AUTOMATED METHOD FOR SIMULTANEOUS BUBBLE DETECTION AND EXPULSION

• US 20150122338A1
• Filed: 10/30/2014
• Published: 05/07/2015
• Est. Priority Date: 11/01/2013
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Hunter, Ian W., Modak, Ashin P.
• Granted Patent: US 9,486,589 B2
• Time in Patent Office: Days
• US Class Current: 137/2
• CPC Class Codes: A61M 2005/1402 Priming
• CPC Class Codes: A61M 2005/3123 having air entrapping or venting means, e.g. purging channels in pistons
• CPC Class Codes: A61M 2205/332 Force measuring means
• CPC Class Codes: A61M 5/16859 Evaluation of pressure response, e.g. to an applied pulse
• CPC Class Codes: A61M 5/3146 Priming, e.g. purging, reducing backlash or clearance
• CPC Class Codes: A61M 5/36 with means for eliminating or preventing injection or infusion of air into body dialysis systems, blood oxygenators A61M1/14; haemofiltration equipment A61M1/34; automatic tube cut-off A61M39/281
• CPC Class Codes: G01B 21/16 for measuring distance of clearance between spaced objects
• CPC Class Codes: G01F 17/00 Methods or apparatus for determining the capacity of containers or cavities, or the volume of solid bodies measuring linear dimensions to determine volume G01B
• CPC Class Codes: G01P 3/02 Devices characterised by the use of mechanical means
• CPC Class Codes: Y10T 137/0324 With control of flow by a condition or characteristic of a fluid
• CPC Class Codes: Y10T 137/2931 Diverse fluid containing pressure systems

Abstract

A method and apparatus for detecting and removing air from a syringe containing a volume of liquid and a volume of gas is described. The method includes moving a piston in the syringe to expel gas through an orifice of the syringe, sensing a movement of the piston in the syringe, and determining when the volume of gas is expelled from the syringe based on a change in the sensed movement. Moving the piston may include applying oscillating force to the piston using an electromagnetic actuator, and displacement and speed of the piston during each oscillation may be sensed. Determining when the volume of gas is expelled may be based on a change in the sensed movement of the piston during one or more oscillations of the piston or based on a comparison to a given reference value.

Claims

1. A method of detecting and removing air from a syringe containing a volume of liquid and a volume of gas, the method comprising:

moving a piston in the syringe to expel gas through an orifice of the syringe;

sensing movement of the piston in the syringe; and

determining when the volume of gas is expelled from the syringe based on a change in the sensed movement.

2. The method of claim 1, wherein moving the piston includes applying oscillating force to the piston using an actuator, and wherein sensing movement of the piston includes sensing oscillating movement of the piston in the syringe.

3. The method of claim 2, wherein applying the oscillating force to the piston further includes applying at least one of the following in alternation to the piston:

a positive and a negative force, a positive and a zero force, and a first positive force and a second positive force, and wherein determining when the volume of gas is expelled from the syringe is based a change in the sensed oscillating movement of the piston during one or more oscillation or based on a comparison to a given reference value.

4. The method of claim 3, wherein sensing the oscillating movement of the piston includes sensing a displacement of the piston, and wherein determining when the volume of gas is expelled from the syringe is based on a change in the sensed displacement of the piston.

5. The method of claim 4, wherein sensing the displacement of the piston includes sensing a forward displacement of the piston for each oscillation, and wherein determining when the volume of gas is expelled from the syringe is based on the sensed forward displacement of the piston.

6. The method of claim 4, wherein sensing the displacement of the piston includes sensing a backwards displacement of the piston for each oscillation, and wherein determining when the volume of gas is expelled from the syringe is based the sensed backwards displacement of the piston.

7. The method of claim 3, wherein sensing the oscillating movement of the piston includes sensing a speed of the piston, and wherein determining when the volume of gas is expelled from the syringe is based on a change in the sensed speed of the piston.

8. The method of claim 7, wherein sensing the speed of the piston includes sensing a forward speed of the piston during each oscillation, and wherein determining when the volume of gas is expelled from the syringe is based on the sensed forward speed of the piston.

9. The method of claim 8, wherein sensing the speed of the piston includes sensing a backwards speed of the piston during each oscillation, and wherein determining when the volume of gas is expelled from the syringe is based on the sensed backwards speed of the piston.

10. The method of claim 2, wherein the volume of liquid further includes a plurality of bubbles, the oscillating force applied by the actuator aggregating at least a portion of the plurality of bubbles into the volume of gas.

11. The method of claim 1, further including stopping movement of the piston upon determining that the volume of gas is expelled from the orifice.

12. The method of claim 1, wherein sensing the movement of the piston further includes sensing a forward speed of the piston, and wherein determining when the volume of gas is expelled from the syringe is based a sensed decrease in the forward speed of the piston.

13. The method of claim 1, wherein determining that the volume of gas is expelled from the orifice includes determining that at least a portion of the volume of liquid is expelled through the orifice.

14. The method of claim 1, wherein moving the piston in the syringe further includes controlling a force applied by an electromagnetic actuator to the piston as a function of the sensed movement of the piston.

15. An apparatus for detecting and removing air from a syringe, the apparatus comprising:

a syringe including a piston and an orifice, the syringe having a volume of liquid and a volume of gas disposed in the syringe between the piston and the orifice, the volume of gas being adjacent to the orifice;

a position sensor adapted to sense movement of the piston in the syringe;

an actuator adapted to move the piston in the syringe; and

a controller responsive to the position sensor, the controller causing the actuator to move the piston and drive the one or more bubbles through the orifice, the controller determining when the volume of gas is expelled from the syringe as a function of a change in the sensed movement of the piston.

16. The apparatus of claim 15, wherein the actuator is configured to apply an oscillating force to the piston, and wherein the position sensor is further adapted to sense oscillating movement of the piston.

17. The apparatus of claim 16, wherein the actuator is a bi-directional Lorentz-force electromagnetic actuator.

18. The apparatus of claim 16, wherein the oscillating force applied to the piston by the actuator includes at least one of the following:

a positive force and a negative force, a positive and a zero force, and a first positive force and a second positive force, and wherein the controller determines when the volume of gas is expelled as a function of a change in the sensed oscillating movement during one or more oscillations of the piston or a as a function of the sensed oscillating movement as compared to a reference value.

19. The apparatus of claim 18, wherein the position sensor is further adapted to sense displacement of the piston, and wherein the controller determining when the volume of gas is expelled from the syringe is a function of the sensed displacement.

20. The apparatus of claim 19, wherein the position sensor is further adapted to sense forward displacement of the piston for each oscillation, and wherein the controller determines when the volume of gas is expelled as a function of the sensed forward displacement.

21. The apparatus of claim 19, wherein the position sensor is further adapted to sense backwards displacement of the piston for each oscillation, and wherein the controller determines when the volume of gas is expelled as a function of the sensed backwards displacement.

22. The apparatus of claim 18, wherein the position sensor is further adapted to sense speed of the piston, and wherein the controller determining when the volume of gas is expelled from the syringe is a function of the sensed speed.

23. The apparatus of claim 22, wherein the position sensor is further adapted to sense forward speed of the piston during each oscillation, and wherein the controller determines when the volume of gas is expelled as a function of the sensed forward speed.

24. The apparatus of claim 22, wherein the position sensor is further adapted to sense backwards speed of the piston during each oscillation, and wherein the controller determines when the volume of gas is expelled as a function of the sensed backwards speed.

25. The apparatus of claim 16, wherein the volume of liquid further includes a plurality of bubbles, the oscillating force applied by the actuator aggregates at least a portion of the plurality of bubbles into the volume of gas.

26. The apparatus of claim 15, wherein the controller is further configured to stop movement of the piston upon the determination that the volume of gas is expelled from the orifice.

27. The apparatus of claim 15, wherein the position sensor is adapted to sense a forward speed of the piston, and wherein determining when the volume of gas is expelled from the syringe is a function of a decrease in the sensed forward speed of the piston.

28. The apparatus of claim 15, wherein the controller is further configured to stop movement of the piston upon the determination that at least a portion of the volume of liquid is expelled through the orifice.

29. The apparatus of claim 15, wherein the controller if further configured to modulate a force applied by the actuator to move the piston as a function of the movement of the piston.