PRESSURE MEASURING SYRINGE

• US 20100179488A1
• Filed: 01/15/2010
• Published: 07/15/2010
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: BETH Israel Deaconess Medical Center (Caregroup Incorporated), Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Slocum, Alexander H., Spiegel, Joan E.
• Granted Patent: US 8,291,768 B2
• Time in Patent Office: Days
• US Class Current: 604/240
• CPC Class Codes: A61M 16/044 External cuff pressure control or supply, e.g. synchronisation with respiration
• CPC Class Codes: A61M 25/10182 Injector syringes
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

A syringe having an internal pressure gauge comprises a syringe barrel; a piston within the barrel; a spring coupled to the piston at a first position of the spring, the spring having a second portion that is movable in response to fluid pressure within a syringe cavity; and a pressure gauge having an indicator correlated to a plurality of positions of the second portion of the spring to indicate a pressure of a fluid. The spring can be a bellows. The first portion of the spring can be coupled to the piston to form a sliding seal with an inner wall of the syringe, and the second portion of the spring can move longitudinally within the syringe without sealing contact. The syringe can indicate fluid pressures within a range of at least about 5 to 35 cm H₂O, for example. The fluid chamber can be in fluid communication with a cuff of an inflatable medical device, such as an endotracheal tube, such that the measured pressure comprises the fluid pressure within the cuff. Methods of measuring pressure using a syringe are also disclosed.

Claims

1. A pressure measuring syringe comprising:

a syringe barrel;

a plunger within the barrel;

a spring coupled to the plunger at a first portion of the spring, the spring having a second portion that is movable in response to fluid pressure within a syringe cavity;

a pressure indicator correlated to a plurality of positions of the second portion of the spring to indicate a fluid pressure.

2. The syringe of claim 1 wherein the second portion of the spring moves longitudinally within the plunger without sealing contact against an inner wall of the plunger.

3. The syringe of claim 1 wherein first portion of the spring is coupled to the plunger to form a sliding seal with an inner wall of the syringe barrel.

4. The syringe of claim 1 wherein the spring comprises a bellows.

5. The syringe of claim 1 wherein the pressure indicator comprises a plurality of at least three pressure levels of a fluid including at least a first level indicating under-inflation and at least a second level indicating over-inflation.

6. The syringe of claim 1 wherein the plunger has a distal end and a proximal end, the first portion of the spring being mounted to the distal end of the plunger.

7. The syringe of claim 1 wherein the spring has a distal end and a proximal end.

8. The syringe of claim 7 wherein the distal end of the spring comprises the first portion and the proximal end of the spring comprises the second portion.

9. The syringe of claim 8 wherein the proximal end of the spring has a visual indicator element that moves longitudinally relative to the piston to indicate fluid pressure.

10. The syringe of claim 1 wherein the fluid comprises a gas.

11. The syringe of claim 1 wherein the fluid comprises a liquid.

12. The syringe of claim 1 wherein the syringe is coupled to an endotracheal cuff to measure gas pressure in the cuff.

13. The syringe of claim 3 wherein the sliding seal comprises an o-ring.

14. The syringe of claim 1 wherein the spring comprises a coiled spring and/or flexible diaphragm.

15. The syringe of claim 1 wherein the syringe has a plurality of markers indicating a pressure range of at least 5 cm H₂O to 35 cm H₂O.

16. The syringe of claim 1 wherein the plunger comprises a tubular body having an internal cavity in which the spring is positioned, the plunger having a distal opening to provide fluid coupling between that spring and a distal cavity of the syringe.

17. The syringe of claim 1 wherein a distal end of the spring is mechanically coupled to a distal end of the plunger.

18. The syringe of claim 1 wherein the syringe is coupled to a needle for injection of a liquid, such as saline, into a mammalian body.

19. The syringe of claim 1 wherein the syringe is coupled to a pediatric endotracheal tube.

29. The syringe of claim 5 further comprising an indicator on a proximal end of the bellows.

20. An endotracheal cuff pressure measuring syringe comprising:

a barrel having an aperture at a tip end and an opening at an opposed end;

a plunger arranged within the barrel and forming a seal against an internal wall of the barrel to define a fluid chamber proximate the plunger;

a bellows arranged within the plunger, the bellows mounted at a first end to the plunger and moveable at a second end to indicate a pressure within the fluid chamber; and

visual indicia that indicate the pressure within the fluid chamber based on a position of the bellows.

21. The syringe of claim 20 wherein plunger includes visual indicia indicate a high pressure limit and low-pressure limit within a range of 5 to 35 cm H₂O.

22. The syringe of claim 20 wherein the visual indicia indicate pressures within a range of 10 to 30 cm H₂O.

23. The syringe of claim 20 wherein the visual indicia are located on an outer wall surface of the plunger.

24. The syringe of claim 20 wherein the piston and the bellows move relative to one another in a telescoping manner.

25. The syringe of claim 23 wherein the bellows includes an internal cavity in fluid communication with the fluid chamber.

26. The syringe of claim 20 wherein the visual indicia comprise markings on the plunger that are visible as the plunger slides axially inside the syringe.

27. The syringe of claim 26 wherein the markings comprise graduated markings indicative of the fluid pressure in the chamber.

28. The syringe of claim 26 wherein the markings comprise variations in the coloration on the plunger.

30. The syringe of claim 20 wherein the bellows has a wall thickness in a range of 0.1 to 1 mm.

31. The syringe of claim 20 wherein the visual indicia comprise a numeric pressure value.

32. The syringe of claim 20 wherein the bellows has a proximal end indicating either underpressure or overpressure in the cuff.

33. The syringe of claim 20 wherein the fluid chamber is in fluid communication with a cuff of an endotracheal tube, and the measured pressure comprises the pressure within the cuff.

34. The syringe of claim 27 wherein the markings include spaced apart markings indicating increments of pressure in a range of 1 to 5 cm H₂O.

35. A method of measuring the pressure within a cuff of an endotracheal tube comprising:

coupling a syringe to the cuff, the syringe comprising a barrel having an aperture at a tip end the syringe having a plunger arranged within the barrel and forming a seal against an internal wall of the barrel to define a fluid chamber proximate the plunger, a spring positioned within the plunger and axially movable relative to the plunger, the spring mounted at a first end to the plunger such that the axial movement of a second end of the spring is indicative of a pressure within the fluid chamber;

actuating the syringe by depressing the plunger relative to the barrel; and

measuring a gas pressure inside the cuff.

36. The method of claim 35 further comprising viewing visual indicia that indicate the pressure within the fluid chamber based on the position of the spring, the visual indicia indicating pressures within a range of approximately 5 to 35 cm H₂O

37. The method of claim 36 wherein the visual indicia further indicates pressure in a range of 10 to 30 cm H₂O.

38. The method of claim 35 wherein the step of measuring the pressure further comprises displacing a spring such as a bellows or diaphragm.

39. The method of claim 35 wherein the second end of the spring is mechanically decoupled from the wall of the plunger.

40. The method of claim 35 further comprising releasing manual pressure on the plunger and monitoring fluid pressure in the cuff.

41. The method of claim 38 further comprising observing a position of an indicator element positioned on a proximal end of the bellows in relation to visual indicia on the plunger.

42. The method of claim 35 further comprising measuring under-inflation or over-inflation of the cuff.

43. The method of claim 35 wherein the actuating step further comprises inflating the cuff with the syringe.

44. The method of claim 43 wherein the step of inflating the cuff comprises manually pushing the plunger into the syringe barrel the plunger having a seal against an inner wall of the barrel that slides in a distal direction.

45. A method of fabricating a pressure measuring syringe comprising:

forming a syringe barrel;

forming a plunger;

forming a spring;

inserting the spring into the plunger, the spring being coupled at a first portion to the plunger, the spring having an uncoupled second portion that is longitudinally moveable relative to the plunger;

inserting the plunger and spring into the syringe barrel to form a seal.

46. The method of claim 45 wherein the spring comprises a molded bellows.

47. The method of claim 45 wherein the syringe barrel, plunger, and spring are non-metallic.

48. The method of claim 45 further comprising forming markings on the plunger to indicate pressure level.

49. The method of claim 45 wherein the plunger comprises a piston at a distal end, a cap at the proximal end and an air vent.

50. The method of claim 45 wherein the syringe has a displaceable volume in a range of 2 to 20 cc.