Method and apparatus for closed-loop flow control system

• US 20030236489A1
• Filed: 06/21/2002
• Published: 12/25/2003
• Est. Priority Date: 06/21/2002
• Status: Abandoned Application

• Current Assignee: Baxter International Inc.
• Original Assignee: Baxter International Inc.
• Inventors: Yardimci, Atif, Jacobson, James D., Slepicka, James S., Garchow, Stephen R., Bui, Tuan
• Application Number:
  US10/177,544
• Publication Number:
  US 20030236489A1
• Time in Patent Office: Days
• US Class Current: 604/67
• CPC Class Codes: A61M 2205/0244 Micromachined materials, e.g. made from silicon wafers, microelectromechanical systems [MEMS] or comprising nanotechnology
• CPC Class Codes: A61M 2205/0294 Piezoelectric materials
• CPC Class Codes: A61M 5/14236 Screw, impeller or centrifugal type pumps
• CPC Class Codes: A61M 5/16886 for measuring fluid flow rate, i.e. flowmeters
• CPC Class Codes: A61M 5/172 electrical or electronic A61M5/16804, A61M5/16831 take precedence
• CPC Class Codes: G05D 7/0676 by action on flow sources G05D7/0688, G05D7/0694 take precedence

Abstract

A fluid delivery system having a closed-loop control process for delivering a medical fluid to a patient. A fluid infusion system includes a pump for delivering a fluid to a patient via an administration tube. A flow sensor associated with the administration tube provides an indication of the actual flow rate of fluid in the administration tube. Such a flow sensor may comprise a positive displacement flow sensor constructed using micro-fabrication and/or micro-molding techniques. A reader reads the actual flow rate signal and provides an indication to a controller for controlling the pump. The flow rate information can also be used for providing status information, such as the existence of a blockage in the fluid delivery system.

Claims

1. A system for delivering a fluid at a desired flow rate from a reservoir to a delivery point associated with a patient, said system comprising:

a delivery channel between the reservoir and the delivery point through which the fluid is delivered to the patient;

a pump associated with the delivery channel for operatively delivering the fluid to the delivery point at an adjustable output rate;

a flow sensor located along the delivery channel for sensing a flow of the fluid in the delivery channel and for generating a flow rate signal indicative of a rate of flow of the fluid in the delivery channel, said flow sensor comprising a positive displacement flow sensor; and

a controller for controlling the pump, said controller causing adjustments to the output rate of the pump as a function of the flow rate signal whereby the desired flow rate is substantially achieved.

2. A system as set forth in claim 1 wherein the flow sensor comprises a passive device having no electrical connections thereto.

3. A system as set forth in claim 1 wherein the delivery channel comprises an administration tube and the flow sensor is sized and shaped for being positioned in fluid communication with the fluid within the delivery channel.

4. A system as set forth in claim 3 wherein the flow sensor comprises a MEMS device.

5. A system as set forth in claim 3 wherein the flow sensor comprises an assembly of micro-molded components.

6. A system as set forth in claim 1 wherein the flow sensor is capable of detecting flow rates from about 0.1 ml/hr to about 2000 ml/hr.

7. A system as set forth in claim 1 further comprising a reader associated with the flow sensor for receiving the flow rate signal and providing a flow control signal indicative of the flow rate signal, said controller receiving the flow control signal and adjusting the output rate of the pump in response thereto.

8. A system as set forth in claim 7 wherein the flow sensor comprises a rotatable impeller for rotating in response to the flow of the fluid in the administration tube and the flow rate signal comprises an optical indication generated by a rotation of the rotatable impeller, and wherein the reader comprises an optical reader responsive to the optical indication for providing the flow control signal.

9. A system as set forth in claim 8 wherein:

the optical reader illuminates the flow sensor causing a reflection from the rotatable impeller; and

the optical indication generated by the rotation of the rotatable impeller comprises a variation in an intensity of the reflection from the rotation of the rotatable impeller.

10. A system as set forth in claim 7 wherein:

the flow sensor includes a rotatable impeller for rotating in response to the flow of the fluid in the administration tube; and

the reader comprises a Hall sensor that senses an electrical signal caused by a rotation of the rotatable impeller and provides the flow control signal in response thereto.

11. A system as set forth in claim 1 further comprising:

a reader associated with the flow sensor for receiving the flow rate signal; and

a wireless communication channel between the reader and the controller, said reader providing a flow control signal indicative of the flow rate signal to the wireless communication channel and said controller receiving the flow control signal via the wireless communication channel and causing adjustments to the output rate of the pump in response thereto.

12. A system as set forth in claim 11 wherein the wireless communication channel comprises a spread spectrum communication channel operating in an unlicensed frequency band.

13. A system as set forth in claim 1 wherein the delivery channel comprises an administration tube and the pump comprises an infusion pump located along the administration tube.

14. A system as set forth in claim 13 wherein the infusion pump is a peristaltic pump, a piezoelectric pump or a valve pump.

15. A system as set forth in claim 13 wherein the infusion pump comprises an ambulatory infusion pump.

16. A system as set forth in claim 13 wherein the infusion pump comprises a volumetric infusion pump.

17. A system as set forth in claim 1 wherein the delivery channel comprises an administration tube and the pump comprises an infusion pump connected to the administration tube, and wherein the reservoir comprises a syringe barrel having an input opening and an output orifice operatively connected to the administration tube, and wherein the infusion pump comprises a syringe plunger slidably inserted into the syringe barrel through the input opening and a plunger driver responsive to the controller and operatively connected to the syringe plunger for causing a positive displacement of said syringe plunger, whereby the positive displacement of the plunger operatively delivers the fluid to the delivery point and the output rate of the infusion pump is adjusted by adjusting the positive displacement of the plunger caused by the plunger driver.

18. A system as set forth in claim 1 wherein the desired flow rate comprises a pulsatile flow profile and the controller adjusts the output rate of the pump such that the output flow rate has a generally pulsatile characteristic corresponding to the desired flow rate.

19. A system as set forth in claim 1 wherein the desired flow rate comprises a time-varying flow rate and the controller adjusts the output rate of the pump such that the output flow rate has a time-varying characteristic corresponding to the desired flow rate.

20. A system as set forth in claim 1 wherein the controller provides a flow rate status signal and further comprising a status monitoring device providing an indication of an operating status of the desired flow rate in response to the flow rate status signal.

21. A system as set forth in claim 20 wherein the flow rate status signal comprises a signal indicative of a blockage in the delivery channel and wherein the indication of the operating status of desired flow rate comprises an indication identifying that the delivery channel has a blockage.

22. A system as set forth in claim 20 further comprising a wireless communication channel for transmitting the flow rate status signal from the controller to the status monitoring device.

23. A system as set forth in claim 22 wherein the wireless communication channel comprises a spread spectrum communication channel operating in an unlicensed frequency band.

24. A closed-loop fluid delivery system for delivering a fluid from a reservoir to a delivery point associated with a patient at a desired delivery rate via an administration tube, said closed-loop fluid delivery system comprising:

fluid delivery means located along the administration tube for operatively supplying the fluid to the delivery point at a controllable output rate;

positive displacement flow sensing means located between the fluid delivery means and the delivery point for sensing an actual flow rate of the fluid in the delivery channel and for generating a flow rate signal indicative of the actual flow rate of the fluid in the delivery channel; and

control means associated with the fluid delivery means receiving and responsive to the flow rate signal for adjusting the output rate of the fluid delivery means such that the desired delivery rate at which the fluid is supplied to the delivery point associated with the patient is substantially achieved.

25. A closed-loop fluid delivery system as set forth in claim 24 wherein the positive displacement flow sensing means is sized and shaped for being positioned in fluid communication with the fluid within the administration tube.

26. A closed-loop fluid delivery system as set forth in claim 24 further comprising detector means associated with the positive displacement flow sensing means for detecting the flow rate signal and for providing a flow control signal indicative of the flow rate signal and wherein the control means receives the flow control signal and adjusts the output rate of the fluid delivery means in response thereto.

27. A closed-loop fluid delivery system as set forth in claim 26 further comprising a wireless communication path between the detector means and the control means wherein the detector means provides the flow control signal to the control means via the wireless communication channel.

28. A closed-loop fluid delivery system as set forth in claim 24 wherein the desired flow rate comprises a pulsatile flow profile and the control means adjusts the output rate of the fluid delivery means such that the output rate has a generally pulsatile characteristic.

29. A closed-loop fluid delivery system as set forth in claim 24 wherein the control means provides a status signal indicative of the actual flow rate and said system further comprising monitoring means receiving the status signal for indicating an operating status of the fluid delivery system.

30. A closed-loop fluid delivery system as set forth in claim 29 wherein the status signal comprises a signal that is indicative of a blockage in the administration tube and wherein the operating status indicated by the monitoring means comprises an indication identifying that the administration tube is blocked.

31. A system for delivering a fluid from a reservoir to a delivery point associated with a patient at a desired delivery rate via an administration tube, said system comprising:

a delivery mechanism operatively connected between the reservoir and the delivery point, said delivery mechanism being constructed and arranged for selectively delivering the fluid to the delivery point via the administration tube at a controllable output flow rate; and

a closed-loop control system controlling the output flow rate of the delivery mechanism, said closed-loop control system comprising;

a positive displacement flow sensor connected in-line with the administration tube for determining an actual flow rate of the fluid in the administration tube and for providing an flow rate indication reflecting the actual flow rate;

a reader associated with the positive displacement flow sensor for receiving the flow rate indication and for providing a flow control signal reflecting the flow rate indication; and

a controller associated with the delivery mechanism receiving and responsive to the flow control signal for controlling the output flow rate of the delivery mechanism as a function of the flow control signal such that the output flow rate is substantially equal to the desired delivery rate.

32. A system as set forth in claim 31 wherein the positive displacement flow sensor is sized and shaped for being positioned within the administration tube in fluid communication with the fluid.

33. A system as set forth in claim 31 wherein the delivery mechanism comprises an infusion pump.

34. A system as set forth in claim 33 wherein the infusion pump comprises a syringe pump, a peristaltic pump, a piezoelectric pump, or a valve pump.

35. A system as set forth in claim 33 wherein the infusion pump comprises an ambulatory infusion pump.

36. A system as set forth in claim 33 wherein the infusion pump comprises a volumetric infusion pump.

37. A system as set forth in claim 31 further comprising a wireless communication path between the reader and the controller, said reader providing the flow control signal to the controller via the wireless communication path.

38. A system as set forth in claim 31 wherein the desired delivery rate comprises a pulsatile delivery profile and wherein the controller controls the delivery mechanism such that output flow rate has a substantially pulsatile characteristic.

39. A system as set forth in claim 31 further comprising a status monitor and wherein the closed-loop control system provides a status signal indicating when the actual flow rate is below a flow rate threshold, said status monitor receiving the status signal and providing an indication that the actual flow rate is below the flow rate threshold.

40. A system as set forth in claim 39 wherein the indication that the actual flow rate is below the flow rate threshold comprises an audible alarm.

41. A system as set forth in claim 39 wherein the indication that the actual flow rate is below the flow rate threshold comprises a visual alarm.

42. A system as set forth in claim 39 wherein the indication that the actual flow rate is below the flow rate threshold comprises a vibrating alarm.

43. A method of delivering a medical fluid to a delivery point associated with a patient at a desired delivery flow rate comprising:

operatively connecting a reservoir to a delivery mechanism, said reservoir containing the medical fluid to be delivered to the delivery point;

operatively connecting the delivery mechanism to an administration tube, said administration tube being in fluid communication with the delivery point, said delivery mechanism receiving the medical fluid from the reservoir and supplying the medical fluid to the delivery point via the administration tube at an output flow rate;

sensing the output flow rate of the medical fluid in the administration tube using a positive displacement flow sensor;

comparing the sensed output flow rate of the medical fluid with the desired delivery flow rate; and

controlling the delivery mechanism such that the output flow rate substantially corresponds to the desired delivery flow rate.

44. A method as set forth in claim 43 wherein sensing the output flow rate of the medical fluid in the administration tube comprises connecting a flow sensor operatively to the administration tube and wherein sensing the output flow rate of the medical fluid in the administration tube comprises sensing a rate of flow through the flow sensor whereby the generated flow rate signal is a function of the rate of flow through the flow sensor.

45. A method as set forth in claim 44 wherein the positive displacement flow sensor is sized and shaped for being positioned in fluid communication with the medical fluid within the administration tube.

46. A method as set forth in claim 45 wherein the positive displacement flow sensor includes a rotatable member and wherein each rotation of the rotatable member corresponds to a fixed volume of the medical fluid passing through the positive displacement flow sensor, and wherein sensing the rate of flow through the positive displacement flow sensor comprises:

sensing a rotation of the rotatable member; and

calculating the rate of flow as a function of a number of rotations of the rotatable member over a sample period.

47. A method as set forth in claim 46 further comprising providing an optical variation based on the rotation of the rotatable member and wherein sensing the rotation of the rotatable member comprises sensing the optical variation provided by the rotation of the rotatable member.

48. A method as set forth in claim 46 wherein the rotation of the rotatable member causes an electrical variation and wherein sensing the rotation of the rotatable member comprises sensing the electrical variation caused by the rotation of the rotatable member.

49. A method as set forth in claim 44 wherein the delivery mechanism comprises an infusion pump and supplying the medical fluid to the administration tube at the output flow rate comprises pumping the medical fluid through the administration tube such that desired delivery flow rate is substantially achieved.

50. A method as set forth in claim 49 wherein the administration tube and flow sensor comprise an administration set constructed and arranged for disposable use.

51. A method as set forth in claim 49 wherein the desired flow rate comprises a pulsatile flow profile and wherein controlling the delivery mechanism comprises controlling the infusion pump such that the output flow rate has a generally pulsatile characteristic.

52. A method as set forth in claim 43 further comprising:

determining if the sensed output flow rate is indicative of a blockage in the administration tube; and

providing an alarm signal if it is determined that the sensed output flow rate indicates a blockage in the administration tube.

53. A method as set forth in claim 43 wherein comparing the sensed output flow rate of the medical fluid with the desired delivery flow rate comprises comparing an average of the output flow rate of the medical fluid with the output flow rate.

54. A method as set forth in claim 43 wherein comparing the sensed output flow rate of the medical fluid with the desired delivery flow rate comprises comparing the sensed output flow rate of the medical fluid with an acceptability range corresponding to the output flow rate.

55. A closed-loop flow control system for controlling a medical fluid delivery system, said medical fluid delivery system delivering a fluid from a reservoir to a delivery point associated with a patient at a desired delivery rate via an administration tube, said medical fluid delivery system including a delivery mechanism operatively connected between the reservoir and the delivery point, said delivery mechanism being constructed and arranged for delivering the fluid to the delivery point via the administration tube at a controllable output flow rate, said closed-loop flow control system comprising:

a positive displacement flow sensor connected in-line with the administration tube for determining an actual flow rate of the fluid in the administration tube and for providing an flow rate indication reflecting the actual flow rate;

a reader associated with the positive displacement flow sensor for receiving the flow rate indication and for providing a flow control signal reflecting the flow rate indication; and

a controller associated with the delivery mechanism receiving and responsive to the flow control signal for controlling the output flow rate of the delivery mechanism as a function of the flow control signal such that the output flow rate is substantially equal to the desired delivery rate.

56. A closed-loop flow control system as set forth in claim 55 wherein the positive displacement flow sensor is sized and shaped for being positioned within the administration tube in fluid communication with the medical fluid.

57. A closed-loop flow control system as set forth in claim 55 further comprising a wireless communication channel between the reader and the controller, said reader providing the flow control signal to the controller via the wireless communication channel.

58. A closed-loop flow control system as set forth in claim 55 wherein the desired delivery rate comprises a pulsatile delivery profile and wherein the controller controls the delivery mechanism such that output flow rate includes a substantially pulsatile characteristic.

59. A method of detecting a blockage in a medical fluid delivery system arranged for delivering a medical fluid to a delivery point associated with a patient at a desired flow rate, the method comprising:

operatively connecting a reservoir to a delivery mechanism, said reservoir containing the medical fluid to be delivered to the delivery point;

operatively connecting the delivery mechanism to an administration tube, said administration tube being in fluid communication with the delivery point, said delivery mechanism receiving the medical fluid from the reservoir and supplying the medical fluid to the delivery point via the administration tube at an output flow rate;

sensing the output flow rate of the medical fluid in the administration tube;

determining if the sensed output flow rate is indicative of a blockage in the administration tube; and

providing an alarm signal if it is determined that the sensed output flow rate indicates that the administration tube is blocked.

60. A method as set forth in claim 59 wherein determining if the sensed output flow rate is indicative of a blockage in the administration tube comprises comparing the sensed output flow rate to a blockage threshold such that the alarm signal is provided if the output flow rate is less than the blockage threshold.

61. A method as set forth in claim 60 wherein determining if the sensed output flow is indicative of a blockage in the administration tube comprises averaging the sensed output flow rate of the medical fluid in the administration tube over a time period and comparing said averaged sensed output flow rate to a blockage reference such that the alarm signal is provided if the averaged sensed flow rate is less than the blockage reference.

62. A method as set forth in claim 59 further comprising receiving the alarm signal at a status monitoring device associated with the medical fluid delivery system and providing an indication of the alarm signal at the status monitoring device.

63. A method as set fort hin claim 62 wherein the indication of the alarm signal comprises an audible alarm.

64. A method as set forth in claim 62 wherein the indication of the alarm signal comprises a visual alarm.

65. A method as set forth in claim 64 wherein the indication of the alarm signal comprises a vibrating alarm.

66. An administration set for use in connection with a fluid delivery system, said fluid delivery system being arranged for delivering a fluid from a reservoir to a delivery point associated with a patient at a desired delivery rate, and wherein said fluid delivery system includes a pump having an output rate for delivering fluid from the reservoir to the delivery point and a controller for adjusting the output rate of the pump such that the desired delivery rate is substantially achieved, the administration set comprising:

an administration tube for providing fluid communication between the reservoir and the delivery point; and

a positive displacement flow sensor located along the administration tube being sized and shaped for being positioned in fluid communication with the fluid within the administration tube, said positive displacement flow sensor for sensing a rate of flow of the fluid in the administration tube and for generating a flow rate signal indicative of the sensed rate of flow of the fluid in the administration tube whereby the controller adjusts the output rate of the pump as a function of the flow rate signal.

67. An administration set as set forth in claim 66 wherein the positive displacement flow sensor is sized and shaped for being positioned within the administration tube such that substantially all of the fluid flowing through the administration tube to the delivery point flows through the flow sensor.

68. A positive displacement flow sensor for use in connection with a medical fluid infusion system including an administration set having an administration tube, the positive displacement flow sensor comprising:

a housing having an inlet port and an outlet port, said ports being operatively connected to the administration tube;

a first rotor positioned within the housing between the inlet port and the outlet port;

a second rotor positioned within the housing between the inlet port and the outlet port, said second rotor being positioned adjacent to the first rotor, said first and second rotors being constructed and arranged to rotate in response to a flow of medical fluid in the administration tube for detecting flow of the medical fluid in the administration tube; and

a cover enclosing the housing such that when the medical fluid flows into the inlet port it causes the first rotor to rotate and thereafter said medical fluid exits through the outlet port.

69. A positive displacement flow sensor as set forth in claim 68 wherein the first and second rotors each have a plurality of lobes, said lobes of the first rotor engaging said lobes of the second rotor in a gearing relationship.

70. A positive displacement flow sensor as set forth in claim 68 wherein the housing and the first and second rotors are fabricated using micro-fabrication techniques.

71. A positive displacement flow sensor as set forth in claim 68 wherein the housing and the first and second rotors are fabricated from one or more molds created via a UV-LIGA process.

72. A positive displacement flow sensor as set forth in claim 68 wherein the housing and the first and second rotors are fabricated using a deep reactive ion etching process.

73. A positive displacement flow sensor as set forth in claim 68 wherein the cover comprises a generally transparent cover allowing light to pass through a portion of the cover.

74. A positive displacement flow sensor as set forth in claim 73 wherein the first rotor comprises a plurality of lobes, at least one of said lobes being marked with a marker indication that is optically detectable through the cover.

75. A positive displacement flow sensor as set forth in claim 73 wherein the cover has a substantially opaque pattern imposed thereon that substantially prevents light from passing through said pattern.

76. A positive displacement flow sensor as set forth in claim 75 wherein the pattern imposed on the cover corresponds to a shape and size of the first rotor.

77. A positive displacement flow sensor as set forth in claim 68 further comprising a reader positioned adjacent the first rotor, said reader being constructed and arranged for detecting a rotation of the first rotor and for providing a signal that is indicative of a rate of the flow of the medical fluid in the administration tube as a function of the detected rotation of the first rotor.

78. A positive displacement flow sensor as set forth in claim 77 wherein the reader is positioned substantially within the cover.