Respiratory or surgical humidifier and method of use

Abstract

To provide an improved system and method of monitoring operation of a respiratory or surgical humidifier system.SOLUTION: A controllable load can be connected across output terminals 204, 205 to a tube heating element 207 to test operation of a tube heating element supply circuit 200. A wide range of tests may be performed by controlling the state of one or more components and monitoring one or more sensors 209. 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 when transient currents outside a permitted range are detected.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to respiratory and / or surgical humidifiers and respiratory or breathing assistance systems for supplying gas to a patient or user via a gas delivery tube incorporating a tube heating element. [Background technology]

[0002] Respiratory and / or surgical humidifiers are used in a variety of settings, such as hospitals, medical facilities, home care, palliative care, and home environments. For a wide range of respiratory applications, it is beneficial to humidify the gases delivered to a patient or user. These applications include where the gas is intended for breathing by the patient or user, as well as where the gas is delivered to a patient or user during surgery.

[0003] In the case of non-invasive ventilation (e.g., using a face or nose mask), inhalation of dry respiratory gases can dry out tissues in the patient's or user's airways (e.g., the nasal mucosa). Humidifying the respiratory gases prior to inspiration can reduce drying of the patient's or user's airway tissues. Furthermore, this humidification can increase the patient's or user's comfort and improve the patient's or user's tolerance to noninvasive ventilation (NIV).

[0004] In high-flow therapy, humidified gas is delivered at a high flow rate through a non-sealed interface to a patient or user who may be spontaneously breathing or may be apneic, such as during anesthesia. As with non-invasive ventilation, humidifying the inspired gas during high-flow therapy can reduce drying of airway tissue, increase comfort, and improve tolerance to the therapy.

[0005] In the case of positive airway pressure (PAP) therapy, a PAP device (including a blower and a humidifier) ​​can be used to provide pressure therapy to the patient or user. This therapy can be in the form of continuous positive airway pressure (CPAP), for example. As with non-invasive ventilation and high-flow therapy, humidifying the gases inspired during PAP therapy can reduce dryness, increase comfort, and improve tolerance.

[0006] In the case of surgical gases, or invasive ventilation (when gases delivered to the patient bypass the upper airways), humidification of the gas has been found to improve patient comfort and provide physiological benefits (such as improved mucus transport). Furthermore, humidification may be necessary to improve postoperative outcomes and ensure patient or user safety. For example, humidification can help prevent airway obstruction (caused by drying of airway secretions) and / or destruction of the airway epithelium.

[0007] In any of the therapies described above, the humidified gas can be delivered to the patient via a gas delivery tube. This tube can be heated by a built-in tube heating element. Heating the gas delivery tube prevents condensation of the warm, moist breathing gases as they travel from the humidifier to the patient. Preventing this condensation helps ensure that breathing gases are delivered to the patient or user at the required temperature and humidity. Summary of the Invention [Problem to be solved by the invention]

[0008] If the humidifier malfunctions during use, then the gas delivered to the patient (through the gas delivery tube) may not be properly humidified. Incorrect humidification may create risks to the patient (or other users). These risks may include, for example, transients in the tube heating element, prolonged exposure of the airways to dry gas, discomfort, condensation that blocks airflow, high enthalpy delivered to the patient, high surface temperatures of the gas delivery tube, or damage to the respiratory humidifier system.

[0009] For a humidifier to operate properly, all of its internal subsystems must operate properly. If a fault (that has the ability to cause a malfunction) occurs in any of these subsystems, the humidifier must have a means to identify the fault and alert the person administering the treatment (e.g., a medical professional or, in the case of home-based administration, the patient themselves). This disclosure focuses on detecting faults associated with two humidifier subsystems: the gas delivery tube heating element, and the power delivery path - which conveys power from the heater base unit to the gas delivery tube heating element.

[0010] Some existing humidifiers have systems that can detect fault conditions (in the gas delivery tube heating element and power supply path). However, these systems have limitations. For example, these fault detection systems can be complex, may perform only a limited range of tests, may not allow for detection of certain faults during treatment, and may only have the ability to detect faults when the gas delivery tube with the heating element is connected.

[0011] The present disclosure provides an example of a humidifier fault detection system that overcomes some of the limitations in existing humidifier fault detection systems, particularly those used to detect faults associated with a gas delivery tube heating element and its power delivery path. The fault detection system and method in the present disclosure is based on monitoring power attributes when a switchable load is being switched into the power delivery path. This switching and monitoring can be performed regardless of whether there is a gas delivery tube (with a functioning heating element) attached. This switching and monitoring can also be performed during treatment without any interruption to the treatment. The fault detection system disclosed herein can also have any of the following advantages and / or other advantages. For example, the monitoring system and method disclosed herein allows a wide range of tests to be performed with relatively simple additional components. Such tests can include detecting any of a number of possible fault conditions. These fault conditions can include a power flow controller failure (such as an open or short circuit fault), a current sensor failure, a tube heating element failure, or a general fault. Such tests can also be used to detect the presence of a tube heating element. Furthermore, it is simple, reliable, robust and inexpensive to implement.

[0012] The detection and / or warning methods described herein can be incorporated into a variety of respiratory and / or surgical humidifier systems, such as CPAP devices, high flow therapy devices, surgical humidifiers, respiratory humidifiers, infant CPAP devices, infant high flow devices, NIV therapy devices, and the like. [Means for solving the problem]

[0013] In some configurations, a respiratory or surgical humidifier may include a power supply line configured to supply power via a supply path to respective output terminals, a switchable load electrically connected between the output terminals, a control circuit configured to control switching of the switchable load, and a sensor that monitors at least one attribute of the power supplied via the supply path and provides the attribute information to the control circuit. The control circuit may be configured to control the switchable load to operate in different conditions and determine operation of the respiratory or surgical humidifier based on the attribute information for the different conditions.

[0014] In some configurations, the control circuit may be configured to control the switchable load to test the respiratory or surgical humidifier while power is supplied to a tube heating element electrically connected between the output terminals.

[0015] In some configurations, the respiratory or surgical humidifier may include a power flow controller controlled by the control circuit to vary the power level provided through the supply path.

[0016] In some configurations, the power flow controller may be a controllable switch in the supply path.

[0017] In some configurations, the control circuitry can control state combinations of the switchable loads and power flow controllers and monitor the operation of the respiratory or surgical humidifier based on attribute information for different state combinations.

[0018] In some configurations, the switchable load may include a controllable switch and an impedance.

[0019] In some configurations, the controllable switch may be a semiconductor switch.

[0020] In some configurations, the impedance can be a resistor.

[0021] In some configurations, the impedance may include a reactive impedance.

[0022] In some configurations, a voltage sensor may be provided across the power supply lines.

[0023] In some configurations, the attribute information may include the voltage across the power supply lines.

[0024] In some configurations, the sensor may be a current sensor.

[0025] Depending on the configuration, the sensor can be an inductive, Hall effect, or shunt resistor based sensor.

[0026] In some configurations, the attribute information includes a current flowing in the supply path.

[0027] In some configurations, the control circuit may be configured to switch the power flow controller on while the switchable load is switched off and to receive current information from the current sensor representative of a first current level.

[0028] In some configurations, the control circuit may be configured to detect a fault if the first current level is outside of an acceptable range.

[0029] In some configurations, the control circuit may be configured to switch on the power flow controller while the switchable load is switched on and to receive current information from the current sensor representative of the second current level.

[0030] In some configurations, the control circuit may be configured to detect a fault if the difference between the first and second current levels is outside an acceptable range.

[0031] In some configurations, the control circuit may be configured to detect an error if a difference between the first current level and an expected first current level or a difference between the second current level and an expected second current level is outside an acceptable range.

[0032] Depending on the configuration, the expected first current level, the expected second current level, or a tolerance range for the difference between the first and second current levels may be determined based on the voltage level between the output terminals, the impedance of the switchable load, and the impedance of the tube heating element.

[0033] Depending on the configuration, the allowable current range can be the allowable current level plus or minus an error.

[0034] In some configurations, the control circuit may be configured to detect a fault if neither the first nor the second currents exceed a minimum threshold level.

[0035] In some configurations, the control circuit may be configured to receive current information from the current sensor when the power flow controller is switched off and the switchable load is switched on, and detect a fault if the current is above a low current threshold level.

[0036] In some configurations, a transient current detector may be provided in the supply path.

[0037] In some configurations, the transient current detector may include a pair of transistors configured to detect positive or negative transient voltages across an inductor in the supply path.

[0038] In some configurations, a respiratory or surgical humidifier may include a power flow controller configured to control power provided via a supply path to a respective output terminal; a switchable load electrically connected between the output terminals; a current sensor that monitors current provided via the supply path and develops current information; and control circuitry configured to receive current information from the current sensor, control the power flow controller to provide power via the output terminals, and control switching of the switchable load, wherein the control circuitry is configured to: switch the power flow controller on while the switchable load is switched off and receive current information from the current sensor representative of a first current level, switch the power flow controller on while the switchable load is switched on and receive current information from the current sensor representative of a second current level, and determine operation of the respiratory humidifier based on at least the first and second current levels.

[0039] In some configurations, a respiratory or surgical humidifier may include a power supply line configured to supply power via a supply path to a respective output terminal, a switchable load electrically connected between the output terminals, a current sensor to monitor current supplied via the supply path and obtain current information, and a control circuit configured to receive current information from the current sensor and control switching of the switchable load, the control circuit configured to switch off the switchable load and receive current information from the current sensor representative of a first current level, switch on the switchable load and receive current information from the current sensor representative of a second current level, and detect a fault if a difference between the first and second current levels is outside an acceptable range.

[0040] In some configurations, a respiratory or surgical humidifier may include a power flow controller configured to supply power via a supply path to a respective output terminal, a switchable load electrically connected between the output terminals, a current sensor to monitor current supplied via the supply path and obtain current information, and a control circuit configured to receive the current information from the current sensor, control switching of the power flow controller to supply power via the output terminals, and control switching of the switchable load, wherein the control circuit is configured to: switch on the power flow controller while the switchable load is switched off and receive current information from the current sensor representative of a first current level, switch on the power flow controller while the switchable load is switched on and receive current information from the current sensor representative of a second current level, detect an error if the second current level is outside of an acceptable range, and detect an error if a difference between the first and second current levels is outside of an acceptable range.

[0041] In some configurations, a respiratory or surgical humidifier may include a power flow controller configured to supply power via a supply path to a respective output terminal, a switchable load electrically connected between the output terminals, a current sensor that monitors current supplied via the supply path and obtains current information, and a control circuit configured to receive the current information from the current sensor, control switching of the power flow controller to supply power via the output terminals, and control switching of the switchable load, wherein the control circuit is configured to switch on the power flow controller while the switchable load is switched on, receive current information from the current sensor indicative of a test current level, and detect a fault if the test current level is outside an acceptable range.

[0042] In some configurations, the respiratory or surgical humidifier may include a power flow controller configured to control power provided via a supply path to respective output terminals, a switchable load electrically connected between the output terminals, and a control circuit configured to control the switchable load to perform in-use monitoring of the respiratory or surgical humidifier while the power flow controller supplies power to the output terminals.

[0043] In some configurations, the respiratory or surgical humidifier may include a housing configured to receive a humidifier chamber, a heater plate configured to transfer heat to the humidifier chamber when received by the housing, a heater element configured to heat the heater plate, and a power controller configured to control a power level supplied to the heater element.

[0044] In some configurations, a method for monitoring operation of a respiratory or surgical humidifier having output terminals for supplying power to a heater element of a gas delivery tube may include temporarily connecting a dummy load across the output terminals while power is supplied to the heater element, evaluating one or more power delivery attributes, and monitoring for correct operation of the respiratory humidifier.

[0045] In some configurations, an error in the operation of the respiratory or surgical humidifier may be detected if the current provided through the output terminal falls below a threshold value.

[0046] In some configurations, a first current supplied through the output terminals may be measured when a dummy load is not connected between the output terminals, and a second current supplied through the output terminals may be measured when a dummy load is electrically connected between the output terminals, and if a difference between the first and second currents is outside an acceptable range, an error in the operation of the respiratory or surgical humidifier may be detected.

[0047] In some configurations, the respiratory or surgical humidifier includes a transient current detector in the power supply path configured to detect positive or negative voltage transients across an inductor in the supply path.

[0048] These and other features, aspects, and advantages of the present disclosure will be described with reference to the drawings of certain embodiments, which are intended to illustrate generally certain embodiments and are not intended to limit the disclosure. [Brief description of the drawings]

[0049] [Figure 1A] FIG. 1A illustrates a schematic of an exemplary respiratory humidifier system. [Figure 1B] FIG. 1B illustrates a schematic diagram of an exemplary heater base unit of the respiratory humidifier system of FIG. 1A. [Figure 1C] FIG. 1C illustrates a schematic of an exemplary respiratory humidifier system. [Figure 1D] FIG. 1D illustrates a schematic diagram of an exemplary heater base unit of the respiratory humidifier system of FIG. 1C. [Figure 1E] FIG. 1E illustrates generally a partial view of the heater base unit and an exemplary breathing circuit tube heating element adapter of FIG. 1C. [Diagram 2] FIG. 2 illustrates an exemplary circuit for monitoring the operation of a respiratory or surgical humidifier. [Diagram 3] FIG. 3 illustrates a modified exemplary circuit for monitoring the operation of a respiratory or surgical humidifier. [Figure 4] FIG. 4 shows an exemplary circuit (including a transient current detector) for monitoring the operation of a respiratory or surgical humidifier. [Diagram 5] FIG. 5 shows an example circuit for the transient current detector circuit shown in FIG. [Figure 6] FIG. 6 shows a modified form of the transient current detector circuit shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Although specific embodiments and examples are described below, those skilled in the art will appreciate that the disclosure extends beyond the specifically disclosed embodiments and / or uses, as well as obvious modifications and equivalents thereof. Therefore, it is intended that the scope of the disclosure disclosed herein should not be limited by any specific embodiments described below. For example, the component values ​​and operating parameters are merely examples and are not limiting.

[0051] Exemplary Respiratory or Surgical Humidifiers The present disclosure provides examples of respiratory humidifiers configured to deliver humidified and / or heated gas to a patient or user in multiple modes. The modes for the respiratory humidifier may include at least an invasive mode (e.g., for a patient with a bypass airway) and a non-invasive mode (e.g., for a patient or user with a respiratory mask). Each mode may have an individualized humidity output, which may be expressed as a dew point output set point. For example, a user may select a set point appropriate for the current mode of operation. The non-invasive mode may have a selectable dew point set point, for example, 31 degrees Celsius, 29 degrees Celsius, 27 degrees Celsius, or other. The invasive mode may have a dew point set point of 37 degrees Celsius or other. Alternatively, the dew point set point may be continuously variable between an upper and lower limit. Some respiratory humidifier systems disclosed herein may also include a high flow, non-sealed mode, or any other mode known to one of skill in the art. The circuits and methods of the present disclosure may similarly be applied in surgical humidifiers, which may be used, for example, in laparoscopic surgery.

[0052] 1A and 1C, an exemplary respiratory humidification system 100, 101 can include a heater base unit 102 having a heater plate 120 (see FIGS. 1B and 1D). The heater plate 120 can include one or more heating element(s). The heater base unit 102 can include a housing and a controller (e.g., a microprocessor) contained within the housing for controlling the supply of energy to the heating element(s) of the heater plate 120.

[0053] The humidifier heater plate 120 can have a temperature sensor (e.g., a temperature transducer, a thermistor, or other type of temperature sensor). Multiple different temperature sensors can be used. The temperature sensor can measure the temperature of the heater plate 120. The temperature sensor can be in electrical communication with a controller in the heater base unit 102, allowing the controller to monitor the temperature of the heater plate 120.

[0054] The humidifier chamber 103 may be removably received and held on the heater base unit 102 such that the humidifier chamber base is positioned in contact with the heater plate 120 within the heater base unit 102. Referring to FIGS. 1B and 1D, which show examples of the heater base unit 102 of FIGS. 1A and 1C, respectively, the humidifier base 102 may have a collar 124 for engaging with a flange on the humidifier chamber 103, such as those shown in FIGS. 1A and 1C. The collar 124 defines a lip that engages with the flange of the humidifier chamber 103 to hold the humidifier chamber 103 in an operative position on the heater base 102. The humidifier chamber 103 may include a thermally conductive base. When engaged with the heater base unit 102, the conductive base of the humidifier chamber 103 may be in contact with the heater plate 120, such as the top surface of the heater plate 120. When a power signal is sent to the heating element, energizing the heating element, the water within the chamber 103 is heated. The chamber 103 may also be connected to a water source 142 (FIG. 1C) that can add water to the chamber 103 when the water level becomes low or runs out completely within the chamber 103. The addition of water may be accomplished manually, such as upon an alert from the system 101 that a low water or water out condition may be occurring, or automatically, such as with a float valve connected to the water source.

[0055] With continued reference to Figures 1A and 1C, the gas to be humidified can include one or more of air, oxygen, anaesthetic, other auxiliary gases, or any mixture of gases. The gas can be supplied to the humidifier chamber 103 through a gas inlet 104, which can be connected to a gas source, such as a ventilator, a CPAP blower in the case of CPAP therapy, or a remote source. For high-flow therapy, a blower, or even alternatively, a wall source with a flow rate and / or pressure regulator can supply the gas. The humidifier chamber 103 also includes a gas outlet 105, which can be connected to a breathing circuit 106. The breathing circuit 106 can carry the humidified and heated gas to a patient or user. As shown in Figure 1A, the patient end 107 of the breathing circuit 106 can be connected to a patient interface, such as a nasal cannula 113 or a nasal mask 114. The breathing circuit 106 may also be connected to other types of patient or user interfaces, such as a full face mask, total face mask, nasal pillows mask, endotracheal tube, or others. The breathing circuit 106 of FIG. 1C may be similarly connected to any suitable patient interface. The breathing circuit 106 may include a gas delivery tube with or without a tube heating element. The respiratory humidification system 100, 101 may be configured for use with both heated and unheated gas delivery tubes or breathing circuits.

[0056] A tube heating element 110 (e.g., one or more heater wires embedded in the gas delivery tube wall, contained within the gas delivery tube, or wrapped around the outer surface of the gas delivery tube) may be provided in the breathing circuit 106. The tube heating element 110 may help prevent condensation of the humidified gas in the breathing circuit 106. The tube heating element 110 may also, optionally, be in electrical communication with a controller in the heater base unit 102. As shown in Figures 1C and 1E, a breathing circuit tube heating element adapter cable 128 may have two connectors at two ends of the cable 128 for coupling the tube heating element 110 to the heater base unit 102 (e.g., to the controller of the heater base unit 102). Alternatively, the tube heating element adapter cable may be permanently electrically connected to the tube heating element supply circuit of the heater base unit 102, for example, by soldering. The tube heating element adapter cable 128 can facilitate easy connection between the tube heating element 110 and the heater base unit 102. The tube heating element 110 is controlled by a controller, including controlling the power to the tube heating element 110. The tube heating element 110 in the breathing circuit 106 reduces condensation and ensures that the temperature and / or humidity of the gas is maintained within a predetermined range. The tube heating element adapter cable 128 can also include an ambient temperature sensor 126, which can enable the system 101 to adjust the power of the tube heating element 110 and / or the power of the heater plate to compensate for the ambient temperature or changes in the ambient temperature. The ambient temperature sensor can alternatively be located anywhere exposed to ambient air. A tube heating element indicator 130 can be incorporated into the connector that couples to the heater base unit 102. The tube heating element indicator 130 can be illuminated when a properly functioning tube heating element 110 is connected to the heater base unit 102, and the system 101 can heat gases inside the breathing circuit 106 via the tube heating element 110 to minimize condensation, in addition to heating gases passing through the humidifier chamber 103 via the heater plate 120.If the tube heating element 110 is malfunctioning or not connected, the tube heating element indicator 130 is not illuminated (or flashes) and the system 101 may only heat gas by heating the water in the chamber 103 via the heater plate 120. Alternatively, the tube heating element indicator 130 may be illuminated when there is a fault or disconnection of the adapter cable 128 from the tube heating element 110. The illuminated indicator 130 may serve as a visual message or warning. The indicator 130 may not be illuminated if the tube heating element 110 is functioning properly.

[0057] The controller of the respiratory humidifier system 100, 101 can control at least the heater plate 120, and preferably or optionally also the tube heating element 110, without the use of additional sensors (e.g., in the humidifier chamber, at the chamber outlet, in the breathing circuit, and / or elsewhere in the system). This can be accomplished by estimating the heater plate operating point required to deliver the required humidity. For a given respiratory humidifier system, the controller can determine an appropriate power level to apply to the heater plate 120. Applying power to the heater 120 can generate humidity and heat the gas. The power and temperature of the heater plate can be controlled to generate a predetermined amount of humidity. In addition, the parameters can also be optionally used by the controller to provide a more appropriate energization level to the tube heating element 110. As shown in Figures 1C and 1E, the system 101 can also include an ambient temperature sensor 126. The ambient temperature sensor can be located anywhere exposed to ambient air. For example, the system 101 may include an ambient temperature sensor 126 on a tube heating element adapter cable 128 .

[0058] As shown in FIG. 1E, the front panel of the heater base unit 102 may include multiple user controls and indicators, such as a power button 132, a humidity setting push button 134, and multiple (e.g., three, four, five, or more) humidity setting indicators 136 (which may include LED lights) next to the humidity setting push button 134. The location, shape, and size of the user controls and indicators are not limiting. There may be four humidity setting levels available, indicated by the four humidity setting indicators 136. The four humidity settings may correspond to different types of therapy provided to the patient. For example, when the humidifier is operating in an invasive therapy mode, the highest amount of humidity may be selected. In a low-flow oxygen therapy mode, the lowest amount of humidity may be applied. The amount of humidity may be selected based on the treatment requirements or type of therapy, or it may be predefined. Alternatively, the humidifier 100, 101 may include a controller configured to automatically select the amount of humidity to be delivered based on the therapy mode, the patient, or the type of therapy applied to the patient. Optionally, the humidifiers 100, 101 may include a display or touch screen that may communicate information to a user. The touch screen may also be configured to accept input from a user.

[0059] The humidity level can be adjusted by pressing the humidity setting push button 134, which can be a momentary push button. The front panel can also include a number of warning indicators 138 (which can include LED lights) to indicate the following non-limiting examples of conditions: an "out of water" condition (including low water level and out of water), when the tube heating element adapter is not connected, when the audible alarm is muted, and a "see manual" indication used to indicate that a fault has occurred within the system 101.

[0060] System 101 may be suitable for providing respiratory therapy for different purposes, such as for life-saving therapy (e.g., in a hospital) and home therapy, etc. System 101 is suitable for providing invasive, non-invasive, and high-flow therapy for both adult and pediatric patients.

[0061] 2, an exemplary tube heating element supply circuit for a respiratory or surgical humidifier can include a power source 201 that can provide power via a power supply path (including a power flow controller 206 and power supply lines 202 and 203) to output terminals 204 and 205. Power source 201 could be an AC or DC power supply, but in this example is an AC power supply (including a transformer that reduces the supply voltage from the mains voltage to about 22 volts). When the respiratory or surgical humidifier is providing therapy, a tube heating element 207 can be connected to output terminals 204 and 205 to heat gas in the gas supply tube. Tube heating element 207 can be in the form of one or more heater wires embedded in the gas supply tube wall, contained within the gas supply tube, wrapped around the exterior surface of the gas supply tube, or otherwise.

[0062] In this example, the power flow controller 206 can be a controllable switch, such as a semiconductor switch, controlled by the control circuit 208 via control line 213. The power flow controller 206 could alternatively provide a number of different power levels or continuously vary the power level provided through the supply path. The control circuit 208 can include a microprocessor. The control circuit 208 can control the switching of the flow controller 206 when the tube heating element is connected to ensure that the required amount of heating is provided to the gas in the gas supply tube. The tube heating element supply circuit can include a current sensor 209 to monitor the current flowing in the supply path and provide attribute information in the form of a current level to the control circuit 208 via data line 214. The current sensor 209 can be an inductive, Hall effect, or shunt resistor based sensor.

[0063] The tube heating element supply circuit may also include a switchable load 210 electrically connected between the output terminals 204 and 205. The switchable load 210 may include a controllable switch 211 in series with a "dummy" load 212. The controllable switch may be a semiconductor switch controlled by the control circuit 208 via control line 215. The load 212 may be a resistance, but may also be another form of impedance or a synthetic impedance.

[0064] The control circuit 208 may be configured to control the switchable load 210 to test the operation of the respiratory or surgical humidifier either when the tube heating element 207 is not connected between the output terminals 204 and 205, or while power is supplied to the output terminals with the tube heating element 207 connected between the output terminals 204 and 205 during treatment.

[0065] The control circuitry 208 may also be configured to control the power flow controller 206 and the switchable load 210 to operate in different state combinations and monitor the operation of the respiratory or surgical humidifier based on attribute information received from the current sensor 209 for the different switching states of the switchable load 210 and the power flow controller 206.

[0066] In one embodiment, the tube heating element supply circuit 200 of FIG. 2 may be used in a fault checking method in which the following steps may be performed (tube heating element 207 is connected between terminals 204 and 205): i. The control circuit 208 controls the power flow controller 206 to switch on (if it is open at the start of the fault check) while the switch 211 of the switchable load 210 is switched off. ii. The control circuit 208 receives attribute information in the form of a current level measurement from the current sensor 209. In this case, when the power flow controller 206 and switch 211 are operating as intended, a first current level (I H ) is measured. iii. The control circuit 208 controls the switch 211 of the controllable load 210 to be turned on. iv. The control circuit 208 receives attribute information in the form of a second current level measurement from the current sensor 209. In this case, when the power flow controller 206 and switch 211 are operating as intended, the measured second current level is I H , and the current I flowing through the dummy load 212 (in this case, a resistor) D is the sum of. v. The control circuit 208 (which in this case includes a microprocessor) determines a current difference (referred to as “ΔI”), which is the second current level measured in step iv. minus the first current level measured in step ii. vi. The control circuit 208 can determine if a fault exists (possibly a fault in the current sensor 209, or alternatively a fault in the dummy load 212, the dummy load switch 211, or the power flow controller 206) by checking if the current difference (ΔI) is within an allowable current range. vii. The control circuit 208 determines the first current level (I H ) is within an acceptable range, it can be determined whether the tube heating element is present or whether a fault is present (possibly a fault in the power flow controller 206 or the tube heating element 207). viii. The control circuit 208 may also determine that a fault in the power flow controller 206 exists if the current measured by the current sensor 209 exceeds a low current threshold level (at or near zero) when the power flow controller 206 is switched off and the dummy load switch 211 is switched on. With the dummy switch 211 switched on, such a fault may be detected whether or not the tube heating element is in the circuit. Alternatively, for example, if the heater wires are permanently connected, the current I may be detected when the power flow controller 206 is switched off and the dummy load switch 211 is switched off. H If the current is above a low current threshold level, for example 0.1 A, it may be determined that a fault in the power flow controller 206 is present.

[0067] It will be appreciated that not all of the steps described above need to be performed, and that in some implementations only one or selected ones of the steps may be performed, and that selected steps may be performed in a different order.

[0068] By using the current difference in step vi., as described below, the above fault checking method can be performed regardless of whether a tube heating element is present, whether the tube heating element (if present) is functioning properly, and whether a connected tube heating element is being used to provide therapy. Since the current difference can be expressed as: ΔI = (I D +I H )-I H therefore: ΔI=I D

[0069] Therefore, whether the heater wire is present or not, the current ΔI is equal to I D This is because in all cases the currents through the heater wires cancel.

[0070] The test in step vi. is performed to check the current component I D Knowing that the load 212 is to be disconnected, the expected current sensed by the current sensor 209 will be the supply voltage divided by the resistance of the load 212. The acceptable current range in step vi. may be the expected current plus or minus a tolerance. For example, with a supply voltage of 22V and a resistance of 470Ω, assuming no faults are present, the tolerance range may be 22 / 470 + / - 20% (or some other acceptable error range). Thus, the test in step vi. may test whether the control circuit is operating outside of the tolerance range (possibly due to a fault in the current sensor or a component in the supply path).

[0071] In step vii. (assuming no other faults were identified in step vi.), the current I through the tube heating element 207 is measured to determine whether the tube heating element 207 is present and, if present, whether it is operating within an acceptable range. Hcan be monitored. The acceptable current range can be the expected current plus or minus a tolerance (e.g., + / - 20%). In this case, the expected current is I H =V / R Heating_Element_207 where V is the supply voltage between the output terminals. Alternatively, the expected current could be based on the current measured in step iv. In this case, the expected current is I D +I H =V / R Resistor_212 +V / R Heating_Element_207 which can be tested against the current measured in step iv. For example, with a supply voltage of 22V, a resistor 212 of 470Ω, and a heater wire of 24Ω, the tolerance can be (22 / 470+22 / 24)+ / -20% (or some other acceptable error range). Alternatively, the test can simply be whether the expected current is below a lower threshold (i.e., I D +I H <(V / R Resistor_212 +V / R Heating_Element_207 )*x%, where x gives the error), or, using the values ​​above, it could be the case when the expected current is less than 0.8*(22 / 470+22 / 24).

[0072] If no fault is detected in step vi., the current I H is zero or negligible, the control circuit 208 may determine that the tube heating element is not present or is not operating correctly. In some configurations, the tube heating element may only be needed when a high humidification level is required. In such a configuration, if the user attempts to use a high humidification level when the tube heating element is not present or is not operating correctly, the control circuit 208 may provide a visual warning via the indicator 136, provide an audible warning, communicate the warning condition to a remote device, and / or inhibit certain functionality (depending on the nature of the detected fault). For lower humidification levels, therapy may be provided without requiring the tube heating element to be activated.

[0073] The control circuit 208 can perform fault checks when the humidifier starts up and then intermittently during operation (e.g., every 10 minutes or every 2 hours). Because of the independence of the controllable load 210 from the tube heating element current path, the occurrence of each fault check has negligible effect on the operation of the humidifier.

[0074] Referring to FIG. 3, an exemplary tube heating element supply circuit for a respiratory or surgical humidifier may also include a voltage sensor 216 for sensing the voltage across the voltage source and providing the voltage information via data line 217. The remaining circuit components are similar to those in FIG. 2, and therefore the same reference numbers are used. The operation may be the same as for FIG. 2, except that instead of assuming a constant voltage supply, the actual supply voltage may be used by the control circuit 208. This circuit may be appropriate when there is substantial variation in the supply voltage. This circuit also allows for the identification of faults due to the supply voltage not being within the required range.

[0075] In one embodiment, the tube heating element supply circuit of FIG. 3 can perform a fault checking method in which the following steps are performed (tube heating element 207 is connected between terminals 204 and 205): i. The control circuit 208 controls the power flow controller 206 to switch it on (if it is open at the start of the fault check) while the switch 211 of the switchable load 210 is switched off. ii. The control circuit 208 receives attribute information from the current sensor 209 in the form of a first current level measurement. In this case, the current I H The control circuit 208 also receives attribute information in the form of a voltage level measurement from the voltage sensor 216. Ohm's law is then used to determine the resistance R of the tube heating element 207. H A resistance representing the iii. The control circuit 208 controls the switch 211 of the controllable load 210 to be turned on. iv. The control circuit 208 receives attribute information in the form of a second current level measurement from the current sensor 209. In this case, the current I H , and the current I flowing through resistor 212 D The sum of is measured (I D +I H ). The control circuit 208 also controls the voltage level (V iv ) from the voltage sensor 216. v. The control circuit 208 (which in this case includes a microprocessor) calculates the expected second current level I according to the following formula: exp Determine: I exp =(V iv / R H +V iv / R) where R is the known resistance 212. vi. The control circuit 208 determines the second expected current level I exp · Minus · the first current level measured in step ii. (I H ) to determine the difference in current levels (εI). vii. The control circuit 208 determines if there is a fault in the current sensor 209 (or another component in the supply path) by checking if the current difference (εI) is within the allowed current range. viii. The control circuit 208 also determines the second current level (I D +I H ) is within an acceptable range, it can be determined whether a fault exists in the power flow controller 206. The control circuit 208 determines whether the first current level (I H ) is the expected first current level V iv / R H By checking whether the temperature is within an acceptable difference from the temperature, it can be determined whether the tube heating element is present or whether a fault is present (possibly a fault in the power flow controller 206 or the tube heating element 207). ix. The control circuit 208 also controls a second current level (I D +I H It can be determined whether there is a fault in the power flow controller 206 by checking whether the first current level (I ) exceeds a low current threshold level (at or near zero). Alternatively, for example, if the heater wires are permanently connected, the first current level (I ) can be determined when the power flow controller 206 is switched off and the dummy load switch 211 is switched off. H ) may only be measured. If the current is above a low current threshold level, for example 0.1 A, it may be determined that a fault in the power flow controller 206 is present.

[0076] Should a fault condition be determined to exist, the control circuitry 208 may turn off the power flow controller 206, and / or provide a visual warning via the indicator 136, and / or provide an audible warning, and / or communicate the warning condition to a remote device, and / or inhibit certain functionality (depending on the nature of the fault detected).

[0077] Referring to FIG. 4, an exemplary tube heating element supply circuit for a respiratory or surgical humidifier may also include a transient current detector capable of detecting out-of-tolerance transient currents. In the event of a heater wire break, a transient current in the form of a short-lived non-periodic spike in the supply current could possibly cause the gas supply tube to have a high surface temperature, melt, or catch fire from sparking. These situations may also arise from EMI and / or utility power surges. To prevent these situations, the transient current detector may shut off power to the tube heating element if an out-of-tolerance transient current is detected.

[0078] In the circuit shown in FIG. 4, elements similar to those shown in FIG. 2 and FIG. 3 are given similar reference numbers. As shown in FIG. 4, an inductor 218 may be included in the power supply path with sense lines 221 and 222 connected to a transient current detection circuit 219. When the transient current detection circuit 219 detects an out-of-tolerance transient current, it may send a transient current detection signal or feedback signal via signal line 220 to the control circuit 208. In response, the control circuit 208 may turn off the power flow controller 206 and terminate the power supply to the tube heating element. Additionally and / or alternatively, the transient current detection circuit 219 may directly turn off the power flow controller 206 via signal line 231 and terminate the power supply to the tube heating element. Additionally and / or alternatively, when the transient current detection circuit 219 detects an out-of-tolerance transient current, the control circuit 208 may turn off other components, such as the heater plate, or generate an alarm. Although FIG. 4 shows a circuit further including the switchable load 210 described above, it will be understood that the transient current detector of the present disclosure may alternatively be used independently of the fault detection methods and circuits of the present disclosure.

[0079] 5 shows a simple transient current detection circuit 219 that can be used to detect transient currents. A first transistor detection circuit, including a transistor 225 and bias resistors 223 and 224, is connected to sense lines 221 and 222 and detects the difference in the sense line voltages (V 221 -V 222 ) exceeds an acceptable level. A second transistor detection circuit, including transistor 228 and bias resistors 226 and 227, is also connected to sense lines 221 and 222 and detects the difference in the sense line voltages (V 222 -V 221) exceeds an acceptable level. When both transistors 225 and 228 are switched off (high resistance), a bias resistor 229 holds the transient current detection output signal line 230 high. The output signal line 230 is connected to the power flow controller 206 by a line 220. When either transistor 225 or 228 is switched on, the transient current detection output signal line 230 is pulled down and accordingly the control circuit 208 can turn off the power flow controller 206. FIG. 6 shows a modified transient current detection circuit 219 which is the same as FIG. 5 except that a signal conditioning circuit 240 is provided before the output signal line 230. It may be desirable for the output signal line 230 to be held or continued in a pulled down state for a period other than only the period during which a transient current is detected. The signal conditioning circuit 240 can be a monostable multivibrator with a predefined delay, or some other suitable circuit.

[0080] By connecting the sense lines 221 and 222 with opposite polarity to a transistor detection circuit, a window detector can be provided for detecting positive and negative transient currents using a simple circuit utilizing only two transistors, without the use of a bridge rectifier or a negative power supply.

[0081] The methods and processes described herein may be embodied in and partially or fully automated through software code modules executed by one or more general-purpose and / or special-purpose computers. The word "module" refers to logic embodied in hardware and / or firmware, or in some cases a collection of software instructions, with entry and exit points, written in a programming language, such as, for example, C or C++. Software modules may be compiled and linked into executable programs installed in dynamically linked libraries, or written in interpreted programming languages, such as, for example, BASIC, Perl, or Python. It will be understood that software modules may be callable from other modules or from themselves, and / or may be activated in response to detected events or interrupts. Software instructions may be embedded in non-volatile memory, such as erasable programmable read-only memory (EPROM). It will be further understood that a hardware module may include connected logic units such as gates, flip-flops, and / or application specific integrated circuits, and / or may include programmable units such as programmable gate arrays and / or processors. The modules described herein may be implemented as software modules, but may also be represented in hardware and / or firmware form. Additionally, while in some embodiments a module may be separately compiled, in other embodiments a module may represent a subset of a separately compiled program's instructions and may not have an interface available to other logical program units.

[0082] In particular embodiments, the code modules may be embodied and / or stored in any type of computer readable medium or other computer storage device. In some systems, data (and / or metadata) entered into the system, data generated by the system, and / or data used by the system may be stored in any type of computer data repository, such as a relational database and / or a flat file system. Any of the systems, methods, and processes described herein may include interfaces configured to enable interaction with users, operators, other systems, components, programs, and the like.

[0083] It must be emphasized that many variations and modifications to the embodiments described herein may be made, and that these elements should be understood to fall within other acceptable examples. All such modifications and modifications are intended to be included herein within the scope of this disclosure and protected by the accompanying claims. Moreover, nothing in the above disclosure is intended to imply that any particular component, feature, or process step is essential or critical.

Claims

1. a. a power supply line configured to supply power to a respective output terminal via a supply path; b. a switchable load electrically connected between said output terminals; c. a control circuit configured to control the switching of the switchable load; d. a sensor that monitors at least one attribute of the electrical power provided via said supply path and provides attribute information to said control circuitry; A respiratory or surgical humidifier comprising: A respiratory or surgical humidifier, wherein the control circuit is configured to control the switchable load to operate in different states and to determine operation of the respiratory or surgical humidifier based on the attribute information for the different states.

2. 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 while power is supplied to a tube heating element electrically connected between the output terminals.

3. 3. A respiratory or surgical humidifier as claimed in claim 1 or 2, comprising a power flow controller controlled by the control circuit to vary the level of power supplied through the supply path.

4. 4. A respiratory or surgical humidifier according to claim 3, wherein the power flow controller is a controllable switch in the supply path.

5. A respiratory or surgical humidifier as described in claim 3 or 4, wherein the control circuit controls combinations of states of the switchable loads and power flow controllers and monitors operation of the respiratory or surgical humidifier based on the attribute information for the different state combinations.

6. A respiratory or surgical humidifier according to any preceding claim, wherein the switchable load comprises a controllable switch and an impedance.

7. 7. A respiratory or surgical humidifier according to claim 6, wherein the controllable switch comprises a solid-state switch.

8. 8. A respiratory or surgical humidifier according to claim 6 or 7, wherein the impedance comprises a resistor.

9. 8. A respiratory or surgical humidifier according to claim 6 or 7, wherein the impedance comprises a reactive impedance.

10. A respiratory or surgical humidifier according to any preceding claim, including a voltage sensor between the power supply lines.

11. 11. A respiratory or surgical humidifier according to claim 10, wherein the attribute information comprises a voltage across the power supply lines.

12. A respiratory or surgical humidifier according to any preceding claim, wherein the sensor comprises a current sensor.

13. 13. A respiratory or surgical humidifier according to claim 12, wherein the sensor comprises an inductive, Hall effect, or shunt resistor based sensor.

14. 14. A respiratory or surgical humidifier according to claim 13, wherein the attribute information comprises a current flowing in the supply path.

15. 15. A respiratory or surgical humidifier as described in any one of claims 12 to 14, wherein the control circuit is configured to switch on the power flow controller while the switchable load is switched off and to receive current information from the current sensor representative of a first current level.

16. 16. A respiratory or surgical humidifier as claimed in claim 15, wherein the control circuit is configured to detect an absence or error of a tube heating element if the first current level is outside an acceptable range.

17. 17. A respiratory or surgical humidifier as described in claim 15 or 16, wherein the control circuit is configured to switch on the power flow controller while the switchable load is switched on and to receive current information from the current sensor representative of a second current level.

18. 18. A respiratory or surgical humidifier according to claim 17, wherein the control circuit is configured to detect a fault if a difference between the first and second current levels is outside an acceptable range.

19. 18. The respiratory or surgical humidifier of claim 17, wherein the control circuit is configured to detect an error if a difference between the first current level and an expected first current level or a difference between the second current level and an expected second current level is outside an acceptable range.

20. 20. A respiratory or surgical humidifier as described in claim 18 or 19, wherein the tolerance range for the expected first current level, the expected second current level, or the difference between the first and second current levels is determined based on the voltage level between the output terminals, the impedance of a switchable load, and the impedance of a tube heating element.

21. A respiratory or surgical humidifier according to any one of claims 18 to 20, wherein the acceptable current range is an acceptable current level plus or minus an error.

22. A respiratory or surgical humidifier as claimed in any one of claims 19 to 21, wherein the control circuit is configured to detect a fault if neither the first nor second currents exceed a minimum threshold level.

23. 23. A respiratory or surgical humidifier according to any one of claims 1 to 22, wherein the control circuit is configured to receive current information from the current sensor when the power flow controller is switched off and the switchable load is switched on, and to detect a fault if the current is above a low current threshold level.

24. A respiratory or surgical humidifier according to any preceding claim, including a transient current detector in the supply path.

25. 25. A respiratory or surgical humidifier according to claim 24, wherein the transient current detector comprises a pair of transistors configured to detect positive or negative transient voltages across an inductor in the supply path.

26. 26. A respiratory or surgical humidifier according to claim 24 or 25, wherein the control circuitry turns off the power flow controller if an out of tolerance current transient is detected.

27. A respiratory or surgical humidifier according to any preceding claim, wherein the control circuitry comprises a microprocessor.

28. A respiratory or surgical humidifier according to any preceding claim comprising a tube heating element electrically connected across the output terminals in parallel with the switchable load.

29. a. a power flow controller configured to control power provided to each output terminal via a supply path; b. a switchable load electrically connected between said output terminals; c. a current sensor that monitors the current supplied through the supply path and obtains current information; d. A control circuit comprising: i. receiving the current information from the current sensor; ii. controlling the power flow controller to supply power through the output terminal; and iii. Controlling the switching of the switchable load; A control circuit configured to: A respiratory or surgical humidifier comprising: The control circuit, switching on the power flow controller while the switchable load is switched off and receiving current information from the current sensor representative of a first current level; switching on the power flow controller while the switchable load is switched on and receiving current information from the current sensor representative of a second current level; and determining operation of the respiratory humidifier based on at least the first and second current levels; 1. A respiratory or surgical humidifier configured to:

30. a. a power supply line configured to supply power to a respective output terminal via a supply path; b. a switchable load electrically connected between said output terminals; c. a current sensor that monitors the current supplied through the supply path and obtains current information; d. A control circuit comprising: i. receiving the current information from the current sensor; and ii. Controlling the switching of the switchable load; A control circuit configured to: A respiratory or surgical humidifier comprising: The control circuit, i. switching off the switchable load and receiving current information from the current sensor representative of a first current level; ii. switching on the switchable load and receiving current information from the current sensor representative of a second current level; iii. detecting a fault if a difference between the first and second current levels is outside an acceptable range; 1. A respiratory or surgical humidifier configured to:

31. a. a power flow controller configured to supply power via a supply path to a respective output terminal; b. a switchable load electrically connected between said output terminals; c. a current sensor that monitors the current supplied through the supply path and obtains current information; d. A control circuit comprising: i. receiving the current information from the current sensor; ii. controlling switching of the power flow controller to supply power through the output terminal; and iii. Controlling the switching of the switchable load; A control circuit configured to: A respiratory or surgical humidifier comprising: The control circuit, i. switching on the power flow controller while the switchable load is switched off and receiving current information from the current sensor representative of a first current level; ii. switching on the power flow controller while the switchable load is switched on and receiving current information from the current sensor representative of a second current level; iii. detecting a fault if the second current level is outside an acceptable range; and iv. detecting a fault if a difference between the first and second current levels is outside an acceptable range; 1. A respiratory or surgical humidifier configured to:

32. a. a power flow controller configured to supply power via a supply path to a respective output terminal; b. a switchable load electrically connected between said output terminals; c. a current sensor that monitors the current supplied through the supply path and obtains current information; d. A control circuit comprising: i. receiving the current information from the current sensor; ii. controlling switching of the power flow controller to supply power through the output terminal; and iii. Controlling the switching of the switchable load; A control circuit configured to: A respiratory or surgical humidifier comprising: The control circuit, i. switching on the power flow controller while the switchable load is switched on and receiving current information from the current sensor representative of a test current level; ii. detecting a fault if the test current level is outside an acceptable range; 1. A respiratory or surgical humidifier configured to:

33. a. a power flow controller configured to control power provided to each output terminal via a supply path; b. a switchable load electrically connected between said output terminals; c. a control circuit configured to control the switchable load to perform in-use monitoring of a respiratory or surgical humidifier while the power flow controller provides power to the output terminals; A respiratory or surgical humidifier comprising:

34. a. a housing configured to receive a humidifier chamber; b. a heater plate configured to transfer heat to a humidifier chamber when received by the housing; c. a heater element configured to heat the heater plate; d. a power controller configured to control the power level supplied to the heater element; A respiratory or surgical humidifier according to any one of claims 1 to 33, comprising:

35. 1. A method for monitoring the operation of a respiratory or surgical humidifier having output terminals for supplying power to a tube heating element of a humidifier supply tube, the method comprising temporarily connecting a dummy load between the output terminals while power is supplied to the tube heating element, evaluating one or more power supply attributes, and monitoring correct operation of the respiratory humidifier.

36. 36. The method of claim 35, wherein an error in the operation of the respiratory or surgical humidifier is detected if the current provided through the output terminal falls below a threshold value.

37. 37. The method of claim 35 or 36, wherein a first current supplied through the output terminals is measured when the dummy load is not connected between the output terminals, and a second current supplied through the output terminals is measured when the dummy load is electrically connected between the output terminals, and an error in the operation of the respiratory or surgical humidifier is detected if a difference between the first and second currents is outside an acceptable range.

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