Method and apparatus for fluid flow control

• US 4,037,598 A
• Filed: 08/12/1974
• Issued: 07/26/1977
• Est. Priority Date: 08/12/1974
• Status: Expired due to Term

• Current Assignee: IVAC Medical Systems, Inc. (Becton, Dickinson & Co)
• Original Assignee: Ivax Corporation (Teva Pharmaceutical Industries, Ltd.)
• Inventors: Georgi, Heinz W.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/496,553
• Time in Patent Office: 1,079 Days
• Field of Search: 128/214 E, 128/214 F, 128/DIG. 12, 128/DIG. 13, 128/14, 222/14, 222/52, 222/59, 222/63, 222/71, 222/76, 125/2.06 A, 125/419 PG
• US Class Current: 604/65
• CPC Class Codes: A61M 5/1689 Drip counters
• CPC Class Codes: Y10S 128/12 Pressure infusion
• CPC Class Codes: Y10S 128/13 Infusion monitoring

Abstract

A digital system wherein a wide variety of different electromechanical output control devices, e.g., stepping motor pump or solenoid actuated I.V. tube pincher, is driven by electrical output pulses of varible frequency and pulse width from a digital pulse generation and control system, the frequency and pulse width of the output pulses being selected and controlled by the system to establish drop flow rates with digital precision over an extremely wide dynamic range. Pulse width is determined by the relative states of a pair of digital counters in a digital memory, frequency being determined by a high, preferably non-integral, multiple of the desired drop flow rate. The equivalent of negative pulse width in the digital memory can be effectively utilized to expand the effective dynamic range of the memory for specified types of electromechanical output devices. A start up subsystem temporarily presets the initial pulse rate and speeds up early regulation. Duty cycle limitation and visual output pulse width monitoring is also provided. Appropriate alarms also respond to a variety of out-of-limit conditions.

Claims

1. In a system for parenteral administration of liquids at desired drop flow rates through a feeding tube from a liquid source to a patient, the combination comprising:

electromechanical output control means for manipulating the feeding tube to vary the flow of liquid in the feeding tube;

electrical pulsing means for providing output pulses to operate said output control means, said output control means being inactive during the periods between said output pulses in a pulse train, said output pulses being at a substantially higher frequency than the desired drop flow rate frequency; and

digital memory and timing means for automatically predetermining and varying the pulse width of said output pulses operating said control means, to achieve the desired drop flow rate.

2. A system as set forth in claim 1, wherein said digital memory and timing means includes at least one counter.

3. A system as set forth in claim 2, and further including:

means for providing a negative pulse width by overflow of said counter through successive incrementing of said counter when a plurality of drops have been detected in rapid succession.

4. A system as set forth in claim 1, wherein said digital memory and timing means includes a pair of digital counters.

5. A system as set forth in claim 1, wherein said digital memory and timing means includes a digital counter which undergoes successive counting cycles, a single counting cycle for each of said output pulses produced by said pulsing means, the count state of said counter at the beginning of each counting cycle determining the pulse width of the corresponding output pulse produced during that counting cycle.

6. A system as set forth in claim 5, and further including:

means for decrementing said counter by a first prescribed number of counts during each of said counting cycles, and for incrementing said counter by a second prescribed number of counts only during a counting cycle after a drop of liquid flow has been detected.

7. A system as set forth in claim 6, wherein the ratio of said second prescribed number of counts to said first prescribed number of counts is a predetermined value.

8. A system as set forth in claim 7, wherein said ratio is the same as the ratio of the frequency of said output pulses produced by said pulsing means to the desired drop flow rate frequency.

9. A system as set forth in claim 7, wherein the frequency of said output pulses is a high, non-integral multiple of the desired drop flow rate.

10. A system as set forth in claim 9, wherein said ratio is 101/2.

11. Apparatus as set forth in claim 1, and further comprising:

means responsive to a predetermined sequence of states of said digital memory means for generating an alarm state.

12. Apparatus as set forth in claim 1, and further comprising:

means responsive to a predetermined sequence of pulse widths of said output pulses for generating an alarm state.

13. Apparatus as set forth in claim 1, and further comprising:

means responsive to a lack of detection of flow of liquid in said feeding tube within a prescribed period of time for generating an alarm state.

14. A system as set forth in claim 1, wherein said digital memory means further comprises:

a first digital counter; and

a second digital counter having a counting cycle under the control of said first counter.

15. Apparatus as set forth in claim 14, including means responsive to a prescribed sequence of states of said second counter for generating an alarm state.

16. A system as set forth in claim 1, and further comprising:

means for selectively overriding said digital memory and timing means for imposing a duty cycle limitation upon said pulse width.

17. A system as set forth in claim 1, and further comprising:

visual display means for indicating the range of magnitudes of the pulse widths of said output pulses.

18. Apparatus as set forth in claim 17, wherein said visual display means includes a pair of lights which are energized in predetermined combinations to indicate a plurality of pulse width ranges of operation.

19. A system as set forth in claim 1, and further comprising:

means for temporarily overriding normal control of said pulsing means and setting said pulsing means to a prescribed pulse rate during predetermined periods of operation.

20. In a system for parenteral administration of liquids at a desired drop flow rate through a feeding tube from a liquid source to a patient, the combination comprising:

output control means for determining the rate of drop flow of liquid in the feeding tube;

electrical pulsing means for providing successive output pulses to said output control means, said output control means being inactive during the periods between said output pulses in a pulse train, said output pulses being at a substantially higher frequency than the desired drop flow rate frequency; and

counting means for varying the pulse width of each of said output pulses, to achieve the desired drop flow rate.

21. A system as set forth in claim 20, wherein said counting means comprises:

a first counter; and

a second counter having a counting cycle under the control of said first counter.

22. A system as set forth in claim 21, and further comprising:

means responsive to a sequence of states of said second counter for generating an alarm state.

23. A system as set forth in claim 21, and further comprising:

means responsive to a lack of detection of fluid flow within a prescribed period of time for generating an alarm state.

24. A system as set forth in claim 21, and further comprising:

means responsive to the lack of detection of drops within a prescribed period of time for generating an alarm state.

25. A system as set forth in claim 24, wherein said time is a function of the number of pulses generated by said electrical pulsing means.

26. A system as set forth in claim 24, wherein said time is a function of the lack of occurrence of drops or output pulses for a prescribed period of time.

27. A system as set forth in claim 21, wherein said first and said second counters undergo successive counting cycles, a single counting cycle for each of said output pulses produced by said pulsing means, the count state of said second counter at the beginning of each counting cycle determining the pulse width of the corresponding output pulse produced during that counting cycle.

28. A system as set forth in claim 27, and further including:

means for decrementing said second counter relative to said first counter by a first prescribed number of counts during each of said counting cycles, and for incrementing said second counter relative to said first counter by a second prescribed number of counts only during a counting cycle after a drop has been detected.

29. A system as set forth in claim 28, and further comprising:

means responsive to a predetermined sequence of pulse widths for generating an alarm state.

30. A system as set forth in claim 29, wherein said predetermined sequence of pulse widths is a narrow pulse width of prescribed magnitude followed by a wide pulse width of prescribed magnitude.

31. A system as set forth in claim 29, wherein said predetermined sequence of pulse widths is a wide pulse width of prescribed magnitude followed by a narrow pulse width of prescribed magnitude.

32. A system as set forth in claim 29, wherein said predetermined sequence of pulse widths is a narrow pulse width of prescribed magnitude followed by a wide pulse width of prescribed magnitude, followed by a narrow pulse width of prescribed magnitude induced by further and successive incrementing rather than further successive decrementing of said second counter.

33. A system as set forth in claim 28, wherein the ratio of said second prescribed number of counts to said first prescribed number of counts is a predetermined value.

34. A system as set forth in claim 33, wherein said ratio is the same as the ratio of the frequency of said output pulses to the desired drop flow rate frequency.

35. A system as set forth in claim 34, wherein said ratio is 101/2.

36. A system as set forth in claim 28, and further comprising:

start-up means for preventing normal system response to a predetermined number of initial drops of liquid flow in the feeding tube.

37. A system as set forth in claim 25, and further including:

means for increasing said first prescribed number of counts by which said counter is decremented during each of said counting cycles to a larger number for each counting cycle which occurs during predetermined periods of operation.

38. A system as set forth in claim 37, and further comprising:

means for temporarily overriding normal control of said pulsing means and setting said pulsing means to a prescribed pulse rate during said predetermined periods of operation.

39. A system as set forth in claim 28 and further including;

means for providing a negative pulse width by overflow of said second counter as a result of successive incrementing of said second counter when a plurality of drops have been detected in rapid succession.

40. In a system for parenteral administration of liquids at a desired drop flow rate via a feeding tube from a liquid source to a patient, the combination comprising:

electromechanical output control means for varying fluid flow in the feeding tube;

electrical pulsing means for providing output pulses to said output control means, said output control means being inactive during the periods between said output pulses in a pulse train, said output pulses being at a substantially higher frequency than the desired drop flow rate frequency;

digital pulse generation and rate determination means for generating command pulses to selectively control the frequency of said output pulses and the time of initiation of each of said output pulses; and

digital memory means for automatically determining the pulse width of each of said output pulses.

41. Apparatus as set forth in claim 40, and further comprising:

means responsive to the lack of detection of drop flow within the period of time determined by a prescribed number of pulses generated by said pulse generation and rate determination means.

42. Apparatus as set forth in claim 40, wherein said pulse width is increased with each command pulse produced by said pulse generation and rate determination means, and said pulse width is decreased with each drop detected.

43. Apparatus as set forth in claim 42, and further comprising:

means responsive to the lack of detection of drop flow within the period of time determined by a prescribed number of said command pulses generated by said pulse generation and rate determination means for generating an alarm state.

44. Apparatus as set forth in claim 40, and further comprising:

means responsive to excessive pulse width for generating an alarm state.

45. Apparatus as set forth in claim 40, and further comprising:

means responsive to a predetermined reduced pulse width for generating an alarm state.

46. Apparatus as set forth in claim 40, and further comprising:

means responsive to a predetermined sequence of pulse widths for generating an alarm state.

47. Apparatus as set forth in claim 46, wherein said predetermined sequence of pulse widths is a narrow pulse width of prescribed magnitude followed by a wide pulse width of prescribed magnitude.

48. Apparatus as set forth in claim 46, wherein said predetermined sequence of pulse widths is a narrow pulse width of prescribed magnitude followed by a wide pulse width of prescribed magnitude, followed by a narrow pulse width of prescribed magnitude.

49. Apparatus as set forth in claim 46, wherein said predetermined sequence of pulse widths is a wide pulse width of prescribed magnitude followed by a narrow pulse width of prescribed magnitude.

50. Apparatus as set forth in claim 40, and further comprising:

means responsive to a predetermined sequence of pulse widths in prescribed ranges of magnitude for generating an alarm state.

51. Apparatus as set forth in claim 40, and further comprising:

means responsive to a predetermined sequence of states of said digital memory means for generating an alarm state.

52. Apparatus as set forth in claim 40, and further comprising:

means responsive to the lack of detection of drop flow within a prescribed period of time for generating an alarm state.

53. Apparatus as set forth in claim 52, wherein said time is a function of the number of said command pulses generated by said pulse generation and rate determination means.

54. Apparatus as set forth in claim 52, wherein said time is a function of the lack of occurrence of drops or output pulses for a prescribed period of time.

55. Apparatus as set forth in claim 40, and further comprising:

digital start-up subsystem means for preventing normal system response to a predetermined number of initial drops.

56. A system as set forth in claim 40, and further comprising:

means for temporarily overriding normal control and setting said pulse generation and rate determination means to a prescribed pulse rate during predetermined periods of operation.

57. In a parenteral infusion system, the combination comprising:

output means for controlling fluid flow in a feeding tube;

electrical pulsing means for providing output pulses to said output means, said output means being inactive during the periods between said output pulses in a pulse train;

digital counting means for predetermining and varying the pulse width of said output pulses; and

visual display means indicating the range of magnitudes of the pulse widths of said output pulses.

58. Apparatus as set forth in claim 57, wherein said visual display means includes a pair of lights which are selectively energized to indicate a plurality of pulse width magnitude ranges of operation.

59. In an I.V. system for producing output drive pulses to drive an electromechanical output control means for varying fluid flow in a feeding tube, the combination comprising:

electrical pulsing means for providing output pulses;

a pair of counters for determining the pulse width of each of said output pulses; and

means to increment or decrement the relative count between said counters depending upon detection or nondetection of drops.

60. Apparatus as set forth in claim 59, wherein said pulse width is increased during each period between initiation of successive of said output pulses and decreased with each drop detected.

61. Apparatus as set forth in claim 60, and further comprising:

means for generating an alarm state in said system in response to the detection of lack of fluid flow in said system.

62. Apparatus as set forth in claim 60, and further comprising:

means for generating an alarm state in said system in response to the detection of excessive pulse width in said system.

63. Apparatus as set forth in claim 60, and further comprising:

means for generating an alarm state in said system in response to the detection of reduced pulse width of prescribed magnitude in said system.

64. In a system for parenteral administration of liquid via a feeding tube from a liquid source to a patient, the combination comprising:

output control means for regulating fluid flow in the feeding tube;

electrical pulsing means for controlling the generation of output pulses to incrementally energize said output control means, said output control means being inactive during the periods between said output pulses in a pulse train;

digital memory and timing means for predetermining and varying the pulse width of said output pulses energizing said output means;

flow monitoring means for monitoring liquid flow in the administration system; and

digital means responsive to said electrical pulsing means and said flow monitoring means for indicating a lack of flow within a time period determined by a specified number of said pulses.

65. In a system for parenteral administration of liquid via a feeding tube from a liquid source to a patient, the combination comprising:

output control means for regulating fluid flow in the feeding tube;

electrical pulsing means for generating output pulses to incrementally energize said output control means, said output control means being inactive during the periods between said output pulses in a pulse train;

digital memory and timing means for predetermining and varying the pulse width of said output pulses energizing said output means;

flow monitoring means for monitoring liquid flow in the administration system; and

digital means responsive to said pulsing means and said flow monitoring means for indicating a lack of either flow or output pulses within a prescribed time period.

66. In a system for parenteral administration of liquid via a feeding tube from a liquid source to a patient, the combination comprising:

output control means for regulating fluid flow in the feeding tube;

electrical pulsing means for generating output pulses to incrementally energize said control means;

means for varying the pulse width of said output pulses energizing said output means;

flow monitoring means for monitoring liquid flow in the administration system;

pulse width monitoring means; and

means responsive to said pulse width monitoring means for indicating the occurrence of a prescribed nontolerated sequence of pulse widths.

67. In a system for parenteral administration of liquid via a feeding tube from a liquid source to a patient, the combination comprising:

electromechanical output means;

driving means for driving said output means;

an open loop digital control means for digitally establishing the frequency of output pulses electrically energizing said driving means, said driving means being inactive during the periods between said output pulses in a pulse train; and

a closed loop digital memory control means for digitally predetermining and varying the pulse width of said output pulses to said driver means.

68. A system as set forth in claim 67, wherein said open loop control means includes:

digital pulse generation means; and

digital rate determination means.

69. A system as set forth in claim 67, wherein said closed loop digital control means includes a digital counter.

70. A system as set forth in claim 67, wherein said driving means is an electrical stepping motor, and said electromechanical output means is a pump.

71. A combination as set forth in claim 67, wherein said electromechanical output means is a feeding tube pincher, and said driving means is an electromagnetic actuator.

72. In a system for parenteral administration of liquid via a feeding tube from a liquid source to a patient, apparatus comprising:

positive pressure infusion pump means;

digital rate setting means for generating an electrical pulse train at a frequency proportional to desired liquid flow rate;

stepping motor means for driving said pump means, said motor means being inactive during the periods between pulses in said pulse train;

digital flow monitoring means for monitoring liquid flow induced by said pump means; and

digital memory means responsive to both said digital rate setting means and said digital flow monitoring means for digitally regulating the pulse width of the output pulses to said electrical motor means.

73. A system as set forth in claim 72, wherein said digital memory means includes a pair of digital counters.

74. A system as set forth in claim 72, wherein said digital memory means includes a digital counter which undergoes successive counting cycles, a single counting cycle for each of said output pulses, the count state of said counter at the beginning of each of said counting cycles determining the pulse width of the corresponding output pulse produced during that counting cycle.

75. A system as set forth in claim 74, and further including:

means for decrementing said counter by a first prescribed number of counts during each counting cycle and for incrementing said counter by a second prescribed number of counts only during a counting cycle after a drop has been detected.

76. A system as set forth in claim 75, and further including:

means for increasing the number of counts by which said counter is decremented during each counting cycle to a larger number for each counting cycle during an initial start-up period of operation of said system.

77. A system as set forth in claim 72, wherein said digital memory means further comprises:

a first counter; and

a second counter having a counting cycle under the control of said first counter.

78. A system as set forth in claim 77, wherein said first and said second counters undergo successive counting cycles, one for each of said output pulses produced, the count state of said second counter at the beginning of each counting cycle determining the pulse width of the output pulse generated during that counting cycle.

79. A system as set forth in claim 78, wherein said second counter is decremented relative to said first counter by a first prescribed number of counts during each counting cycle, and said second counter is incremented relative to said first counter by a second prescribed number of counts only during a counting cycle after a drop has been detected.

80. In the parenteral administration of medical fluids by an intravenous set including drop forming means in a flexible tube coupled to said drop forming means for carrying drop flow, a method of controlling the rate of drop flow through the flexible tube, comprising the steps of:

clamping said tube to a substantially shut-off state;

producing digital control pulses in a pulse train at a selected frequency proportional to the desired rate of drop flow;

monitoring the actual drop flow occurring through said tube;

selectively varying the pulse width of each of said control pulses in a digital memory in accordance with the desired drop flow rate and the actual drop flow rate detected; and

repetitively opening and closing said tube to fluid flow in response to said digital control pulses to regulate the actual drop flow rate so that it conforms to said desired drop flow rate, said tube being closed during the periods between said control pulses in said pulse train.

81. A method as set forth in claim 80, wherein the frequency of opening said tube is a relatively high multiple of the desired drop flow rate.

82. A method as set forth in claim 81, wherein said multiple is approximately 101/2 times the desired drop flow rate.

83. In a system for parenteral administration of medical liquids by drop flow through a feeding tube, apparatus comprising:

clamping means for clamping said feeding tube in a normally shut-off state;

electrical pulsing means for generating control pulses in a pulse train at a rate greater than the desired drop flow rate to periodically energize said clamping means and thereby open said tube to liquid flow, said clamping means being inactive during the periods between control pulses in said pulse train;

digital rate setting means for digitally establishing the frequency of said electrical pulsing means;

flow monitoring means for monitoring actual drop flow through said feeding tube and generating a digital electrical pulse each time a drop is detected; and

digital memory and timing means responsive to both said digital rate setting means and said flow monitoring means for digitally predetermining and varying the pulse width of the pulses from said pulsing means.

84. A system as set forth in claim 83, wherein said digital memory and timing means includes counting means.

85. A system as set forth in claim 83, wherein said digital memory and timing means includes a digital counter which undergoes successive counting cycles, one counting cycle for each of said output pulses, the count state of said counter at the beginning of each counting cycle determining the pulse width of the output pulse produced during that counting cycle.

86. A system as set forth in claim 85, wherein said counter is decremented by a first prescribed number of counts during each counting cycle and said counter is incremented by a second prescribed number of counts only during a counting cycle after a drop has been detected.

87. A system as set forth in claim 86, wherein the ratio of said second prescribed number of counts to said first prescribed number of counts is predetermined.

88. A system as set forth in claim 87, wherein said ratio is the same as the ratio of the frequency of said control pulses to the desired drop flow rate frequency.

89. A system as set forth in claim 88, wherein said ratio is 101/2.

90. A system as set forth in claim 88, and further including:

means for increasing the number of counts by which said counter is decremented during each counting cycle to a larger number for each counting cycle during an initial start-up period of operation of the system.

91. A system as set forth in claim 83, wherein said digital memory and timing means further comprises:

a first counter; and

a second counter having a counting cycle under the control of said first counter.

92. A system as set forth in claim 91, wherein said first and said second counters undergo successive counting cycles, one for each of said output pulses produced, the count state of said second counter at the beginning of each counting cycle determining the pulse width of the output pulse generated during that counting cycle.

93. A system as set forth in claim 92, wherein said second counter is decremented relative to said first counter by a first prescribed number of counts during each counting cycle, and said second counter is incremented relative to said first counter by a second prescribed number of counts only during a counting cycle after a drop has been detected.

94. In a system for parenteral administration of liquids at desired flow rates through a feeding tube from a liquid source to a patient, the combination comprising:

electromechanical output control means for manipulating the feeding tube to vary the flow of liquid in the feeding tube;

electrical pulsing means for providing output pulses to operate said output control means;

digital memory means for automatically varying the pulse width of said output pulses operating said control means, to achieve the desired flow rate, said digital memory means including a digital counter which undergoes successive counting cycles, a single counting cycle for each of said output pulses produced by said pulsing means, the count state of said counter at the beginning of each counting cycle determining the pulse width of the corresponding output pulse produced during that counting cycle;

means for decrementing said counter by a first prescribed number of counts during each of said counting cycles, and for incrementing said counter by a second prescribed number of counts only during a counting cycle after a drop of liquid flow has been detected; and

means for increasing said first prescribed number of counts by which said counter is normally decremented during each counting cycle to a larger prescribed number for each counting cycle during an initial start-up period of operation of said system.

95. In a system for parenteral administration of liquids at desired flow rates through a feeding tube from a liquid source to a patient, the combination comprising:

electromechanical output control means for manipulating the feeding tube to vary the flow of liquid in the feeding tube;

electrical pulsing means for providing output pulses to operate said output control means;

digital memory means for automatically varying the pulse width of said output pulses operating said control means, to achieve the desired flow rate, said digital memory means including a digital counter which undergoes successive counting cycles, a single counting cycle for each of said output pulses produced by said pulsing means, the count state of said counter at the beginning of each counting cycle determining the pulse width of the corresponding output pulse produced during that counting cycle;

means for monitoring the period between initiation of successive of said output pulses;

means for generating a duty cycle limitation signal at a predetermined time in each of said monitored periods; and

means for overriding said digital memory means when said duty cycle limitation signal is imposed.

96. A system as set forth in claim 95, and further comprising:

clocking means for generating two different clock rates, a normal clock rate and a higher clock rate.

97. A system as set forth in claim 96, wherein said duty cycle signal, if imposed during a counting cycle, switches the counting rate of said counter from said normal clock rate to said higher clock rate.

98. In a system for parenteral administration of liquids at desired flow rates through a feeding tube from a liquid source to a patient, the combination comprising:

electromechanical output control means for manipulating the feeding tube to vary the flow of liquid in the feeding tube;

electrical pulsing means for providing output pulses to operate said output control means;

digital memory means for automatically varying the pulse width of said output pulses operating said control means, to achieve the desired flow rate;

clocking means capable of generating clocking pulses at two different rates, a high rate and a low rate; and

means for automatically switching said clocking means from said low rate to said high rate at prescribed times in each period between initiation of successive of said output pulses.

99. In a system for parenteral administration of liquids at a desired drop flow rate through a feeding tube from a liquid source to a patient, the combination comprising:

output control means for determining the rate of drop flow of liquid in the feeding tube;

electrical pulsing means for providing successive output pulses to said output control means;

counting means for varying the pulse width of each of said output pulses, to achieve the desired drop flow rate;

means for monitoring the period between initiation of said successive output pulses;

means for generating a duty cycle limitation signal at a preselected time in each of said monitored periods; and

means for overriding the pulse width determination by said counting means when said duty cycle limitation signal is imposed.

100. A system as set forth in claim 99, and further comprising:

clocking means for generating two different clock rates, a normal clock rate and a higher clock rate.

101. A system as set forth in claim 100, wherein said duty cycle signal, if imposed during a counting cycle, changes the counting rate of said counting means from said normal clock rate to said higher clock rate.

102. In a system for parenteral administration of liquids at a desired drop flow rate through a feeding tube from a liquid source to a patient, the combination comprising:

output control means for determining the rate of drop flow of liquid in the feeding tube;

electrical pulsing means for providing successive output pulses to said output control means;

counting means for varying the pulse width of each of said output pulses, to achieve the desired drop flow rate;

clocking means capable of generating clocking pulses at two different rates, a high rate and a low rate; and

means for automatically switching said clocking means from said low rate to said high rate at prescribed times in each period between initiation of said successive output pulses.