Carbon dioxide indicator

• US 5,124,129 A
• Filed: 01/29/1990
• Issued: 06/23/1992
• Est. Priority Date: 07/29/1988
• Status: Expired due to Fees

• Current Assignee: Mallinckrodt Medical Inc. (Mallinckrodt plc)
• Original Assignee: Mallinckrodt Medical Inc. (Mallinckrodt plc)
• Inventors: Goodman, John F., Dunski, Neil, Riccitelli, Samuel D.
• Primary Examiner(s): Johnston, Jill A.
• Assistant Examiner(s): Alexander, Lyle A.
• Application Number:
  US07/471,065
• Time in Patent Office: 876 Days
• Field of Search: 422/56-60, 436/68, 436/133, 436/163, 436/169, 436/170, 128/719, 128/207.14
• US Class Current: 422/416
• CPC Class Codes: A61M 16/0488 Mouthpieces; Means for guiding, securing or introducing the tubes guiding or introducing with laryngoscopes A61B1/267; holding devices on the body A61M25/02
• CPC Class Codes: A61M 2016/0413 with detectors of CO2 in exhaled gases
• CPC Class Codes: G01N 31/221 for investigating pH value
• CPC Class Codes: G01N 33/84 involving inorganic compounds or pH
• CPC Class Codes: Y10T 436/204998 Inorganic carbon compounds

Abstract

A carbon dioxide indicator for use in determining the proper placement of endotracheal tubes. The indicator is comprised of a pH-sensitive dye suspended in a predominantly hydrophilic polymer matrix. The indicator may be placed inside a tube or connector to form an indicator device. When the pH-sensitive dye changes color due to CO₂ and moisture in exhaled air, the color change is visible from outside the device.

Claims

1. A carbon dioxide indicator comprising a predominantly hydrophilic polymer matrix selected from the group consisting of alkyl methacrylate, alkyl halide quaternary salt of an alkyl methacrylate, copolymer of an alkyl halide quaternary salt of an alkyl methacrylate, polyurethane, polyvinylpyrrolidone, copolymer of polyvinylpyrrolidone, polyethylene oxide derivatives, copolymers of polyethylene oxide derivatives, polypropylene oxide derivatives, copolymers of polypropylene oxide derivatives, corn starch derivatives, copolymers of corn starch derivatives and any of the above polymers which have been crosslinked, and a pH-sensitive dye which indicates the presence of carbon dioxide comprising o-cresolpthalein or salt thereof present in said matrix, wherein said indicator is in a sufficient amount that it does not change color for at least 15 minutes when said indicator is exposed to normal ambient air, but does change color when said indicator is exposed to exhaled air, a color change in response to exposure to exhaled air being at least about 50 times more rapid than would occur with exposure of the indicator to normal ambient air alone.

2. The indicator of claim 1 wherein said polymer matrix is a polyurethane foam.

3. The indicator of claim 1 wherein said pH-sensitive dye is an o-cresolphthalein complexon sodium salt.

4. The indicator of claim 1 wherein said polymer matrix further comprises a solid desiccant.

5. The indicator of claim 1 wherein said indicator changes color upon exposure to two or less exhaled breaths of a patient.

6. The indicator of claim 1 wherein said indicator further comprises a heat-moisture exchanger in said matrix.

7. The indicator of claim 1 wherein said matrix further comprises less than about 30% by weight of a hydrophobic monomer.

8. The indicator of claim 1 wherein said matrix further comprises less than about 20% by weight of a hydrophobic monomer.

9. The indicator of claim 1 wherein said matrix further comprises less than about 10% by weight of a hydrophobic monomer.

10. The indicator of claim 1 wherein said matrix further comprises less than about 5% by weight of a hydrophobic monomer.

11. The indicator of claim 1 further including at least one basic salt present in said matrix.

12. The indicator of claim 11 where said basic salt is sodium hydroxide, potassium phosphate, trisodium phosphate or potassium hydroxide.

13. The indicator of claim 1 wherein said color change occurs in less than about five seconds of exposure to exhaled air.

14. The indicator of claim 13 wherein exhaled air has a carbon dioxide concentration of at least about 15 mm of Hg.

15. The indicator of claim 1 wherein said polymer matrix is UV cured and said matrix further comprises:

a UV-curable methyl chloride quaternary salt of at least one methacrylate;

a cross-linking agent; and

a photoindicator.

16. The indicator of claim 15 wherein said at least one methacrylate is a dimethylaminoethyl methacrylate.

17. The indicator of claim 16 wherein said methyl chloride quaternary salt of dimethylaminoethyl methacrylate is at least 70% of said matrix and lauryl methacrylate comprises no more than 30% of the matrix.

18. The indicator of claim 1 wherein said hydrophilic polymer matrix comprises a hydrogel.

19. The indicator of claim 18 wherein said hydrogel comprises the methyl chloride quaternary salt of dimethylaminoethyl methacrylate.

20. The indicator of claim 18 wherein said polymer matrix further comprises a polyurethane foam.

21. The indicator of claim 1 wherein said matrix is an alkyl methacrylate in which the alkyl portion contains from 1 to about 12 carbon atoms.

22. The indicator of claim 21 wherein said alkyl methacrylate further comprises a hydrophobic portion of said matrix.

23. The indicator of claim 22 wherein the ratio of hydrophilic to hydrophobic portions of said matrix is about 2:

1 by weight.

24. The indicator of claim 22 wherein said hydrophilic portion is comprised of an alkyl halide quaternary salt of an alkyl methacrylate.

25. The indicator of claim 22 wherein said pH-sensitive dye comprises o-cresolphthalein complexon sodium salt.

26. The indicator of claim 25 further including at least one basic salt present in said matrix.

27. The indicator of claim 26 wherein said at least one basic salt is sodium hydroxide, potassium phosphate, trisodium phosphate or potassium hydroxide.

28. The indicator of claim 27 wherein said basic salt is sodium hydroxide.

29. The indicator of claim 22 wherein said hydrophilic portion is comprised of a methyl chloride quaternary salt of dimethylaminoethyl methacrylate.

30. The indicator of claim 29 wherein the ratio of hydrophilic to hydrophobic portions of said matrix is about 2:

1 by weight.

31. The indicator of claim 30 wherein the alkyl portion of the hydrophobic alkyl methacrylate contains from 1 to about 8 carbon atoms.

32. The indicator of claim 30 wherein the alkyl portion of the hydrophobic alkyl methacrylate contains from 1 to about 4 carbon atoms.

33. The indicator of claim 30 wherein the hydrophobic alkyl methacrylate comprises ethyl methacrylate.

34. The indicator of claim 33 wherein the hydrophobic alkyl methacrylate further comprises lauryl methacrylate.

35. The indicator of claim 30 wherein the hydrophobic alkyl methacrylate is a methyl methacrylate.

36. The indicator of claim 35 wherein the hydrophobic alkyl methacrylate further comprises lauryl methacrylate.

37. A carbon dioxide indicator device comprising an indicator housing, and an indicator within the housing, said indicator comprising a predominantly hydrophilic polymer matrix selected from the group consisting of alkyl methacrylate, alkyl halide quaternary salt of an alkyl methacrylate, copolymer of an alkyl halide quaternary salt of an alkyl methacrylate, polyurethane, polyvinylpyrrolidone, copolymer of polyvinylpyrrolidone, polyethylene oxide derivatives, copolymers of polyethylene oxide derivatives, polypropylene oxide derivatives, copolymers of polypropylene oxide derivatives, corn starch derivatives, copolymers of corn starch derivatives and any of the above polymers which have been crosslinked, and a pH-sensitive dye which indicates the presence of carbon dioxide comprising o-cresolpthalein or salt thereof present in said matrix, wherein said indicator is in a sufficient amount that it does not change color for at least 15 minutes when said indicator is exposed to normal ambient air, but does change color when said indicator is exposed to exhaled air, a color change in response to exposure to exhaled air being at least about 50 times more rapid than would occur with exposure of the indicator to normal ambient air alone.

38. The device of claim 37 wherein said polymer matrix is a polyurethane foam.

39. The device of claim 37 wherein said pH-sensitive dye is an o-cresolphthalein complexon sodium salt.

40. The device of claim 37 wherein said indicator housing is part of an endotracheal tube circuit.

41. The device of claim 37 wherein said indicator housing is an endotracheal tube.

42. The device of claim 37 wherein said polymer matrix further comprises a solid desiccant.

43. The device of claim 37 wherein said indicator housing further is a connector having at least one end capable of being connected to an endotracheal tube.

44. The device of claim 37 wherein said indicator changes color upon exposure to two or less exhaled breaths of a patient.

45. The device of claim 37 wherein said housing has an interior surface and said indicator is applied to the interior surface of said housing.

46. The device of claim 37 wherein said matrix further comprises less than about 30% by weight of a hydrophobic monomer.

47. The device of claim 37 wherein said matrix further comprises less than about 20% by weight of a hydrophobic monomer.

48. The device of claim 37 wherein said matrix further comprises less than about 10% by weight of a hydrophobic monomer.

49. The device of claim 37 wherein said matrix further comprises less than about 5% by weight of a hydrophobic monomer.

50. The device of claim 37 wherein said indicator further includes at least one basic salt present in said housing.

51. The device of claim 50 wherein said basic salt is sodium hydroxide, potassium phosphate, trisodium phosphate or potassium hydroxide.

52. The device of claim 37 wherein said color change occurs in less than about five seconds of exposure to exhaled air.

53. The device of claim 52 wherein said exhaled air has a carbon dioxide concentration of at least about 15 mm of Hg.

54. The device of claim 37 wherein said polymer matrix is UV-cured and said matrix further comprises:

a UV-curable methyl chloride quaternary salt of at least one methacrylate;

a cross-linking agent; and

a photoinitiator.

55. The device of claim 54 wherein said at least one methacrylate is a dimethylaminoethyl methacrylate.

56. The device of claim 55 wherein the methyl chloride quaternary salt of dimethylaminoethyl methacrylate is at least 70% of said matrix and lauryl methacry-late comprises no more than 30% of the matrix.

57. The device of claim 37 wherein said hydrophilic polymer matrix comprises a hydrogel.

58. The device of claim 37 wherein said hydrogel comprises methyl chloride quaternary salt of dimethyl methacrylate.

59. The device of claim 58 wherein said polymer matrix further comprises a polyurethane foam.