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 is capable of dynamically adjusting the drive current of the light emitting elements based at least in part upon results of a comparison between a signal-to-noise ratio of a pulse oximeter signal and a threshold, wherein the feedback loop is capable of detecting systolic transitions based at least in part upon a multi-step averaging scheme,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.
919 Citations
29 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 is capable of dynamically adjusting the drive current of the light emitting elements based at least in part upon results of a comparison between a signal-to-noise ratio of a pulse oximeter signal and a threshold, wherein the feedback loop is capable of detecting systolic transitions based at least in part upon a multi-step averaging scheme, 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. 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 dynamically determining a signal-to-noise ratio of a pulse oximeter signal generated by a photodetector in the pulse oximeter sensor, wherein determining the signal-to-noise ratio comprises measuring and storing the noise at each of a plurality of gain stages; and dynamically adjusting the drive current of the light emitting elements based at least in part upon results of a comparison between the signal-to-noise ratio of the pulse oximeter signal and a threshold. - View Dependent Claims (5)
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6. A system coupled to a sensor, the system comprising:
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a transimpedance amplifier capable of receiving a current signal from the sensor and converting the current signal to a voltage signal based at least in part upon a transimpedance gain; an analog-to-digital converter capable of converting the voltage signal into a digital signal; and a feedback loop capable of providing 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 capable of being adjusted in response to the feedback signal to reduce the environmental DC bias on the voltage signal. - View Dependent Claims (7, 8)
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9. A method for controlling drive current of light emitting elements in a pulse oximeter sensor, comprising:
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using a pulse oximeter; measuring a noise component of a pulse oximeter signal; identifying a systolic period of the pulse oximeter signal; performing first pulse qualification tests to qualify a systolic period for pulse rate measurement; performing second pulse qualification tests to qualify the systolic period for oxygen saturation calculations, if the systolic period is qualified for pulse rate measurement; 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 at least in part upon a comparison of the signal-to-noise ratio to a threshold. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17)
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18. A monitor for controlling drive current of light emitting elements in a pulse oximeter sensor, comprising:
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an identification module capable of identifying a systolic period of a pulse oximeter signal; a qualification module capable of performing multiple stages of pulse qualification tests to qualify the systolic period for oxygen saturation calculations; a strength determination module capable of determining a strength of the systolic period if the systolic period is qualified for oxygen saturation calculations; a ratio module capable of identifying 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 capable of controlling the drive current based at least in part upon a comparison of the signal-to-noise ratio to a threshold. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26)
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27. A tangible computer-readable medium, comprising:
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code capable of identifying a systolic period of a pulse oximeter signal, wherein identifying a systolic period comprises calculating a moving average; code capable of performing pulse qualification tests to qualify the systolic period for oxygen saturation calculations; code capable of determining a strength of the systolic period if the systolic period is qualified for oxygen saturation calculations; code capable of identifying 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 capable of controlling the drive current based at least in part upon a comparison of the signal-to-noise ratio to a threshold. - View Dependent Claims (28, 29)
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Specification