Ambulatory medical apparatus and method using a telemetry system with predefined reception listening

• US 6,950,708 B2
• Filed: 07/29/2002
• Issued: 09/27/2005
• Est. Priority Date: 01/21/2000
• Status: Expired due to Term

• Current Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Minimed Incorporated (Medtronic Plc)
• Inventors: Villegas, Daniel H., Lebel, Ronald J., Gord, John C., Bowman, Sam W. IV
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US10/208,721
• Publication Number:
  US 20030069614A1
• Time in Patent Office: 1,156 Days
• Field of Search: 607 30- 32, 607/60, 358/287
• US Class Current: 607/60
• 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 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/6847 mounted on an invasive device
• CPC Class Codes: A61M 2005/14208 with a programmable infusion control system, characterised by the infusion program
• CPC Class Codes: A61M 2205/18 with alarm
• CPC Class Codes: A61M 2205/3507 with implanted devices, e.g. external control
• CPC Class Codes: A61M 2205/3523 using telemetric means
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2205/581 by audible feedback
• CPC Class Codes: A61M 2205/582 by tactile feedback
• CPC Class Codes: A61M 2205/6018 providing set-up signals for the apparatus configuration
• CPC Class Codes: A61M 2205/8206 battery-operated
• CPC Class Codes: A61M 2207/00 Methods of manufacture, assembly or production
• CPC Class Codes: A61M 5/14244 adapted to be carried by the patient, e.g. portable on the body
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: A61M 5/168 Means for controlling media flow to the body or for metering media to the body, e.g. drip meters, counters ; Monitoring media flow to the body flow control in general G05D7/00
• CPC Class Codes: A61M 5/16831 Monitoring, detecting, signalling or eliminating infusion flow anomalies low-level float-valves causing cut-off A61M5/40; indicating or recording presence, absence or direction of flow in general G01P13/0066
• CPC Class Codes: A61M 5/172 electrical or electronic A61M5/16804, A61M5/16831 take precedence
• CPC Class Codes: A61N 1/37211 Means for communicating with stimulators
• CPC Class Codes: A61N 1/37247 : User interfaces, e.g. input or presentation means
• CPC Class Codes: A61N 1/37254 : Pacemaker or defibrillator security, e.g. to prevent or inhibit programming alterations by hackers or unauthorised individuals
• CPC Class Codes: A61N 1/37258 : Alerting the patient
• CPC Class Codes: A61N 1/37264 : Changing the program; Upgrading firmware
• CPC Class Codes: A61N 1/3727 : characterised by the modulation technique
• CPC Class Codes: A61N 1/37276 : characterised by means for reducing power consumption during telemetry
• CPC Class Codes: A61N 1/37512 : Pacemakers
• CPC Class Codes: G06F 3/0619 : in relation to data integrity, e.g. data losses, bit errors
• CPC Class Codes: G06F 3/065 : Replication mechanisms
• CPC Class Codes: G06F 3/0673 : Single storage device
• CPC Class Codes: G06F 8/60 : Software deployment
• CPC Class Codes: G06F 8/65 : Updates security arrangements therefor G06F21/57
• CPC Class Codes: G16H 20/17 : delivered via infusion or injection
• CPC Class Codes: G16H 40/40 : for the management of medical equipment or devices, e.g. scheduling maintenance or upgrades
• CPC Class Codes: Y02D 10/00 : Energy efficient computing, e.g. low power processors, power management or thermal management
• CPC Class Codes: Y10S 128/13 : Infusion monitoring
• CPC Class Codes: Y10S 128/903 : Radio telemetry
• CPC Class Codes: Y10T 29/49117 : Conductor or circuit manufacturing
• CPC Class Codes: Y10T 29/49826 : Assembling or joining

Abstract

An implanted medical device (e.g. infusion pump) and an external device communicate with one another via telemetry messages that are receivable only during windows or listening periods. Each listening period is open for a prescribed period of time and is spaced from successive listening periods by an interval. The prescribed period of time is typically kept small to minimize power consumption. To increase likelihood of successful communication, the window may be forced to an open state, by use of an attention signal, in anticipation of an incoming message. To further minimize power consumption, it is desirable to minimize use of extended attention signals, which is accomplished by the transmitter maintaining an estimate of listening period start times and attempting to send messages only during listening periods. In the communication device, the estimate is updated as a result of information obtained with the reception of each message from the medical device.

Claims

1. An apparatus for synchronizing a first clock with a second clock, comprising:

an oscillator for producing a first pulse stream that oscillates at an initial frequency; and

a circuit for calculating a drift rate based on a difference in time between the first clock and the second clock, and for removing selected pulses from the first pulse stream based on the drift rate to produce a second pulse stream that is used to control at least one of the first clock and the second clock.

2. The apparatus recited in claim 1, wherein the second pulse stream generates a system timing signal that has a frequency less than that of the second pulse stream.

3. The apparatus recited in claim 1, wherein the circuit is activated to steal at least two consecutive pulses from the first pulse stream.

4. The apparatus recited in claim 1, further including at least one counter, wherein the circuit is activated upon receipt of a pulse from the at least one counter.

5. The apparatus recited in claim 1, wherein the oscillator provides basic timing for an ambulatory medical device (MD) including MD electronic control circuitry that further includes at least one MD telemetry system and at least one MD processor that controls, at least in part, operation of the MD telemetry system and operation of the medical device, wherein the medical device is configured to provide a treatment to a body of a patient or to monitor a selected state of the body.

6. The apparatus recited in claim 5, wherein the oscillator provides basic timing for a communication device (CD) including CD electronic control circuitry that further includes at least one CD telemetry system and at least one CD processor that controls, at least in part, operation of the CD telemetry system and operation of the communication device, wherein the CD telemetry system sends messages to or receives messages from the MD telemetry system.

7. The apparatus recited in claim 6, wherein both the medical device and the communication device produce at least one timing signal from the second pulse stream for synchronizing communication between the medical device and the communication device.

8. The apparatus recited in claim 1,

wherein the first clock is part of a transmitting device for transmitting communication signals;

and

wherein the second clock is part of a receiving device for receiving the communication signals; and

wherein the transmission of the communication signals by the transmitting device and the reception of the communication signals by the receiving device can be synchronized by synchronizing the first clock with the second clock.

9. An apparatus for synchronizing a first clock with a second clock, comprising:

means for producing a first pulse stream that oscillates at an initial frequency;

means for calculating a drift rate based on a difference in time between the first clock and the second clock; and

means for removing selected pulses from the first pulse stream based on the drift rate to produce a second pulse stream that is used to control at least one of the first clock and the second clock.

10. The apparatus recited in claim 9, wherein the second pulse stream generates a system timing signal that has a frequency less than that of the second pulse stream.

11. The apparatus recited in claim 9,

wherein the first clock is part of a transmitting device for transmitting communication signals;

wherein the second clock is part of a receiving device for receiving the communication signals; and

wherein the transmission of the communication signals by the transmitting device and the reception of the communication signals by the receiving device can be synchronized by synchronizing the first clock with the second clock.

12. A method of synchronizing a first clock with a second clock, the method comprising:

producing a first pulse stream that oscillates at an initial frequency;

determining a drift rate based on a difference in time between the first clock and the second clock;

removing selected pulses from the first pulse stream based on the drift rate to produce a second pulse stream; and

controlling at least one of the first clock and the second clock based on the second pulse stream.

13. The method recited in claim 12, wherein the first pulse stream is generated by an oscillator.

14. The method recited in claim 12, wherein the second pulse stream generates a system timing signal that has a frequency less than that of the second pulse stream.

15. The method recited in claim 12, wherein removing selected pulses from the first pulse stream includes removing one or more consecutive pulses from the first pulse stream.

16. The method recited in claim 12,

wherein the first clock is part of a transmitting device for transmitting communication signals;

wherein the second clock is part of a receiving device for receiving the communication signals; and

wherein the transmission of the communication signals by the transmitting device and the reception of the communication signals by the receiving device can be synchronized by synchronizing the first clock with the second clock.

17. A method of generating a system timing signal, the method comprising:

producing a first pulse stream that oscillates at an initial frequency that is greater than a desired frequency; and

removing selected pulses from the first pulse stream to produce a second pulse stream that oscillates with an average frequency closer to a desired frequency than the initial frequency;

wherein the second pulse stream generates a system timing signal that has a frequency less than that of the second pulse stream; and

wherein the timing signal has a frequency less than about 1/100 of an average frequency of the second pulse stream.

18. A method of generating a system timing signal, the method comprising:

producing a first pulse stream that oscillates at an initial frequency that is greater than a desired frequency; and

removing selected pulses from the first pulse stream to produce a second pulse stream that oscillates with an average frequency closer to a desired frequency than the initial frequency;

wherein the average frequency of the second pulse stream is no less than 90% of the initial frequency.

19. A method of generating a system timing signal, the method comprising:

producing a first pulse stream that oscillates at an initial frequency that is greater than a desired frequency; and

removing selected pulses from the first pulse stream to produce a second pulse stream that oscillates with an average frequency closer to a desired frequency than the initial frequency;

wherein the average frequency of the second pulse stream is no less than 99% of the initial frequency.

20. A method of generating a system timing signal, the method comprising:

producing a first pulse stream that oscillates at an initial frequency that is greater than a desired frequency; and

removing selected pulses from the first pulse stream to produce a second pulse stream that oscillates with an average frequency closer to a desired frequency than the initial frequency;

wherein removing selected pulses from the first pulse stream includes repetitively counting to a first predefined value and then removing a pulse from the first pulse stream to produce the second pulse stream.

21. The method recited in claim 20, further including generating a timing signal from the second pulse stream by counting to a second predefined value and then outputting a pulse.

22. The method recited in claim 21, wherein the second predefined value is defined by software.

23. The method recited in claim 21, wherein the second predefined value is defined by hardware.

24. The method recited in claim 20, wherein the first predefined value is defined by software.

25. The method recited in claim 24, wherein the first predefined value is subject to modification during a normal course of operation.

26. The method recited in claim 25, wherein the modification of the first predefined value causes the second pulse stream to oscillate at a frequency closer to the desired frequency than before the modification.

27. The method recited in claim 25, wherein the initial frequency varies with temperature and wherein the modification of the first predefined value is based at least in part on (1) an anticipated change in the initial frequency as a function of temperature, and (2) on an estimated or measured temperature, or variations in temperature.

28. The method recited in claim 25, wherein the first predefined value is modifiable by software.

29. The method recited in claim 25, wherein the first predefined value is, at least in part, modified based on measured variations in temperature.

30. The method recited in claim 25, wherein the first predefined value is modified based on a difference in time between a first clock operated, at least indirectly, from the second pulse stream and a second clock that does not operate from the second pulse stream.

31. The method recited in claim 30, wherein the first predefined value is modified based on, at least in part, a current value of the first predefined value and on a difference in lapsed time between at least two readings from the second clock.

32. The method recited in claim 30, wherein the first pulse stream is provided, at least indirectly, from a crystal oscillator circuit that has an oscillation frequency at least somewhat greater than that to be used in a given application.

33. The method recited in claim 32, wherein the crystal oscillator circuit and the first clock is part of a communication device and the second pulse stream operates with the communication device and wherein the second clock operates within a medical device communicating with the communication device.

34. The method recited in claim 32, wherein the crystal oscillator circuit has a stability that is acceptable for the given application but has an oscillation tolerance greater than that acceptable for the given application.

35. The method recited in claim 32, wherein an oscillator is selected for use in the given application that has a lower oscillation frequency tolerance limit that is greater than the desired oscillation frequency for the given application.

36. A method of generating a system timing signal the method comprising:

producing a first pulse stream that oscillates at an initial frequency that is greater than a desired frequency; and

removing selected pulses from the first pulse stream to produce a second pulse stream that oscillates with an average frequency closer to a desired frequency than the initial frequency;

wherein the second pulse stream generates a system timing signal that has a frequency less than that of the second pulse stream; and

wherein the selected pulses are removed upon receipt of a pulse from at least one counter programmed to begin counting from a predefined value.

37. A method of generating a system timing signal, the method comprising:

producing a first pulse stream that oscillates at an initial frequency that is greater than a desired frequency;

removing selected pulses from the first pulse stream to produce a second pulse stream that oscillates with an average frequency closer to a desired frequency than the initial frequency, wherein the second pulse stream generates a system timing signal that has a frequency less than that of the second pulse stream;

measuring at least one predetermined parameter in a system for which the system timing signal is generating; and

removing the selected pulses from the first pulse stream at times determined at least in part based on the measured predetermined parameter.

38. The method recited in claim 37, wherein the at least one predetermined parameter is a temperature within the system.

39. An apparatus for generating a timing signal, comprising:

an oscillator for producing a first pulse stream that oscillates at an initial frequency that is greater than a desired frequency;

a counter for repetitively counting to a first value; and

a circuit for removing at least one pulse from the first pulse stream each time the counter counts to the first value to produce a second pulse stream that oscillates with an average frequency closer to a desired frequency than the initial frequency.

40. The apparatus recited in claim 39,

wherein the first value is subject to modification during a normal course of operation.