Respiratory or surgical humidifier and method of use
An improved system and method of monitoring the operation of a respiratory or surgical humidifier system. A controllable load can be connected across output terminals to a tube heating element to test the operation of a tube heating element supply circuit. A range of tests may be performed by controlling the state of one or more components and monitoring one or more sensors. Tests may be performed either during or not during therapy and either with a gas supply tube connected or not. Transient currents may also be detected and the power supply to a tube heating element can be stopped where transient currents outside a permitted range are detected.
1 . A respiratory or surgical humidifier configured to connect to a gas supply tube, the respiratory or surgical humidifier comprising:
power supply lines configured to supply power via a supply path to respective output terminals, the output terminals configured such that a heating element of a gas supply tube can be connected across the output terminals;
a switchable load within the respiratory or surgical humidifier, the switchable load electrically connected across the output terminals;
a control circuit configured to control switching of the switchable load; and
a sensor that monitors at least one attribute of power supplied via the supply path and provides attribute information to the control circuit, wherein the control circuit is configured to control the switchable load to operate in different states and detect a fault of the respiratory or surgical humidifier based on the attribute information for the different states.
2 . The respiratory or surgical humidifier of claim 1 , wherein the control circuit is configured to control the switchable load to test the respiratory or surgical humidifier whilst power is supplied to the heating element electrically connected across the output terminals.
3 . The respiratory or surgical humidifier of claim 1 , wherein the switchable load comprises one or more of a controllable switch, an impedance, a reactive impedance, a resistor, or a semiconductor switch.
4 . The respiratory or surgical humidifier of claim 1 , further comprising a voltage sensor across the power supply lines and wherein the attribute information comprises the voltage across the power supply lines.
5 . The respiratory or surgical humidifier of claim 1 , wherein the sensor comprises one or more of an inductive sensor, a Hall effect sensor, or a shunt resistance-based sensor; and wherein the attribute information comprises a current flowing in the supply path.
6 . A respiratory or surgical humidification system comprising the respiratory or surgical humidifier of claim 1 , the system further comprising a gases supply tube, wherein the heating element of the gases supply tube is electrically connected across the output terminals, in parallel with the switchable load.
7 . The respiratory or surgical humidifier of claim 1 , wherein the sensor comprises a current sensor.
8 . The respiratory or surgical humidifier of claim 1 , the control circuit is configured to receive first attribute information from the sensor representing a first attribute level while the switchable load is switched off, and receive second attribute information from the sensor representing a second attribute level while the switchable load is switched on.
9 . The respiratory or surgical humidifier of claim 8 , wherein the control circuit is configured to receive current information from a current sensor and wherein the first attribute information is current information from the current sensor representing a first current level flowing in the supply path whilst the switchable load is switched off.
10 . The respiratory or surgical humidifier of claim 9 , wherein the control circuit is configured to detect an absence of the heating element or an error if the first current level is outside a permitted range.
11 . The respiratory or surgical humidifier of claim 10 , wherein the control circuit is configured to receive current information from the current sensor and wherein the second attribute information is current information from the current sensor representing a second current level flowing in the supply path whilst the switchable load is switched on.
12 . The respiratory or surgical humidifier of claim 10 , wherein the permitted current range for the difference between a first and second current levels is determined on a basis of a voltage level across the output terminals, and a switchable load.
13 . The respiratory or surgical humidifier of claim 8 , wherein the control circuit is configured to detect a fault of the respiratory or surgical humidifier if a comparison between the first and second attribute levels is outside a permitted range.
14 . The respiratory or surgical humidifier of claim 13 , wherein the comparison comprises a difference between the first and second attribute levels.
15 . A method of monitoring an operation of a respiratory or surgical humidifier having a power supply path and output terminals for supplying power to a tube heating element of a humidifier supply tube, the method comprising:
temporarily connecting a dummy load across the output terminals while power is supplied to the tube heating element;
evaluating a first power supply attribute when the dummy load is connected across the output terminals and a second power supply attribute when the dummy load is not connected across the output terminals;
determining a difference between the first and second power supply attributes; and
detecting a fault of the respiratory humidifier if the difference between the first and second power supply attributes is outside a permitted range.
16 . The method of claim 15 , wherein the first power supply attribute is a first current flowing in the power supply path when the dummy load is electrically connected across the output terminals and the second power supply attribute is a second current flowing in the power supply path when the dummy load is not electrically connected across the output terminals.
17 . The method of claim 15 , further comprising terminating power to the tube heating element if the fault is detected.