Methods and systems for detecting physiology for monitoring cardiac health
AssigneeTerumo Kabushiki Kaisha
InventorReza Naima
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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.
Claims17
A photoplethysmograph system to measure a physiologic parameter of interest, the system comprising:
- one or more light-emitting diodes (LED) each configured to emit an adjusted, constantly-on light signal during a measurement period, wherein the one or more light-emitting diodes are in optical contact with an epidermal surface, wherein each of the one or more light-emitting diodes emits the constantly-on light signal into a tissue via the epidermal surface, and wherein the tissue contains a pulsating blood flow;
- one or more bioimpedance circuits arranged adjacent to the light-emitting diodes and configured to measure a tissue impedance via one or more electrodes contacting the epidermal surface;
- a light-intensity sensor circuit comprising an amplifier configured to convert a reflected LED light from the tissue into an electric signal proportional to a reflected light intensity, wherein the electric signal is bandpass filtered with a narrow filter tuned to the physiologic parameter of interest to yield a filtered signal specific to the physiologic parameter of interest;
- a strap in which the light-emitting diodes, the light-intensity sensor circuit, and the bioimpedance circuits are arranged in a row;
- an active LED current adjustment circuit operatively connected to both the light-intensity sensor circuit and the one or more light-emitting diodes and comprising a current controlling device configured to take a sample of the filtered electrical signal and adjust the intensity of the constantly-on light signal emitted from each of the one or more light-emitting diodes until the filtered electric signal generated from the reflected LED light intensity is within a desired voltage range;
- and
- a processor configured to determine the physiologic parameter of interest based on at least one of the measured tissue impedance and the filtered signal, wherein
- the current controlling device comprises a digital to analog converter and a transistor configured to supply a constant current signal to the one or more light-emitting diodes.
Dependencies are inferred from the claim text.