System and method for controlling humidity output in a humidifier

Abstract

A humidifier used to deliver heated and humidified gas to a patient can include a humidification chamber with an inlet and associated sensor, an associated heater and sensor, an inspiratory conduit with an associated heater and sensor, and an unheated patient connection device, such as a face mask. The humidifier can include a control system configured to vary, for example, a humidification chamber outlet temperature setpoint, including a maximum outlet temperature setpoint, or the amount of humidity generated, depending on the inlet gas temperature. This control system can reduce and / or minimize rainout (i.e., condensation) while maintaining a substantially consistent humidity in the gas delivered to the patient.

Description

[Technical Field]

[0001] The present disclosure relates generally to humidifying gases for medical procedures, such as respiratory humidification, humidification during high flow therapy, and humidification during anesthesia / sedation, or other medical procedures in which humidified gases are delivered to a patient. More particularly, the present disclosure relates to a respiratory assistance system including at least a humidifier and a method of operating the humidifier to control the temperature and / or humidity level of respiratory gases. [Background technology]

[0002] During unassisted inspiration, the upper airway heats and humidifies the inhaled gas to humidity conditions of approximately 100% relative humidity, or approximately 44 mg / L absolute humidity, at a body temperature of approximately 37° C. A humidifier operating as part of a respiratory support system can be beneficial in heating and humidifying the respiratory gas to humidity conditions such that the respiratory gas reaching the patient's lungs is humidified, thereby mitigating any adverse physiological effects resulting from the delivery of dry gas to the patient's airways. Summary of the Invention [Problem to be solved by the invention]

[0003] Many humidifiers can monitor the amount of humidity added to the incoming gas, for example, by controlling the power to the humidifier's heater plate to control the absolute humidity of the gas being humidified. However, some humidifiers do not necessarily have an integrated hygrometer or other moisture meter to obtain information about the incoming gas, making it more difficult to directly detect the humidity of the incoming gas. Humidifiers are often used with dry gas sources, such as canister or wall gas sources, or ventilators that supply dry gas (i.e., unhumidified gas). When a humidifier is connected to a room air entrainment ventilator as a gas source, the inability to directly detect the incoming humidity can result in inaccurate delivered humidity, which can often lead to over-humidification of the gas and result in undesirable amounts of condensation (also known as "rainout") in the inspiratory tubing (i.e., gas delivery conduit) or patient-connection equipment.

[0004] This undesirable amount of condensation (i.e., rainout) may result from the fact that the humidity of the air entrained by the room air entrainment ventilation system is typically higher than the dry gas from the wall source or canister. The humidity difference between the room air and the gas from the wall source or canister may be even more pronounced in more tropical countries and regions. Furthermore, room air entrainment ventilation systems typically use turbines, which may heat the gas.

[0005] Because most humidifiers heat and humidify the incoming gas under the assumption that the incoming gas is dry, high humidity in the incoming air can result in excessive humidity being delivered to the patient. Such humidifiers may add excess humidity to the incoming room air to reach a predetermined set point at the humidification chamber outlet, under the assumption that the incoming gas is dry.

[0006] Operating under the aforementioned assumptions, existing humidity from the existing room air can cause the dew point of the gas in the gas flow path to be higher than when dry gas is used as the gas source to the humidifier. Therefore, when room air is used as the gas source, the humidity of the gas at the chamber outlet is typically relatively high. The relatively high humidity of the gas at the chamber outlet requires that the temperature of the gas be maintained above the dew point to prevent condensation. In comparison, when dry gas is used as the gas source, the gas at the chamber outlet may have a relatively low humidity and a relatively low dew point. Therefore, the temperature of the gas when dry gas is used as the gas source may be lower due to the relatively low dew point. As the gas flow cools along the flow path between the humidification chamber and the patient connection device, the humidity is higher than expected for gas from the room entrainment ventilation system. This narrows the available temperature range to which the gas can be cooled before reaching the dew point, resulting in rainout. Rainout is particularly a problem in the patient connection device at the distal end or patient side of the intake tubing (i.e., guide tube), thereby causing discomfort and / or inconvenience to the patient. Furthermore, rainout is a greater problem because the patient connection device and its components are not heated, resulting in a relatively rapid temperature drop compared to the intake tubing, which is typically heated. Furthermore, condensation within the tubing or patient connection device can be dangerous to the patient. [Means for solving the problem]

[0007] The present disclosure provides systems and methods for reducing rainout in the inspiratory tract and / or patient connection device while still delivering a substantially consistent target humidity to the patient. The present disclosure relates to systems and methods for reducing rainout while humidifying ambient air and still providing a minimum therapeutic humidity to the patient. The minimum therapeutic humidity reduces dehumidification or drying of the patient's airway, improving patient comfort.

[0008] The humidifier can provide various levels of therapeutic humidity in various therapy applications, such as in a hospital or home health care environment. For example, the humidifier can deliver a desired humidity level of about 44 mg / L BTPS (fully saturated at about 37° C.) for invasive and / or high-flow therapy, and / or about 32 mg / L BTPS (fully saturated at about 31° C.) for non-invasive therapy. Other appropriate patient comfort settings can also be delivered for various therapy types.

[0009] The system can output a desired humidity level in the gas delivered to the patient over a range of inlet source conditions, such as a gas source including various chamber inlet temperatures (i.e., inlet temperatures) and / or room air entrainment ventilation. Advantageously, the system can reduce rainout, for example, by reducing the humidity output of the humidification chamber below the desired humidity.

[0010] In some examples, the desired humidity of the gas delivered to the patient by the humidifier may be based on one or more assumptions about the input gas, such as that the input gas is dry. However, such assumptions are not always correct. For example, when the input gas, such as ambient air, contains some moisture, the humidity of the gas delivered to the patient may be too high, resulting in rainout. In some systems, rainout may be managed by using a humidity sensor or by otherwise directly measuring the humidity of the input gas. However, the system may reduce the humidity output of the humidifier's humidification chamber while maintaining a substantially consistent humidity in the gas delivered to the patient without using a humidity sensor and / or receiving direct input of the humidity of the input gas. For example, the system may determine a parameter of the input gas and use the determined parameter as an indication of the type of input gas and / or the type of gas source.

[0011] Described herein are exemplary systems and methods for reducing excess condensation in a humidifier while still delivering a substantially consistent humidity level of the gas delivered to a patient, regardless of the type of gas source (e.g., regardless of the type of ventilator). Certain aspects, advantages, and novel features of the present disclosure are described herein. It is understood that not all such advantages may necessarily be achieved in accordance with any particular embodiment of the present disclosure. Thus, the features, aspects, and advantages of the present disclosure may be implemented or carried out in a manner that achieves or selects one advantage or group of advantages taught herein without necessarily achieving other advantages that may be taught or suggested herein.

[0012] A humidifier for humidifying a gas stream supplied to a user may include a base unit that may include a heater plate; a humidification chamber that may be configured to hold a humidifying fluid, the humidification chamber may include a conductive base, one or more wall portions that may be configured to be coupled to the base portion, an inlet, and an outlet; at least one inlet temperature sensor disposed within or adjacent to the inlet of the humidification chamber; and at least one outlet temperature sensor disposed within or adjacent to the outlet of the humidification chamber; and a controller that may be configured to output a heater plate control signal to control the amount of power supplied to the heater plate in response to an outlet temperature being measured from a signal received from the outlet temperature sensor; determine an inlet temperature of gas received by the humidification chamber based on the signal received from the inlet temperature sensor; determine when the inlet temperature exceeds a threshold temperature; and reduce a target humidity of gas exiting the outlet of the humidification chamber in response to the inlet temperature exceeding the threshold temperature.

[0013] The humidifier may reduce the target humidity, and the controller may be configured to reduce the amount of power supplied to the heater plate in response to the inlet temperature exceeding a threshold temperature. This reduced target humidity is achieved by controlling the power supplied to the heater plate. The amount of power supplied to the heater plate produces the required target humidity. The target humidity is reduced from the target humidity limit to a relatively lower target humidity. In another exemplary implementation, the controller is configured to cap or limit the target humidity to a second humidity when the inlet temperature exceeds the threshold temperature.

[0014] The controller may be configured to reduce the amount of power below a power threshold.

[0015] The power threshold may be set to achieve a minimum dew point of 19°C.

[0016] The power threshold may be set to achieve a minimum humidity output of 15 mg / L.

[0017] The power threshold may be set to achieve a dew point of 25°C.

[0018] The power threshold may be set to achieve a humidity output of 22 mg / L.

[0019] The controller may be configured to control the amount of power supplied to the heater plate in a first mode when the inlet temperature is below a threshold temperature and in a second mode when the inlet temperature is above the threshold temperature.

[0020] In a first mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum humidity of at least 15 mg / L.In a second mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum humidity of at least 22 mg / L.

[0021] In a first mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum dew point of at least 19° C. In a second mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum dew point of at least 25° C.

[0022] The controller may be configured to control the amount of power supplied to the heater plate power according to a first function that is applied when the inlet temperature is below a threshold temperature.

[0023] The controller may be configured to control the amount of power supplied to the heater plate power according to a second function, which may be different from the first function, that is applied when the inlet temperature exceeds a threshold temperature. The first function and the second function may together define a piecewise function.

[0024] The controller may be configured to lower the target outlet temperature if the inlet temperature exceeds a threshold temperature. If the inlet temperature exceeds the threshold temperature, the target outlet temperature is lowered from a target outlet temperature limit to a lower target outlet temperature. In another example, the controller is configured to limit or cap the target outlet temperature.

[0025] The controller may be configured to decrease the target heater plate temperature if the inlet temperature exceeds the threshold temperature. If the inlet temperature exceeds the threshold temperature, the target heater plate temperature is decreased from the target heater plate temperature limit to a lower target heater plate temperature. In another example, the controller is configured to limit or cap the target heater plate temperature.

[0026] The threshold temperature may be between 22°C and 24°C.

[0027] The threshold temperature may be 22°C.

[0028] The threshold temperature may be 24°C.

[0029] This threshold temperature may vary depending on the outlet temperature set point.

[0030] The desired dew point may be selected by the user.

[0031] The humidifier may be operable in one of a plurality of modes, each mode defining a plurality of desired dew points, and when operating in any one of the plurality of modes, the controller may be configured to reduce the amount of humidity generated based on an inlet temperature exceeding a threshold value.

[0032] The multiple modes may include an invasive mode, a non-invasive mode, and a high flow mode.

[0033] The mode may be manually selectable by the user.

[0034] The non-invasive mode may include desired dew points of 31°C, 29°C, 27°C, and 25°C.

[0035] The humidifier may be operable in one of a plurality of modes, each mode defining a plurality of outlet temperature set points, and when operating in any one of the plurality of modes, the controller may be configured to reduce the amount of humidity generated based on the inlet temperature exceeding a threshold.

[0036] A target humidity for the outlet temperature setpoint may be predetermined when the inlet temperature may fall below a threshold temperature, and if the inlet temperature exceeds the threshold, the amount of humidity produced at that outlet temperature setpoint may be reduced to a relatively low, predetermined value.

[0037] A humidifier for humidifying a gas stream supplied to a user may include a base unit that may include a heater plate; a humidification chamber that may be configured to hold a humidifying fluid, the humidification chamber may include a conductive base, one or more wall portions that may be configured to be coupled to the base portion, an inlet, and an outlet; at least one inlet temperature sensor disposed within or adjacent to the inlet of the humidification chamber; and at least one outlet temperature sensor disposed within or adjacent to the outlet of the humidification chamber; and an electronic controller that may be configured to: output a heater plate control signal to control the amount of power supplied to the heater plate in response to an outlet temperature being measured from a signal received from the outlet temperature sensor; determine an inlet temperature of the gas received by the humidification chamber based on the signal received from the inlet temperature sensor; determine whether the inlet temperature exceeds a threshold temperature; and reduce a target humidity of the gas exiting the outlet of the humidification chamber in response to the inlet temperature exceeding the threshold temperature.

[0038] The humidifier may reduce the target humidity and the controller may be configured to reduce the amount of power supplied to the heater plate in response to the inlet temperature exceeding a threshold temperature.

[0039] The controller may be configured to reduce the amount of power below a power threshold.

[0040] A decrease in the amount of power delivered to the heater plate below the power threshold decreases the humidity output of the humidifier. The controller is configured to deliver power to the heater plate corresponding to the target humidity. The power delivered to the heater plate of the humidifier causes the humidifier to output a humidity at or near the target humidity.

[0041] The power threshold may be set to achieve a minimum dew point of 19°C.

[0042] The power threshold may be set to achieve a minimum humidity output of 15 mg / L.

[0043] The power threshold may be set to achieve a dew point of 25°C.

[0044] The power threshold may be set to achieve a humidity output of 22 mg / L.

[0045] The controller may be configured to control the amount of power supplied to the heater plate in a first mode when the inlet temperature is below a threshold temperature and in a second mode when the inlet temperature is above the threshold temperature.

[0046] In a first mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum humidity of at least 15 mg / L.In a second mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum humidity of at least 22 mg / L.

[0047] In a first mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum dew point of at least 19° C. In a second mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum dew point of at least 25° C.

[0048] The controller may be configured to control the amount of power supplied to the heater plate power according to a first function that is applied when the inlet temperature is below a threshold temperature.

[0049] The controller may be configured to control the amount of power supplied to the heater plate power according to a second function, which may be different from the first function, that is applied when the inlet temperature exceeds a threshold temperature.

[0050] The first function and the second function define a piecewise function. The piecewise function may define heater plate power. A further piecewise function may define a target humidity. The piecewise function for the target humidity may correspond to or be related to the piecewise function that defines the heater plate power.

[0051] If the inlet temperature exceeds the threshold temperature, the controller may be configured to decrease the target outlet temperature.

[0052] If the inlet temperature exceeds a threshold temperature, the controller may be configured to decrease the target heater plate temperature.

[0053] The threshold temperature may be between 22°C and 24°C.

[0054] The threshold temperature may be 22°C.

[0055] The threshold temperature may be 24°C.

[0056] This threshold temperature may vary depending on the outlet temperature set point.

[0057] The desired dew point may be selected by the user.

[0058] The humidifier may be operable in one of a plurality of modes, each mode defining a plurality of desired dew points, and when operating in any one of the plurality of modes, the controller may be configured to reduce the amount of humidity generated based on an inlet temperature exceeding a threshold value.

[0059] The multiple modes may include an invasive mode, a non-invasive mode, and a high flow mode.

[0060] The mode may be manually selectable by the user.

[0061] The non-invasive mode may include desired dew points of 31°C, 29°C, 27°C, and 25°C.

[0062] The humidifier may be operable in one of a plurality of modes, each mode defining a plurality of outlet temperature set points, and when operating in any one of the plurality of modes, the controller may be configured to reduce the amount of humidity generated based on the inlet temperature exceeding a threshold.

[0063] A target humidity for the outlet temperature setpoint may be predetermined when the inlet temperature may fall below a threshold temperature, and if the inlet temperature exceeds the threshold, the amount of humidity produced at that outlet temperature setpoint may be reduced to a relatively low, predetermined value.

[0064] A humidifier for humidifying a gas stream delivered to a user includes a base unit including a heater plate; a removable humidification chamber that can include a conductive base and one or more walls extending from the conductive base, the one or more walls and the conductive base defining a chamber space for holding a humidification fluid, the humidification chamber further including an inlet and an outlet; at least one inlet temperature sensor disposed within or adjacent to the inlet of the humidification chamber; and at least one outlet temperature sensor disposed within or adjacent to the outlet of the humidification chamber. and an electronic controller that may be configured to output a heater plate control signal to control the amount of power supplied to the heater plate in response to determining an outlet temperature from a signal received from the outlet temperature sensor, measure an inlet temperature of gas received by the humidification chamber based on a signal received from the inlet temperature sensor, determine that the inlet temperature exceeds a threshold temperature, set a first outlet temperature setpoint if the inlet temperature is below the threshold temperature, and set a second outlet temperature setpoint if the gas inlet temperature exceeds or equals the threshold temperature.

[0065] The threshold temperature may be between 22°C and 24°C.

[0066] The first outlet temperature set point may be between 24°C and 32°C.

[0067] The second outlet temperature set point may be between 19°C and 27°C.

[0068] The electronic controller may be configured to control the power supplied to the heater plate based on the chamber outlet temperature set point.

[0069] The electronic controller may be configured to reduce heater plate power when the inlet temperature exceeds a threshold temperature.

[0070] The electronic controller is configured to control power delivery such that a first power is delivered to the heater plate when the inlet temperature is below a threshold temperature and a second power is delivered to the heater plate when the inlet temperature exceeds or equals the threshold temperature.

[0071] The electronic controller is configured to cap or limit the amount of power delivered to the heater plate when the inlet temperature exceeds or equals a threshold temperature.

[0072] The electronic controller may be configured to set the first chamber outlet temperature setpoint corresponding to a humidity value between 21 mg / L and 34 mg / L.

[0073] The electronic controller may be configured to set a second chamber outlet temperature setpoint corresponding to a humidity value between 14 mg / L and 25 mg / L.

[0074] The electronic controller may be configured to reduce the power supplied to the heater plate if the inlet temperature exceeds a temperature threshold.

[0075] The power supplied to the heater plate may be reduced from a power limit. In another example, the power supplied to the heater plate may be capped or limited if the inlet temperature exceeds a temperature threshold.

[0076] The electronic controller may be configured to supply heater plate power corresponding to the first or second chamber outlet setpoint temperature so that the required amount of humidity can be produced.

[0077] A humidifier for humidifying a gas flow supplied to a user may include a base unit including a heater plate, a removable humidification chamber that may include a conductive base and one or more walls extending from the conductive base, the one or more walls and the conductive base defining a chamber space for holding a humidification fluid, the humidification chamber may further include an inlet and an outlet, at least one inlet temperature sensor positioned within or adjacent to the inlet of the humidification chamber and configured to determine an inlet temperature, at least one outlet temperature sensor positioned within or adjacent to the outlet of the humidification chamber and configured to determine an outlet temperature, and an electronic controller configured to determine whether the inlet temperature exceeds a threshold temperature and to set an upper limit on a maximum allowable chamber outlet temperature, heater plate temperature, or allowable heater plate power at a corresponding inlet temperature.

[0078] The maximum allowable chamber outlet temperature defined by the second function may be lower than the maximum allowable chamber outlet temperature defined by the first function.

[0079] The absolute humidity produced by the first function may be higher than the humidity output produced by the second function.

[0080] The humidifier may include a heater plate, and the controller may be configured to control power supplied to the heater plate based on a maximum allowable outlet temperature.

[0081] The controller may be configured to control the power supplied to the heater plate based on the first function or the second function.

[0082] When the gas source may be a low temperature dry gas source, the controller may be configured to use the first function.

[0083] When the gas source may be a room air entrained gas source, the controller may be configured to use a second function.

[0084] A humidifier for humidifying a gas flow supplied to a user may comprise: a base unit including a heater plate; a removable humidification chamber that may include a conductive base and one or more walls extending from the conductive base, the one or more walls and the conductive base defining a chamber space for holding a humidification fluid, the humidification chamber may further include an inlet and an outlet; at least one inlet temperature sensor disposed within or adjacent to the inlet of the humidification chamber and configured to measure an inlet temperature; at least one outlet temperature sensor disposed within or adjacent to the outlet of the humidification chamber and configured to measure an outlet temperature; and an electronic controller configured to control to a predetermined maximum allowable outlet temperature for a corresponding inlet temperature, the maximum allowable outlet temperature may be related to the inlet temperature defined by a first function, and to apply a second function that defines a new maximum allowable outlet temperature for the corresponding inlet temperature based on the inlet temperature.

[0085] The maximum allowable chamber outlet temperature defined by the second function may be lower than the maximum allowable chamber outlet temperature defined by the first function.

[0086] The absolute humidity produced by the first function may be higher than the humidity output produced by the second function.

[0087] The humidifier may include a heater plate, and the controller may be configured to control power supplied to the heater plate based on a maximum allowable outlet temperature.

[0088] The controller may be configured to control the power supplied to the heater plate based on the first function or the second function.

[0089] When the gas source may be a low temperature dry gas source, the controller may be configured to use the first function.

[0090] When the gas source may be a room air entrained gas source, the controller may be configured to use a second function.

[0091] The controller is configured to use or implement a first function when the inlet temperature is below a threshold temperature, and is further configured to use or implement a second function when the inlet temperature is equal to or greater than the threshold temperature.

[0092] An electronic control device for controlling humidity in a gas stream supplied to a user using a humidifier may include a heater plate in a base unit; and a humidification chamber including a conductive base and one or more walls extending from the conductive base, the humidification chamber further including an inlet and an outlet, and configured to hold a humidifying fluid; and may be configured to: output a heater plate control signal to control the amount of power supplied to the heater plate of the humidifier in response to an outlet temperature of the humidification chamber being measured from a signal received from the outlet temperature sensor; measure an inlet temperature of the gas received by the humidification chamber based on a signal received from the inlet temperature sensor; determine that the inlet temperature exceeds a threshold temperature; and reduce a target humidity of the gas exiting the outlet of the humidification chamber in response to the inlet temperature exceeding the threshold temperature.

[0093] To reduce the target humidity, the controller may be configured to reduce the amount of power supplied to the heater plate in response to the inlet temperature exceeding a threshold temperature.

[0094] The controller may be configured to reduce the amount of power below a power threshold.

[0095] The power threshold may be set to achieve a minimum dew point of 19°C.

[0096] The power threshold may be set to achieve a minimum humidity output of 15 mg / L.

[0097] The power threshold may be set to achieve a dew point of 25°C.

[0098] The power threshold may be set to achieve a humidity output of 22 mg / L.

[0099] The electronic controller may be configured to control the amount of power supplied to the heater plate in a first mode when the inlet temperature is below a threshold temperature and in a second mode when the inlet temperature is above the threshold temperature.

[0100] In a first mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum humidity of at least 15 mg / L.In a second mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum humidity of at least 22 mg / L.

[0101] In a first mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum dew point of at least 19° C. In a second mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum dew point of at least 25° C.

[0102] The electronic controller may be configured to output a heater plate control signal according to a first function that is applied when the inlet temperature is below a threshold temperature.

[0103] The electronic controller may be configured to output the heater plate control signal according to a second function, which may be different from the first function, that is applied when the inlet temperature exceeds a threshold temperature.

[0104] In one example, the first function and the second function define a piecewise function.

[0105] If the inlet temperature exceeds the threshold temperature, the electronic controller may be configured to decrease the target outlet temperature.

[0106] If the inlet temperature exceeds a threshold temperature, the electronic controller may be configured to reduce the target heater plate temperature.

[0107] The threshold temperature may be between 22°C and 24°C.

[0108] The threshold temperature may be 22°C.

[0109] The threshold temperature may be 24°C.

[0110] The threshold temperature may vary depending on the desired dew point.

[0111] This desired dew point may be selected by the user.

[0112] The controller may be configured to determine a humidifier mode from a plurality of modes, a mode defining a plurality of desired dew points, and determine a temperature threshold based on the humidifier mode.

[0113] The multiple modes may include an invasive mode, a non-invasive mode, and a high flow mode.

[0114] The mode may be manually selectable by the user.

[0115] The non-invasive mode may include desired dew points of 31°C, 27°C, and 25°C.

[0116] A target humidity for the outlet temperature setpoint may be predetermined when the inlet temperature may fall below a threshold temperature, and if the inlet temperature exceeds the threshold, the amount of humidity produced at that outlet temperature setpoint may be reduced to a relatively low, predetermined value.

[0117] A method for reducing condensation at an outlet of a humidifier may include receiving an inlet temperature of gas received in a humidifier chamber based on a signal received from an inlet temperature sensor, determining that the inlet temperature exceeds a threshold temperature, and reducing a target humidity of the gas exiting the outlet of the humidifier chamber in response to the inlet temperature exceeding the threshold temperature.

[0118] Reducing the target humidity can include reducing the amount of power supplied to the heater plate in response to the inlet temperature exceeding a threshold temperature. In response to the inlet temperature exceeding the threshold temperature, the amount of power supplied to the heater plate is capped or limited.

[0119] Reducing the amount of power supplied to the heater plate may include reducing the amount of power below a power threshold.

[0120] The power threshold may be set to achieve a minimum dew point of 19°C.

[0121] The power threshold may be set to achieve a minimum humidity output of 15 mg / L.

[0122] The power threshold may be set to achieve a dew point of 25°C.

[0123] The power threshold may be set to achieve a humidity output of 22 mg / L.

[0124] Reducing the amount of power can include controlling the amount of power supplied to the heater plate in a first mode when the inlet temperature is below a threshold temperature and in a second mode when the inlet temperature is above the threshold temperature.

[0125] In a first mode, the power setpoint, or chamber exit setpoint, or heater plate temperature setpoint may be set to achieve a minimum humidity of at least 15 mg / L.In a second mode, the power setpoint, or chamber exit setpoint, or heater plate temperature setpoint may be set to achieve a minimum humidity of at least 22 mg / L.

[0126] In a first mode, the power setpoint, or chamber outlet setpoint, or heater plate temperature setpoint may be set to achieve a minimum dew point of at least 19° C. In a second mode, the power setpoint, or chamber outlet setpoint, or heater plate temperature setpoint may be set to achieve a minimum dew point of at least 25° C.

[0127] Reducing the amount of power can include controlling the amount of power supplied to the heater plate power according to a first function that is applied when the inlet temperature is below a threshold temperature.

[0128] Reducing the amount of power can include controlling the amount of power supplied to the heater plate power according to a second function, which may be different from the first function, that is applied when the inlet temperature exceeds a threshold temperature.

[0129] Decreasing the target outlet temperature when the inlet temperature exceeds a threshold temperature.

[0130] Decrease the target heater plate temperature if the inlet temperature exceeds the threshold temperature.

[0131] The threshold temperature may be between 22°C and 24°C.

[0132] The threshold temperature may be 22°C.

[0133] The threshold temperature may be 24°C.

[0134] The threshold temperature may vary depending on the desired dew point.

[0135] This desired dew point may be selected by the user.

[0136] The method may further include determining a humidifier mode from a plurality of modes, a mode defining a plurality of desired dew points, and determining a temperature threshold based on the humidifier mode.

[0137] The multiple modes may include an invasive mode, a non-invasive mode, and a high flow mode.

[0138] This mode may be manually selectable by the user.

[0139] The non-invasive mode may include desired dew points of 31°C, 29°C, 27°C, and 25°C.

[0140] A target humidity for the outlet temperature setpoint may be predetermined when the inlet temperature may fall below a threshold temperature, and if the inlet temperature exceeds the threshold, the amount of humidity produced at that outlet temperature setpoint may be reduced to a relatively low, predetermined value.

[0141] A controller for operating the humidifier may be configured to receive an inlet temperature of the gas received in the humidifier chamber based on a signal received from the inlet temperature sensor, determine that the inlet temperature exceeds a threshold temperature, and reduce a target heater plate power or a target heater plate temperature of the gas exiting the outlet of the humidifier chamber in response to the inlet temperature exceeding the threshold temperature.

[0142] To reduce the amount of power supplied to the heater plate, the controller may be configured to reduce this amount of power below a power threshold.

[0143] The power threshold may be set to achieve a minimum dew point of 19°C.

[0144] The power threshold may be set to achieve a minimum humidity output of 15 mg / L.

[0145] The power threshold may be set to achieve a dew point of 25°C.

[0146] The power threshold may be set to achieve a humidity output of 22 mg / L.

[0147] To reduce the amount of power, the controller may be configured to control the amount of power supplied to the heater plate in a first mode when the inlet temperature is below a threshold temperature and in a second mode when the inlet temperature is above the threshold temperature.

[0148] In a first mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum humidity of at least 15 mg / L.In a second mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum humidity of at least 22 mg / L.

[0149] In a first mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum dew point of at least 19° C. In a second mode, the controller may be configured to set a power setpoint, or a chamber outlet setpoint, or a heater plate temperature setpoint to achieve a minimum dew point of at least 25° C.

[0150] To reduce the amount of power, the controller may be configured to control the amount of power supplied to the heater plate power according to a first function that is applied when the inlet temperature is below a threshold temperature.

[0151] To reduce the amount of power, the controller may be configured to control reducing the amount of power supplied to the heater plate power according to a second function, which may be different from the first function, that is applied when the inlet temperature exceeds a threshold temperature.

[0152] The threshold temperature may be between 22°C and 24°C.

[0153] The threshold temperature may be 22°C.

[0154] The threshold temperature may be 24°C.

[0155] The threshold temperature may vary depending on the desired dew point.

[0156] This desired dew point may be selected by the user.

[0157] The controller may be configured to determine a humidifier mode from a plurality of modes, a mode defining a plurality of desired dew points, and determine a temperature threshold based on the humidifier mode.

[0158] The multiple modes may include an invasive mode, a non-invasive mode, and a high flow mode.

[0159] This mode may be manually selectable by the user.

[0160] The non-invasive mode may include desired dew points of 31°C, 29°C, 27°C, and 25°C.

[0161] A target humidity for the outlet temperature setpoint may be predetermined when the inlet temperature may fall below a threshold temperature, and if the inlet temperature exceeds the threshold, the amount of humidity produced at that outlet temperature setpoint may be reduced to a relatively low, predetermined value.

[0162] In a further aspect, a humidifier for humidifying a gas flow delivered to a user is disclosed, the humidifier comprising: a base unit including a heater plate; A humidification chamber configured to hold a humidification fluid, Conductive base, one or more wall portions configured to be coupled to the base portion; Entrance, and Exit a humidification chamber comprising: at least one inlet temperature sensor located within or adjacent to an inlet of the humidification chamber; at least one outlet temperature sensor located in or adjacent to an outlet of the humidification chamber; outputting a heater plate control signal to control the amount of power supplied to the heater plate based at least in part on a function of the outlet temperature measured from the signal received from the outlet temperature sensor; determining an inlet temperature of the gas received by the humidification chamber based on a signal received from the inlet temperature sensor; It is determined that the inlet temperature exceeds a threshold temperature, In response to the inlet temperature exceeding a threshold temperature, reducing the maximum target humidity of the gas exiting the outlet of the humidification chamber. and an electronic control device configured as follows: The controller is configured to calculate an amount of power to be supplied to the heater plate based on a function of the outlet temperature. The controller is configured to cap a maximum allowable heater plate power based on a maximum allowable chamber outlet temperature setpoint.

[0163] The terms conduit and tube are used interchangeably herein. [Brief explanation of the drawings]

[0164] [Figure 1] 1 shows a diagram of an exemplary respiratory assistance system. [Figure 2A] 1 shows a block diagram of an exemplary control system that interacts with and / or controls and directs components of a respiratory assistance system. [Figure 2B]1 shows a block diagram of an exemplary control device. [Figure 3] 1 shows the potential gas types at the inlet of the humidification chamber. [Figure 4A] 1 shows an exemplary graph of actual humidity in outlet gas as a function of inlet temperature in a room air entrainment ventilation system. [Figure 4B] 1 shows an exemplary graph of actual humidity in outlet gas as a function of inlet temperature in a room air entrainment ventilation system for various non-invasive user settings of the humidifier. [Figure 5A] 10 is a graph showing an exemplary effect of additional room air humidity at an inlet temperature of 36° C. [Figure 5B] 10 is a graph showing an exemplary effect of additional room air humidity at an inlet temperature of 26° C. [Figure 5C] 10 is a graph showing an exemplary effect of additional room air humidity at an inlet temperature of 21° C. [Figure 6A] 10 illustrates an exemplary process for setting the maximum chamber outlet set point based on the inlet temperature. [Figure 6B] 10 illustrates another exemplary process for setting the maximum chamber outlet set point based on the inlet temperature. [Figure 7] 10 shows exemplary improved outlet humidity levels for gas conditions at the inlet of the humidifier. [Figure 8] 10 shows exemplary maximum chamber outlet temperature limits as a function of chamber inlet temperature at various exemplary user settings for the humidifier. [Figure 9A] 1 shows an example of humidity added by an exemplary humidifier as a function of inlet temperature and humidity added by the humidifier. [Figure 9B] 1 shows an example of humidity added by an exemplary humidifier as a function of inlet temperature and humidity added by the humidifier. [Figure 10A] 10 is a graph illustrating an exemplary operation of an exemplary humidity delivery control system in non-invasive mode at an inlet temperature of 36° C. [Figure 10B]10 is a graph illustrating an exemplary operation of an exemplary humidity delivery control system in non-invasive mode at an inlet temperature of 26° C. [Figure 10C] 10 is a graph illustrating an exemplary operation of an exemplary humidity delivery control system in non-invasive mode at an inlet temperature of 21° C. DETAILED DESCRIPTION OF THE INVENTION

[0165] Overview A respiratory assistance system for delivering heated and humidified gas to a patient may include a patient connection device configured to deliver a flow of respiratory gas received from a gas source, and an inhalation conduit configured to fluidly connect with the patient connection device and the gas source via a humidifier. The humidifier may include a humidification chamber having at least one wall defining the chamber such that the chamber can hold a liquid, a chamber inlet, a chamber outlet, and a gas flow path between the chamber inlet and the chamber outlet. The chamber inlet may be configured to be fluidly connected with the gas source, and the chamber outlet may be configured to be fluidly connected with the inhalation conduit. The humidification chamber may hold a quantity of liquid (e.g., water). The humidifier may include a heater plate configured to heat a quantity of liquid and the flow of respiratory gas in the gas flow path within the humidification chamber to heat and humidify the flow of respiratory gas. The humidifier may also include a controller having one or more hardware processors configured to control the amount of power supplied to the heater plate.

[0166] Examples of humidifiers disclosed herein can include a controller configured to vary the humidification chamber outlet temperature setpoint as a function of the chamber inlet temperature. For example, the controller can be configured to detect the inlet gas temperature. As the chamber inlet temperature increases, the controller can reduce the desired humidity level at the outlet to a relatively low level (e.g., a relatively low therapeutic level) to allow for and account for additional humidity that may be added if a room air entrainment ventilation system is connected to the humidifier. The controller can decrease the desired humidity level by optionally changing the heater plate power setpoint or heater plate temperature setpoint. These two parameters may be used in addition to or instead of the chamber outlet setpoint. The controller may be configured to limit or cap the chamber outlet temperature setpoint when the inlet temperature exceeds a threshold value, thereby capping the amount of humidity generated by the humidifier to account for increased humidity in the ambient air. The capped chamber outlet temperature setpoint may define a maximum allowable temperature setpoint. The humidifier controller is configured to stay below a capped chamber outlet temperature setpoint (i.e., the highest allowable temperature setpoint). Additionally or alternatively, the power supplied to the heater plate may be capped or limited if the inlet gas temperature exceeds a threshold to define a maximum allowable heater plate power setpoint. If the inlet gas temperature exceeds the threshold, the controller may also cap or limit the heater plate temperature setpoint. The capped heater plate temperature setpoint defines the highest allowable heater plate temperature setpoint for the state (i.e., mode) when the inlet gas temperature exceeds the threshold. This threshold may be a temperature threshold. This process may enable the humidifier to maintain and / or deliver therapeutic levels of humidity while reducing condensation that may occur on the inspiratory tubing and / or patient connection equipment as a result of adding humidity to the incoming gas.Thus, the systems and methods described herein can take into account various inlet humidity levels within a respiratory assistance system and can improve patient comfort by reducing rainout when the humidity of the inlet gas is higher than that of dry gas.

[0167] The humidifier and / or humidifier controller disclosed herein may be configured to control the humidifier to operate in two modes: a first mode is a relatively cool and / or low humidity inlet gas mode, and a second mode is a relatively warm and / or high humidity inlet gas mode, e.g., ambient air. The controlled operating mode may be based on the inlet gas temperature. If the inlet gas temperature (or inlet temperature) is below a threshold, the humidifier functions in the first mode. If the inlet gas temperature exceeds the threshold (i.e., the inlet temperature, i.e., the inlet gas temperature exceeds the threshold), the controller operates in the second mode. The second mode reduces the humidity output of the humidifier. This can be achieved by capping or limiting the chamber outlet temperature setpoint to reduce the amount of humidity generated by the humidifier. In other words, the chamber outlet temperature setpoint may be limited or capped based on the gas inlet temperature to define a maximum allowable chamber outlet setpoint. The humidifier controller is configured to modify the maximum allowable chamber outlet setpoint based on the determined inlet temperature. The controller is configured to control heater plate power to ensure the gas temperature is below the maximum allowable chamber outlet setpoint. Additionally or alternatively, the controller may cap or limit the heater plate temperature setpoint or heater plate power to reduce or cap or further reduce or cap the humidity generated in the second mode compared to the first mode. Thus, the second mode can compensate for humidity present in the inlet gas (e.g., when the inlet gas is relatively humid ambient air).

[0168] The humidifiers and methods of use described herein can be used to achieve high-flow, non-invasive, invasive, and / or other therapies. The humidifiers can be operated in invasive, non-invasive, high-flow, or other modes. The humidifiers can be operated with a variety of patient connection devices, such as an endotracheal tube (ET tube), full face mask, nasal mask, nasal cannula, nasal pillows, sealing prongs, or any other connection device. Other desired humidity levels may be achievable, and other types of therapy systems may be used. The chamber outlet temperature setpoint can be adjusted depending on the therapy being provided and the desired humidity level.

[0169] Exemplary Humidifier 1 shows a schematic diagram of an exemplary respiratory assistance system 100. As shown, the respiratory assistance system 100 includes a humidifier 104, a gas source 102, a patient-to-patient interface 116, and an inspiratory conduit 106 configured to transport respiratory gas from the humidifier 104 to the patient-to-patient interface 116. The gas source 102 and the humidifier 104 may be in separate housings, may be located adjacent to each other in the same housing, and / or may be included in a single device. The respiratory assistance system 100 also includes an optional expiratory conduit 120 configured to transport gas from the patient-to-patient interface 116 to the gas source 102, and an optional Y-piece 114 configured to connect the inspiratory conduit 106 and the expiratory conduit 120 to the patient-to-patient interface 116. The respiratory assistance system 100 may not include the expiratory conduit 120 or may include an expiratory port. Depending on whether an expiratory conduit or an expiratory port is included, the operating parameters of the respiratory assistance system 100 may need to be adjusted. In one example, the humidifier is configured to operate with multiple operating parameters that are modifiable to allow the humidifier to operate in various configurations, for example, a single lobe configuration (i.e., inspiratory conduit only) or a dual lobe configuration (i.e., inspiratory and expiratory conduits).

[0170] As shown, the gas source 102 includes a ventilator 124, which may include a blower or, alternatively, a turbine. The gas source 102 may also include other mechanisms for delivering or pumping a flow of breathing gas to the humidifier 104, such as a valve arrangement or a pump. The gas source 102 in FIG. 1 is an exemplary room entrainment ventilator or ambient air entrainment ventilator. The gas source 102 may include an inlet 122 through which ambient air is drawn into the gas source 102, for example, by the ventilator 124. The gas source 102 may include a controller 126 configured to control operation of the ventilator 124. The gas source 102 may include a user interface 132 that can present information about user input to the controller 126. The controller 126 can control operation of the ventilator 124 based on information presented by the user interface 132 and / or based on other information, such as, but not limited to, feedback from the ventilator 124, such as from sensors associated with the ventilator 124. Instead of drawing in ambient air, inlet 122 can be connected to a source of dry gas, such as a gas cylinder or tank. This type of ventilator is sometimes referred to as a non-entrained ventilator and may be controlled by one or more valves, such as proportional valves. The valves may be controlled by a controller, such as controller 126.

[0171] The humidifier 104 may include a base unit, a humidification chamber 134, and a heater plate 136. The heater plate 136 is disposed on the base unit. The humidification chamber 134 may be configured to hold a quantity of water W or other suitable liquid. The humidification chamber 134 is disposed on the base unit and in contact with the heater plate 136. The chamber 134 is removable from the base unit. The heater plate 136 may be configured to heat the quantity of water W and respiratory gas in the humidification chamber 134, increase the temperature of the respiratory gas, and generate steam from the quantity of water W entrained by the respiratory gas. The heater plate 136 is a plate-shaped member. In one example, the heater plate 136 includes a metal plate and a heating element disposed in contact with the heating element. The heating element is disposed within the metal plate. The heating element includes a substrate with an electrical wire wound around the substrate. The humidification chamber 134 may include a chamber inlet 111 and a chamber outlet 112. The inhalation conduit 106 may be configured to connect to the chamber outlet 112 so that heated and humidified breathing gas may be transported from the humidification chamber 134 to the patient connection device 116 by the inhalation conduit 106 and then delivered to the patient P. Gas exhaled by the patient P into the patient connection device 116 may be returned to the gas source 102 by the exhalation conduit 120. The respiratory assistance system 100 may not include the exhalation conduit 120, and thus gas exhaled by the patient P into the patient connection device 116 may be vented to the atmosphere, such as directly or optionally through an exhalation port.

[0172] The humidifier 104 may include a controller 130 that can control, for example, but not limited to, the operation of the heater plate 136. The controller 130 is preferably located in the base unit. When the humidifier 104 and the gas source 102 form an integrated device, the controllers 126, 130 may be the same hardware processor or separate processors. In one example, the controller 130 may be a microprocessor. The humidifier 104 may also include a user interface 140 for providing and / or receiving user input information to and / or from the controller 130. The user interface 140 may be located in the base unit. The humidifier 104 further includes an inlet temperature sensor 113. The inlet temperature sensor 113 may be configured to detect the temperature of gas entering the humidifier. The inlet temperature sensor 113 may measure a characteristic of the ambient air proximate the location of the inlet temperature sensor 113, such as the ambient air temperature. The inlet temperature sensor 113 may also be a temperature sensor located at or near the chamber inlet 111. A temperature sensor at the chamber inlet 111 may be capable of measuring both the temperature and flow rate of the air entering from the gas source 102. This measurement may be indicative of ambient conditions. In one example, the inlet temperature sensor 113 may be a thermistor. Additionally and / or alternatively, the respiratory assistance system 100 may include two or more sensors located at or near the chamber inlet 111. The inlet sensor may include a temperature sensor and a separate flow rate sensor. The inlet sensor(s) may be located anywhere from the gas source 102 to the humidification chamber 134. The outlet sensor(s) 110 and the inlet sensor(s) may be integrated with the humidification chamber 134. The controller 130 may receive information from the inlet temperature sensor 113 about the characteristics of the ambient air proximate the location of the inlet temperature sensor 113.The controller 130 may be configured to control the operation of the heater plate 136 based on information presented by the user interface 140, based on information presented by the inlet temperature sensor 113, and / or based on other information, such as feedback from the heater plate 136, such as, but not limited to, from a temperature sensor 146 disposed on or near the heater plate 136. The controller 130 may be configured to determine the amount of power or power duty cycle to supply to the heater plate 136 so that the heater plate 136 delivers a desired amount of heat to the breathing gas and the volume of water W in the humidification chamber 134. In the illustrated example, the humidifier does not include a hygrometer, but only temperature sensors at the inlet, outlet, and heater plate, and an optional flow sensor at the outlet. Because temperature sensors can be relatively inexpensive, the lack of a hygrometer allows this humidifier to be cheaper than humidifiers that include one or more hygrometers.

[0173] The respiratory assistance system 100 may include one or more outlet sensors 110 associated with the chamber outlet location 112. The one or more outlet sensors 110 may also be located at or near the chamber outlet 112. The outlet sensor 110 may include two sensors: a temperature sensor and a flow sensor. The temperature sensor may be a thermistor (such as a heated thermistor). The thermistor may also be used as a flow sensor. Thus, a single sensor 110 may be present at or near the chamber outlet 112. Other types of temperature and flow sensors operable with the respiratory assistance system 100 may also be used. The outlet sensor 110 may be located at the chamber outlet 112, in the inspiratory conduit 106 near the connection between the chamber outlet 112 and the inspiratory conduit 106, or in another suitable location downstream of the humidification chamber 134. The controller 130 may receive information from the outlet sensor 110 regarding the characteristics of the respiratory gas flowing through the location of the outlet sensor 110. The controller 130 may be configured to control the operation of the heater plate 136 based on information provided by the outlet sensor 110 instead of, or in addition to, other sources of information such as those previously mentioned.

[0174] The outlet sensor 110 may be integrated into the heater base (i.e., base unit) or may be located on any cartridge that can be removably attached to a vertical portion of the heater base (i.e., base unit). When the chamber 134 is placed in its operating position on the heater base, the sensors may be insertable into the inlet and outlet ports. The chamber inlet and outlet may include openings to accommodate and receive the inlet temperature sensor 113 and outlet sensor 110. The sensor openings in the chamber may include a polymer cover configured to cover the sensor tip when the sensor is inserted into the gas path; therefore, the sensors do not actually come into contact with the gas and therefore do not need to be (re)sterilized.

[0175] Respiratory gas flowing through the inhalation conduit 106 may lose heat through the walls of the inhalation conduit 106, thereby reducing the temperature of the respiratory gas and causing condensation within the inhalation conduit 106. The inhalation conduit 106 may include a conduit heater 144 configured to heat the inhalation conduit 106 to reduce or prevent this heat loss. As discussed above, the controller 130 may be configured to control the operation of the conduit heater 144 based on one or several sources of information. Specifically, the controller 130 may be configured to determine the amount of power or power duty cycle to supply to the conduit heater 144 so that the conduit heater 144 delivers a desired amount of heat to the inhalation conduit 106. The conduit heater may be disposed within the wall of the conduit or within the lumen of the conduit.

[0176] The respiratory assistance system 100 may include one or more conduit sensors 142 disposed within the inspiratory conduit 106. The conduit sensors 142 may be disposed in the inspiratory conduit 106 near the connection between the inspiratory conduit 106 and the Y-piece 114, at the connection between the inspiratory conduit 106 and the patient connection device 116 if the inspiratory conduit 106 is directly connected to the patient connection device 116, or at the Y-piece 114 or the patient connection device 116. The conduit sensors 142 may measure characteristics of the respiratory gas flowing past the location of the conduit sensor 142, such as the temperature of the respiratory gas. The conduit sensors 142 may include a temperature sensor. The conduit sensors 142 may also include a separate flow sensor. As described herein, the conduit sensors 142 may include an integrated flow and temperature sensor capable of measuring both temperature and flow rate. The controller 130 may receive information regarding the characteristics of the respiratory gas flowing past the location of the conduit sensors 142 from the conduit sensors 142. Controller 130 may determine the flow rate of breathing gas flowing through conduit sensor 142. Controller 130 may be configured to control operation of conduit heater 144 and / or heater plate 136 based on information received from conduit sensor 142, instead of or in addition to other sources of information such as those described above. The conduit sensor may be integrated into the conduit or may extend within the gas path defined by the conduit. Additionally, the conduit sensor wire may be integrated into the wall of the conduit or may extend along the conduit.

[0177] The breathing gas may also lose heat through the walls of the patient connection device 116, the Y-piece 114, and / or any other breathing system components that may connect the patient connection device 116 to the inspiratory conduit 106. One or more of the patient connection device 116, the Y-piece 114, and any other breathing system components that may connect the patient connection device 116 to the inspiratory conduit 106 may have associated heaters and / or associated sensors. The controller 130 may receive information from such associated sensors regarding the characteristics of the breathing gas flowing past the sensor locations. The controller 130 may use the information received from such associated sensors to control the operation of each associated heater.

[0178] One or more of the patient connection device 116, the Y-piece 114, and any other respiratory system components that may connect the patient connection device 116 to the inspiratory conduit 106 may not have an associated heater and / or associated sensor. The controller 130 may use an estimate of the heat lost by respiratory gas flowing through the unheated respiratory system components to control other heaters associated with the humidifier 104, such as the heater plate 136 and / or the conduit heater 144. The controller 130 may calculate such heat loss estimates for the unheated respiratory system components based on other information received, for example, but not limited to, information received from the outlet sensor 110, the conduit sensor 142, the inlet temperature sensor 113, and / or the user interface 140, and / or based on information retrieved from a data storage device that may be located within the controller. Data received from each sensor described herein may also be stored in the data storage device.

[0179] The humidifier 104 may be used in the respiratory assistance system 100 to deliver heated and humidified respiratory gas to the patient P for multiple types of respiratory therapy, including, but not limited to, invasive ventilation, non-invasive ventilation, high-flow therapy, BiPaP therapy, continuous positive airway pressure therapy, or other respiratory assistance therapy. The humidity state of the respiratory gas supplied to the humidifier 104 by the gas source 102 may vary. For example, the type of gas source 102 used in the respiratory assistance system 100 may depend on the type of respiratory therapy, the configuration of the breathing system, the location of use (e.g., home or hospital), or the availability of various gas sources. Gas from various sources may have different characteristics, including temperature and humidity. Ambient air, particularly ambient air in tropical weather and / or in the summer, may be more humid than gas obtained from a tank or bottle of compressed gas. For example, it may be beneficial to adjust the operating parameters of respiratory assistance system 100 using control system 220 (described below) to reduce and / or minimize rainout on the inspiratory tubing and / or patient connection devices to provide a comfortable patient experience while still receiving adequately humidified gas despite varying supply gas characteristics. The control system may be able to automatically adjust the operating parameters based on an inference of whether the supply gas is dry or ambient. The operating parameters may include certain temperature setpoints, described below. Additionally or alternatively, the operating parameters may be dew point, humidity output of a humidifier, or other suitable parameters.

[0180] FIG. 2A illustrates an exemplary control system 220 for detecting input conditions of the gas source 102 and automatically controlling the aforementioned components of the respiratory support system 100 to change the output state of gas delivered to the patient. Based on the received inputs, the control system 220 can generate outputs configured to control the operation of the components of the respiratory support system 100. The control system can generate a heater element output 230 to change the temperature setpoint of one of the heating elements, such as the heater plate 136, to control the output state of gas delivered to the patient. The control system 220 can also change the operation or duty cycle of the heater plate. The control system 220 may not require direct communication between the humidifier 104 and the gas source 102 to determine the input conditions. The control system 220 can also generate other outputs, such as a flow control output to change the flow rate of gas and / or output 234 to a display device. User input 210 can be received, for example, via a user interface, such as a touchscreen. The user input may be a selection of a particular mode corresponding to a type of therapy (e.g., invasive ventilation, non-invasive ventilation, or high-flow therapy such as Fisher & Paykel Healthcare's Optiflow therapy). A further user input may specify a desired dew point, i.e., a desired humidity value, to be delivered to the patient. For example, each mode may include multiple pre-set desired dew point values ​​(e.g., 31°C, 29°C, 27°C, or others) that the user can select. This selected dew point enables the controller to control the heater plate and / or heater wires in the inspiratory conduit to deliver saturated gas at the selected temperature (i.e., the selected dew point).

[0181] The control system 220 may include programming instructions described herein to detect input conditions and control output conditions. As shown in FIG. 2B, the programming instructions may be stored in memory 924 of the controller 126, 130. The programming instructions may include instructions corresponding to the processes and functions described herein. The control system 220 may be executed by a hardware processor 922 of the controller 126, 130. The programming instructions may be implemented in C, C++, JAVA, or any other suitable programming language. Some or all of the portions of the control system 220 may be implemented in application-specific circuitry 928, such as ASICs and FPGAs.

[0182] 2A, the control system 220 can receive inputs from multiple components of the respiratory assistance system 100. Other types of inputs may also be present. A humidity sensor may or may not be included. The controller may also receive inputs from various sensors in the system. Additionally or alternatively, the humidifier may receive signals or inputs from a user device, such as a cell phone or tablet.

[0183] Excessive humidity in indoor entrained air FIG. 3 illustrates potential gas conditions at the inlet of the humidification chamber. Without knowledge of the inlet humidity conditions, the humidifier can deliver humidity close to the desired humidity level in at least three of four types of gas conditions, namely, QI (high temperature, high humidity), QII (low temperature, low humidity), and QIV (low temperature, low humidity), as shown in FIG. 3. "Q" may correspond to temperatures approximately at or below ambient temperature, which may be approximately 24°C, and "Q" may correspond to temperatures above ambient. In the example shown in FIG. 3, a low temperature is considered to be below 24°C, and a high temperature is considered to be above 24°C. In some examples, an inlet temperature above 24°C may be caused by heat generated by a turbine in a room air entrainment ventilation system. Ambient air passing through the turbine of the room air entrainment ventilation system is heated above ambient temperature due to the turbine rotating the gas. In some examples, the generated heat may be added to the high ambient temperature. Compressed air (e.g., from a gas tank) is generally considered cool and dry because it is not humidified (e.g., has lower humidity than ambient) and is generally below 24°C (e.g., the temperature may be 18°C).

[0184] The humidifiers described herein can modify the maximum amount of added humidity; that is, the humidifiers described can modify the amount of added humidity based on the inlet temperature of the gas. In some examples, when the inlet temperature is low (i.e., when the gas is cold, as shown in quadrants I and II in FIG. 3), the relative humidity (RH) of the gas at the chamber outlet may be close to saturation, regardless of the inlet gas humidity level. This is because the heater plate of the humidifier may heat and add humidity to the gas. In other words, the temperature difference between the inlet and outlet temperatures must be large enough so that the humidifier can add enough humidity to saturate the gas.

[0185] On the other hand, in instances where the chamber inlet temperature is high or well above ambient conditions (i.e., the gas is hot, as shown in quadrants III and IV of Figure 3), the RH level at the chamber outlet may be reduced. This is because the heater plate may have a safety temperature limit that prevents it from heating above a certain temperature. Therefore, the heater plate may have a relatively small buffer or range for heating and adding humidity before reaching the maximum allowable chamber outlet temperature setpoint. An example of a maximum allowable chamber outlet temperature setpoint may be approximately 36°C.

[0186] Additionally, or alternatively, at a relatively high temperature with the same level of humidity, evaporation of water from the water surface may be slowed due to increased vapor pressure of moist gases at the water surface. Thus, different inlet humidity levels may have different effects on outlet humidity levels.

[0187] In another example, the delivery of hot, (relatively) dry gas to a patient can cause irreversible damage to the patient's airways. Therefore, to help prevent this problem, the system may avoid the delivery of hot, dry gas when the incoming hot, dry gas has low humidity by effectively treating the incoming hot, dry gas to a cool, dry state. If this assumption holds, the incoming gas can be heated by the heater plate as it passes through the humidification chamber, thereby increasing humidity.

[0188] Humidifiers generally add more heat and humidity to the incoming gas. Depending on the temperature and humidity of the incoming gas, this may result in excessive humidification and / or overheating. For example, air drawn in by a room air entrainment ventilation system may contain some humidity. The humidity of room air may be higher than that from a compressed gas source, such as a gas bottle or wall-fed gas. Furthermore, as mentioned above, room air entrainment ventilation systems typically use blowers or turbines, which can unfortunately heat the gas. This excess heat causes the room entrained air to be further humidified before entering the humidification chamber, as the gas temperature may increase, raising the dew point.

[0189] FIG. 4A shows an exemplary graph of outlet gas dew point as a function of the inlet temperature of a room air entrainment ventilation system when the humidifier assumes that all incoming gas is dry. This dew point corresponds to an absolute humidity value. Specifically, FIG. 4A illustrates how a humidifier may add unnecessary humidity to room-entrained air because the humidifier may not take into account the humidity already present in the room-entrained air. As previously mentioned, a humidifier may use a gas source to reliably deliver a desired humidity level over a range of different chamber inlet temperatures. The solid black line in FIG. 4A is the humidity added by the chamber and represents the humidity added by the chamber when a cold, dry gas is used. The double black line in FIG. 4A shows the cumulative humidity when ambient air is entrained (specifically, the chamber humidity plus the ambient humidity). Under dry air source conditions, the desired humidity level may be approximately the same as the humidity level added by the humidifier. However, when used in conjunction with a room air entrainment ventilation system, the additional humidity from the room air can cause the humidifier to deliver more than the desired or target humidity level, increasing the level of condensation, as shown in FIG. 4A.

[0190] Based on the desired humidity level, excessive humidification may occur at various chamber inlet temperatures for room entrainment air. Figure 4B shows an exemplary graph of outlet gas humidity as a function of inlet temperature for various user settings of a room air entrainment ventilation system. For example, as shown in Figure 4B, a 31°C humidifier mode (shown as the desired humidity level for mask 31) may begin to over-humidify at a chamber inlet temperature of approximately 20°C. A 29°C humidifier mode (shown as the desired humidity level for mask 29) may begin to over-humidify at a chamber inlet temperature of approximately 22°C. A 27°C humidifier mode (shown as the desired humidity level for mask 27) may begin to over-humidify at a chamber inlet temperature of approximately 24°C. The solid lines in Figure 4B represent the humidity (or dew point) delivered to the patient. The lines for mask 31, mask 29, and mask 27 represent the desired dew point delivered to the patient in "mask mode." The desired dew point corresponds to the amount of humidity delivered to the patient. Mask mode refers to noninvasive therapy. More specifically, "mask mode" refers to respiratory therapy delivered using a sealed mask, e.g., a full mask. Mask mode refers to both pressurized and non-pressurized airways, e.g., bilevel pressurized and continuous positive airway pressure (CPAP), or other noninvasive ventilation modes. The excess humidification curve (the lighter double line) indicates the additional humidity, i.e., excess humidification due to ambient humidity, when ambient air is used in mask mode at three different set points. The upward curve represents the increased dew point of the gas, i.e., the gas delivered at a relatively high desired humidity. The controller in the first mode operates under the assumption that dry gas is being delivered, and therefore, excess humidification often occurs when ambient air is used in this first mode. Each system disclosed herein operates the humidifier in a second mode when the inlet temperature exceeds a threshold to reduce excess humidification.

[0191] 5A-5C illustrate three different use cases of the humidifier at three different inlet gas temperatures. FIG. 5A is a graph showing the effect of additional room air humidity at an inlet temperature of 36°C (i.e., when the actual inlet gas temperature is 36°C). As shown in FIG. 5A, the inlet gas temperature 510 may be relatively higher than ambient. For example, the ambient temperature may be 24°C, and the inlet gas temperature may be 36°C (i.e., hot inlet gas). To achieve a desired humidity level using a dry gas source, the humidifier may set the maximum chamber outlet setpoint to a target humidity corresponding to a dew point of, for example, 31°C, as shown by line 514. Line 514 may represent a first function (i.e., first mode) of operation when the humidifier assumes the inlet gas is dry gas. In standard operation of the humidifier, hot, dry inlet gas, as it passes over the evaporative water surface in the humidification chamber, can attain a desired level of humidity corresponding to a chamber outlet temperature corresponding to a desired dew point at the patient, for example, 31°C. The exemplary value of 31°C represents the desired dew point at the patient. This desired dew point can be used to calculate and / or set the chamber outlet setpoint temperature and / or the patient-side setpoint temperature. Furthermore, the chamber outlet setpoint can be used to control the heating / power of the heater plate to achieve the chamber outlet setpoint. However, when a humidifier is used with a room air entrainment ventilation system, the hot inlet gas already contains more moisture than the dry gas and may be over-humidified, as shown by line 512, because it gains humidity in the humidification chamber with an actual humidity equivalent to a 36°C dew point. This over-humidification may result in unwanted condensation at the patient interface and, potentially, in the conduits.

[0192] Condensation may occur as the temperature of the gas drops below the actual dew point of the gas. For example, condensation may occur because the actual dew point of the gas in the respiratory support system may be higher than the desired humidity level (e.g., line 514, which corresponds to a dew point of 31°C in this example) due to additional room air humidity. In the example shown in FIG. 5A, the actual dew point at the chamber outlet may be 36°C, as shown by line 512. The duty cycle of the inspiratory wire in the respiratory support system may be controlled to cool the gas from the chamber outlet temperature (e.g., 36°C as shown in FIG. 5A) to the patient side temperature (e.g., 34°C as shown in FIG. 5A). Once the gas cools to the patient side temperature, the water vapor that can no longer be contained in the gas with a relatively low dew point, e.g., 34°C in this example, will condense into liquid. This condensation is represented by the gray area in FIG. 5A. FIG. 5A illustrates a first operating mode (i.e., standard operation assuming dry gas is used). A desired patient-side dew point of 31°C may be used to define the temperature at the patient-side sensor and the chamber outlet setpoint. In this mode, the humidifier may be controlled to achieve an exemplary dew point of 34°C at the patient side. The gas outlet temperature may be 36°C. Because this outlet temperature is higher than the chamber outlet temperature setpoint and / or the desired temperature at the patient side, 34°C in this example, the system will be configured to cool the gas as it travels from the chamber outlet to the patient side, as shown by line 510 between the chamber outlet and the patient side. However, the gas dew point may also correspond to 36°C at the chamber outlet. The gas dew point cannot be higher than the actual temperature of the gas. Therefore, as the gas cools between the chamber outlet and the patient side, the gas dew point will also decrease, and may be equivalent to, but not exceed, line 510. As previously mentioned, the water vapor that can no longer be contained in the gas at its relatively low dew point of 34°C condenses into liquid. This condensation is represented by the gray area in FIG. 5A. FIG. 5A also illustrates the additional cooling that may occur in the patient interface area, which may be any area beyond the distal end of the inspiratory tube.Such areas may include patient connection devices such as an endotracheal tube for invasive respiratory therapy or a full face mask for non-invasive therapy.

[0193] When operating with bottled or dry gas, the patient-side temperature can be calculated and targeted to be above the dew point corresponding to the desired humidity level. For example, a patient-side temperature of 34°C may be targeted, which is 3°C above the desired dew point temperature of 31°C. This targeting takes into account the temperature drop as the gas travels through the patient interface. Because the patient interface is typically not heated, the gas generally cools throughout the patient interface. A temperature drop of 3°C may be calculated during operation of the respiratory support system, although any suitable temperature drop may be used. As shown in FIG. 5A, because the gas is below the actual dew point, more condensation forms in the patient interface as the gas further cools to 31°C throughout the patient interface. This can cause patient discomfort and may interrupt therapy as the patient disconnects the patient interface and / or inspiratory tube to address the condensation. Furthermore, additional condensation can also pose a safety risk, as condensation inside the patient interface may increase the risk of drowning or cause patient discomfort.

[0194] 5B-5C illustrate the effect of additional room air humidity for inlet temperatures of 26°C and 21°C, respectively. As shown in FIG. 5B, for a gas inlet temperature of 26°C (gas temperature shown by line 520), the actual dew point at the chamber outlet may be 33°C, as shown by line 522, and the desired dew point at the chamber outlet may be 31°C, as shown by line 524. In such a case, condensation may form in the patient interface, as shown by the shaded area in FIG. 5B. As shown in FIG. 5C, for a gas inlet temperature of 21°C (gas temperature shown by line 530), the actual dew point at the chamber outlet (line 534) and the desired dew point (line 532) may be 31°C. In such a case, as previously discussed, condensation may not form in the inspiratory tubing or patient interface because the inlet gas is not hot relative to the ambient air and, therefore, the relative humidity of the gas at the chamber outlet may be close to saturation, regardless of the humidity level of the inlet gas. In the case shown in Figure 5C, the temperature of the gas exceeds the dew point, and therefore no condensation occurs, where the dew points of the dry and wet inlets remain substantially constant between the chamber outlet and the patient interface outlet.

[0195] Controlling outlet humidity as a function of inlet temperature The control systems described herein can minimize or at least reduce condensation levels and improve humidity delivery to the patient through the process of monitoring the chamber inlet temperature. The described control systems for humidifiers are configured to control the heater plate power delivered and / or modify the chamber outlet temperature or humidity setpoint, or the heater plate power or temperature setpoint, based on the monitored chamber inlet temperature to reduce condensation within the conduit and / or within the patient-connected device and / or within downstream unheated sections of the conduit. For example, the behavior of the chamber outlet temperature and / or humidity can operate as a function of the chamber inlet temperature. For example, the chamber outlet temperature setpoint may be capped (i.e., limited) based on the gas inlet temperature. In another example, the humidity setpoint or heater plate temperature setpoint or heater plate power setpoint may be capped based on the gas inlet temperature. The control system may use this functional relationship to help ensure that excessive humidity is not added to the gas via the humidifier. Specifically, this functional relationship may assume that incoming gas above a threshold temperature is likely to contain excessive humidity. Thus, the control system may adjust the target humidity so that the humidifier adds relatively less humidity to the inlet gas. For example, in a given treatment mode of the humidifier, if the chamber inlet temperature is below a threshold, a desired humidity level range can be delivered to the patient. If the chamber inlet temperature exceeds the threshold, the delivered humidity can be reduced to a humidity level range lower than the initial desired humidity level range. The humidity level can be controlled by controlling the chamber outlet temperature setpoint, the heater plate temperature setpoint, or the heater plate power. For example, as shown in the flow diagram in FIG. 6A and the schematic diagram in FIG. 7, the chamber outlet temperature setpoint may be limited or capped based on the gas inlet temperature. The illustrated example is based on controlling the chamber outlet temperature setpoint by capping the chamber outlet temperature setpoint.Additionally or alternatively, if the inlet temperature exceeds a threshold, the heater plate setpoint or heater plate power may be capped or limited to reduce the humidity output of the humidifier. Additionally or alternatively, the humidity level may be controlled by lowering the maximum chamber outlet temperature setpoint (i.e., maximum allowable chamber outlet temperature setpoint), as shown in the flow chart of FIG. 6B and the schematic diagram of FIG. 7. A maximum chamber outlet temperature setpoint may be established after which power to the heater plate is disabled. If the chamber outlet temperature exceeds the maximum allowable chamber outlet temperature setpoint, the controller is configured to disable or shut down the heater plate. In one example, the heater plate power may be limited or capped to define a maximum allowable heater plate power based at least in part on the gas inlet temperature. In a non-limiting example, the controller is configured to modify the maximum allowable heater plate power based at least in part on the determined inlet temperature. The controller is configured to control this heater plate power up to the maximum allowable heater plate power. The controller is configured to control this heater plate power to any heater plate power that may be calculated to be less than or equal to the maximum allowable heater plate power. In a further example, the heater plate temperature setpoint may be limited or capped based at least in part on the gas inlet temperature to define a maximum allowable heater plate temperature setpoint. In a non-limiting example, the controller is configured to modify the maximum allowable heater plate temperature setpoint based at least in part on the determined inlet temperature. The controller is configured to control this heater plate power to the maximum allowable heater plate temperature setpoint. The controller is configured to control this heater plate power to any heater plate temperature setpoint that may be calculated to be less than or equal to the maximum allowable heater plate temperature setpoint.

[0196] The humidifier may include a second operating mode that sets the humidity output or other parameters of the humidifier based on, for example, the inlet temperature. In this second mode, the humidifier may control either the chamber outlet setpoint, the heater plate temperature setpoint, or the heater plate power based on the inlet temperature. In the second operating mode, the power to the heater plate may be capped based on the gas inlet temperature. The second mode may be activated when the inlet temperature exceeds a temperature threshold. In some examples, the temperature threshold may be a predetermined threshold. In one example, the temperature threshold is 24°C. In one example, in the second mode, the chamber outlet setpoint may be capped (i.e., limited) when the gas inlet temperature exceeds the temperature threshold. In a further example, the heater plate temperature setpoint may be capped (i.e., limited) when the gas inlet temperature exceeds the temperature threshold. The chamber outlet temperature setpoint may be capped at the maximum allowable chamber outlet when the gas inlet temperature exceeds the temperature threshold. If the inlet temperature exceeds the temperature threshold, the heater plate temperature setpoint may be capped at the maximum allowable heater plate temperature setpoint. If the inlet temperature exceeds the temperature threshold, the heater plate power may be capped to the maximum allowable heater plate. The capped chamber outlet temperature setpoint, or heater plate temperature setpoint, or heater plate power may be adjusted (i.e., modified) based on the gas inlet temperature. For example, when the inlet temperature exceeds the temperature threshold, such maximum allowable setpoint may be modified as a function of the inlet temperature in the second mode.

[0197] Advantageously, using the methods described herein, the humidifier control device does not need to directly determine the humidity of the input gas or adjust control parameters if a room air entrainment ventilation device is detected. The described humidifier control method (and humidifier) ​​also does not require any specific sensor configuration or detection method to determine the type of ventilation device or gas source connected to the humidifier. Furthermore, the humidifier does not require complex and expensive humidity sensors (e.g., hygrometers). Thus, the control system and method can provide a relatively simple and cost-effective solution for reducing condensation levels during operation of a humidifier using room entrainment air, at least because it does not require a humidity sensor upstream of the humidification chamber.

[0198] FIG. 6A illustrates an exemplary process 600 for setting a maximum allowable chamber outlet temperature setpoint using an inlet gas temperature threshold. For example, this process 600 may include step 610, in which the system measures the gas temperature of the gas at or near the inlet to the humidification chamber, or anywhere in the gas flow path upstream of the humidification chamber. Then, in decision block 612, the system may determine whether the measured gas temperature exceeds the temperature threshold. If the gas temperature exceeds the threshold, the system may reduce the maximum chamber outlet temperature setpoint in step 616. When the inlet temperature is below the temperature threshold, the maximum allowable chamber outlet temperature setpoint is reduced to a lower value compared to the maximum allowable chamber outlet temperature setpoint. In other words, if the gas temperature (i.e., the inlet gas temperature) does not exceed the threshold, the system may continue under standard operation under step 614, for example, by maintaining a predetermined chamber outlet setpoint and / or a predetermined power or duty cycle of the heater plate. Step 614 may correspond to a first, or standard, operating mode. Step 616 may correspond to a second operating mode in which the outlet humidity is capped or limited. This may be achieved by capping or further capping the chamber outlet setpoint, capping the heater plate temperature (i.e., heater plate temperature setpoint), or capping the heater plate power. The capped values ​​are capped based on the inlet temperature exceeding a threshold, e.g., a temperature threshold. The capped chamber outlet temperature setpoint defines the highest allowable chamber outlet temperature setpoint. The capped heater plate temperature (i.e., heater plate temperature setpoint) defines the highest allowable heater plate temperature setpoint. The capped heater plate power (i.e., heater plate power setpoint) is the maximum allowable heater plate power (i.e., maximum allowable heater plate power setpoint). The capped values ​​may be adjusted by the controller as a function of the inlet temperature. The capped value defines the maximum allowable value in the second mode, ie when the gas inlet temperature exceeds the temperature threshold.In one example, the maximum allowable set point in the second mode may be lower than the maximum set point in the first mode.

[0199] FIG. 6B illustrates an exemplary process 601 for setting a maximum chamber outlet temperature setpoint (i.e., a maximum allowable chamber outlet temperature setpoint) using an inlet gas temperature threshold. For example, this process 601 may include step 620, in which the system measures the temperature of the gas at or near the inlet to the humidification chamber, or anywhere in the gas flow path upstream of the humidification chamber. The system may then determine a chamber outlet temperature setpoint based on the inlet gas temperature in step 620. In addition to the inlet gas temperature, other inputs may be used to define the chamber outlet temperature setpoint. Then, in decision block 612, the system may determine whether the measured inlet gas temperature exceeds a temperature threshold. If the inlet gas temperature does not exceed the threshold, the system may control the heater plate in step 630 to the chamber outlet temperature setpoint determined in step 620. In one example, the chamber outlet temperature setpoint determined in step 620 may define a maximum allowable chamber outlet temperature setpoint, i.e., define an upper limit on the chamber outlet temperature. If the inlet gas temperature exceeds the threshold, the system may cap or limit the maximum allowable chamber outlet temperature setpoint based on the inlet gas temperature in step 626, i.e., may cap or limit the allowable temperature of the gas at the chamber outlet. Once the system caps or limits the maximum allowable chamber outlet temperature setpoint in step 626, it may set a new chamber outlet setpoint temperature in step 628. Once the new chamber outlet setpoint temperature is set in step 628, the system (i.e., the humidifier controller) is configured to control the heater plate in step 630 to the chamber outlet temperature setpoint determined in step 628. The controller may be configured to adjust the chamber outlet temperature setpoint determined in 628 based on at least the inlet temperature and flow rate to achieve the desired humidity level. The controller is configured to control the chamber outlet temperature setpoint so that it does not exceed the maximum allowable temperature setpoint determined in step 626.The controller is further configured to control the heater plate power based on feedback from a chamber exit temperature sensor (e.g., sensor 110) so that the temperature of the gas does not exceed the maximum allowable chamber exit temperature sensor.

[0200] The chamber outlet temperature determined in step 620 may be unlimited in some circumstances. For example, in “standard operation” (or the first function / mode), the chamber outlet temperature can rise up to approximately 36°C without being limited. The 36°C maximum may be a hard limit, meaning that if the gas temperature at the chamber outlet exceeds 36°C, the heater plate power is turned off via either a software shutoff or a hardware shutoff, or a combination thereof. The chamber outlet setpoint may be based on some combination of the inlet temperature, the heater plate temperature, and / or input from one or more other sensors (e.g., an ambient temperature sensor and / or flow rate). In step 626, the chamber outlet setpoint may be capped or limited. For example, in “new operation” (i.e., in the second function / mode), the maximum outlet temperature achievable at a given inlet temperature may be limited / capped (i.e., capped to define the maximum allowable chamber outlet temperature), thereby limiting the amount of moisture generated at that particular inlet temperature.

[0201] As described above, in step 610, the system may measure the gas temperature using an inlet temperature sensor. The inlet gas sensor may be an inlet gas temperature sensor that can be used at the inlet. The inlet temperature sensor may be coupled to the inlet to the humidification chamber so that the temperature of the gas in the inlet can be measured. The temperature sensor may be any sensor configured to measure the temperature of the gas, such as a thermistor or a probe sensor. However, the temperature sensor need not be directly attached to the inlet; it may be near the inlet, on the inlet, or within the inlet. The gas in the inlet may be any gas entering the humidification chamber that has not yet been humidified by the humidification chamber. Such gas may include dry gas, such as bottled gas, or gas containing excess humidity, such as room-entrained gas.

[0202] The temperature thresholds may include a single temperature threshold or multiple temperature thresholds, for example, in the case of multiple thresholds, the system may determine whether the inlet gas temperature exceeds a first temperature threshold to set a first chamber outlet setpoint, and determine whether the inlet gas temperature exceeds a second temperature threshold to set a second chamber outlet setpoint.

[0203] Additionally, or alternatively, in step 612, the system may determine whether the inlet temperature passes a different humidity scale. For example, the system may use a functional relationship between inlet gas heat and humidity to determine whether to reduce the maximum chamber outlet setpoint in steps 616, 626, or 628, or continue standard control in steps 614 or 630. This functional relationship may take into account factors other than the current inlet temperature. If the ambient air pressure reading is above, below, or within a threshold value, this pressure value can be used to cap the maximum chamber outlet temperature and / or define the chamber outlet temperature.

[0204] The threshold value in step 612 may include a predetermined temperature threshold or set of temperature thresholds. By predetermined, it is meant that the temperature threshold value is preprogrammed into the controller. Alternatively, the temperature threshold value may not be predetermined but instead may be dynamically calculated based on one or more of the chamber outlet setpoint, heater plate temperature setpoint, flow rate, or target humidity. The temperature threshold value may also be calculated by the controller based on other factors, such as the patient temperature setpoint or a desired (i.e., selected) patient dew point. The temperature threshold value may correspond to several temperatures. For example, the temperature threshold value may be between 19°C and 26°C. Throughout this disclosure, a temperature range between a first temperature and a second temperature includes both the first temperature and the second temperature. For example, the threshold temperature may preferably be between 22°C and 24°C. The predetermined temperature threshold value may vary depending on the humidifier outlet temperature setpoint. The predetermined temperature threshold value may also vary depending on the target humidity value of the gas after it passes through the humidification chamber. The target humidity may differ for various modes of the humidifier. For example, a humidifier may have various operating modes, such as invasive or non-invasive modes, that deliver different temperature and humidity conditions of gas to a patient based on therapeutic needs. Each operating mode may include multiple desired dew points or modes for delivery to the patient. For example, a non-invasive mode (i.e., corresponding to non-invasive ventilation delivery) may include a desired dew point mode of 27°C, a mode of 29°C, and a mode of 31°C, or other temperature mode. Each desired dew point or mode may correspond to a target humidity of the gas. Each desired dew point may have a corresponding temperature threshold, either shared or unique. For example, the 27°C mode may have a corresponding temperature threshold of 22°C. Both the 29°C and 31°C modes may have corresponding temperature thresholds of 24°C. In addition to or instead of a desired dew point mode, an operating mode may include multiple chamber outlet setpoints.

[0205] Table 1 shows some exemplary associated ranges for the maximum allowable chamber outlet temperature setpoint and corresponding chamber inlet temperature threshold for the non-invasive treatment mode. As can be seen from this table, humidity levels are defined both as mg / L and as dew point temperatures. The dew point temperature can correspond to the desired temperature of the gas at the chamber outlet. The "chamber inlet threshold" refers to the chamber inlet temperature that instructs the controller when to reduce the desired humidity level output by the humidifier and incorporated into the incoming gas to a relatively lower humidity level. The "dry humidity level range when chamber inlet is below threshold" refers to the desired humidity level that the humidifier delivers when the inlet gas temperature is below the chamber inlet temperature threshold. This can correspond to what the humidifier does during standard operating conditions in step 614 of FIG. 6A or under step 630 of FIG. 6B if the gas inlet temperature does not exceed the threshold temperature at decision block 612. The "dry humidity level range when chamber inlet is above threshold" refers to the reduced humidity level that the humidifier delivers when the chamber inlet temperature exceeds the threshold temperature. This range may correspond to the minimum allowable tolerance for humidity levels.

[0206] [Table 1]

[0207] In other examples, there may be other ranges of acceptable chamber outlet temperature setpoints for other therapy modes. For example, in an invasive therapy mode (corresponding to invasive ventilation therapy), the dry humidity level range when the chamber inlet temperature exceeds a threshold may include 36-40 mg / L, which may equate to a dew point of 33-35° C. in a 37° C. mode. In another example, in a high flow mode (corresponding to delivery of a humidified high flow therapy), the dry humidity level range when the chamber inlet temperature exceeds a threshold may include 36-40 mg / L, which may equate to a dew point of 33-35° C. in a 37° C. mode; this threshold may include 26-34 mg / L, which may equate to a dew point of 28° C. in a 35° C. mode; and / or this threshold may include 22-20 mg / L, which may equate to a dew point of 26° C. in a 33° C. mode.

[0208] The system may control the amount of power provided to a heater in the humidifier to achieve a chamber outlet temperature setpoint. The heater may be a heater plate in the humidifier. For example, the system may control the amount of power to the heater plate to achieve the chamber outlet setpoint. The system may use a closed-loop system that controls the amount of power to the heater plate using feedback from the actual measured temperature at the chamber outlet. An error value between the measured chamber outlet temperature and the chamber outlet setpoint may be used to increase or decrease the power provided to the heater plate. The system may control the power by controlling a PWM module that provides a voltage to the power. The system may reduce the amount of power provided to the heater. For example, the system may set a power threshold or limit. The power threshold or limit may correspond to a gas dew point and / or a target humidity. For example, the power threshold may correspond to a dew point at 19°C. In another example, the power threshold may correspond to a humidity output of 15.3 mg / L. Additionally or alternatively, the system may reduce the amount of power by limiting the power by a function or set of functions. For example, the system may cause the heater to output an amount of power according to a first function when the inlet temperature does or does not exceed a threshold temperature, and may cause the heater to output an amount of power according to a second function when the inlet temperature does or does not exceed a second threshold temperature. The first function may operate to control the amount of power to the heater plate, where this power may be capped by a maximum allowable power when the temperature (i.e., the gas inlet temperature) is below a threshold. The maximum allowable power may correspond to a safety limit on the power supplied to the heater plate. The second function may cap the maximum allowable heater plate power at a given inlet temperature when the gas inlet temperature exceeds a threshold. That is, the second function may operate to control the amount of power to the heater plate, where this power is further limited to be below the maximum allowable power to the heater plate when the inlet temperature exceeds a threshold. The first and second functions may correspond to several functions.In the second function, the controller is configured to define a second maximum allowable power to the heater plate. The second maximum allowable power defines a new limit. The second maximum allowable power to the heater plate may be lower than the maximum allowable power defined by the first function (i.e., the first maximum allowable heater plate power). The second maximum allowable power to the heater plate is a reduced value. The second maximum allowable power may correspond to a maximum allowable chamber outlet setpoint when the gas inlet temperature exceeds a temperature threshold. The relatively lower second allowable heater plate power caps the humidifier output humidity. This cap reduces the possibility of over-humidifying the gas and helps account for humidity in the gas resulting from an air-entraining gas source, such as an air-entraining ventilation system. The maximum allowable heater plate power may be defined by a piecewise function. This piecewise function may be similar to, or at least correspond to, the piecewise function defining the maximum allowable chamber outlet temperature setpoint. For example, the first function and the second function may operate together or separately as piecewise functions.

[0209] FIG. 7 shows exemplary improved outlet humidity levels for gas conditions at the inlet of the humidifier chamber. As described with respect to FIG. 3, without knowledge of the inlet humidity conditions, the humidifier can deliver humidity close to the desired humidity level in three of four types of gas conditions: low temperature and high humidity (QI), low temperature and low humidity (QII), and high temperature and low humidity (QIV). However, at least when the inlet gas is high temperature and high humidity (QIII), excessive rainout may occur in the inspiratory tubing and / or patient connection equipment. Using processes 600 and 601 shown in FIGS. 6A and 6B, the system can more effectively deliver the desired humidity levels in quadrants I, II, and III and therapeutic humidity levels in quadrant IV, even when used with turbine-driven ventilators or room-entrained gas. Because high temperature inlet gas conditions are typically associated with room-air-entrained ventilators with turbines that generate heat, high temperature and low humidity inlet gas conditions are less common. Therefore, the gas is typically "dry" and may have significantly higher humidity levels than compressed bottle gas or wall gas. In this less common case of hot, low humidity inlet gas conditions, the delivered humidity level can be reduced while still delivering therapeutic levels of humidity to the patient.

[0210] FIG. 8 illustrates exemplary different outlet setpoints or exemplary maximum chamber outlet temperature setpoints as a function of chamber inlet temperature in user modes (shown as mask 27, mask 29, and mask 31 modes) for a humidifier operating as part of a noninvasive respiratory assistance system. The humidifier is operating in noninvasive mode, which may be selected via a graphical user interface, such as a touchscreen located on the humidifier's base unit. The system may modify existing temperature and humidity control algorithms, such as in step 616 of FIG. 6A, to set the chamber outlet temperature setpoint to an appropriate value below the curve shown in FIG. 8 based on each outlet setpoint or user mode temperature threshold. Line 810 represents a first mode / function in which the chamber outlet temperature setpoint is not limited and the only limit is the high temperature limit (or temperature safety limit), and a first system operation when the inlet temperature falls below the threshold temperature. In the first mode (i.e., first function), the maximum allowable chamber outlet temperature setpoint is defined as 36°C, as defined by line 810. As can be seen in FIG. 8 , the actual chamber outlet temperature setpoint used to control power to the heater plate corresponds to the selected dew point, i.e., 27°C, 29°C, or 31°C, according to lines 812, 814, and 816. While such chamber outlet setpoint may vary depending on gas conditions, such as flow rate, such chamber outlet temperature setpoint will not exceed the maximum allowable limit defined by line 810 when in the first mode (i.e., when the inlet temperature is below the temperature threshold). Line 810 may correspond to a temperature safety limit. In the first mode / function, the system may set the chamber outlet temperature setpoint anywhere below line 810, which may correspond to a temperature below 36°C, for example, which may act as a temperature safety limit. That is, under the first mode / function, which may occur with an inlet temperature below the threshold temperature, the system may cap the maximum chamber outlet temperature set point at a predetermined value, and the system may adjust the chamber outlet temperature set point to any value up to 36°C to achieve the desired humidity.Lines 812, 814, and 816 represent a second mode / function in which the chamber outlet temperature setpoint is capped and cannot exceed the maximum chamber outlet temperature setpoint along each line, and a second system operation when the inlet temperature exceeds a threshold temperature. The chamber outlet temperature setpoint is set below the curve of lines 812, 814, and 816 when the inlet temperature exceeds the threshold. Each line 812, 814, and 816 may correspond to the temperature difference between the inlet temperature and the chamber outlet temperature. This difference may be sufficient to achieve the desired therapeutic humidity level (according to Table 1). Lines 812, 814, and 816 define the maximum allowable chamber outlet temperature setpoint in the second mode or function (i.e., when the gas inlet temperature exceeds the temperature threshold). Lines 812, 814, and 816 indicate the chamber outlet setpoint in both the first and second modes. In the second mode, i.e., when the inlet temperature exceeds the temperature threshold, lines 812, 814, and 816 define the maximum allowable chamber outlet temperature setpoint. This maximum allowable setpoint is less than the first maximum allowable setpoint in the first mode (i.e., when the inlet temperature is below the temperature threshold), as defined by line 810. Line 810, along with any one of lines 812, 814, and 816, represents a piecewise function that defines the maximum allowable chamber outlet temperature setpoint. In the first mode, i.e., the first portion of the piecewise function, the maximum allowable setpoint is defined by line 810. In the second portion of the piecewise function, the maximum allowable setpoint is defined by lines 812, 814, or 816, respectively (depending on the dew point selected by the user). As can be seen in FIG. 8 , in the second mode, when the inlet temperature exceeds the second temperature threshold, the maximum allowable chamber outlet temperature setpoint reaches and remains at 36°C. The second temperature threshold corresponds to an inlet temperature exceeding the required minimum temperature differential. The second temperature threshold may be a single temperature value or a range of temperature values. Each mode, e.g., 27°C, 29°C, or 31°C, may have its own second temperature threshold. As can be seen in Figure 8, the controller attempts to maintain a temperature difference between the chamber outlet setpoint and the gas inlet temperature. This temperature difference is used to define the chamber outlet temperature setpoint.The temperature difference depends at least on the flow rate and may further depend on the ambient temperature and heater plate temperature. As shown in Figure 8, when the gas inlet temperature exceeds a second temperature threshold, the chamber outlet temperature setpoint is set to the highest allowable chamber outlet temperature setpoint of 36°C. As shown in Figure 8, lines 812, 814, and 816 flatten out at 36°C when the temperature difference between the inlet temperature and the chamber outlet setpoint falls below the difference threshold.

[0211] 9A shows an example of humidity added by an exemplary humidifier depending on the inlet temperature and the humidity added when the inlet gas is dry. For example, when the chamber inlet temperature is low (e.g., below a threshold of 24°C), the humidifier can deliver a desired humidity level to the inlet gas under standard operating conditions (e.g., when the gas inlet temperature does not exceed the threshold temperature at decision block 612, as shown in step 614 of FIG. 6A and below step 630 of FIG. 6B). When the chamber inlet temperature rises above about 24°C, the system can reduce the humidity level to a relatively lower desired humidity level for the inlet gas (e.g., when the gas inlet temperature exceeds the threshold temperature at decision block 612, as shown in step 616 of FIG. 6A and below step 630 of FIG. 6B). As discussed above, when this algorithm is used with dry gas that exceeds the temperature threshold (i.e., hot, low-humidity gas, as shown in Figure 7) but has the same inlet temperature, the humidity level delivered to the patient will be relatively lower, but still therapeutic. When this algorithm is used with a room air entrainment ventilation system (i.e., generating hot, high-humidity gas, as shown in Figure 7), the humidity level delivered to the patient or user will be the desired relatively lower humidity level plus humidity from the room air. That is, this relatively lower humidity level takes into account the room entrainment humidity, as shown in Figures 4A-4B and 5A-5B, in this case, ignoring room air humidity can raise the dew point to an undesirable relatively high level and minimize problems that could result in condensation (such as excessive condensation causing patient discomfort and / or interruptions to therapy to clean the patient connection device and / or inspiratory tubing). In other words, as shown in Figure 9A, when the inlet temperature threshold is exceeded, the controller may control the heater plate to generate a relatively lower absolute humidity to account for the increased humidity from the ambient air. The relatively low absolute humidity values ​​and humidity from the incoming air can result in therapeutic or above-therapeutic absolute humidity values, reducing or minimizing condensation in tubing or patient connection devices.

[0212] FIG. 9B illustrates an example of the humidity added by an exemplary humidifier as a function of the inlet temperature and the humidity added when the inlet gas is dry, for different exemplary user settings or outlet temperature setpoints. Specifically, FIG. 9B illustrates the effect of a relatively low humidity level for the humidifier's non-invasive mode of operation, with different user settings or chamber outlet temperature setpoints of 27° C., 29° C., and 31° C. corresponding to masks 27, 29, and 31, respectively. Additionally or alternatively, the maximum chamber outlet temperature setpoint may be set at a reduced level to minimize condensation (e.g., 25° C., 27° C., and 29° C. corresponding to masks 27, 29, and 31, respectively). A similar approach may be employed by the controller for high-flow mode. Alternatively, the maximum allowable humidity may remain unchanged in high-flow mode. During invasive mode, humidity is maximized and remains unchanged across the full range of inlet temperatures.

[0213] Exemplary Humidity Delivery Control System 10A-10C are illustrative overlays of FIGS. 5A-5C that provide solutions to condensation that may form under standard operation as shown in FIGS. 5A-5C.

[0214] FIG. 10A is a graph illustrating an exemplary effect of an exemplary humidity delivery control system at an inlet temperature of 36° C. Specifically, FIG. 10A illustrates a comparison between operating a humidifier under standard operating conditions where the target or desired humidity corresponds to a 31° C. dew point (e.g., as shown in FIG. 5A ) and operating a humidifier where the reduced maximum chamber outlet set point corresponds to a 29° C. dew point. An exemplary actual gas temperature as the gas passes through the humidifier is shown by line 1010. The gas temperature may decrease from the outlet temperature, shown as 36° C. in FIG. 10A , to the target temperature at the patient interface outlet, shown as 31° C. in FIG. 10A . When gas is entrained, it may contain excess moisture. When gas is not entrained, it may be considered “dry.” Under process 601 shown in FIG. 6A or process 600 shown in FIG. 6B, the target or desired humidity level (line 1014A) represented by the dry inlet humidity (i.e., dry gas) may be reduced to a relatively lower desired humidity level (line 1014B), corresponding to a dew point of, for example, 29° C. Line 1014A may represent the dew point when the system does not cap the chamber outlet set point if the inlet gas temperature threshold is not exceeded. Line 1014B may represent the dew point that results from lowering the chamber outlet set point when the temperature threshold is exceeded. For room-entrained gas, the effective target humidity of the outlet gas may be reduced from line 1012A to line 1012B. Line 1012A may represent the dew point of the ambient gas humidity in addition to the chamber humidity (shown in FIG. 5A). Line 1012B may represent the dew point of the ambient gas humidity in addition to the chamber humidity as a result of exceeding the temperature threshold and lowering the chamber outlet temperature setpoint (i.e., capping the maximum allowable chamber outlet temperature setpoint). Lines 1012B and 1014B may represent the change in dew point due to lowering the chamber outlet setpoint, for example, by capping the chamber outlet temperature setpoint. Lines 1012B and 1014B may represent the decrease in dew point due to the reduced amount of humidity added to the gas by the humidifier when the chamber outlet setpoint is reduced.When the inlet temperature threshold is exceeded, the controller may cap the chamber outlet temperature setpoint (or heater plate power setpoint or heater plate temperature setpoint or humidity setpoint) at a relatively lower chamber outlet setpoint (or relatively lower heater plate power setpoint or heater plate temperature setpoint or relatively lower humidity setpoint) compared to standard control (shown by line 1014A). In addition to or as an alternative to capping the chamber outlet temperature setpoint, the heater plate setpoint temperature may be capped or the heater plate power setpoint may be capped. A relatively lower chamber outlet temperature setpoint may result in a relatively lower dew point and a relatively lower absolute humidity output by the humidifier. If the humidifier is connected to a room air entrainment ventilation system, the dew point will decrease from 1012A to 1012B, which may result in less condensation forming, as shown by the hatched triangles. This is achieved by capping the chamber outlet temperature setpoint (or capping the heater plate power setpoint or heater plate temperature setpoint) to reduce the humidity produced. The capped chamber outlet temperature setpoint (or capped heater plate power setpoint or heater plate temperature setpoint) corresponds to the maximum allowable setpoint. In the second mode (i.e., when the inlet temperature is equal to or exceeds the temperature range), the capped setpoint is less than the maximum setpoint in the first mode (i.e., when the inlet temperature is below the temperature threshold). While some condensation may still occur due to the high inlet temperature, as shown in FIG. 5A, the condensation in FIG. 10A may be significantly reduced compared to the gas condensation level during normal operation of the humidifier. As previously mentioned, lines 1012A, 1012B, 1014A, and 1014B are shown as horizontal lines representing estimated dew points for illustrative purposes to indicate one or more points at which condensation may occur in the humidifier or respiratory assistance system.

[0215] FIG. 10B is a graph illustrating an exemplary effect of an exemplary humidity delivery control system at an inlet temperature of 26° C. Specifically, FIG. 10B illustrates a comparison between operating a humidifier under standard operating conditions where the target humidity corresponds to a 31° C. dew point (e.g., as shown in FIG. 5B ) and operating a humidifier where the reduced maximum chamber outlet setpoint corresponds to a 29° C. dew point. An exemplary gas temperature as the gas passes through the humidifier is shown by line 1030. Under process 600, the target humidity level (line 1013A) represented by the dry inlet humidity may be reduced to a relatively lower desired humidity level (line 1034B), corresponding to, for example, a 29° C. dew point. Line 1034A may represent the chamber outlet dew point when the system does not further cap the chamber outlet temperature setpoint when the inlet gas temperature threshold is exceeded. Line 1034B may represent the dew point at the chamber outlet that results from reducing (i.e., capping) the chamber outlet temperature setpoint when the temperature threshold is exceeded. The chamber outlet temperature setpoint is capped at the highest allowable chamber outlet temperature setpoint. For room-entrained gas, the effective target humidity of the outlet gas may be reduced from line 1032A to line 1032B. Line 1032A may represent the dew point at the chamber outlet (shown in FIG. 5B). The gas outlet temperature may be 33°C. Because this outlet temperature is lower than the chamber outlet temperature setpoint and / or the desired temperature at the patient side, which is 34°C in this example, as shown by line 1030 between the chamber outlet and the patient-side sensor, the system will be configured to heat the gas as it travels from the chamber outlet to the patient side. The gas will then cool as it travels through the patient interface, where it is not heated to approximately 31°C at the patient interface outlet, as shown by line 1030 between the patient-side sensor and the patient interface outlet. As the gas cools between the patient side and the patient interface outlet, the dew point of the gas will also decrease. As previously mentioned, the water vapor that can no longer be contained in the gas with a relatively low dew point of 31° C. will condense into a liquid. This condensation is represented by the gray area in FIG. 10B. Line 1032B may represent the resulting dew point at the chamber outlet when the inlet temperature threshold is exceeded and the chamber outlet setpoint is reduced.Lines 1032B and 1034B may represent the change in dew point due to a lowering of the chamber outlet setpoint, for example, by capping the chamber outlet setpoint. Lines 1032B and 1034B may represent a decrease in dew point due to a reduction in the amount of humidity added to the gas by the humidifier when the chamber outlet setpoint is reduced (i.e., the maximum allowable chamber outlet setpoint is capped). When the inlet temperature threshold is exceeded, the controller may cap the chamber outlet setpoint (or heater plate power setpoint or heater plate temperature setpoint) at a relatively lower chamber outlet setpoint compared to standard control (represented by line 1014A). In addition to, or as an alternative to, capping the chamber outlet setpoint, the heater plate setpoint temperature may be capped, or the heater plate power setpoint may be capped. A relatively lower chamber outlet setpoint may result in a relatively lower dew point and a relatively lower absolute humidity. The relatively low, or capped, chamber outlet setpoint corresponds to the maximum allowable chamber setpoint in the second mode (i.e., when the inlet gas temperature exceeds the temperature threshold). The maximum allowable chamber setpoint may vary based on changes in inlet gas temperature. Condensation, represented by the shaded area, may be avoided by lowering the desired humidity dew point, also referred to as the actual dew point. For example, when the inlet gas temperature exceeds the temperature threshold, reduced condensation can be achieved by capping the chamber outlet temperature setpoint (or capping the heater plate temperature setpoint or heater plate power setpoint). As previously mentioned, lines 1032A, 1032B, 1034A, and 1034B are shown as horizontal lines representing estimated dew points for illustrative purposes to indicate one or more points at which condensation may occur in the humidifier or respiratory support system.

[0216] FIG. 10C is a graph illustrating an exemplary effect of an exemplary humidity delivery control system at an inlet temperature of 21°C, which is below the threshold temperature of 24°C. An exemplary gas temperature as the gas passes through the humidifier is shown by line 1040. The target humidity dew point may remain at line 1042A rather than decrease because the inlet temperature threshold is not exceeded. In the example shown in FIG. 10C, the humidifier is able to heat and humidify the gas until it saturates at a reduced humidity level, regardless of the inlet humidity resulting from the low inlet temperature (i.e., lower than ambient temperature). This is illustrated by merging the dry and wet inlet humidity lines (i.e., lines 1042A and 1044A are the same after the gas exits the chamber outlet). Lines 1042A and 1044A are shown as horizontal lines representing estimated dew points for illustrative purposes to indicate one or more points at which condensation may occur in the humidifier or respiratory assistance system.

[0217] In an alternative configuration, the humidifier may include a humidity sensor at the humidifier outlet instead of a temperature sensor. The controller is configured to control the power supplied to the heater plate based on the measured inlet temperature. The controller may be configured to operate in a first mode when the gas inlet temperature is below a threshold temperature and in a second mode when the gas inlet temperature exceeds the temperature threshold. The controller may be configured to define a first maximum allowable humidity value in the first mode and a second maximum allowable humidity value in the second mode. The second allowable humidity is below the first maximum allowable humidity. The controller determines the humidity of the gas based on the outlet humidity sensor. The controller is configured to control the power to the heater plate to achieve a desired humidity output at the chamber outlet. In the second mode, the power level of the heater plate is controlled to ensure that the output humidity at the chamber outlet is below the second maximum allowable humidity. The humidity setpoint may be defined by a piecewise function. A first portion of the piecewise function defines a first maximum allowable humidity output when the gas inlet temperature is below the temperature threshold. The second portion of the segmented function defines a second humidity output. In the second mode, the humidity setpoint may be adjusted by the controller based on at least the inlet temperature and flow rate readings. However, the maximum allowable humidity corresponds to a second maximum allowable humidity. The humidity setpoint may be adjusted to be lower than the second maximum allowable humidity corresponding to the desired humidity input by the user. However, in the second mode (i.e., when the gas inlet temperature exceeds the temperature threshold), the humidity output does not exceed the second maximum allowable humidity. If the humidity output exceeds the second maximum allowable humidity, the heater plate power is turned off by the controller. The relatively low humidity when the inlet temperature exceeds the temperature threshold reduces condensation in the tubing and / or patient-connected devices. The relatively low humidity output helps prevent excessive humidification of gases, particularly gases received from air-entraining ventilators. In a further alternative configuration, the system can operate with a humidity sensor that measures the inlet gas to determine whether the gas is hot and humid or hot and humid. The system may use this additional information to modify or refine the outlet temperature setpoint.Additionally or alternatively, the system may operate with a pressure sensor measuring the inlet gas configured to determine the ambient air pressure, which may be used to determine the indicated humidity of the inlet gas.

[0218] Terminology Many other variations beyond those described herein will be apparent from this disclosure. For example, depending on the embodiment, certain acts, events, or functions of any algorithm described herein may be performed in a different order, added, combined, or omitted altogether (e.g., not all described acts or events are necessary to execute an algorithm). Furthermore, in certain embodiments, acts or events may be performed simultaneously, rather than serially, for example, via multithreading, interrupt handling, or multiple processors or processor cores, or in other parallel architectures. Furthermore, various tasks or processes may be performed by different machines and / or computing systems that can function together.

[0219] The various illustrative logical blocks, modules, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or a combination of both. To clearly illustrate this interchangeability of hardware and software, the various illustrative components, blocks, modules, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the particular application and design constraints imposed on the overall system. The described functionality can be implemented in various ways for each particular application, and such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.

[0220] For example, the various illustrative logic blocks and modules described in connection with the embodiments disclosed herein may be implemented or executed by machines such as hardware processors comprising digital logic circuitry, general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor; alternatively, the processor may be a controller, microcontroller, or state machine, combinations thereof, or the like. A processor may comprise electrical circuitry configured to process computer-executable instructions. In other embodiments, a processor comprises an FPGA or other programmable device that performs logical operations without processing computer-executable instructions. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration. The computing environment may comprise any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computing engine within an appliance, to name a few.

[0221] Each step of a method, process, or algorithm described in connection with each embodiment disclosed herein may be embodied directly in hardware, in a software module stored in one or more memory devices and executed by one or more processors, or in a combination of the two. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of persistent computer-readable storage medium, media, or physical computer storage device known to those skilled in the art. An exemplary storage medium may be coupled to the processor such that the processor can read information from and write information to the storage medium. In the alternative, the storage medium may be integrated with the processor. The storage medium may be volatile or non-volatile. The processor and the storage medium may reside in an ASIC.

[0222] Unless otherwise indicated or understood otherwise within the context of use, conditional language used herein, such as "can," "might," "may," "e.g.," among others, is intended to generally convey that certain embodiments include certain features, elements, and / or states, while other embodiments do not. Thus, such conditional language generally does not imply that each feature, element, and / or state is required in any way for one or more embodiments, or that one or more embodiments necessarily include logic for determining whether such features, elements, and / or states are included or should be implemented in any particular embodiment, with or without author input or direction. Terms such as "comprising," "including," and "having" are synonymous and used interchangeably, inclusively, and do not exclude additional elements, features, acts, operations, etc. The term "or" is also used in its inclusive (rather than exclusive) sense; thus, for example, when used to connect consecutive elements, "or" may refer to one, some, or all of the consecutive elements. Furthermore, the term "each" as used herein, in addition to having its inherent meaning, can refer to any subset of the set of elements to which the term "each" applies.

[0223] For example, disjunctive language such as the phrase "at least one of X, Y, and Z," unless otherwise indicated, should be understood with the context in which it is generally used to convey whether an item, term, etc. may be X, Y, or Z, or a combination thereof. Thus, such disjunctive language does not generally imply that a particular embodiment requires that there be at least one X, at least one Y, and at least one Z, respectively.

[0224] Unless expressly stated otherwise, articles such as "a" or "an" should generally be construed to include one or more of the listed items. Thus, a phrase such as "an apparatus configured to" is intended to include one or more of the listed apparatuses. Such one or more listed apparatuses may also be collectively configured to perform the referenced and listed items. For example, "a processor configured to perform the listed items A, B, and C" may include a first processor configured to perform the listed item A working in conjunction with a second processor configured to perform the listed items B and C.

[0225] While detailed descriptions have been shown and described above, and novel features applicable to various embodiments have been pointed out, it will be understood that various omissions, substitutions, and changes may be made in the form and details of the illustrated apparatus or algorithms without departing from the spirit of the present disclosure. It will be recognized that certain embodiments of the invention described herein may utilize some of the features or be practiced separately from other features, and therefore may be practiced within forms that do not provide all of the features and advantages set forth herein.

Claims

1. 1. A humidifier for humidifying a gas flow supplied to a user in a humidification chamber, comprising: at least one inlet temperature sensor configured to sense a temperature of gas within or adjacent to the inlet of the humidification chamber; at least one outlet temperature sensor configured to sense the temperature of gas within or adjacent to the outlet of the humidification chamber; determining an inlet temperature of the gas received by the humidification chamber based on a signal received from the inlet temperature sensor; determining an outlet temperature of the gas exiting the humidification chamber outlet based on the signal received from the outlet temperature sensor; determining that the inlet temperature exceeds a threshold temperature; determining an upper limit for a target outlet temperature based on the inlet temperature exceeding the threshold temperature; determining a target outlet temperature that is lower than the upper limit; controlling the humidifier to humidify the gas flow so that the outlet temperature detected by the outlet temperature sensor is controlled to be the target outlet temperature; and an electronic control device configured as follows: A humidifier comprising:

2. The humidifier of claim 1 , wherein the threshold temperature is determined by a dew point corresponding to an amount of humidity delivered to a user.

3. 3. A humidifier according to claim 1 or 2, comprising a base unit including a heater plate.

4. 4. The humidifier of claim 3, wherein the controller is configured to output a heater plate control signal to control the amount of power supplied to the heater plate based at least in part on the outlet temperature of gases exiting the humidification chamber outlet.

5. 5. A humidifier according to claim 3 or 4, wherein the controller is configured to control the amount of power supplied to the heater plate so that the outlet temperature of gases leaving the humidification chamber outlet is below the upper limit.

6. A humidifier as described in claim 3 or 4, wherein the control device is configured to control the heater plate temperature set point so that the outlet temperature of the gas exiting the outlet of the humidification chamber is below the upper limit.

7. The control device a first mode when the inlet temperature is below the threshold temperature; and a second mode when the inlet temperature exceeds the threshold temperature. A humidifier according to any one of claims 3 to 6, configured to control the amount of power supplied to the heater plate.

8. 7. The humidifier of claim 3, wherein the control device is configured to control the amount of power supplied to the heater plate according to a first function that is applied when the inlet temperature is below the threshold temperature.

9. 9. The humidifier of claim 8, wherein the controller is configured to control the amount of power supplied to the heater plate according to a second function that is applied when the inlet temperature exceeds the threshold temperature and that is different from the first function and that defines the upper limit for the target outlet temperature relative to the inlet temperature.

10. A humidifier according to any one of claims 1 to 9, wherein the threshold temperature is between 22°C and 24°C.

11. 11. A humidifier as described in any one of claims 1 to 10, operable in one of a plurality of treatment modes, each treatment mode defining a plurality of dew points corresponding to an amount of humidity delivered to a user, the plurality of dew points being user selectable.

12. 12. The humidifier of claim 11, wherein the plurality of therapy modes includes an invasive mode, a non-invasive mode, and a high-flow mode.

13. 13. The humidifier of claim 12, wherein in the non-invasive mode, the plurality of dew points include 31°C, 29°C, and 27°C.

14. A humidifier according to any one of claims 11 to 13, wherein the therapy mode is manually selectable by a user.

15. 15. The humidifier of claim 11, wherein the plurality of dew points include 31°C, 34°C, and 37°C.

16. 16. A humidifier according to any preceding claim, wherein the upper limit is predetermined when the inlet temperature is below the threshold temperature, and wherein the upper limit is limited to a relatively low, pre-defined value when the inlet temperature exceeds the threshold temperature.

17. A humidifier according to any preceding claim, wherein the at least one inlet temperature sensor is configured to be inserted into an inlet port of the humidification chamber when the humidification chamber is placed in an operating position on the humidifier.

18. The humidification chamber includes: Conductive base, one or more wall portions configured to be coupled to the conductive base; the inlet, and Exit or said exit 18. The humidifier of any one of claims 1 to 17, comprising:

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