Pressure sensing in implantable medical devices

• US 20050075624A1
• Filed: 04/30/2004
• Published: 04/07/2005
• Est. Priority Date: 10/02/2003
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Miesel, Keith A.
• Granted Patent: US 7,320,676 B2
• Time in Patent Office: Days
• US Class Current: 604/505
• CPC Class Codes: A61M 2205/3355 Controlling downstream pump pressure
• CPC Class Codes: A61M 2205/3523 using telemetric means
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: A61M 5/16854 by monitoring line pressure

Abstract

An implantable medical device for delivering a therapeutic substance to a delivery site in a patient. A reservoir holds a supply of the fluid therapeutic substance. A catheter has a proximal end, a delivery region and a lumen extending from the proximal end to the delivery region. The proximal end of the catheter is operatively coupled to the reservoir. The delivery region of the catheter is adapted to be placed proximate the delivery site in the patient. The therapeutic substance is adapted to be delivered through the lumen to the patient. A sensing device is operatively coupled with the lumen of the catheter being capable of detecting a pressure of the therapeutic substance in the lumen. A controller is operatively coupled to the sensing device, the controller being capable of taking an action in response to the pressure in the lumen.

Claims

1. An implantable medical device for delivering a therapeutic substance to a delivery site in a patient, comprising:

a reservoir holding a supply of said fluid therapeutic substance;

a catheter having a proximal end, a delivery region and a lumen extending from said proximal end to said delivery region, said proximal end of said catheter being operatively coupled to said reservoir, said delivery region of said catheter being adapted to be placed proximate said delivery site in said patient, said therapeutic substance adapted to be delivered through said lumen to said patient;

a sensing device operatively coupled with said lumen of said catheter being capable of detecting a pressure of said therapeutic substance in said lumen; and

a controller operatively coupled to said sensing device, said controller being capable of taking an action in response to said pressure in said lumen.

2. An implantable medical device as in claim 1 wherein said therapeutic substance comprises a fluid.

3. An implantable medical device as in claim 2 wherein said therapeutic substance comprises a liquid.

4. An implantable medical device as in claim 3 wherein said sensing device is further capable of detecting a reference pressure outside of said lumen and wherein said controller is capable of taking action in response to relative pressures between said pressure in said lumen and said reference pressure outside of said lumen.

5. An implantable medical device as in claim 4 wherein said location outside of said lumen is in proximity to said implantable medical device.

6. An implantable medical device as in claim 4 wherein said location outside of said lumen is in proximity to said delivery region of said catheter.

7. An implantable medical device as in claim 6 wherein said lumen is a first lumen and wherein said catheter has a second lumen and wherein said location outside of said first lumen is in said second lumen.

8. An implantable medical device as in claim 4 wherein said location outside of said lumen is outside of said patient.

9. An implantable medical device as in claim 4 wherein said sensing device comprises:

a first pressure sensor operatively coupled with said lumen of said catheter being capable of detecting a pressure of said therapeutic substance in said lumen; and

a second pressure sensor being capable of detecting a pressure at a location outside of said lumen.

10. An implantable medical device as in claim 2 wherein said action is taken when said pressure exceeds a predetermined level.

11. An implantable medical device as in claim 10 wherein said action is based upon an obstruction in said lumen.

12. An implantable medical device as in claim 3 wherein said lumen of said catheter has a restriction and wherein said sensing device is positioned between said reservoir and said restriction.

13. An implantable medical device as in claim 12 wherein said action is taken when said pressure drops below a predetermined level.

14. An implantable medical device as in claim 13 wherein said action is based upon a leak of said catheter.

15. An implantable medical device as in claim 12 wherein said action is taken when said pressure has a characteristic signature.

16. An implantable medical device as in claim 15 wherein said characteristic signature follows a transient in delivery rate of said therapeutic substance.

17. An implantable medical device as in claim 16 wherein said transient comprises a rise in said delivery rate of said therapeutic substance.

18. An implantable medical device as in claim 16 wherein said transient comprises a fall in said delivery rate of said therapeutic substance.

19. An implantable medical device as in claim 16 wherein said transient comprises a rise and subsequent fall in said delivery rate of said therapeutic substance.

20. An implantable medical device as in claim 19 wherein said characteristic signature is a function of a decay time of said pressure following said fall of said delivery rate of said therapeutic substance.

21. An implantable medical device as in claim 19 wherein said characteristic signature is a function of an increase in said pressure in response to an increase of said delivery rate.

22. An implantable medical device as in claim 12 further comprising a pump fluidly coupled between said reservoir and said sensing device, said pump being capable of driving said therapeutic substance through said catheter under pressure.

23. An implantable medical device as in claim 22 wherein said pump comprises a peristaltic pump.

24. An implantable medical device as in claim 23 wherein said peristaltic pump comprises a tubular structure and a plurality of rollers driving said therapeutic substance through said tubular structure, said peristaltic pump creating a pressure dip each time one of said plurality of rollers lifts off of said tubular structure and wherein said characteristic signature comprises said pressure dropping below a predetermined threshold in combination with a lack of said pressure dip.

25. An implantable medical device as in claim 24 wherein said action comprises modifying operation of said pump.

26. An implantable medical device as in claim 1 wherein said action comprises ceasing delivery of said therapeutic substance to said patient.

27. An implantable medical device as in claim 26 further comprising a pump fluidly coupled between said reservoir and said catheter, said pump being capable of driving said therapeutic substance through said catheter under pressure.

28. An implantable medical device as in claim 27 wherein said action comprises modifying operation of said pump.

29. A drug delivery system for delivering a liquid therapeutic substance to a delivery site in a patient, comprising:

an implantable medical device, comprising;

a reservoir holding a supply of said fluid therapeutic substance; and

a pump fluidly coupled to said reservoir, said pump being capable of fluidly driving said therapeutic substance to said delivery site under pressure;

a catheter having a proximal end, a delivery region and a lumen extending from said proximate end to said delivery region, said proximal end of said catheter being operatively coupled to said pump, said delivery region of said catheter being adapted to be placed proximate said delivery site in said patient, said therapeutic substance adapted to be delivered through said lumen to said patient;

a sensing device operatively coupled with said lumen of said catheter being capable of detecting a pressure of said therapeutic substance in said lumen; and

a controller operatively coupled to said sensing device, said controller being capable of taking an action in response to said pressure in said lumen.

30. A drug delivery system as in claim 29 wherein said sensing device is further capable of detecting a reference pressure outside of said lumen and wherein said controller is capable of taking action in response to relative pressures between said pressure in said lumen and said reference pressure outside of said lumen.

31. A drug delivery system as in claim 30 wherein said location outside of said lumen is in proximity to said implantable medical device.

32. A drug delivery system as in claim 30 wherein said location outside of said lumen is in proximity to said delivery region of said catheter.

33. A drug delivery system as in claim 32 wherein said lumen is a first lumen and wherein said catheter has a second lumen and wherein said location outside of said first lumen is in said second lumen.

34. A drug delivery system as in claim 30 wherein said location outside of said lumen is outside of said patient.

35. A drug delivery system as in claim 30 wherein said sensing device comprises:

a first pressure sensor operatively coupled with said lumen of said catheter being capable of detecting a pressure of said therapeutic substance in said lumen; and

a second pressure sensor being capable of detecting a pressure at a location outside of said lumen.

36. A drug delivery system as in claim 29 wherein said action is taken when said pressure exceeds a predetermined level.

37. A drug delivery system as in claim 36 wherein said action is based upon an obstruction in said lumen.

38. A drug delivery system as in claim 29 wherein said lumen of said catheter has a restriction and wherein said sensing device is positioned between said reservoir and said restriction.

39. A drug delivery system as in claim 38 wherein said restriction is located near said distal end of the said catheter.

40. A drug delivery system as in claim 38 wherein said action is taken when said pressure drops below a predetermined level.

41. A drug delivery system as in claim 40 wherein said action is based upon a leak of said catheter.

42. A drug delivery system as in claim 41 wherein said action is taken when said pressure has a characteristic signature.

43. A drug delivery system as in claim 42 wherein said characteristic signature follows a transient in delivery rate of said therapeutic substance.

44. A drug delivery system as in claim 43 wherein said transient comprises a rise in said delivery rate of said therapeutic substance.

45. A drug delivery system as in claim 43 wherein said transient comprises a fall in said delivery rate of said therapeutic substance.

46. A drug delivery system as in claim 43 wherein said transient comprises a rise and subsequent fall in said delivery rate of said therapeutic substance.

47. A drug delivery system as in claim 46 wherein said characteristic signature is a function of a decay time of said pressure following said fall of said delivery rate of said therapeutic substance.

48. A drug delivery system as in claim 46 wherein said characteristic signature is a function of an increase in said pressure in response to an increase of said delivery rate.

49. A drug delivery system as in claim 29 wherein said pump comprises a peristaltic pump.

50. A drug delivery system as in claim 49 wherein said peristaltic pump comprises a tubular structure and a plurality of rollers driving said therapeutic substance through said tubular structure, said peristaltic pump creating a pressure dip each time one of said plurality of rollers lifts off of said tubular structure and wherein said characteristic signature comprises said pressure dropping below a predetermined threshold in combination with a lack of said pressure dip.

51. A drug delivery system as in claim 50 wherein said action comprises stopping operation of said pump.

52. A drug delivery system as in claim 29 wherein said action comprises ceasing delivery of said therapeutic substance to said patient.

53. A drug delivery system as in claim 52 wherein said action comprises stopping operation of said pump.

54. A method of delivering a therapeutic substance to a delivery site in a patient, comprising the steps of:

pumping said therapeutic substance under pressure from a reservoir through a catheter fluidly coupled to said reservoir, said catheter having a proximal end, a delivery region and a lumen extending between said proximal end and said delivery region, said delivery region of said catheter placed in proximity to said delivery site in said patient;

detecting a pressure of said therapeutic substance in said lumen; and

taking an action in response to said pressure in said lumen.

55. A method as in claim 54 wherein said therapeutic substance comprises a fluid.

56. A method as in claim 55 wherein said therapeutic substance comprises a liquid.

57. A method as in claim 56 said detecting step further comprises detecting a reference pressure outside of said lumen and wherein said taking an action step further comprises acting in response to relative pressures between said pressure in said lumen and said pressure outside of said lumen.

58. A method as in claim 57 wherein said location outside of said lumen is in proximity to said implantable medical device.

59. A method as in claim 57 wherein said location outside of said lumen is proximity to said delivery region of said catheter.

60. A method as in claim 57 wherein said location outside of said lumen is outside of said patient.

61. A method as in claim 54 wherein said action is taken when said pressure exceeds a predetermined level.

62. A method as in claim 61 wherein said action is based upon an obstruction in said lumen.

63. A method as in claim 54 wherein said lumen has a restriction and wherein said action is taken when said pressure drops below a predetermined level.

64. A method as in claim 63 wherein said action is based upon a leak of said catheter.

65. A method as in claim 54 wherein said action is taken when said pressure has a characteristic signature.

66. A method as in claim 65 wherein said transient comprises a rise in said delivery rate of said therapeutic substance.

67. A method as in claim 65 wherein said transient comprises a fall in said delivery rate of said therapeutic substance.

68. A method as in claim 65 wherein said transient comprises a rise and subsequent fall in said delivery rate of said therapeutic substance.

69. A method as in claim 68 wherein said characteristic signature is a function of a decay time of said pressure following said fall of said delivery rate of said therapeutic substance.

70. A method as in claim 65 wherein said characteristic signature comprises said pressure dropping below a predetermined threshold in combination with a lack of a pressure dip created each time one of a plurality of rollers lifts off of a tubular structure in a peristaltic pump.

71. A method as in claim 54 wherein said action comprises ceasing delivery of said therapeutic substance to said patient.

72. A sensor for a medical device for detecting pressure in a lumen of a catheter, comprising:

a base having a first side and a second side;

a first pressure sensing diaphragm operatively coupled to said first side of said base;

a second pressure sensing diaphragm operatively coupled to said second side of said base;

a connector having a first end operatively coupled to a movable portion of said first pressure sensing diaphragm and a second end operatively coupled to a movable portion said second pressure sensing diaphragm, said connector moving with said first pressure sensing diaphragm and said second pressure sensing diaphragm in response to a change in pressure; and

an electrical element responsive to movement of said first pressure sensing diaphragm and said second pressure sensing diaphragm.

73. A sensor as in claim 72 wherein said electrical element comprises:

a first electrical sensor producing a first output in response to movement of said first pressure sensing diaphragm; and

a second electrical sensor producing a second output in response to movement of said second pressure sensing diaphragm;

wherein said first output and said second output are combined to produce a pressure output.

74. A sensor as in claim 73 wherein said first output and said second output are additive resulting in a doubled electrical output.

75. A sensor as in claim 74 wherein said pressure output comprises a ratio of said first output and said second output.

76. A sensor as in claim 74 wherein said pressure output comprises a duty cycle of one of said first output and said second output divided by a sum of both of said first output and said second output.

77. A sensor as in claim 74 wherein said pressure output comprises a difference of said first output and said second output.

78. A sensor as in claim 73 wherein said first electrical sensor comprises a first capacitor and wherein said second electrical sensor comprises a second capacitor, wherein a capacitance of said first capacitor is a function of a displacement of said first diaphragm and wherein a capacitance of said second capacitor is a function of a displacement of said second diaphragm.

79. A sensor as in claim 73 further comprising a primary coil positioned between said first electrical sensor and said second electrical sensor, wherein said connector comprises a magnetic element, wherein said first electrical sensor comprises a first secondary coil and wherein said second electrical sensor comprises a second secondary soil, wherein a fluctuating electrical current is induced in said primary coil, wherein a current induced in said first secondary coil and in said second secondary coil by inductive coupling from said primary coil being proportional to a position of said magnetic element which in turn is a function of a displacement of said first diaphragm and said second diaphragm.