• providing a plurality of electrode arrays, each of said electrode arrays having a plurality of terminals, at least two of said terminals being spaced a predetermined distance apart;
• positioning the electrode arrays at respective locations in relation to the thoracic cavity of the subject;
• generating an electrical current, said current passing from a first electrode of at least one of said electrode arrays through said subject and to a second electrode of at least one of said arrays;
• measuring the voltage at said second electrode of said at least one electrode array;
• determining stroke volume from the measured voltage;
• and
• determining cardiac output based at least in part on said stroke volume.

A cardiac electrode assembly for use on a living subject, comprising:

• a substrate, said substrate having a plurality of apertures formed therein, at least two of said apertures being formed a predetermined distance apart;
• a plurality of terminals disposed within respective ones of said apertures, at least a portion of each of said terminals being capable of conducting an electrical current;
• and
• at least one gel element, said at least one gel element being adapted to transfer electrical current between the skin of said subject and at least one of said plurality of terminals.

A cardiac electrode assembly adapted for measuring the cardiac output of a living subject, comprising:

• a flexible substrate, said substrate having at least two apertures formed therein, said at least two apertures being formed a predetermined distance apart;
• at least two terminals disposed within respective ones of said apertures, at least a portion of each of said terminals being capable of conducting an electrical current;
• and
• a first electrolytic element disposed proximate to a first of said at least two apertures, said first electrolytic element adapted to transfer an electrical potential between the skin of said subject and a first of said at least two terminals;
• a second electrolytic element disposed proximate to a second of said at least two apertures, said second electrolytic element adapted to transfer an electrical potential between the skin of said subject and a second of said at least two terminals;
• an attachment element, said attachment element cooperating with said substrate and the skin of said living subject to removably affix said electrode assembly to said skin.

A method of monitoring the electrical continuity of a plurality of electrodes in an impedance cardiography system, comprising:

• providing a plurality of electrically conductive terminals;
• disposing the terminals in relation to the thoracic cavity of a subject;
• generating a current between a first of said terminals and a second of said terminals, said current passing through at least a portion of said thoracic cavity;
• obtaining an impedance waveform from said second terminal;
• and
• comparing said impedance waveform to a similar waveform obtained from another of said terminals;
• wherein the difference between said impedance waveform and said similar waveform is d to evaluate the electrical continuity of said first terminal.

A system for determining the cardiac output of a living subject, comprising:

• a plurality of electrode assemblies, each electrode assembly having:
• a substrate having a plurality of apertures formed therein;
• a plurality of electrically conductive terminals disposed within respective ones of said apertures, each terminal having a central axis, a sidewall portion substantially parallel to said axis, and a top portion, said top portion having a diameter greater of that of said vertical sidewall portion, at least two of said plurality of terminals being spaced from one another by a predetermined distance;
• and
• at least one gel element, said at least one gel element adapted to transfer electrical current between the skin of said subject and said at least two of said plurality of terminals;
• a current source capable of generating a substantially constant current;
• a plurality of electrical leads connecting said current source with individual ones of said terminals of said electrode assemblies, said electrical leads each comprising a connector, said connector being adapted to form an electrical conduction path between said connector and a respective one of said terminals, said connector further comprising a plurality of electrically conductive arms biased against said sidewall portion of said terminal when said connector is mated with said terminal;
• a circuit for measuring the difference in voltage at said terminals resulting from the flow of said current through said subject and said terminals under varying cardiac conditions of said subject;
• and
• a circuit for measuring ECG potentials from at least one of said electrode assemblies.

A system for determining the cardiac output of a living subject, comprising:

• a plurality of electrode assemblies, each electrode assembly having a plurality of terminals, at least two of said plurality of terminals being spaced from one another by a predetermined distance;
• a current source capable of generating a substantially constant current;
• a plurality of electrical leads connecting said current source with individual ones of said terminals of said electrode assemblies,
• a circuit for measuring the difference in voltage at said terminals resulting from the flow of said current through said subject and said terminals under varying cardiac conditions of said subject;
• and
• a circuit for measuring ECG potentials from at least one of said electrode assemblies;
• wherein at least a first portion of said plurality of electrode assemblies are adapted for placement on the neck of said subject;
• and a second portion of said plurality of electrode assemblies are adapted for placement at or near the level of the xiphoid process of said subject.

A method of measuring the cardiac output of a living subject, comprising:

• providing a plurality of electrode arrays, each of said electrode arrays having a plurality of terminals, at least two of said terminals being spaced a predetermined distance apart;
• positioning the electrode arrays at respective locations on the neck and thorax xiphoid process of the subject;
• generating an electrical current, said current passing from a first electrode of at least one of said electrode arrays through said subject and to a second electrode of at least one of said arrays;
• measuring the voltage at said second electrode of said at least one electrode array;
• determining stroke volume from the measured voltage;
• and
• determining cardiac output based at least in part on said stroke volume.

A method of monitoring the electrical continuity of a plurality of electrodes in an impedance cardiography system, comprising:

• providing a plurality of electrically conductive terminals;
• disposing the terminals in relation to the thoracic cavity of a subject;
• generating a current between a first of said terminals and a second of said terminals, said current passing through at least a portion of said thoracic cavity;
• obtaining a first impedance waveform from said second terminal;
• and
• comparing said first impedance waveform to a threshold value;
• wherein the difference between said first impedance waveform and said threshold impedance value is used to evaluate the electrical continuity of said first terminal.

A method of monitoring the electrical continuity of a plurality of electrodes in an impedance cardiography system, comprising:

• providing a plurality of electrically conductive terminals;
• disposing respective ones of the terminals at the neck and approximately the level of the xiphoid process of the thorax of a subject, at least two of said terminals being disposed at predetermined spacing with respect to each other;
• generating a current between a first of said terminals and a second of said at least two terminals, said current passing through at least a portion of said thoracic cavity;
• obtaining a first impedance waveform from said second terminal;
• and
• comparing said first impedance waveform to a threshold value;
• wherein the difference between said first impedance waveform and said threshold impedance value is used to evaluate the electrical continuity of said first terminal.