METHODS AND SYSTEMS FOR DETECTING PHYSIOLOGY FOR MONITORING CARDIAC HEALTH

• US 20160183813A1
• Filed: 12/03/2015
• Published: 06/30/2016
• Est. Priority Date: 12/03/2014
• Status: Active Grant

• Current Assignee: Terumo Kabushiki Kaisha
• Original Assignee: ReThink Medical, INC
• Inventors: Naima, Reza
• Granted Patent: US 10,004,408 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/02055 Simultaneously evaluating both cardiovascular condition and temperature
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0535 Impedance plethysmography for measuring blood flow A61B5/0295
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F

Abstract

In one aspect, a photoplethysmograph system to measure a user'"'"'s heart rate includes one or more light-emitting diodes (LED) that provide a constantly-on light signal during a measurement period. The one or more light-emitting diodes are in optical contact with an epidermal surface of the user. The one or more light-emitting diodes emit a light signal into the tissue of the user, and wherein the tissue contains a pulsating blood flow. A light-intensity sensor circuit converts the reflected LED light from the tissue into a second signal that is proportional to a reflected light intensity. The second signal includes a voltage or current signal. A computer-processing module calculates the user'"'"'s beat-to-beat heart rate from the second current signal.

Claims

1. A bioimpedance spectrometer system comprising:

two current-delivery electrodes that convey an alternating current (AC) signal through a user'"'"'s tissue, wherein the two current-delivery electrodes are placed in contact with a surface of the user'"'"'s tissue;

two sense electrodes that measure the differential voltage on the tissue;

an instrumentation amplifier that measures the differential voltage on the surface of the user'"'"'s tissue through the two sense electrodes, and generates a voltage measurement signal corresponding to the difference in voltage between each of the two sense electrodes;

a low-impedance or high-impedance current source circuit that maintains a specified-range value of the AC current passing through the user'"'"'s tissue such that the magnitude of a tissue impedance is equal to a differential voltage between two sense electrodes on the tissue divided by a known or measured current provided by the current source circuit; and

a processing module that calculates an impedance magnitude or a complex impedance value calculated from the impedance magnitude and a phase shift between the differential voltage and the AC current and determines a relative amount of intracellular and extracellular fluid from the impedance magnitude or complex impedance value.

2. The bioimpedance spectrometer system of claim 1, wherein the two current-delivery electrodes and the two sense electrodes are in a tetrapolar configuration.

3. The bioimpedance spectrometer system of claim 1, wherein the instrumentation amplifier comprises an instrumentation amplifier, a differential amplifier, or combination of operational amplifiers configured to provide a differential voltage output.

4. The bioimpedance spectrometer system of claim 1, wherein a frequency of the AC current is set to specified frequencies.

5. The bioimpedance spectrometer system of claim 4, wherein the measured impedance magnitude or complex impedance is sampled for at one or more specified frequencies.

6. The bioimpedance spectrometer system of claim 1 further comprising:

wherein the bioimpedance spectrometer system comprises a high impedance bioimpedance spectrometer system, and

a current-sense resistor of a known-fixed value;

a differential voltage sensor that measures the voltage across current-sense resistor.

7. The bioimpedance spectrometer system of claim 6, wherein the processing module fits a measured impedance to a cole-cole plot and extrapolates the real impedance at a direct current (DC) and at an infinite frequency.

8. The bioimpedance spectrometer system of claim 7, wherein the processing module measures the magnitude of impedance at a low frequency and a high frequency.

9. The bioimpedance spectrometer system of claim 8, wherein the processing module compares a magnitude of the impedance of the tissue at both low and high frequencies and based on these impedance values determines the amount of intracellular and extracellular fluid from the complex impedance value.

10. A photoplethysmograph system to measure a user'"'"'s heart rate comprising:

one or more light-emitting diodes (LED) that provide a constantly-on light signal during a measurement period, wherein one or more light-emitting diodes are in optical contact with an epidermal surface of the user, wherein the one or more light-emitting diodes emit a light signal into the tissue of the user, and wherein the tissue contains a pulsating blood flow;

a light-intensity sensor circuit that converts the reflected LED light from the tissue into a second signal that is proportional to a reflected light intensity, and wherein the second signal is a voltage signal or a current signal; and

a computer-processing module that calculates the user'"'"'s beat-to-beat heart rate from the second current signal.

11. The photoplethysmograph system of claim 10, wherein in the light-intensity sensor circuit comprises a PIN photodiode, a PN photodiode, a phototransistor or a light-detecting integrated circuit.

12. The photoplethysmograph system of claim 11, wherein the PIN photodiode or PN photodiode is reversed biased to increase sensitivity and decrease capacitance.

13. The photoplethysmograph system of claim 12 further comprising:

a microcontroller that directly outputs a voltage signal through a digital to analog converter; and

a transistor that converts the voltage signal to a current signal that is used to illuminate the one or more light-emitting diodes.

14. The photoplethysmograph system of claim 13 further comprising:

wherein the current signal of the second signal is proportional to an incident light and is converted to a third voltage signal through a transimpedance amplifier;

wherein the voltage signal of the second signal is proportional to the incident light and is buffered and amplified through an amplifier to the third voltage signal; and

the third voltage signal is band-pass filtered to physiologically relevant frequencies to reduce the noise and external interference of the third voltage signal.

15. The photoplethysmograph system of claim 14, wherein the physiologically relevant low-pass filter frequency comprises five (5) Hertz (Hz).

16. The photoplethysmograph system of claim 15, wherein the epidermal surface of the user comprises a wrist region.

17. The photoplethysmograph system of claim 16,

wherein the one or more light-emitting diodes are constantly on, then a bandwidth of the filter is tuned to the relevant bandwidth of a PPG pulsatile signal,

wherein the one or more light-emitting diodes comprise one or more infrared light-emitting diodes, and

wherein the light-intensity sensor circuit is maximally sensitive at a same frequency of the one or more light-emitting diodes comprise one or more infrared light-emitting diodes.

18. A computerized system for measuring one or more physiologic parameters used to quantify a cardiac state related to heart failure comprising:

a heart rate sensor means that measures the physiologic parameters used to quantify the cardiac state related to a heart failure state;

a telemetry system means that communicates the physiologic parameters to a data analysis means; and

a data analysis means that receives the physiologic parameters and determines a cardiac state.

19. The computerized system of claim 18 further comprising:

an edema sensor means to measure an edema-related physiological parameter used to quantify an edema state, and wherein the data analysis means receives the edema-related physiological parameter and determines the edema state.

20. The computerized system of claim 19,

wherein the edema sensor means comprises a bioimpedance spectrometer,

wherein the heart rate sensor means comprises a either a photoplethysmograph, a bioimpedance spectrometer, an accelerometer, or a piezoelectric vibration sensor, or an Electrocardiography (ECG) system,

wherein the computerized system comprises a temperature sensor that obtains a user'"'"'s temperature that is provided to the data analysis means, and

wherein the cardiac status is relayed to a specified computer application.