Electrical heater with particular application to humidification and fluid warming

1. A respiratory humidifier adapted to humidify a flow of breathable gas to a patient's airway, the breathable gas being pressurized relative to atmosphere, the humidifier comprising:

a tub configured to contain a supply of water;

a gas inlet configured to receive the flow of pressurized breathable gas into the tub;

a gas outlet configured to deliver the humidified flow of pressurized breathable gas from the tub to the patient's airways by way of a gas conduit; and

a heater comprising a first polymer film having an electrically conductive circuit provided upon a surface, wherein the first polymer film is electrically insulating and the tub is formed of molded resin and the heater is molded at least partially within the resin.

2. A respiratory humidifier according to claim 1 , wherein the electrically conductive circuit comprises at least one of electrically conductive ink, a second polymer film, and a conductive or resistive material that is overmolded on the heater element.

3. A respiratory humidifier according to claim 1 , wherein the first polymer film is a thermoplastic or thermoset polymer.

4. A respiratory humidifier according to claim 3 , wherein the first polymer film is polyester, polyimide, polycarbonate, or polypropylene.

5. A respiratory humidifier according to claim 1 , wherein the first polymer film has a thickness of about 0.01 mm-1 mm.

6. A respiratory humidifier according to claim 1 , wherein the molded resin is polycarbonate, polycarbonate ABS blends, polyethylene, or polypropylene.

7. A respiratory humidifier according to claim 1 , wherein the resin is injection molded.

8. A respiratory humidifier according to claim 1 , wherein the resin is extrusion molded.

9. A respiratory humidifier according to claim 2 , wherein the layer of electrically conductive ink is about 5 μm-40 μm thick.

10. A respiratory humidifier according to claim 2 , wherein the layer of electrically conductive ink is screen printed on the first polymer film.

11. A respiratory humidifier according to claim 2 , wherein the layer of electrically conductive ink is etched on the first polymer film.

12. A respiratory humidifier according to claim 2 , wherein the layer of electrically conductive ink is carbon ink, silver ink, or a combination thereof.

13. A respiratory humidifier according to claim 1 , wherein the circuit comprises a single continuous pattern.

14. A respiratory humidifier according to claim 1 , wherein the single continuous pattern comprises a spiral or helix.

15. A respiratory humidifier according to claim 1 , wherein the circuit comprises a plurality of parallel bands linked by at least one band perpendicular to the parallel bands.

16. A respiratory humidifier according to claim 15 , wherein the parallel bands are carbon ink and the at least one perpendicular band is silver ink or a metal.

17. A respiratory humidifier according to claim 1 , wherein the circuit is configured to provide a predetermined resistance.

18. A respiratory humidifier according to claim 2 , further comprising a layer of protective ink over the layer of electrically conductive ink.

19. A respiratory humidifier according to claim 2 , further comprising a metal layer over the layer of electrically conductive ink.

20. A respiratory humidifier according to claim 19 , wherein the metal layer comprises copper, gold, nickel, chrome, or any other electrically conductive metal or alloy.

21. A respiratory humidifier according to claim 19 , further comprising a second polymer film over the metal layer.

22. A respiratory humidifier according to claim 21 , wherein the second polymer film is laminated.

23. A respiratory humidifier according to claim 2 , wherein the second polymer film is positioned over the layer of electrically conductive ink.

24. A respiratory humidifier according to claim 1 , wherein the tub comprises an upper portion and a lower portion, and the upper portion is removable from the lower portion.

25. A respiratory humidifier according to claim 24 , wherein the upper portion comprises an inlet and an outlet for a flow of breathable gas.

26. A respiratory humidifier according to claim 24 , wherein the heater is in the upper portion.

27. A respiratory humidifier according to claim 24 , wherein the heater is in the lower portion.

28. A respiratory humidifier according to claim 1 , wherein the heater is provided below a maximum water fill line of the tub.

29. A respiratory humidifier according to claim 1 , wherein the tub comprises a base and the heater is at least partially molded into an exterior surface of the base.

30. A respiratory humidifier according to claim 29 , further comprising a base cover attached to the base.

31. A respiratory humidifier according to claim 30 , wherein the base cover is sealingly attached to the base.

32. A respiratory humidifier according to claim 30 , wherein a cavity is formed between the base and the base cover.

33. A respiratory humidifier according to claim 32 , wherein the cavity is filled with insulating material.

34. A respiratory humidifier according to claim 29 , wherein the base is an open base.

35. A respiratory humidifier according to claim 1 , further comprising an electrical connector configured to connect the heater to a power supply.

36. A respiratory humidifier according to claim 35 , wherein the electrical connector comprises an exposed portion of the circuit configured to contact an electrical contact of the power supply.

37. A respiratory humidifier according to claim 35 , wherein the electrical connector comprises a wire connected to the circuit and molded partially in the resin.

38. A respiratory humidifier according to claim 37 , wherein the wire is connected to the circuit by a fastening electrical connection, such as crimping or terminal blocks.

39. A respiratory humidifier according to claim 37 , wherein the wire is fastened to the circuit by a mechanical contact connector, for example a plug and socket type connector, such as a spade or bullet connector.

40. A respiratory humidifier according to claim 35 , wherein the electrical connector comprises a conductive material in contact with the circuit and molded partially in the resin.

41. A respiratory humidifier according to claim 40 , wherein the conductive material is a metal contact.

42. A respiratory humidifier according to claim 35 , wherein the electrical connector comprises a pin-like element extending through the molded resin and the heater so as to be in contact with a layer of electrically conductive ink.

43. A respiratory humidifier according to claim 42 , wherein the pin-like element comprises a head on an interior surface of the tub.

44. A respiratory humidifier according to claim 43 , further comprising a seal between the head of the pin-like element and the interior surface.

45. A respiratory humidifier according to claim 42 , further comprising a securement unit connected to a pin portion of the pin-like element, wherein the securement unit comprises an electrically conductive interface in contact with the layer of electrically conductive ink.

46. A respiratory humidifier according to claim 35 , wherein the power supply is provided in a base or stand unit.

47. A respiratory humidifier according to claim 1 , wherein at least a portion of the heater is exposed on an interior surface of the tub.

48. A respiratory humidifier according to claim 1 , wherein at least a portion of the heater is exposed on an exterior surface of the tub.

49. A respiratory humidifier according to claim 1 , wherein at least a portion of the heater is through a wall of the tub.

50. A respiratory humidifier according to claim 1 , wherein the heater comprises a temperature sensor.

51. A respiratory humidifier according to claim 50 , wherein the temperature sensor comprises a thermocouple.

52. A respiratory humidifier according to claim 50 , wherein the temperature sensor comprises a positive thermal coefficient or a negative thermal coefficient thermistor.

53. A respiratory humidifier according to claim 1 , wherein the heater comprises a thermal fuse.

54. A respiratory humidifier according to claim 1 , wherein the heater comprises a humidity sensor.

55. A respiratory humidifier according to claim 1 , wherein the heater comprises a switching control element.

56. A respiratory humidifier according to claim 1 , wherein the heater comprises a water level sensor.

57. A respiratory humidifier according to claim 56 , wherein the water level sensor comprises a cathodic probe.

58. A respiratory humidifier according to claim 56 , wherein the water level sensor comprises a thermal gradient.

59. A respiratory humidifier according to claim 1 , wherein the heater comprises zones.

60. A respiratory humidifier according to claim 59 , wherein some of the zones are configured to heat water contained in the tub and some of the zones are configured to heat air in the tub.

61. A respiratory humidifier according to claim 59 , wherein each zone comprises a temperature sensor, a humidity sensor, a water level sensor, a thermal fuse, and/or a switching control element.

62. A respiratory humidifier according to claim 61 , wherein the heater is configured to heat only a zone corresponding to a surface of water contained in the tub.

63. A respiratory humidifier according to claim 2 , wherein the overmolded material is configured to isolate portions of the electrically conductive ink and/or the second polymer film such that at a first water level a conductive path is formed between at least some of the isolated portions and at a second water level no conductive path is provided between any of the isolated portions.

64. A respiratory humidifier according to claim 2 , wherein the overmolded material includes at least one portion configured to support at least one of a temperature sensor, a fuse or a second heater, such that at a first water level the temperature sensor, the fuse, and/or the second heater is covered by the water and at a second water level the temperature sensor, the fuse, and/or the second heater are not covered by the water.

65. A respiratory humidifier according to claim 5 , wherein the first polymer film has a thickness of about 0.05 mm-0.5 mm.

66. A respiratory humidifier according to claim 9 , wherein the layer of electrically conductive ink is about 10 μm-25 μm thick.

67. A respiratory apparatus for delivering a flow of breathable gas to a patient comprising a humidifier according to claim 1 .

68. A respiratory humidifier according to claim 1 , further comprising a water level indicator.

69. A respiratory humidifier according to claim 68 , wherein the water level indicator comprises material overmolded over the heater, the material comprising at least one mound projecting away from the heater.

70. A respiratory humidifier according to claim 69 , wherein the at least one mound comprises at least one of a mound heater, a thermistor, a temperature sensor and a thermal fuse.

71. A respiratory humidifier according to claim 70 , wherein the mound heater is one of a printed ink film heater and a stamped film heater.

72. A respiratory humidifier according to claim 70 , wherein the mound heater is electrically conductive when a water level in the tub is above the mound and electrically non-conductive when the water level in the tub is below the mound.

73. A respiratory humidifier according to claim 1 , wherein the molded resin includes a cavity defined by a continuous surface of the molded resin,

the cavity is shaped by the heater and

the heater is at least partially retained within the cavity.

74. A respiratory humidifier according to claim 1 , wherein the conductive ink is positioned between the first polymer film and an adjacent portion of the molded resin.

75. A respiratory humidifier according to claim 1 , wherein the heater forms a laminated structure with the resin, and at least one major face of the heater is fully covered by the resin.

76. A respiratory apparatus according to claim 67 further comprising:

a flow generator in communication with the humidifier;

a patient interface configured to engage a patient; and

an air delivery tube for directing pressurized gas from the humidifier and the flow generator to the patient interface.

77. A method of humidifying a flow of breathable gas to a patient interface engaging a patient's face, the breathable gas being pressurized relative to atmosphere, the method comprising:

receiving the flow of pressurized breathable gas from a respiratory device;

passing the flow of pressurized breathable gas over a supply of water contained in a tub, wherein the tub is formed of molded resin and a heater comprising a first polymer film having an electrically conductive circuit on a first surface is molded at least partially within the resin; and

delivering the humidified flow of pressurized breathable gas to the patient interface.