REDUNDANT POWER CONTROL FOR RESPIRATORY SYSTEM HEATERS

• US 20090107493A1
• Filed: 10/29/2007
• Published: 04/30/2009
• Est. Priority Date: 10/29/2007
• Status: Active Grant

• Current Assignee: Smiths Medical ASD, Inc. (Smiths Group International Holdings Ltd.)
• Original Assignee: Smiths Medical ASD, Inc. (Smiths Group International Holdings Ltd.)
• Inventors: Liu, Zhan, Snyder, Robert L.
• Granted Patent: US 8,511,305 B2
• Time in Patent Office: Days
• US Class Current: 128/202.220
• CPC Class Codes: A61M 16/026 specially adapted for predicting, e.g. for determining an information representative of a flow limitation during a ventilation cycle by using a root square technique or a regression analysis
• CPC Class Codes: A61M 16/1075 by influencing the temperature A61M16/1045 takes precedence
• 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 16/162 Water-reservoir filling system, e.g. automatic
• CPC Class Codes: A61M 2205/17 with redundant control systems
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: A61M 2205/3653 by Joule effect, i.e. electric resistance
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A62B 9/00 Component parts for respiratory or breathing apparatus A62B19/00, A62B21/00, A62B23/00 take precedence
• CPC Class Codes: F24V 99/00 Subject matter not provided for in other main groups of this subclass
• CPC Class Codes: G05B 2219/24125 Watchdog, check at timed intervals
• CPC Class Codes: G05B 2219/24186 Redundant processors are synchronised
• CPC Class Codes: G05B 9/03 with multiple-channel loop, i.e. redundant control systems

Abstract

A humidification system is provided for a respiratory system is provided with a controller having two processors that monitor the operation of each other and of heating elements in the respiratory system to provide CPU redundancy and heating element control. Each heating element is provided with two control paths, for example a relay and a triac connected in series with the heating element and a power supply. Each heater has one control path connected to a first one of the processors and at least one heating element has at least one control path connected to a second one of the controllers. A hardware watchdog monitors the operation of the first processor, and can be triggered by a signal from the second processor, in response to which it can disable all heating elements.

Claims

1. A humidifier system comprising:

at least one heating element;

at least two processors connected to, and configured to disable, the at least one heating element upon the failure of any one of the processors;

at least two control paths from the at least two processors to the at least one heating element, both of the control paths being necessary for activating the respective heating element; and

a watchdog configured to monitor at least one of the processors and to disable the at least one heating element in response to the monitoring of the at least one processor.

2. The system of claim 1 wherein:

the at least two control paths include two switching devices connected in series with each of the at least one heating element, each path being responsive to a control signal from the at least two processors, at least one control path to each of the at least one heating element being operable to disable the at least one heating element in response to an output from the watchdog.

3. The system of claim 2 wherein:

the at least two processors include a main processor and an auxiliary processor;

the at least one control path to each of the at least one heating element being responsive to the output of the main processor.

4. The system of claim 3 wherein:

the at least one heating element including at least two heating elements; and

at least one control path to at least one heating element being responsive to the output of the auxiliary processor.

5. The system of claim 4 wherein:

the auxiliary processor is configured to activate the watchdog to disable the at least two heating elements.

6. The system of claim 5 wherein:

one heating element is a respiratory humidifier heater having two control paths thereto that are both responsive to the main processor and the watchdog; and

another heating element is a respiratory conduit heater element having two control paths thereto, one that is responsive to the main processor and the watchdog and the other of which that is responsive to the auxiliary processor.

7. The system of claim 2 wherein:

one path to each heating element includes a relay and another path to the heating element includes a triac or other solid state switching element.

8. A respiratory system comprising the humidifier system of claim 1 wherein:

the at least two processors include a main processor and an auxiliary processor;

the at least one heating element includes a hotplate heater having two control paths responsive to signals from the main processor;

the respiratory system includes an inspiratory conduit and an expiratory conduit, each conduit connected to the humidification system and each having a heating element therein having a control having two control paths thereto, one responsive to a control signal from the main processor and the other responsive to a control signal from the auxiliary processor.

9. The respiratory system of claim 8 wherein:

the watchdog is configured to monitor the main processor and to disable the heating elements in response to the monitoring of the main processor, the watchdog having an override responsive to the auxiliary processor and operable to disable the heating elements in response to a signal from the auxiliary processor.

10. The system of claim 1 wherein:

each of the at least two processors is programmed to monitor a timing signal from another of the at least two processors and to disable all heating elements in response to a detected failure of one of the timing signals.

11. A humidifier system controller for use in a respiratory system having one or more heating elements, the controller comprising:

at least two CPUs, including a first CPU and a second CPU that are interdependent on the operation of the other;

a first set of at least two switching devices;

conductors for connecting the at least one heating element to a power supply through the at least two switching devices so as to energize the at least one heating element in response to a plurality of the at least two switching devices being in a conductive state; and

a hardware monitoring override; and

at least two control signals, one to each switching device from a CPU, to control the states of the at least two switching devices, the control signals being responsive to the hardware monitoring override.

12. The humidifier system controller of claim 11 further comprising:

at least one second set of at least two switching devices;

conductors for connecting the at least one heating element to the power supply through the at least two switching devices of the second set so as to energize the at least one heating element in response to a plurality of the at least two switching devices of the second set being in a conductive state;

at least one of the control signals being from the second CPU; and

at least one control signal to each switching device being from the first CPU.

13. The humidifier system controller of claim 11 wherein:

each of the at least two CPUs is programmed to monitor a timing signal from the other CPU over an interval, and to disable all heating elements if the monitored timing signals are not as expected over the interval.

14. A humidifier system comprising:

a power supply;

at least one processor;

at least one heating element, each heating element having a triac connecting it to the power supply to provide independent control of the power to the heating element;

at least one relay connected between the power supply and at least one of the triacs;

at least two control paths from the at least one processor, one control path connecting to each of the triacs to control power from the power supply to the respective heating element, and another control path connecting to the at least one relay to control power to the triacs.

15. The system of claim 14 wherein:

the at least one processor includes at least two processors connected to, and configured to disable, the at least one heating element upon the failure of any one of the processors.

16. The system of claim 14 wherein:

the at least one processor includes at least two processors, one processor controlling power to the triacs along the one control path thereto and another processor controlling power to the at least one relay along the other control path.

17. A method of controlling a humidifier system having at least one heating element and at least two processors connected to, and configured to disable, the at least one heating element upon the failure of any one of the processors, the method comprising:

providing at least two control paths from the at least two processors to the at least one heating element, both of the control paths being necessary for activating the respective heating element; and

monitoring at least one processor and to disable the at least one heating element in response to the monitoring of the at least one processor.

18. The method of claim 17 wherein:

the providing of the at least two control paths includes providing two switching devices connected in series with each of the at least one heating element, each path being responsive to a control signal from the at least two processors, at least one control path to each of the at least one heating element being operable to disable the at least one heating element in response to an output from the watchdog.

19. The method of claim 18 wherein the at least two processors include a main processor and an auxiliary processor, and wherein:

the at least one control path provided to each of the at least one heating element are responsive to the output of the main processor.

20. The method of claim 19 wherein the at least one heating element includes at least two heating elements, and wherein:

the at least one control path provided to at least one heating element is responsive to the output of the auxiliary processor.

21. The method of claim 20 wherein the auxiliary processor is configured to activate a watchdog to disable the at least two heating elements.

22. The method of claim 21 wherein one heating element is a respiratory humidifier heater having two control paths thereto that are both responsive to the main processor and the watchdog, and another heating element is a respiratory conduit heater element having two control paths thereto, one that is responsive to the main processor and the watchdog and the other of which that is responsive to the auxiliary processor.

23. The method of claim 18 wherein:

the providing of the paths includes providing a relay in one path to a heating element and a triac or other solid state switching element another path to the heating element.

24. The method of claim 17 further comprising:

monitoring with each of the at least two processors a timing signal from another of the at least two processors and to disable all heating elements in response to a detected failure of one of the timing signals.