Complete ECG contact impedance determination

An Electrocardiogram (“ECG”) system, comprising:

• a plurality of ECG electrodes;
• a plurality of electrical leads;
• and
• an ECG monitor electrically connected to the ECG electrodes by the electrical leads, the ECG monitor including:
• a sensor interface through which the ECG monitor receives signals from and sends signals to the ECG electrodes;
• and
• a processor-based control unit programmed to, through the sensor interface:
• monitor the ECG electrodes when the ECG electrodes are ostensibly electrically connected to a human body;
• drive a plurality of electrical currents through the ECG electrodes in a predetermined pattern;
• determine a respective contact impedance for each of the ECG electrodes as the plurality of electrical currents is driven through the ECG electrodes in the predetermined pattern, each respective contact impedance including a resistive component and a capacitive component, including determining the respective resistive component and the respective capacitive component for each respective contact impedance of each respective ECG electrode, the determining including:
• selecting a first reference ECG electrode from among the plurality of ECG electrodes, the remainder of the ECG electrodes becoming non-reference ECG electrodes;
• determining the respective contact impedance for each of the non-reference ECG electrodes from a first transition from a respective first ECG electrode voltage to a respective second ECG electrode voltage as the plurality of electrical currents driven through the ECG electrodes change, each respective contact impedance including a resistive component and a capacitive component;
• selecting a second reference ECG electrode from among the ECG electrodes, the second reference ECG electrode being different from the first reference ECG electrode, the rest of the ECG electrodes becoming second non-reference ECG electrodes;
• and
• determining the respective contact impedance for the non-reference ECG electrode previously identified as the first reference electrode from a second transition from a respective second ECG electrode voltage to a respective third ECG electrode voltage as the electrical currents driven through the ECG electrodes changes, the respective contact impedance including a resistive component and a capacitive component;
• ascertain whether any of the determined respective contact impedances exceeds a predetermined threshold;
• when any of the determined respective contact impedances exceeds the predetermined threshold, issue a lead-off alarm.

A non-transitory computer readable medium encoded with instructions that, when executed by a processor, perform a method comprising:

• monitoring a plurality of Electrocardiogram (“ECG”) electrodes ostensibly electrically connected to a human body;
• driving a plurality of electrical currents through the monitored ECG electrodes in a predetermined pattern;
• determining a respective contact impedance for each of the ECG electrodes as the electrical currents are driven through the ECG electrodes in the predetermined pattern, each respective contact impedance including a resistive component and a capacitive component, including determining the respective resistive component and the respective capacitive component for each respective contact impedance of each respective ECG electrode, the determining including:
• selecting a first reference ECG electrode from among the plurality of ECG electrodes, the remainder of the ECG electrodes becoming non-reference ECG electrodes;
• determining the respective contact impedance for each of the non-reference ECG electrodes from a first transition from a respective first ECG electrode voltage to a respective second ECG electrode voltage as the plurality of electrical currents driven through the ECG electrodes change, each respective contact impedance including a resistive component and a capacitive component;
• selecting a second reference ECG electrode from among the ECG electrodes, the second reference ECG electrode being different from the first reference ECG electrode, the rest of the ECG electrodes becoming second non-reference ECG electrodes;
• and
• determining the respective contact impedance for the non-reference ECG electrode previously identified as the first reference electrode from a second transition from a respective second ECG electrode voltage to a respective third ECG electrode voltage as the electrical currents driven through the ECG electrodes changes, the respective contact impedance including a resistive component and a capacitive component;
• ascertaining whether any of the determined respective contact impedances exceeds a predetermined threshold;
• when any of the determined respective contact impedances exceeds the predetermined threshold exceeds the predetermined threshold, issuing a lead-off alarm.