Low power pulse oximeter

• US 20030028085A1
• Filed: 06/26/2002
• Published: 02/06/2003
• Est. Priority Date: 07/02/2001
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Al-Ali, Ammar
• Granted Patent: US 6,697,658 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14551 for measuring blood gases

Abstract

A pulse oximeter adaptively samples an input signal from a sensor in order to reduce power consumption in the absence of overriding conditions. Various sampling mechanisms may be used individually or in combination, including reducing the duty cycle of a drive current to a sensor emitter, intermittently powering-down a front-end interface to a sensor detector, or increasing the time shift between processed data blocks. Both internal parameters and output 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.

Claims

1. A low power pulse oximeter comprising:

a sensor interface adapted to drive a pulse oximetry sensor and receive a corresponding input signal;

a processor that derives a physiological measurement corresponding to said input signal;

a display driver adapted to communicate said measurement to a display; and

a controller generating a sampling control output to at least one of said sensor interface and said processor so as to reduce the average power consumption of said pulse oximeter consistent with a predetermined power target.

2. The low power pulse oximeter according to claim 1 further comprising a calculator that derives a signal status output responsive to said input signal, said signal status output being communicated to said controller to override said sampling control output.

3. The low power pulse oximeter according to claim 2 wherein said signal status output indicates the occurrence of a low signal quality.

4. The low power pulse oximeter according to claim 2 wherein said signal status output indicates the occurrence of a physiological event.

5. The low power pulse oximeter according to claim 1 wherein:

said sensor interface comprises an emitter driver adapted to provide a current output to an emitter portion of said sensor; and

said sampling control output determines a duty cycle of said current output.

6. The low power pulse oximeter according to claim 5 wherein said duty cycle is in the range of about 3.125% to about 25%.

7. The low power pulse oximeter according to claim 1 wherein:

said sensor interface comprises a front-end adapted to receive said input signal from a detector portion of said sensor and to provide a corresponding digitized signal; and

wherein;

said sampling control output determines a powered-down period of said front-end.

8. The low power pulse oximeter according to claim 7 further comprising a confidence indicator that is responsive to a duration of said powered-down period, said confidence indicator communicated to said display driver.

9. The low power pulse oximeter according to claim 1 further comprising a plurality of data blocks responsive to said input signal, wherein said sampling control output determines a time shift of successive ones of said data blocks.

10. The low power pulse oximeter according to claim 9 wherein said time shift varies in the range of about 1.2 seconds to about 4.8 seconds.

11. A low power pulse oximetry method comprising the steps of:

storing a power target;

receiving an input signal from a pulse oximetry sensor;

calculating signal status related to said input signal;

calculating power status related to said power target; and

sampling based upon the result of said calculating signal status and said calculating power status steps.

12. The low power pulse oximetry method according to claim 11 wherein said calculating signal status step comprises the substeps of:

receiving a signal statistic related to said input signal;

receiving a physiological measurement related to said input signal;

determining a low signal quality condition from said signal statistic;

determining an event occurrence from said physiological measurement; and

indicating an override based upon said low signal quality condition or said event occurrence.

13. The low power pulse oximetry method according to claim 12 wherein said calculating power status step comprises the substeps of:

estimating an average power consumption for at least a portion of said pulse oximeter; and

indicating an above power target condition when said average power consumption is above said power target.

14. The low power pulse oximetry method according to claim 12 wherein said sampling step comprises the substep of increasing sampling as the result of said override.

15. The low power pulse oximetry method according to claim 13 wherein said sampling step comprises the substep of decreasing sampling as the result of said above power target condition, except during said override.

16. A low power pulse oximetry method comprising the steps of:

detecting an override related to a measure of signal quality or a physiological measurement event;

increasing said pulse oximeter to a higher power level when said override exists; and

reducing said pulse oximeter to a lower power level if said override does not exist.

17. The low power pulse oximetry method according to claim 16 comprising the further steps of:

predetermining a target power level for a pulse oximeter; and

cycling between said lower power level and said higher power level so that an average power consumption is consistent with said target power level.

18. The low power pulse oximetry method according to claim 16 wherein said reducing step comprises the substep of decreasing the duty cycle of an emitter driver output.

19. The low power pulse oximetry method according to claim 16 wherein said reducing step comprises the substep of powering-down a detector front-end.

20. The low power pulse oximetry method according to claim 19 comprising the further step of displaying a confidence indication related to the duration of said powering-down substep.

21. The low power pulse oximetry method according to claim 16 wherein said reducing step comprises the substep of increasing the time-shift of post-processor data blocks.

22. A low power pulse oximeter comprising:

a sensor interface adapted to receive an input signal from a sensor;

a signal processor configured to communicate with said sensor interface and to generate an internal parameter responsive to said input signal; and

a sampling controller responsive to said internal parameter so as to generate a sampling control to alter the power consumption of at least one of said sensor interface and said signal processor.

23. The low power pulse oximeter according to claim 22 wherein said signal processor is configured to generate an output parameter and said sampling controller is responsive to a combination of said internal and output parameters so as to generate a sampling control to alter the power consumption of at least one of said sensor interface and said signal processor.

24. The low power pulse oximeter according to claim 22 wherein said internal parameter is indicative of the quality of said input signal.

25. The low power pulse oximeter according to claim 23 wherein said internal parameter is indicative of the quality of said input signal and said output parameter is indicative of oxygen saturation.

26. The low power pulse oximeter according to claim 22 wherein said sampling controller is responsive to a predetermined power target in combination with said internal parameter so as to generate a sampling control to alter the power consumption of at least one of said sensor interface and said signal processor.

27. The low power pulse oximeter according to claim 26 wherein said signal processor is configured to generate an output parameter and said sampling controller is responsive to a combination of said internal and output parameters and said power target so as to generate a sampling control to alter the power consumption of at least one of said sensor interface and said signal processor.

28. The low power pulse oximeter according to claim 22 wherein said sensor interface comprises an emitter driver and said sampling control modifies a duty cycle of said emitter driver.

29. The low power pulse oximeter according to claim 22 wherein said sensor interface comprises a detector front-end and said sampling control intermittently powers-down said detector front-end.

30. The low power pulse oximeter according to claim 22 where said processor generates a plurality of data blocks corresponding to said input signal, each of said data blocks having a time shift from a preceding one of said data blocks, said sampling control determining the amount of said time shift.

31. A low power pulse oximeter comprising:

an interface means for communicating with a sensor;

a processor means for generating an internal parameter and an output parameter; and

a controller means for selectively reducing the power consumption of at least one of said interface means and said processor means based upon said parameters.

32. The low power pulse oximeter according to claim 31 wherein said interface means comprises a driver means for determining the duty cycle of emitter current to said sensor, said driver means being responsive to said controller means.

33. The low power pulse oximeter according to claim 31 wherein said interface means comprises a detector front-end means for receiving an input signal from said sensor, the power for said detector front-end means being responsive to said controller means.

34. The low power pulse oximeter according to claim 31 wherein said processor means comprises a post-processor means for determining a time shift between data blocks, said post-processor means responsive to said controller means.

35. The low power pulse oximeter according to claim 31 wherein said controller means comprises:

a signal status calculator means for generating an indication of a low signal quality or a physiological event based upon at least one of an internal signal statistic and an output physiological measurement; and

a control engine means in communications with said signal status calculator means for generating a sampling control responsive to said indication.

36. The low power pulse oximeter according to claim 31 wherein said controller means comprises:

a power status calculator means for generating a power indication of power consumption relative to a power target; and

a control engine means in communications with said power status calculator means for generating a sampling control responsive to said power indication.