Humidity controller

• US 9,186,477 B2
• Filed: 06/13/2011
• Issued: 11/17/2015
• Est. Priority Date: 06/17/1997
• Status: Expired due to Fees

• Current Assignee: Fisher & Paykel Healthcare Limited
• Original Assignee: Fisher & Paykel Healthcare Limited
• Inventors: Hunt, Peter John, Thudor, Mohammad, Wixey, David, McPhee, Stephen William
• Primary Examiner(s): PAIK, SANG YEOP
• Application Number:
  US13/159,345
• Publication Number:
  US 20120118288A1
• Time in Patent Office: 1,618 Days
• Field of Search: 392394-404, 12820312-20326, 128/204.17, 128/204.21, 128/204.22, 261/129, 261/130, 261/139
• US Class Current: 1/1
• 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. In a humidifier comprising a heater plate, a fan, and a conduit, a method of delivering humidified gases to a patient, the method comprising:

supplying an initial level of power to the heater plate until heater plate temperature stabilizes or energizing the heater plate until the heater plate temperature reaches an initial temperature set-point;

determining an amount of power drawn by the fan;

determining, based on the amount of power drawn by the fan, a level of power to supply to the heater plate to change a temperature of the gases to achieve a desired level of humidity or determining, based on the amount of power drawn by the fan, a temperature set-point to change the temperature of the gases to achieve the desired level of humidity;

supplying the level of power to the heater plate or energizing the heater plate to maintain the heater plate temperature at the temperature set-point;

monitoring the amount of power drawn by the fan to determine a change in the amount of power drawn by the fan;

comparing the change in the amount of power drawn by the fan to first and second thresholds;

in response to determining that the change in the amount of power drawn by the fan meets the first threshold and does not meet the second threshold, determining an adjusted level of power and supplying the adjusted level of power to the heater plate or determining an adjusted temperature set-point and energizing the heater plate to maintain the adjusted temperature set-point; and

in response to determining that the change in the amount of power drawn by the fan meets the second threshold, supplying the initial level of power to the heater plate until the heater plate temperature stabilizes or energizing the heater plate until the heater plate temperature reaches the initial temperature set-point.

2. The method of claim 1, further comprising determining the adjusted level of power and supplying the adjusted level of power to the heater plate or determining the adjusted temperature set-point and energizing the heater plate to maintain the adjusted temperature set-point in response to determining that the change in the amount of power drawn by the fan is more than the first threshold and less than the second threshold.

3. The method of claim 2, wherein the second threshold is higher than the first threshold.

4. The method of claim 1, further comprising:

determining a level of conduit heater power to deliver the gases at the desired level of humidity based on the amount of power drawn by the fan; and

energizing a conduit heater to the level of conduit heater power.

5. The method of claim 4, further comprising re-determining the level of conduit heater power to deliver the gases at the desired level of humidity when the change in the amount of power drawn by the fan meets the first threshold and does not meet the second threshold.

6. The method of claim 4, wherein the conduit heater comprises a wire.

7. The method of claim 5, wherein the wire is disposed in a conduit wall.

8. The method of claim 7, wherein the wire is disposed in the conduit wall such that air surrounds the wire.

9. The method of claim 1, wherein determining the amount of power drawn by the fan comprises determining a current drawn from the fan.

10. The method of claim 1, wherein determining the amount of power drawn by the fan is based at least in part on determining a fan speed.

11. The method of claim 1, further comprising determining an ambient temperature, and wherein determining the level of power to be supplied to the heater plate or determining the temperature set-point is based on the amount of power drawn by the fan and on the ambient temperature.

12. The method of claim 1, further comprising:

without determining temperature of the gases in the conduit, determining a level of conduit heater power to deliver the gases at the desired level of humidity based on the amount of power drawn by the fan; and

energizing a conduit heater to the level of conduit heater power.

13. A humidifier comprising:

a heater configured to heat a body of water to create humidified gases;

a fan configured to blow the humidified gases;

a conduit configured to deliver the humidified gases to a patient; and

a controller configured to;

supply an initial level of power to the heater until heater temperature stabilizes or energize the heater until the heater temperature reaches an initial temperature set-point;

determine an amount of power drawn by the fan;

determine, based on the amount of power drawn by the fan, a level of power to be supplied to the heater to change a temperature of the gases to achieve a desired level of humidity or determine, based on the amount of power drawn by the fan, a temperature set-point to change the temperature of the gases to achieve the desired level of humidity;

supply the level of power to the heater or energize the heater to maintain the heater temperature at the temperature set-point;

monitor the amount of power drawn by the fan to determine a change in the amount of power drawn by the fan;

compare the change in the amount of power drawn by the fan to first and second thresholds;

in response to the change in the amount of power drawn by the fan meeting the first threshold and not meeting the second threshold, determine an adjusted level of power and supply the adjusted level of power to the heater or determine an adjusted temperature set-point and energize the heater to maintain the adjusted temperature set-point; and

in response to the change in the amount of power drawn by the fan meeting the second threshold, supply the initial level of power to the heater until the heater temperature stabilizes or energize the heater until the heater temperature reaches the initial temperature set-point.

14. The humidifier of claim 13, wherein the controller is configured to determine the adjusted level of power and supply the adjusted level of power to the heater or determine the adjusted temperature set-point and energize the heater to maintain the adjusted temperature set-point when the change in the amount of power drawn by the fan is more than the first threshold and less than the second threshold.

15. The humidifier of claim 14, wherein the second threshold is higher than the first threshold.

16. The humidifier of claim 13, further comprising a conduit heater configured to heat gases flowing through the conduit, wherein the controller is further configured to:

determine a level of conduit heater power to deliver the gases at the desired level of humidity based on the amount of power drawn by the fan; and

energize the conduit heater to the level of conduit heater power.

17. The humidifier of claim 16, wherein the controller is further configured to re-determine the level of conduit heater power to deliver the gases at the desired level of humidity when the change in the amount of power drawn by the fan meets the first threshold and does not meet the second threshold.

18. The humidifier of claim 16, wherein the conduit heater comprises a wire.

19. The humidifier of claim 18, wherein the wire is disposed in a conduit wall.

20. The humidifier of claim 19, wherein the wire is disposed in the conduit wall such that air surrounds the wire.

21. The humidifier of claim 13, wherein the controller is configured to determine the amount of power drawn by the fan based on a current drawn from the fan.

22. The humidifier of claim 13, wherein the controller is configured to determine the amount of power drawn by the fan based at least in part on a fan speed.

23. The humidifier of claim 13, wherein the controller is configured to determine the level of power to be supplied to the heater or determine the temperature set-point based on the amount of power drawn by the fan and on an ambient temperature.

24. The humidifier of claim 23, further comprising an ambient temperature sensor configured to measure the ambient temperature.

25. The humidifier of claim 13, wherein the heater comprises a heater plate.

26. The humidifier of claim 13, wherein the controller is further configured to:

determine a level of conduit heater power to deliver the gases at the desired level of humidity based on the amount of power drawn by the fan and not based on a temperature of the gases in the conduit; and

energize a conduit heater to the level of conduit heater power.

27. In a breathing assistance apparatus, a controller configured to:

supply an initial level of power to a heater plate until heater plate temperature stabilizes or energize the heater plate until the heater plate temperature reaches an initial temperature set-point;

determine an amount of power drawn by the fan;

determine, based on the amount of power drawn by the fan, a level of power to be supplied to the heater plate to change a temperature of the gases to achieve a desired level of humidity or determine, based on the amount of power drawn by the fan, a temperature set-point to change the temperature of the gases to achieve the desired level of humidity;

supply the level of power to the heater plate or energize the heater plate to maintain the heater plate temperature at the temperature set-point;

monitor the amount of power drawn by the fan to determine a change in the amount of power drawn by the fan;

compare the change in the amount of power drawn by the fan to first and second thresholds;

in response to the change in the amount of power drawn by the fan meeting the first threshold and not meeting the second threshold, determine an adjusted level of power and supply the adjusted level of power to the heater plate or determine an adjusted temperature set-point and energize the heater plate to maintain the adjusted temperature set-point; and

in response to the change in the amount of power drawn by the fan meeting the second threshold, supply the initial level of power to the heater plate until the heater temperature stabilizes or energize the heater plate until the heater plate temperature reaches the initial temperature set-point.

28. The controller of claim 27, wherein the controller is configured to determine the level of power to be supplied to the heater plate or determine the temperatures set-point based on the amount of power drawn by the fan and on an ambient temperature.