Techniques for detecting heart pulses and reducing power consumption in sensors
First Claim
1. A pulse oximeter system comprising:
- a drive interface that controls drive current of light emitting elements in a pulse oximeter sensor; and
a feedback loop coupled around the pulse oximeter sensor and the drive interface that dynamically adjusts the drive current of the light emitting elements based on results of a comparison between a signal-to-noise ratio of a pulse oximeter signal and a threshold, wherein the pulse oximeter signal is generated by a photodetector in the pulse oximeter sensor.
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Abstract
Low power techniques for sensing cardiac pulses in a signal from a sensor are provided. A pulse detection block senses the sensor signal and determines its signal-to-noise ratio. After comparing the signal-to-noise ratio to a threshold, the drive current of light emitting elements in the sensor is dynamically adjusted to reduce power consumption while maintaining the signal-to-noise ratio at an adequate level. The signal component of the sensor signal can be measured by identifying systolic transitions. The systolic transitions are detected using a maximum and minimum derivative averaging scheme. The moving minimum and the moving maximum are compared to the scaled sum of the moving minimum and moving maximum to identify the systolic transitions. Once the signal component has been identified, the signal component is compared to a noise component to calculate the signal-to-noise ratio.
128 Citations
45 Claims
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1. A pulse oximeter system comprising:
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a drive interface that controls drive current of light emitting elements in a pulse oximeter sensor; and
a feedback loop coupled around the pulse oximeter sensor and the drive interface that dynamically adjusts the drive current of the light emitting elements based on results of a comparison between a signal-to-noise ratio of a pulse oximeter signal and a threshold, wherein the pulse oximeter signal is generated by a photodetector in the pulse oximeter sensor. - View Dependent Claims (2, 3)
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4-13. -13. (canceled)
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14. A method for reducing power consumption in a pulse oximeter sensor, the method comprising:
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providing drive current to light emitting elements in the pulse oximeter sensor; and
determining a signal-to-noise ratio of a pulse oximeter signal generated by a photodetector in the pulse oximeter sensor; and
dynamically adjusting the drive current of the light emitting elements based on results of a comparison between the signal-to-noise ratio of the pulse oximeter signal and a threshold. - View Dependent Claims (15)
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16-21. -21. (canceled)
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22. A system coupled to a sensor, the system comprising:
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a transimpedance amplifier that receives a current signal from the sensor and converts the current signal to a voltage signal based on a transimpedance gain;
an analog-to-digital converter that converts the voltage signal into a digital signal; and
a feedback loop that provides a feedback signal indicating a magnitude of the voltage signal from the transimpedance amplifier when light emitting elements in the sensor are on or off, wherein the transimpedance gain is adjusted in response to the feedback signal to accommodate the environmental DC bias on the voltage signal. - View Dependent Claims (23, 24)
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25. A method for controlling drive current of light emitting elements in a pulse oximeter sensor, comprising:
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measuring a noise component of a pulse oximeter signal;
identifying a systolic period of the pulse oximeter signal;
performing pulse qualification tests to qualify the systolic period for oxygen saturation calculations;
determining a strength of the systolic period if the systolic period is qualified for oxygen saturation calculations;
identifying a signal-to-noise ratio by comparing the strength of the systolic period to the noise component; and
controlling the drive current based on a comparison of the signal-to-noise ratio to a threshold. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33)
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34. A monitor for controlling drive current of light emitting elements in a pulse oximeter sensor, comprising:
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an identification module configured to identify a systolic period of a pulse oximeter signal;
a qualification module configured to perform pulse qualification tests to qualify the systolic period for oxygen saturation calculations;
a strength determination module configured to determine a strength of the systolic period if the systolic period is qualified for oxygen saturation calculations;
a ratio module configured to identify a signal-to-noise ratio by comparing the strength of the systolic period to a measured value of a noise component of the pulse oximeter signal stored in a memory; and
a controller configured to control the drive current based on a comparison of the signal-to-noise ratio to a threshold. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42)
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43. A tangible computer-readable medium, comprising:
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code configured to identify a systolic period of a pulse oximeter signal;
code configured to perform pulse qualification tests to qualify the systolic period for oxygen saturation calculations;
code configured to determine a strength of the systolic period if the systolic period is qualified for oxygen saturation calculations;
code configured to identify a signal-to-noise ratio by comparing the strength of the systolic period to a measured value of a noise component of the pulse oximeter signal; and
code configured to control the drive current based on a comparison of the signal-to-noise ratio to a threshold. - View Dependent Claims (44, 45)
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Specification