HUMIDITY CONTROLLER

• US 20090065002A1
• Filed: 11/19/2008
• Published: 03/12/2009
• Est. Priority Date: 06/17/1997
• Status: Active Grant

• Current Assignee: Fisher & Paykel Healthcare Limited
• Original Assignee: Fisher & Paykel Healthcare Limited
• Inventors: McPHEE, STEPHEN WILLIAM, WIXEY, DAVID, HUNT, PETER JOHN, THUDOR, MOHAMMAD
• Granted Patent: US 7,962,018 B2
• Time in Patent Office: Days
• US Class Current: 128/203.170
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/024 including calculation means, e.g. using a processor
• CPC Class Codes: A61M 16/0875 Connecting tubes
• CPC Class Codes: A61M 16/1075 by influencing the temperature A61M16/1045 takes precedence
• CPC Class Codes: A61M 16/1085 after being humidified or mixed with a beneficial agent
• CPC Class Codes: A61M 16/109 the humidifying liquid or the beneficial agent
• CPC Class Codes: A61M 16/1095 in the connecting tubes
• CPC Class Codes: A61M 16/16 Devices to humidify the respiration air A61M16/1045 takes precedence
• CPC Class Codes: A61M 16/161 with means for measuring the humidity
• CPC Class Codes: A61M 16/162 Water-reservoir filling system, e.g. automatic
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/18 with alarm
• CPC Class Codes: A61M 2205/33 Controlling, regulating or measuring
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: A61M 2205/3653 by Joule effect, i.e. electric resistance
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 1/6888 Thermoelectric elements, e.g. thermocouples, thermopiles
• CPC Class Codes: G05D 22/02 characterised by the use of electric means

Abstract

A breathing assistance apparatus adapted to deliver humidified gases at a desired level of humidity to a patient including a humidifier and a heated conduit is disclosed. The humidifier includes a controller which controls the humidifier, or the humidifier and the heated conduit to deliver the gases to the patient at the required humidity or temperature, without the requirement for sensors in the gases stream. The controller uses information already available to the controller, without the requirement for additional information to be provided by sensors in the gases stream. This means the need for sensors in the gases stream is dispensed with. A significant benefit is achieved as sensors are not required in the conduit and thus the apparatus is simple and less bulky.

Claims

1. A breathing assistance apparatus adapted to deliver humidified gases at a desired level of humidity or at a desired temperature to a patient, comprising:

a humidifier including a heater, a heater temperature sensor providing an indication of the heater temperature, and a heater power input for energising said heater, said humidifier adapted to receive a chamber for holding a volume of water, said heater adapted to transfer heat to water within said chamber to produce water vapour within said chamber, said gases in use passing through water vapour within said chamber thereby being humidified,

a controller adapted to monitor and control said heater power input so as to energise said heater to humidify said gases to said desired level of humidity or said desired temperature, said controller configured or programmed to;

a) energise said heater to a level of heater power required to maintain the heater temperature at a predetermined initial heater temperature,

b) based on said level of heater power required to maintain the heater temperature at said predetermined initial heater temperature, determine a heater temperature set-point required to humidify said gases to said desired level of humidity or said desired temperature,

c) energise said heater to substantially maintain the heater temperature at said heater temperature set-point.

2. A breathing assistance apparatus as claimed in claim 1 wherein said breathing assistance apparatus includes:

a conduit for conveying said gases from said humidifier to said patient,

a conduit heater associated with said conduit wherein said gases flowing through said conduit are heated either directly or indirectly by said conduit heater,

a conduit heater power input for energising said conduit heater, and

an ambient temperature sensor for providing an indication of the ambient temperature, and wherein

said instruction (b) also;

determines a conduit heater power level required to humidify said gases to said desired level of humidity or said desired temperature based on the ambient temperature sensed by said ambient temperature sensor, and

said instruction (c) also;

energises said conduit heater with a level of power substantially similar to said conduit heater power level determined in step (b).

3. A breathing assistance apparatus as claimed in claim 1 wherein said breathing assistance apparatus includes an ambient temperature sensor for providing an indication of the ambient temperature, and said determination of said heater temperature set-point in instruction (b) is also based on the ambient temperature.

4. A breathing assistance apparatus as claimed in claim 2 wherein said determination of said conduit heater power level is also based on said level of heater power required to substantially maintain the heater temperature at said predetermined initial heater temperature.

5. A breathing assistance apparatus as claimed in either claim 1 or 2 wherein said controller is configured or programmed to perform additional instructions:

(d) continue to monitor said heater power input and based on the heater power required to substantially maintain the heater temperature at said heater temperature set-point, re-determine said heater temperature set-point required to humidify said gases to said desired level of humidity or said desired temperature,

(e) continuously repeat instruction (d).

6. A breathing assistance apparatus as claimed in claim 5 wherein when performing instruction (d) said controller also:

continues to monitor the ambient temperature and re-determines said conduit heater power level required to humidify said gases to said desired level of humidity or said desired temperature based on the ambient temperature.

7. A breathing assistance apparatus as claimed in claim 5 wherein said breathing assistance apparatus further includes an ambient temperature sensor for providing an indication of the ambient temperature, and said re-determination of said heater temperature set-point in instruction (d) is also based on the ambient temperature.

8. A breathing assistance apparatus as claimed in claim 6 wherein said re-determination of said conduit heater power level is also based on the heater power required to substantially maintain the heater temperature at said heater temperature set-point.

9. A breathing assistance apparatus as claimed in claim 5 wherein instruction (d) further includes the following steps:

when a change in the heater power is more than a first threshold and less than a second threshold, said controller re-determines said heater temperature set-point required to humidify said gases to said desired level of humidity or said desired temperature, and

when a change in the heater power is more than said second threshold, said controller reverts to instruction (a),

said second threshold being higher than said first threshold.

10. A breathing assistance apparatus as claimed in claim 9 wherein instruction (d) further includes the following steps:

when a change in the heater power is more than said first threshold and less than said second threshold and the change is a decrease, said controller causes a first delay before re-determining said heater temperature set-point, and

when a change in the heater power is more than said first threshold and less than said second threshold and the change is an increase, said controller causes a second delay before re-determining said heater temperature set-point,

said first delay being shorter than said second delay.

11. A breathing assistance apparatus as claimed in claim 9 wherein said second threshold relates to a rate of change of the heater power with respect to time.

12. A breathing assistance apparatus adapted to deliver humidified gases at a desired level of humidity or at a desired temperature to a patient, comprising:

a humidifier including a heater, a heater temperature sensor providing an indication of the heater temperature, and a heater power input for energising said heater, said humidifier adapted to receive a chamber for holding a volume of water, said heater adapted to transfer heat to water within said chamber to produce water vapour within said chamber, said gases in use passing through water vapour within said chamber thereby being humidified,

a controller adapted to monitor and control said heater power input for energising said heater, said controller configured or programmed to;

a) energise said heater to a predetermined heater power first level until the heater temperature stabilises at a resulting first heater temperature, or, energise said heater to a level of heater power required to maintain the heater temperature at a predetermined initial heater temperature,

b) based on said resulting first heater temperature, or said level of heater power required to maintain the heater temperature at said predetermined initial heater temperature, determine either;

a heater power second level required to humidify said gases to said desired level of humidity or said desired temperature, or

determine a heater temperature set-point required to humidify said gases to said desired level of humidity or said desired temperature, and

c) energise said heater with a level of heater power substantially similar to said heater power second level, or, energise said heater to substantially maintain the heater temperature at said heater temperature set-point.

13. A breathing assistance apparatus as claimed in claim 12 wherein said breathing assistance apparatus includes:

a conduit for conveying said gases from said humidifier to said patient,

a conduit heater associated with said conduit wherein said gases flowing through said conduit are heated either directly or indirectly by said conduit heater,

a conduit heater power input for energising said conduit heater, and

an ambient temperature sensor for providing an indication of the ambient temperature, and wherein

said instruction (b) also;

determines a conduit heater power level required to humidify said gases to said desired level of humidity or said desired temperature based on the ambient temperature sensed by said ambient temperature sensor, and

said instruction (c) also;

energises said conduit heater with a level of conduit heater power substantially similar to said conduit heater power level determined in step (b).

14. A breathing assistance apparatus as claimed in claim 12 wherein said breathing assistance apparatus includes an ambient temperature sensor for providing an indication of the ambient temperature, and said determination of said heater power second level in instruction (b), or said determination of said heater temperature set-point in instruction (b), is also based on the ambient temperature.

15. A breathing assistance apparatus as claimed in claim 13 wherein said determination of said conduit heater power level is also based on:

said first heater temperature, or

said level of heater power required to substantially maintain the heater temperature at said predetermined initial heater temperature.

16. A breathing assistance apparatus as claimed in either claim 12 or 13 wherein said controller is configured or programmed to perform additional instructions:

(d) continue to monitor the heater temperature or the heater power input and based on either;

the heater temperature resulting from said heater being energised with a level of heater power substantially similar to said heater power second level, or

the heater power required to substantially maintain the heater temperature at said heater temperature set-point,

re-determine said heater power second level or said heater temperature set-point required to humidify said gases to said desired level of humidity or said desired temperature,

(e) continuously repeat instruction (d).

17. A breathing assistance apparatus as claimed in claim 16 wherein when performing instruction (d), said controller also:

continues to monitor the ambient temperature and re-determines the conduit heater power level required to humidify said gases to said desired level of humidity or said desired temperature based on the ambient temperature.

18. A breathing assistance apparatus as claimed in claim 16 wherein said breathing assistance apparatus further includes an ambient temperature sensor for providing an indication of the ambient temperature, and said re-determination of said heater power second level or said heater temperature set-point in instruction (d) is also based on the ambient temperature.

19. A breathing assistance apparatus as claimed in claim 17 wherein said re-determination of said conduit heater power level is also based on either:

the heater temperature resulting from said heater being energised with a level of heater power substantially similar to said heater power second level, or

the heater power required to substantially maintain the heater temperature at said heater temperature set-point.

20. A breathing assistance apparatus as claimed in claim 16 wherein instruction (d) further includes the following step:

when a change in the heater temperature or the heater power is more than a first threshold and less than a second threshold, said controller re-determines said heater power second level or said heater temperature set-point required to humidify said gases to said desired level of humidity or said desired temperature, and

when a change in the heater temperature or the heater power is more than said second threshold, said controller reverts to instruction (a),

said second threshold being higher than said first threshold.

21. A breathing assistance apparatus as claimed in claim 20 wherein instruction (d) further includes the following steps:

when a change in the heater temperature or the heater power is more than said first threshold and less than said second threshold and the change is a decrease, said controller causes a first delay before re-determining said heater power second level or said heater temperature set-point, and

when a change in the heater temperature or the heater power is more than said first threshold and less than said second threshold and the change is an increase, said controller causes a second delay before re-determining said heater power second level or said heater temperature set-point,

said first delay being shorter than said second delay.

22. A breathing assistance apparatus as claimed in claim 20 wherein said second threshold relates to a rate of change of the heater temperature with respect to time or the heater power with respect to time.

23. A breathing assistance apparatus adapted to deliver humidified gases at a desired level of humidity or at a desired temperature to a patient comprising:

a humidifier including a heater, a heater power input for energising said heater, said humidifier adapted to receive a chamber for holding a volume of water, said heater adapted to transfer heat to water within said chamber to produce water vapour within said chamber, said gases in use passing through water vapour within said chamber thereby being humidified,

a conduit for conveying said gases from said humidifier to said patient,

a conduit heater associated with said conduit wherein said gases flowing through said conduit are heated either directly or indirectly by said conduit heater,

a conduit heater power input for energising said conduit heater, and

a controller adapted to control said heater power input and conduit heater input so as to energise said heater and said conduit heater to humidify said gases to said desired level of humidity or said desired temperature,

a connector adapted to electrically connect said conduit heater to said controller, said connector including an indicator in use being electrically connected to said controller,

said controller adapted to energise said indicator when said conduit heater is connected to said controller and operating within predefined limits.