Power saving techniques for continuous heart rate monitoring

• US 20070244398A1
• Filed: 04/12/2006
• Published: 10/18/2007
• Est. Priority Date: 04/12/2006
• Status: Active Grant

• Current Assignee: Salutron, Inc.
• Original Assignee: Salutron, Inc.
• Inventors: Lo, Thomas, Katingari, Karthik
• Granted Patent: US 7,559,899 B2
• Time in Patent Office: Days
• US Class Current: 600/500
• CPC Class Codes: A61B 2560/0209 adapted for power saving
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/02444 Details of sensor A61B5/02427 takes precedence
• CPC Class Codes: A61B 5/411 Detecting or monitoring allergy or intolerance reactions to an allergenic agent or substance
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 8/02 Measuring pulse or heart rate
• CPC Class Codes: A61B 8/4236 characterised by adhesive patches
• CPC Class Codes: A61B 8/4472 Wireless probes
• CPC Class Codes: A61B 8/4483 characterised by features of the ultrasound transducer
• CPC Class Codes: A61B 8/56 Details of data transmission or power supply

Abstract

A heart rate monitor implements power saving algorithms while monitoring a subject'"'"'s heart rate. The monitor continuously monitors a subject during an initial period to determine an initial heart rate. After the initial heart rate is acquired, power may not be provided for portions of the monitor until a heart beat is expected to occur. At some point before the expected heart beat occurs, power is returned to the components which have not received power. The expected heart beat is then detected, and power to selected portions of the monitor is terminated again until another expected heart beat approaches in time. By providing power to monitor components just before an expected heart beat, the monitor may still detect the heart beat and determine the corresponding heart rate of the user. The period of time during which power is terminated for some components may be determined from the detected heart rate. The number of heart beats during which power is terminated for selected monitor components may vary.

Claims

1. A method for determining a heart rate, comprising:

detecting a heart rate of a subject by a monitor; and

changing power for the monitor based on the detected heart rate.

2. The method of claim 1, wherein said step of changing power includes:

providing full power during an initial period to determine a heart rate; and

changing the power based on subject heart beats expected to occur after the initial period.

3. The method of claim 2, wherein said step of changing power includes:

terminating power for a subsequent period of time after a heart beat is detected; and

providing power after the subsequent period of time to detect a heart beat at an expected time.

4. The method of claim 1, wherein said step of changing power includes:

changing the power provided to a signal transmitter.

5. The method of claim 1, wherein said step of detecting a heart rate includes:

driving a monitor transmitter to transmit a signal towards a subject'"'"'s artery.

6. The method of claim 1, wherein said step of changing power includes:

determining a first period of time until a heart beat of the subject will occur; and

reducing power to the monitor transmitter for a second period of time derived from the first period of time.

7. The method of claim 1, wherein said step of changing power a monitor includes:

determining a heart rate is stable for a plurality of heart beats; and

reducing power to the monitor transmitter for a period of time encompassing a plurality of heart beats.

8. The method of claim 7, further comprising:

increasing power to the monitor transmitter at a time derived from the heart beats, said step of increasing power performed after said step of reducing power.

9. The method of claim 1, wherein the monitor is a wrist worn device.

10. A method for determining a heart rate, comprising:

transmitting a continuous signal towards a subject'"'"'s artery for an initial period of time;

determining an initial heart rate of the subject from a reflected continuous signal received during the initial period of time;

transmitting a non-continuous signal towards the artery for a subsequent period of time after the initial period of time; and

determining a subsequent heart rate of the subject from a reflected non-continuous signal.

11. The method of claim 10, wherein the initial period of time corresponds to between three to five heart beats of the subject.

12. The method of claim 10, wherein said step of transmitting a non-continuous signal includes:

transmitting a signal towards the subject during a window of time associated with an expected heart beat.

13. The method of claim 12, wherein the expected heart beat is the next occurring heart beat.

14. The method of claim 12, wherein the expected heart beat is not the next occurring heart beat.

15. The method of claim 10, wherein said step of transmitting a non-continuous signal includes:

determining a heart rate period between two previous heart beats of the subject;

terminating power to a transmitting device for a period of time comprising a majority of the heart rate period; and

providing power to the transmitting device for the remainder of the heart rate period after the majority of the heart rate period has transpired.

16. The method of claim 15, wherein said step of terminating power to a transmitting device for a period of time includes:

terminating power to the transmitting device for seven eighths of the heart rate period.

17. The method of claim 10, wherein said step of transmitting a non-continuous signal includes:

not providing a signal towards the subject for a first time period which includes at least one heart beat; and

providing a signal during a second time period associated with an expected heart beat.

18. The method of claim 10, further comprising:

determining the subject heart rate is stable for two or more heart beats after the initial period.

19. The method of claim 10, further comprising:

determining the subject'"'"'s heart rate is not associated with vigorous activity by the subject.

20. One or more processor readable storage devices having processor readable code embodied on said processor readable storage devices, said processor readable code for programming one or more processors to perform a method comprising:

driving a transmitter device continuously for an initial period of time, the transmitter device configured to transmit a signal to a subject when driven;

detecting a heart rate for the subject from a reflected signal during the initial period of time; and

driving the transmitter device non-continuously for a second period of time in response to detecting the heart rate.

21. The one or more processor readable storage devices of claim 20, wherein the initial period of time is associated with at least two heart beats.

22. The one or more processor readable storage devices of claim 20, wherein said step of driving the transmitter device non-continuously includes:

driving the transmitter device in response to determining a subject heart beat is expected to occur.

23. The one or more processor readable storage devices of claim 20, wherein said step of driving the transmitter device non-continuously includes:

terminating power to the transmitter device in response to said step of detecting the heart rate;

determining a heart beat is expected to occur; and

providing power to the transmitter device in response to said step of determining the heart beat is expected to occur.

24. The one or more processor readable storage devices of claim 20, wherein said step of driving the transmitter device non-continuously includes:

determining the subject is not exercising; and

determining not to drive the transmitter to send a signal to the subject during the next occurring subject heart beat in response to determining the subject is not exercising.

25. The one or more processor readable storage devices of claim 20, wherein said step of driving the transmitter device non-continuously includes:

determining the subject'"'"'s heart rate has been stable for a period of time; and

determining not to drive the transmitter to send a signal to the subject during the next occurring subject heart beat in response to determining the subject heart rate has been stable.

26. A heart rate monitor, comprising:

a transmitter device that transmits a signal towards a subject;

a receiver device, said receiver detects a reflected signal;

a driving circuit in communication with said transmitter device and said receiver device, the driving circuit drives the transmitter device at full power and at reduced power in response to detecting a heart rate of the subject; and

signal processing circuitry connected to the signal receiver.

27. The heart rate monitor of claim 26, wherein said driving circuit drives the transmitter device for an initial period of time at full power before driving transmitter device at reduced power while detecting a heart rate.

28. The heart rate monitor of claim 26, wherein said driving circuit drives the transmitter device at a reduced power for a period of time between two or more consecutive heart beats, the period of time derived from a detected heart rate for the subject.

29. The heart rate monitor of claim 26, wherein said driving circuit includes:

a timer, the timer configured to be set to expire in a period of time derived from the subject'"'"'s heart rate.

30. The heart rate monitor of claim 26, further comprising:

a microcontroller, the microcontroller able to enter an idle state while said driving circuit drives said transmitter device at reduced power.

31. The heart rate monitor of claim 26, wherein the transmitter device is a transducer.

32. A heart rate monitor, comprising:

a transmitting element that transmits a signal towards a subject'"'"'s artery;

a receiving element which receives a reflected signal from the subject'"'"'s artery;

signal processing circuitry in communication with said receiving element, said signal processing circuitry determining a subject'"'"'s heart rate from the reflected signal; and

a driving circuit in communication with said transmitting element, said receiving element and said signal processing circuitry, the driving circuit driving the transmitting element at full power for an initial period of time, and alternately driving the transmitting element at full power and low power for a subsequent period of time in response to the heart rate determined by the signal processing circuitry.

33. The heart rate monitor of claim 32, the signal processing circuitry determining a period of time for which said driving circuit will drive the transmitting element at low power.

34. The heart rate monitor of claim 33, the signal processing circuitry determining the period of time based on the subject'"'"'s initial heart rate.

35. The heart rate monitor of claim 33, the signal processing circuitry determining the period of time based on the number of heart beats the subject'"'"'s heart rate has been stable.

36. The heart rate monitor of claim 33, the signal processing circuitry determining the period of time based on the range of the subject'"'"'s heart rate.

37. The heart rate monitor of claim 32, wherein the heart rate monitor is a wrist worn device.