# US 10,307,073 B2 · ECG sensor with capacitive defibrillation protection

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- Number: US 10,307,073 B2
- Document ID: US10307073B2
- Status: Granted
- Kind: B2
- Application number: 15/387,276
- Filed: 2016-12-21
- Published: 2018-06-21
- Granted: 2019-06-04
- Earliest claimed: 2016-12-21
- Assignees: General Electric Company
- Applicants: General Electric Company
- Inventors: Otto Valtteri Pekander
- Web page: https://patentgrep.com/patent/US10307073B2

## CPC

- A61B 5/302: for capacitive or ionised electrodes, e.g. metal-oxide-semiconductor field-effect transistors [MOSFET]
- A61B 5/276: Protection against electrode failure
- A61B 5/277: Capacitive electrodes
- A61B 5/28: for electrocardiography [ECG]
- A61B 5/308: for electrocardiography [ECG]
- A61N 1/3925: {Monitoring; Protecting}
- A61B 5/08: Measuring devices for evaluating the respiratory organs
- A61B 2562/0214: Capacitive electrodes
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B)

## Abstract

A patient monitoring system includes a capacitive electrode connectable to a patient to detect an output signal and a signal generator unit that transmits a carrier signal to the capacitive electrode, the carrier signal having a carrier frequency and a carrier amplitude. The patient monitoring system further includes an amplifier unit that amplifies the output signal detected by the capacitive electrode to generate an amplified output signal. A gain determination module in the patient monitoring system determines an output amplitude of a carrier frequency portion of the amplified output signal, and determines a system gain based on a comparison between the output amplitude and the carrier amplitude. A voltage determination module in the patient monitoring system filters the output signal to isolate a physiological signal detected from the patient, and determines a voltage of the physiological signal based on the system gain.

## Claims

### Claim 1

A patient monitoring system comprising:
a capacitive electrode connectable to a patient to detect an output signal;
a signal generator unit that transmits a carrier signal to the capacitive electrode, the carrier signal having a carrier frequency and a carrier amplitude;
an amplifier unit that that amplifies the output signal detected by the capacitive electrode to generate an amplified output signal;
a gain determination module that:
determines an output amplitude of a carrier frequency portion of the amplified output signal;
determines a system gain based on a comparison between the output amplitude and the carrier amplitude;
a voltage determination module that:
filters the output signal to isolate a physiological signal detected from the patient; and
determines a voltage of the physiological signal based on the system gain.

### Claim 2 (depends on 1)

The patient monitoring system of claim 1, wherein the voltage of the physiological signal is determined by dividing an amplitude of the physiological signal by the system gain.

### Claim 3 (depends on 1)

The patient monitoring system of claim 1, wherein the amplifier unit:
applies a known amplifier gain to the output signal, and wherein the gain determination module determines an expected amplitude by multiplying the carrier amplitude by the known amplifier gain;
determines an attenuation amount of the carrier amplitude due to the capacitive electrode by comparing the output amplitude to the expected amplitude; and
determines an electrode capacitance between the capacitive electrode and the patient based on the attenuation amount.

### Claim 4 (depends on 3)

The patient monitoring system of claim 3, wherein the signal generator unit includes a filter to remove low frequencies from the carrier signal prior to transmitting it to the capacitive electrode.

### Claim 5 (depends on 4)

The patient monitoring system of claim 4, wherein the gain determination module determines the electrode capacitance based on a known filter capacitance of the filter.

### Claim 6 (depends on 1)

The patient monitoring system of claim 1, wherein the voltage determination module filters the output signal with a low pass filter having a cut off frequency of 150 Hz or lower.

### Claim 7 (depends on 6)

The patient monitoring system of claim 6, wherein the carrier frequency is greater than 150 Hz.

### Claim 8 (depends on 1)

The patient monitoring system of claim 1, wherein the carrier frequency is at least 1 kHz.

### Claim 9 (depends on 8)

The patient monitoring system of claim 8, wherein the carrier frequency is at least 50 kHz.

### Claim 10 (depends on 1)

The patient monitoring system of claim 1, wherein the system gain is determined at a predetermined interval by generating the carrier signal at that interval.

### Claim 11

A method of patient monitoring using at least one capacitive electrode, the method comprising:
generating a carrier signal at a carrier frequency and carrier amplitude;
transmitting the carrier signal to a capacitive electrode attached to a patient;
receiving an output signal from the capacitive electrode;
amplifying the output signal to create an amplified output signal;
determining an output amplitude of a carrier frequency portion of the amplified output signal;
comparing the carrier amplitude to the output amplitude to determine a system gain;
filtering the output signal to isolate a physiological signal of the patient; and
determining voltage of the physiological signal based on the system gain.

### Claim 12 (depends on 11)

The method of claim 11, wherein the voltage of the physiological signal is determined by dividing an amplitude of the physiological signal by the system gain.

### Claim 13 (depends on 11)

The method of claim 11, wherein amplifying the output signal includes applying a known amplifier gain to the output signal, and further comprising:
determining an expected amplitude by multiplying the carrier amplitude by the known amplifier gain;
determining an attenuation amount of the carrier amplitude due to the capacitive electrode by comparing the output amplitude to the expected amplitude; and
determining an electrode capacitance between the capacitive electrode and the patient based on the attenuation amount.

### Claim 14 (depends on 13)

The method of claim 13, further comprising filtering the carrier signal with a high pass filter prior to transmitting it to the capacitive electrode, wherein the high pass filter at least removes frequencies below 150 Hz.

### Claim 15 (depends on 14)

The method of claim 14, wherein the electrode capacitance is determined based on a known filter capacitance of the high pass filter.

### Claim 16 (depends on 11)

The method of claim 11, wherein the step of filtering the output signal to isolate the physiological signal includes filtering the output signal with a low pass filter with a cut off frequency of 150 Hz.

### Claim 17 (depends on 11)

The method of claim 11, wherein the carrier frequency is greater than 150 Hz.

### Claim 18 (depends on 17)

The method of claim 17, wherein the carrier frequency is at least 1 kHz.

### Claim 19 (depends on 18)

The method of claim 18, wherein the carrier frequency is at least 50 kHz.

### Claim 20 (depends on 11)

The method of claim 11, wherein the system gain is determined at a predetermined interval and the carrier signal is generated at that interval.