Pressure-measurement flow control system

• US 4,808,161 A
• Filed: 03/05/1987
• Issued: 02/28/1989
• Est. Priority Date: 03/04/1986
• Status: Expired due to Term

• Current Assignee: Deka Products Limited Partnership
• Original Assignee: Dean Kamen
• Inventors: Kamen, Dean L.
• Primary Examiner(s): Pellegrino, Stephen C.
• Application Number:
  US07/022,167
• Time in Patent Office: 726 Days
• Field of Search: 604/65, 604/67, 604/251, 604/253, 604/247, 128/DIG. 12, 128/DIG. 13, 73/149, 47/384-389, 47/395, 47/411
• US Class Current: 604/67
• CPC Class Codes: A61M 2005/1403 Flushing or purging
• CPC Class Codes: A61M 2205/15 Detection of leaks
• CPC Class Codes: A61M 39/26 Valves closing automatically on disconnecting the line and opening on reconnection thereof check valves A61M39/24
• CPC Class Codes: A61M 5/16809 by repeated filling and emptying of an intermediate volume pressure infusion using positive displacement pumps A61M5/142
• CPC Class Codes: A61M 5/16813 by controlling the degree of opening of the flow line
• CPC Class Codes: A61M 5/16859 Evaluation of pressure response, e.g. to an applied pulse
• CPC Class Codes: A61M 5/365 Air detectors A61M5/1684 takes precedence; in extracorporeal blood circuits A61M1/3626
• CPC Class Codes: F04B 43/043 Micropumps
• CPC Class Codes: F16K 31/005 Piezoelectric benders
• CPC Class Codes: G01F 11/086 using an auxiliary pressure to cooperate with the diaphragm or bellows
• CPC Class Codes: G01P 13/0066 by using differences of pressure in the fluid
• CPC Class Codes: Y10S 128/12 Pressure infusion
• CPC Class Codes: Y10S 128/13 Infusion monitoring
• CPC Class Codes: Y10T 137/7782 With manual or external control for line valve
• CPC Class Codes: Y10T 137/7796 Senses inlet pressure
• CPC Class Codes: Y10T 137/88005 Biased valve

Abstract

A system is provided for controlling flow of a first fluid through a line. Dispensing means isolates a region of the first fluid in the line from effects of pressure in the line outside of the region and repetitively dispenses into and out of the region volume increments of first fluid. Measurement fluid housing means houses measurement fluid in communication with the region such that the dispensing of increments of first fluid into or out of the region causes a change in the measurement fluid pressure. Displacement means displaces a predetermined volume increment of measurement fluid into and out of the measurement fluid housing means, such that displacement of the predetermined volume increment causes a change in the measurement fluid pressure when the region is isolated by the dispensing means. Pressure measurement means measures changes in measurement fluid pressure. Control means, in communication with the pressure measurement means, the displacement means, and the dispensing means, causes the dispensing means to dispense first fluid in increments based on data from the pressure measurement means, such that at least one of the predetermined volume increments of measurement fluid displaced serves as a reference for the volume increments of first fluid outputted.

Claims

1. A system for controlling flow of a first fluid through a line, the system comprising:

dispensing means (i) for isolating a region of the first fluid in the line from effects of pressure in the line outside of the region, the region having an input and an output for the first fluid, and (ii) for repetitively dispensing into and out of the region volume increments of first fluid;

measurement fluid housing means for housing measurement fluid in communication with the region such that the dispensing of increments of first fluid into or out of the region causes a change in the measurement fluid pressure;

displacement means for displacing a predetermined volume increment of measurement fluid into and out of the measurement fluid housing means, such that displacement of the predetermined volume increment causes a change in the measurement fluid pressure when the region is isolated by the dispensing means;

pressure measurement means for measuring changes in measurement fluid pressure; and

control means, in communication with the pressure measurement means, the displacement means, and the dispensing means, for causing the dispensing means to dispense first fluid in increments based on data from the pressure measurement means, such that at least one of the predetermined volume increments of measurement fluid displaced serves as a reference for the volume increments of first fluid outputted.

2. A system according to claim 1, wherein the dispensing means includes an input valve at the first fluid input to the region and an output valve at the first fluid output from the region.

3. A system according to claim 2, wherein the measurement housing means is disposed in relation to the region so as to define collectively therewith a fixed volume that is varied by the displacement means, and wherein the region includes a flexible interface surface defining a boundary between the measurement fluid and the first fluid.

4. A system according to claim 3, wherein the region includes a rigid enclosure with an input, an output, and a window, the flexible interface surface covering the window.

5. A system according to claim 3, wherein the rigid enclosure is substantially hemispherical in shape.

6. A system according to claim 3, wherein the region includes a flexible tube, and the walls of the tube comprise the flexible interface surface.

7. A system according to claim 6, wherein the flexible tube includes a bulge with thinner walls than the remainder of the tube, and wherein the walls of the bulge comprise the flexible interface surface.

8. A system according to claim 7, further comprising a case in which the bulge is housed and having fluidtight seals at the input and output of the tube.

9. A system according to claim 8, including means for forming the bulge inside of the case.

10. A system according to claim 3, wherein the control means includes means for causing the dispensing means to dispense first fluid in the same increments of volume as displaced by the displacement means.

11. A system according to claim 2, wherein the measurement fluid is a gas.

12. A system according to claim 11, wherein the gas is air.

13. A system according to claim 11, wherein the dispensing means includes a heat sink in communication with the measurement fluid for reducing gas that might otherwise affect system accuracy owing to pressure changes not attributable to volume changes in first fluid in the region or in measurement fluid.

14. A system according to claim 13, wherein the heat sink comprises a porous plug disposed between the displacement means and the region of isolated first fluid.

15. A system according to claim 14, wherein the porous plug is made of sintered stainless steel.

16. A system according to claim 11, wherein the dispensing means includes a drip chamber through which the first fluid flows and having an upper region that is in communication with the measurement fluid housing means.

17. A system according to claim 16, wherein the control means includes means for causing the dispensing means to dispense first fluid in the same increments of volume as displaced by the displacement means.

18. A system according to claim 1, wherein the displacement means includes a motor-driven cam drive.

19. A system according to claim 1, wherein the displacement means comprise bellows.

20. A system according to claim 1, wherein the displacement means comprises a piston arrangement.

21. A system according to claim 2, wherein control means includes means for controlling first fluid flow in accordance with a pumping cycle as follows:

(A) with input and output valves closed, actuating the displacement means to a predetermined negative volume increment to decrease the volume of measurement fluid;

(B) opening the output valve to let first fluid out of the region until the pressure measurement means indicates that the pressure of measurement fluid has returned to the pressure at the beginning of step (A), and then closing the output valve;

(C) activating the displacement means to displace a predetermined positive volume increment equal in absolute value to the foregoing negative increment;

(D) opening the input valve to admit first fluid until the pressure measurement means indicates that the pressure of the measurement fluid has returned to the pressure at the beginning of step (A), whereupon the cycle may be repeated.

22. A system according to claim 21, wherein the pressure of the measurement fluid at the beginning of step (A) is approximately at that of the ambient atmosphere.

23. A system according to claim 21, wherein the control means further includes means for detecting an occlusion in the first fluid line or infiltration of the intravenenous needle into surrounding tissue, the occlusion detection means comprising means for detecting an unusually slow pressure return in step (B) and step (D), such unusually slow pressure return being characteristic of an occlusion at the output or at the input or of infiltration of the intravenous needle into surrounding tissue.

24. A system according to claim 2, wherein control means includes means for controlling first fluid flow in accordance with a pumping cycle as follows:

(A) with input and output valves closed, calibrating the system by measuring pressure of the measurement fluid before and after the predetermined volume increment is displaced, storing these measurements, and then restoring the original volume and pressure of the measurement fluid;

(B) opening the output valve to let first fluid flow out of the region until the pressure measurement means indicates that the pressure of the measurement fluid has reached a value equal in absolute value to the absolute value of the pressure measured in step (A) after the displacement of the predetermined volume increment, and then closing the output valve;

(C) opening the input valve to let first fluid flow into the region until the pressure measurement means indicates that the pressure of the measurement fluid has reached a value equal to the pressure measure in step (A) before the displacement of the predetermined volume increment, and then closing the input valve, whereupon steps (B) and (C) may be repeated.

25. A system according to claim 2, wherein the control means includes means for controlling first fluid flow in accordance with a pumping cycle as follows:

(A) with input and output valves closed, activating the displacement means to displace a predetermined negative volume increment;

(B) opening the output valve to let first fluid out of the region until the pressure measurement means indicates that the pressure of the measurement fluid has returned to the pressure at the beginning of step (A), and then closing the output valve, whereupon the cycle may be repeated.

32. A system according to claim 11, wherein the control means includes means for controlling first fluid flow in accordance with a pumping cycle as follows:

(A) with input and output valves closed, calibrating the system by measuring pressure P₀ of the measurement fluid, displacing a predetermined volume increment N₀ v of measurement fluid, determining the resulting change in pressure Δ

P₀ and deriving the chamber volume V₀ using the relation

space="preserve" listing-type="equation">V.sub.0 =(P.sub.0 +Δ

P.sub.0)N.sub.0 v/Δ

P.sub.0 ;

(B) with input valve closed, measuring the pressure P_i, and causing the displacement means to displace a volume N_i v of measurement fluid, where N_i v can be zero, positive or negative;

(C) opening the output valve to let first fluid out of the region, and then measuring the resulting pressure at a given time, and determining the change from P_i in pressure Δ

P_i at the given time;

(D) calculating the volume flow F_i of first fluid out of the region from the beginning of the cycle in step (B) to the given time in accordance with the relation

space="preserve" listing-type="equation">F.sub.i =N.sub.iil v-Δ

P.sub.i P.sub.0 V.sub.0 / (P.sub.i +Δ

P.sub.i)P.sub.i

whereupon the cycle beginning in step (B) may be repeated.

26. A method for controlling flow of a first fluid through a line, the method comprising the following steps:

(A) isolating a region of the fluid in the line from effects of pressure in the line outside of the region;

(B) housing a measurement fluid in communication with the region such that input and output of first fluid into and out of the region cause a change in the pressure of the measurement fluid;

(C) displacing a predetermined volume increment of measurement fluid;

(D) measuring the pressure of the measurement fluid; and

(E) inputting and outputting first fluid into and out of the region based on measurement fluid pressure data obtained in step (D), such that the predetermined increment of measurement fluid displaced serves as a reference for the amount of first fluid outputted.

27. A method for controlling flow of a first fluid through a line, the method comprising the following steps:

(A) isolating a region of the first fluid in the line from effects of pressure in the line outside of the region;

(B) housing a measurement fluid in communication with the region such that a change in volume of the first fluid in the region causes a change in the pressure of the measurement fluid;

(C) inputting and outputting liquid into and out of the region while displacing a predetermined volume increment of measurement fluid and maintaining a substantially constant measurement fluid pressure.

28. A method for controlling flow of a liquid through a line, the method comprising the following steps:

(A) isolating a region of the liquid in the line from effects of pressure in the line outside of the region;

(B) housing a measurement gas in communication with the region such that changes in volume of the liquid in the region cause a proportionate change in the pressure of the measurement gas;

(C) measuring the pressure of the measurement gas before and after the volume of the gas is changed by a predetermined amount while the volume of liquid in the region remains substantially constant;

(D) inputting and outputting liquid into and out of the region based on the data obtained in step (C) and o measurement of the pressure of the measurement gas while liquid is being inputted and outputted into and out of the region.

29. A method for monitoring blood pressure in a patient, comprising the following steps:

(A) isolating a region of intravenous fluid in an intravenous line from effects of pressure in the line outside of the region;

(B) housing a measurement gas in communication with the region such that changes in volume of the fluid in the region cause a proportion change in the pressure of the measurement gas;

(C) measuring the pressure of the measurement gas before and after the volume of the gas is changed by a predetermined amount while the volume of intravenous fluid in the region remains substantially constant;

(D) measuring the pressure of the measurement gas before and after the volume of the gas is changed by a predetermined amount while the output from the region to the patient is open;

(E) calculating the blood pressure in the patient based on a comparison of the data obtained in steps (C) and (D).

30. A method for detecting occlusion in an intravenous line or infiltration of an intravenous needle into surrounding tissue, comprising the following steps:

(A) isolating a region of intravenous fluid in an intravenous line from effects of pressure in the line outside of the region;

(B) housing a measurement gas in communication with the region such that changes in volume of the fluid in the region cause a proportionate change in the pressure of the measurement gas;

(C) measuring the pressure of the measurement gas before and after the volume of the gas is changed by a predetermined amount while the volume of intravenous fluid in the region remains substantially constant;

(D) inputting and outputting liquid into and out of the region based on the data obtained in step (C) and on measurement of the pressure of the measurement gas while liquid is being inputted and outputted into and out of the region;

(E) causing an alarm state to be entered into if there is detected a substantial delay in change of pressure of the measurement gas in response to actuated input or output of intravenous fluid, such delay being characteristic of occlusion in the intravenous line or infiltration of surrounding tissue by the intravenous needle.

31. A method for measuring first fluid output along a line, comprising the following steps:

(A) isolating a region of the fluid in the line from effects of pressure in the line outside of the region;

(B) housing a measurement fluid in communication with the region such that input and output of first fluid into and out of the region cause a change in the pressure of the measurement fluid;

(C) displacing a predetermined volume increment of measurement fluid;

(D) measuring the pressure of the measurement fluid; and

(E) calculating the volume of first fluid output along the line based on data obtained from the measurement of the pressure of the measurement fluid when a predetermined increment of measurement fluid is displaced and during movement of first fluid into and out of the region, such that the predetermined increment of measurement fluid displaced serves as a reference for the amount of first fluid outputted.