Low power pulse oximeter
A pulse oximeter may reduce power consumption in the absence of overriding conditions. Various sampling mechanisms may be used individually or in combination. Various parameters may be monitored to trigger or override a reduced power consumption state. In this manner, a pulse oximeter can lower power consumption without sacrificing performance during, for example, high noise conditions or oxygen desaturations.
1. A processing device configured to operate a non-invasive optical sensor at different non-zero duty cycles, the processing device comprising:
one or more light emitting diodes (LED) configured to emit light toward tissue of a wearer of the non-invasive optical sensor;
a detector configured to detect the emitted light after attenuation by the tissue of the wearer; and
one or more processors configured to:
operate the one or more LEDs at a first non-zero duty cycle,
receive one or more first signals responsive to the detected light during the first non-zero duty cycle,
determine measurements of a physiological parameter based on at least the received one or more first signals,
determine one or more signal-related indications,
responsive to at least one of the measurements or the one or more signal-related indications, operate the one or more LEDs at a second non-zero duty cycle different than the first non-zero duty cycle,
receive one or more second signals responsive to the detected light during the second non-zero duty cycle, and
determine measurements of the physiological parameter based on at least the received one or more second signals.
2. The processing device of claim 1 , wherein the one or more signal-related indications comprise signal statistics.
3. The processing device of claim 1 , wherein the one or more signal-related indications comprise a signal level.
4. The processing device of claim 1 , wherein the one or more signal-related indications comprise a signal strength.
5. The processing device of claim 1 , wherein the one or more signal-related indications comprise a signal quality.
6. The processing device of claim 1 , wherein the one or more signal-related indications comprise a signal to noise ratio.
7. The processing device of claim 1 , wherein the one or more signal-related indications are responsive to a noise level.
8. The processing device of claim 1 , wherein the one or more signal-related indications are responsive to motion.
9. The processing device of claim 8 , wherein the one or more signal-related indications are responsive to motion comprising an artifact.
10. The processing device of claim 1 , wherein the measurements are responsive to a cardiac event.
11. The processing device of claim 1 , wherein the measurements are responsive to an above-normal pulse rate.
12. The processing device of claim 1 , wherein the measurements are responsive to an irregular pulse rate.
13. The processing device of claim 1 , wherein the measurements are responsive to an oxygen desaturation.
14. The processing device of claim 1 , wherein the measurements are responsive to an irregular plethysmograph waveform.
15. The processing device of claim 1 , wherein the physiological parameter comprises a pulse rate.
16. The processing device of claim 1 , wherein the physiological parameter comprises an oxygen saturation.
17. The processing device of claim 1 , wherein the physiological parameter comprises a plethysmograph waveform.
18. The processing device of claim 1 , wherein one or more of the one or more LEDs emit visible light.
19. The processing device of claim 1 , wherein the second non-zero duty cycle is four times the first non-zero duty cycle.
20. A pulse rate measurement device comprising:
a wearable noninvasive sensor including one or more light emitting diodes (LED) configured upon activation to emit light toward tissue of a wearer and a photodiode detector responsive to light from the one or more LEDs after attenuation by the tissue of the wearer;
a sensor interface including one or more emitter drivers configured to provide one or more drive signals to the one or more LEDs, and a detector front-end configured to receive one or more signals from the detector responsive to light attenuated by the tissue of the wearer;
a controller configured to change a duty cycle of the one or more drive signals in response to a trigger, the controller causing the one or more emitter drivers to transition from operation at a first non-zero duty cycle of the one or more drive signals to operation at a second non-zero duty cycle of the one or more drive signals to provide higher or lower fidelity monitoring of the wearer, wherein the first non-zero duty cycle is different from the second non-zero duty cycle, and wherein the trigger is responsive to a physiological indication or a signal-related indication; and
a processor configured to receive the one or more signals from the detector front-end, to process the one or more signals, and to determine a pulse rate of the wearer responsive to the processing of the one or more signals received during operation of the one or more emitter drivers at each of the first and the second non-zero duty cycles.
21. The pulse rate measurement device of claim 20 , wherein the emitter drivers are further configured to activate the one or more LEDs with a substantially constant drive current interspaced with dark bands for demodulating LED channels.
22. The pulse rate measurement device of claim 20 , wherein the signal-related indication comprises signal statistics.
23. The pulse rate measurement device of claim 20 , wherein the physiological indication comprises a cardiac event.
24. The pulse rate measurement device of claim 20 , wherein the controller is further configured to change the duty cycle of the one or more drive signals by transitioning from the second non-zero duty cycle back to the first non-zero duty cycle.
25. A pulse oximeter comprising:
a wearable noninvasive sensor including one or more light emitting diodes (LED) configured upon activation to emit light toward tissue of a wearer and a photodiode detector responsive to light from the one or more LEDs after attenuation by the tissue of the wearer;
a sensor interface including one or more emitter drivers configured to provide one or more drive signals to the LEDs, and a detector front-end configured to receive one or more signals from the detector responsive to light attenuated by the tissue of the wearer;
a controller configured to select a duty cycle of e signals in response to a trigger, the controller selecting between operating at one of a low-duty cycle and a high-duty cycle of the one or more drive signals upon an occurrence of the trigger, and wherein the trigger is responsive to a physiological indication or a signal-related indication; and
a processor configured to receive the one or more signals from the detector front-end, to process the one or more signals, and to determine an oxygen saturation of the wearer responsive to the processing of the one or more signals received during operation of the one or more emitter drivers at each of the low-duty cycle and the high-duty cycle.
26. The pulse oximeter of claim 25 , wherein the signal-related indication comprises a noise level.
27. The pulse oximeter of claim 25 , wherein the signal-related indication comprises motion.
28. The pulse oximeter of claim 27 , wherein the signal-related indication comprises motion comprising an artifact.
29. The pulse oximeter of claim 25 , wherein the physiological indication comprises a cardiac event.
30. The pulse oximeter of claim 25 , wherein the physiological indication comprises oxygen desaturation.