Method and system for compressing and storing data in a medical device having limited storage

• US 6,719,689 B2
• Filed: 04/30/2001
• Issued: 04/13/2004
• Est. Priority Date: 04/30/2001
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Kerver, Harry B. A., Munneke, Dave
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US09/847,049
• Publication Number:
  US 20020193668A1
• Time in Patent Office: 1,079 Days
• Field of Search: 600/300, 600/301, 600/509, 600/523, 600/524, 600/902, 600/521, 600/522, 607/4, 607/5, 607/9
• US Class Current: 600/300
• CPC Class Codes: A61B 5/335 using integrated circuit memory devices
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period

Abstract

A method for compressing data in an implantable device is provided. A current data sample is received. A difference value is determined between the current data sample and a previous data sample. The current data sample is compressed to at least one output symbol based on the difference value between the current sample and the previous data sample. Systems and programs of using the method are also provided.

Claims

1. A method for compressing data in an implantable device, comprising the steps of:

receiving a current data sample;

determining a difference value between the current data sample and a previous data sample;

converting a sequence of similar output symbols to an escape output symbol; and

compressing the current data sample to at least one output symbol based on the difference value between the current sample and the previous data sample.

2. The method of claim 1 wherein the output symbol is a compressed bit pattern.

3. The method of claim 1 wherein the output symbol comprises more than one character.

4. The method of claim 1 further comprising:

reducing the amplitude resolution of the current data sample.

5. The method of claim 1 further comprising:

converting the output symbol to a variable bit length code.

6. The method of claim 1 wherein the output symbol is a 0 symbol, further comprising:

converting the output symbol to a 1 bit sequence.

7. The method of claim 1 wherein the output symbol is a 1_symbol, further comprising:

converting the output symbol to a 3 bit sequence.

8. The method of claim 1 wherein the output symbol is a 0_RLL-escape_symbol, further comprising:

converting the output symbol to a 6 bit sequence.

9. The method of claim 1 wherein the output symbol 2_RLL-escape_symbol, further comprising:

converting the output symbol to a 6 bit sequence.

10. The method of claim 1 further comprising:

inserting an absolute signal value after the current sample.

11. The method of claim 1 further comprising:

determining if a trigger event has occurred.

12. The method of claim 11 further comprising:

inserting a trigger symbol as the output symbol to indicate a point at which the trigger event occurred.

13. The method of claim 1 wherein the difference value is zero.

14. The method of claim 13, further comprising:

compressing the current data sample such that the output symbol is bit pattern 0.

15. The method of claim 1, further comprising:

compressing the current data sample such that the output symbol is bit pattern 0.

16. The method of claim 1 wherein the difference value indicates that the current data sample has a value of one less than the previous data sample.

17. The method of claim 1 wherein the difference value indicates that the current data sample has a value of one more than the previous data sample.

18. The method of claim 1 wherein the difference value indicates that the current data sample has a value of two less than the previous data sample.

19. The method of claim 1 wherein the difference value indicates that the current date sample has a value of two more than the previous data sample.

20. The method of claim 1 wherein the difference value indicates that the current data sample has a value of three less than the previous data sample.

21. The method of claim 1 wherein the difference value indicates that the current data sample has a value of three more than the previous data sample.

22. The method of claim 21, further comprising:

compressing the current data sample such that the output symbol is bit pattern 11110 followed by bit pattern 110.

23. The method of claim 1, further comprising:

compressing the current data sample such that the output symbol is bit pattern 11110 followed by bit pattern 110.

24. The method of claim 1 wherein the difference value indicates that the current data sample has a value of four less than the previous data sample.

25. The method of claim 24, further comprising:

compressing the current data sample such that the output symbol is bit pattern 1110 110 followed by bit pattern 110.

26. The method of claim 1, further comprising:

compressing the current data sample such that the output symbol is bit pattern 1110 110 followed by bit pattern 110.

27. The method of claim 1, wherein the difference values

comprises a plurality of sequential zeroes.

28. The method of claim 27, further comprising:

compressing the current data sample such that the output symbol is 111110 followed by a binary value of the plurality of sequential zeroes.

29. The method of claim 1, further comprising:

compressing the current data sample such that the output symbol is 111110 followed by a binary value of the plurality of sequential zeroes.

30. The method of claim 1, wherein the difference value indicates that the current data sample has a markedly different value than the previous data sample.

31. The method of claim 30, comprising:

compressing the current data sample such that the output symbol is bit pattern 111111 followed by a binary value of the current data sample.

32. The method of claim 30, further comprising:

compressing the current data sample such that the output symbol is bit pattern 111111 followed by a binary value of the difference value.

33. The method of claim 1, further comprising:

compressing the current data sample such that the output symbol is bit pattern 111111 followed by a binary value of the current data sample.

34. The method of claim 1, further comprising:

compressing the current data sample such that the output symbol is bit pattern 111111 followed by a binary value of the difference value.

35. The method of claim 1 wherein the difference value has a value of greater than four.

36. The method of claim 1 wherein the difference value has a value of less than negative five.

37. An implantable medical device comprising:

a processor;

at least one sensor operably connected to the processor for collecting at least one data sample;

wherein

the processor receives a current data sample, determines a difference value between the current data sample and a previous data samples, converts a sequence of similar output symbols to an escape output symbol and compresses the current data sample to at least one output symbol based on the difference value.

38. The device of claim 37, further comprising:

a memory location operably connected to the processor for storing the data sample.

39. The device of claim 37, further comprising:

a memory location operably connected to the processor for storing the difference value.

40. The device of claim 37, further comprising:

a converter operably connected to the processor for converting at least one signal to the data sample.

41. An implantable medical system, comprising:

means for receiving a current data sample;

means for determining a difference value between the current data sample and a previous data sample;

means for converting a sequence of similar output symbols to an escape output symbol; and

means for compressing the current data sample to at feast one output symbol based on the difference value between the current sample and the previous data sample.

42. The system of claim 41 wherein the output symbol is a compressed bit pattern.

43. The system of claim 41 wherein the output symbol comprises more than one character.

44. The system of claim 41 further comprising:

means for reducing the amplitude resolution of the current data sample.

45. The system of claim 41 wherein the output symbol is a 0_RLL-escape_symbol, further comprising:

means for converting the output symbol to a 6 bit sequence.

46. The system of claim 41 wherein the output symbol is a 2_RLL-escape_symbol, further comprising:

means for converting the output symbol to a 6 bit sequence.

47. The system of claim 41 further comprising:

means for inserting an absolute signal value after the current sample.

48. The system of claim 41 further comprising:

means for determining if a trigger event has occurred.

49. The system of claim 48 further comprising:

means for inserting a trigger symbol as the output symbol to indicate a point at which the trigger event occurred.

50. The system of the claim 41 wherein the difference value is zero, further comprising:

means for compressing the current data sample such that the output symbol is bit pattern 0.

51. The system of claim 41, further comprising:

means for compressing the current data sample such that the output symbol is bit pattern 0.

52. A computer usable medium including a program for compressing data in an implantable device, comprising:

computer program code that receives a current data sample;

computer program code that determines a difference value between the current data sample and a previous data sample;

computer program code that converts a sequence of similar output symbols to en escape output symbol; and

computer program code that compresses the current data sample to at least one output symbol based on the difference value between the current sample and the previous data sample.

53. The program of claim 52 wherein the output symbol is a compressed bit pattern.

54. The program of claim 52 wherein the output symbol comprises more than one character.

55. The program of claim 52 further comprising:

computer program code that reduces the amplitude resolution of the current data sample.

56. The program of claim 52 further comprising:

computer program code that converts the output symbol to a variable bit length code.

57. The program of claim 52 wherein the output symbol is a −

2_symbol, further comprising;

computer program code that converts the output symbol to a 4 bit sequence.

58. The program of claim 52 wherein the output symbol is a 0 symbol, further comprising:

computer program code that converts the output symbol to a 1 bit sequence.

59. The program of claim 52 wherein the output symbol is a 1_symbol, further comprising:

computer program code that converts the output symbol to a 3 bit sequence.

60. The program of claim 52 further comprising:

computer program code that inserts an absolute signal value after the current sample.

61. The program of claim 52 further comprising:

computer program code that determines it a trigger event has occurred.

62. The program of claim 61 further comprising:

computer program code that inserts a trigger symbol as the output symbol to indicate a point at which the trigger event occurred.

63. The program of claim 52 wherein the difference value is zero, further comprising:

computer program code that compresses the current data sample such that the output symbol is bit pattern 0.

64. The program of claim 52, further comprising:

computer program code that compresses the current data sample such that the output symbol is bit pattern 0.