Deterministic controlled humidification system

Abstract

A respiratory humidification system for providing humidification to a gas passing through a gas passage before being provided to an airway of a patient. The respiratory humidification system can include a liquid flow controller providing a controlled liquid flow, a heating system including a heating surface, the heating system configured to be located within the gas passage and to provide humidification to a gas passing through the passage, wherein the heating system receives the controlled liquid flow, and one or more hardware processors providing deterministic control of a humidity level of a gas passing through the gas passage by instructing the liquid flow controller to adjust the controlled liquid flow received at the heating system.

Description

[0001] This application is a divisional application of the invention patent application filed on September 3, 2015, with application number 201580058101.7 (international application number PCT / NZ2015 / 050128) and entitled "deterministically controlled humidification system".

[0002] By citing any priority claim

[0003] Any and all applications for foreign or domestic priority specified in the application data sheet filed with this application are incorporated herein by reference in accordance with 37 CFR 1.57. This application claims priority to provisional application US62 / 045,358, filed September 3, 2014, and US 62 / 213,534, filed September 2, 2015, the contents of which are incorporated herein by reference in their entirety. background

[0004] This disclosure generally relates to humidifying gas therapy. More specifically, this disclosure relates to humidification systems used in humidifying gas therapy.

[0005] Patients with respiratory diseases such as chronic obstructive pulmonary disease (COPD) may struggle to breathe effectively. This difficulty can result from a variety of causes, including weakened lung tissue, small airway dysfunction, excessive sputum accumulation, infection, genetic disorders, or heart failure. In cases of respiratory diseases, providing therapies that improve ventilation is useful. In some situations, patients may be equipped with a respiratory therapy system, which includes a gas source, an interface for delivering gas to the patient's airway, and a conduit extending between the gas source and the interface. The gas delivered from the gas source to the patient's airway can help promote adequate ventilation. The gas source may include, for example, a container of air and / or another gas suitable for inhalation (e.g., oxygen or nitric oxide), a mechanical blower capable of propelling the gas through the conduit to the interface, or some combination of both. The respiratory therapy system may include a gas humidifier that can humidify and heat the gas delivered through the respiratory therapy system to improve patient comfort and / or improve the prognosis of the patient's respiratory disease. A gas humidifier may include a water reservoir and a heating element for heating the water in the reservoir. As the water is heated and its temperature rises, water vapor is formed that can be incorporated into the airflow passing through the gas humidifier.

[0006] Conventional gas humidifiers are useful for relieving cold discomfort and in dry gas therapy, but they are typically configured so that all or any excess water in the reservoir must be heated before the generated steam rises to an acceptable level to provide adequate humidification. In some cases, it can take up to half an hour from turning on the humidifier to starting to generate enough steam. Furthermore, conventional gas humidifiers may not respond adequately to changes in input conditions, or may have an impaired response, partly due to the high thermal inertia of the water in the reservoir.

[0007] Overview

[0008] This disclosure provides a water evaporation system that does not require heating of water or excess water in a storage tank. The disclosed embodiments allow a desired amount of water to evaporate rapidly, thereby improving response time to changes in the system or environment and significantly reducing the warm-up period.

[0009] According to a first aspect of this disclosure, a respiratory humidification system for humidifying a gas before it is delivered to a patient's airway via a gas passage may include a liquid flow controller for providing a controlled liquid flow; a heating system including a heating surface configured to be located in the gas passage and to provide humidification to the gas delivered through the passage, wherein the heating system receives a controlled liquid flow and is configured to maintain the heating surface at a predetermined temperature between approximately 30 degrees Celsius (°C) and approximately 99.9°C; and one or more hardware processors that provide deterministic control of the humidity level of the gas delivered through the gas passage by instructing the liquid flow controller to regulate the controlled liquid flow received at the heating system.

[0010] The heating system can be configured to maintain the heated surface at a predetermined temperature between approximately 35°C and approximately 90°C, between approximately 40°C and approximately 80°C, between approximately 45°C and approximately 70°C, between approximately 45°C and approximately 60°C, between approximately 50°C and approximately 60°C, or a predetermined temperature of approximately 50°C.

[0011] The liquid can be water. The liquid flow controller can include a metering system. The liquid flow controller can be a pump. The pump can be a positive displacement pump. A positive displacement pump can be a piezoelectric pump, a diaphragm pump, or a peristaltic pump. The liquid flow controller can be a pressure supply (such as gravity supply) and a control valve. The liquid flow controller can include a check valve configured to maintain the liquid flow controller's startup and / or protect the system from contamination. The liquid flow controller can be configured to use wicking or capillary action. The breathing humidification system can include a safety valve to prevent liquid flow in the event of a liquid controller failure. The breathing humidification system can include a reservoir. The breathing humidification system can include a flow restrictor located between the reservoir and the liquid flow controller and configured to prevent gravity-driven flow from affecting the delivered liquid flow. The flow restrictor can be a resilient protrusion that limits the flow path. The liquid flow controller can be an open-loop pump. The liquid flow controller is a closed-loop pump or flow actuator connected in series with a flow sensor. The liquid flow controller can provide a continuous water flow in the range of 0 mL / min to approximately 10 mL / min. The liquid flow controller can provide a continuous liquid flow in the range of 0 mL / min to approximately 7 mL / min. The liquid flow controller can provide a continuous liquid flow in the range of 0 mL / min to approximately 5 mL / min. The liquid flow controller can provide a continuous liquid flow in the range of approximately 40 μL / min to approximately 4 mL / min, or approximately 70 μL / min to approximately 2.5 mL / min. The liquid flow controller can provide a controlled liquid flow with the following accuracy: approximately ±15% of the desired liquid flow rate, approximately ±10% of the desired liquid flow rate, approximately ±6.5% of the desired liquid flow rate, or approximately ±5% of the desired liquid flow rate.

[0012] A breathing humidification system may include a flow sensor. The flow sensor may be a calorimeter, a drop-by-drop counter, or a differential pressure flow sensor.

[0013] One or more hardware processors can provide deterministic control of humidity levels based on gas flow rate. One or more hardware processors can provide deterministic control of humidity levels based on the evaporation rate of water from the heating surface. One or more hardware processors can provide deterministic control of humidity levels based on the temperature of the heating surface, wherein the temperature of the heating surface is maintained at a constant temperature. One or more hardware processors can provide deterministic control of humidity levels based on the temperature of the heating surface, wherein the temperature of the heating surface is controlled. One or more hardware processors can provide deterministic control of humidity levels based on the absolute pressure of the gas at the inlet or atmospheric pressure. One or more hardware processors can provide deterministic control of humidity levels based on the dew point temperature of the gas at the inlet. One or more hardware processors can provide deterministic control of humidity levels based on the heat content provided by the heating surface. One or more hardware processors can provide deterministic control of humidity levels based on the temperature of the gas before interacting with the heating system. One or more hardware processors can provide deterministic control of humidity levels based on the relative humidity of the gas before interacting with the heating system. One or more hardware processors can provide deterministic control of humidity levels based on the effective heating surface area of ​​the heating surface. One or more hardware processors can provide deterministic control of humidity levels based on the pressure of the gas. One or more hardware processors can provide deterministic control of humidity levels as a function of gas velocity. One or more hardware processors can provide deterministic control of humidity levels based on the temperature of the liquid in a controlled liquid flow. The breathing humidification system may include a water temperature sensor. The breathing humidification system may include a gas flow rate sensor. The breathing humidification system may include a gas flow rate sensor located at the inlet of the gas passage. The breathing humidification system may include a liquid flow rate determined by a model. The breathing humidification system may include a gas flow rate determined by a model. The breathing humidification system may include an ambient pressure sensor. The breathing humidification system may include a pressure sensor located at or near the heating surface. The breathing humidification system may include a heating surface temperature sensor. The breathing humidification system may include an ambient dew point temperature sensor or an ambient humidity sensor located upstream of the humidification zone. The breathing humidification system may include an ambient dew point temperature sensor located upstream of the gas preheater. The breathing humidification system may include an ambient dew point temperature sensor located downstream of the gas preheater. The breathing humidification system may include an ambient dew point temperature sensor located downstream of the gas preheater and a temperature sensor located at the inlet of the gas passage. The breathing humidification system may include at least one temperature sensor forming part of the heating system. At least one temperature sensor can be used to determine the proportion of the heater permeated with liquid. The breathing humidification system may include a gas preheater. The temperature of the gas at the gas inlet is controlled in an open-loop manner by controlling the power of the preheater. The breathing humidification system may also include a liquid preheater. The heating surface may include a wicking surface.Heat can be supplied to the heating surface via a PCB with resistive traces or strips. Heat can also be supplied via etched foil or one or more flexible PCBs. Heat can be supplied via a heating wire. Heat can be supplied via PTC ceramic. Heat can be supplied by a Peltier device or a thermoelectric device. The heating surface can be overmolded, and microchannels can be included in the overmolding configured to draw water cores onto the heater. The surface temperature of the heating surface can be at least partially determined by using the resistance or other characteristics of the heating system. Resistance can indicate the average heater system temperature. In some configurations, the heating system is arranged to provide a higher density of heat in designated areas of the heater, thus providing these areas with a higher power density. This higher density of heat can be located near the outlet of the water supply system. This higher density of heat can be provided in the water preheating area. The breathing humidification system may include a temperature sensor located at the outlet of the gas passage.

[0014] According to another aspect of this disclosure, a highly efficient respiratory humidification system for providing heated and humidified respiratory gases to a patient is described. The respiratory humidification system may include a respiratory gas passage having an inlet and an outlet, wherein gas flows from the inlet to the outlet during operation; a preheater configured to heat the gas flow; and a heating surface separated from and located downstream of the preheater, the heating surface including a wicking feature configured to wick a liquid across its surface, the heating surface being further configured to heat the liquid during and / or after wicking. The respiratory humidification system may include a gas flow generator. The preheater may be a gas heating element. The gas heating element may be one of a PCB including a resistive element (e.g., a trace or strip), an etched foil, a heating coil, or a PTC element, etc. The respiratory humidification system may include a temperature sensor located downstream of the preheater. The power supplied to the gas heating element can be controlled based on measurements obtained from the downstream temperature sensor. The respiratory humidification system may include a temperature sensor located upstream of the preheater. The power supplied to the gas heating element can be controlled based on gas flow rate and measurements obtained from the upstream temperature sensor. The gas heating element can be used as a temperature sensor. A desired downstream temperature can be set based on the evaporation rate of the liquid from the heating surface. The desired downstream temperature can be set to ensure that approximately all sensible heat is supplied to the gas flow by the preheater. The desired downstream temperature can be set between 0°C and approximately 5°C, above the output dew point temperature. The desired downstream temperature can be set to obtain a predetermined output absolute humidity. The desired downstream temperature can be set to obtain a given output absolute humidity. The desired downstream temperature can be set to approximately 25°C to approximately 43°C, or approximately 31°C to approximately 43°C, or approximately 31°C to approximately 41°C, or approximately 31°C to approximately 37°C, or approximately 37°C. A breathing humidification system may include a liquid flow generator. A breathing humidification system may include a device for preheating the liquid flow. The device for preheating the liquid flow can be integrated into the heating surface structure by increasing the number of resistance strips into which water is introduced. The device for preheating the liquid flow can be located in the water supply line. The wicking feature can be one or more of the following: absorbent fabric or absorbent paper, microchannels, hydrophilic coated surfaces, capillary wicks or contact wicks, or thin porous media. The wicking feature may include a connector configured to distribute liquid onto a heating surface. The connector may be a section of wicking medium bonded or incorporated into contact with the heating surface or the wicking feature. The connector may be a second surface forming an acute angle with the wicking feature. The connector may be a cavity in contact with the heating surface or the wicking feature. The connector may be a line source, a point source, a radial source, or multiple lines, multiple points, and multiple radial sources, or any combination thereof.The heated surface can be maintained at the following predetermined temperatures: between approximately 30°C and approximately 99.9°C, between approximately 35°C and approximately 90°C, between approximately 40°C and approximately 80°C, between approximately 45°C and approximately 70°C, between approximately 45°C and approximately 60°C, between approximately 50°C and approximately 60°C, or approximately 50°C. The wicking feature can be mechanically configured to be positioned within the liquid delivery tubing. The respiratory humidification system can be configured to be located within or as part of the inhalation tubing for delivering gas to the patient. The respiratory humidification system may include a filter. The filter may be located in the liquid delivery line. The filter may be positioned downstream of the pump. The filter may be positioned at the inlet leading to the heated surface. The filter may be a biofilter. The respiratory humidification system may include a UV source to achieve sterility.

[0015] According to another aspect of this disclosure, a respiratory humidification system for providing heated and humidified respiratory gases to a patient may include a liquid flow controller providing a controlled liquid flow; a heating system including a heating surface configured to receive the controlled liquid flow and provide humidification to the gas passed through the humidification system; one or more temperature sensors measuring the surface temperature of the heating surface; one or more hardware processors providing deterministic control of the humidity level of the gas passed through the respiratory system by instructing the liquid flow controller to regulate the controlled liquid flow received at the heating system and instructing the heating system to regulate the surface temperature of the heating surface, wherein regulating the surface temperature of the heating surface provides control to produce a known evaporation area; and one or more liquid sensors configured to detect whether the heating surface is wetted in at least one area. The one or more liquid sensors may be at least two liquid sensors configured to detect whether the heating surface is wetted in two or more areas of the heating surface. The at least two liquid sensors may be two temperature sensors. The one or more liquid sensors may be located at the heating surface, on the heating surface, adjacent to the heating surface, or near the heating surface. The liquid may be water.

[0016] A liquid flow controller can be a metering system. A liquid flow controller can include a pump. The pump can be a positive displacement pump. A positive displacement pump can be a piezoelectric diaphragm pump or a peristaltic pump. The liquid flow controller can include a pressure supply (such as gravity supply) and a control valve. The liquid flow controller can include a check valve configured to maintain the liquid flow controller's operation and / or reduce the possibility of backflow. The liquid flow controller can be configured to use wicking or capillary action. A breathing humidification system can include a safety valve to prevent liquid flow in the event of a liquid controller failure. The breathing humidification system can include a reservoir. The breathing humidification system can include a flow restrictor located between the reservoir and the liquid flow controller and configured to prevent gravity-driven flow from affecting the delivered liquid flow. The flow restrictor can be a resilient protrusion that limits the flow path. The liquid flow controller can be an open-loop pump. The liquid flow controller is a closed-loop pump or flow actuator connected in series with a flow sensor. The pump can be a piezoelectric pump. The flow sensor can be a calorimeter. Liquid flow actuators can provide a continuous water flow in the range of 0 mL / min to 10 mL / min. Liquid flow actuators can provide a continuous water flow in the range of 0 mL / min to 7 mL / min. Liquid flow actuators can provide a continuous water flow in the range of 0 mL / min to 5 mL / min. Liquid flow actuators can provide a continuous water flow in the range of 40 μL / min to 4 mL / min, or 70 μL / min to 2.5 mL / min. Flow controllers can provide controlled liquid flow with the following accuracy: approximately ±15% of the desired liquid flow rate, approximately ±10% of the desired liquid flow rate, approximately ±6.5% of the desired liquid flow rate, or approximately ±5% of the desired liquid flow rate.

[0017] One or more hardware processors can provide deterministic control of humidity levels based on gas flow rate. One or more hardware processors can provide deterministic control of humidity levels based on the evaporation rate of liquid from the heating surface. One or more hardware processors can provide deterministic control of humidity levels based on the temperature of the heating surface, wherein the temperature of the heating surface is maintained at a constant temperature. One or more hardware processors can provide deterministic control of humidity levels based on the temperature of the heating surface, wherein the temperature of the heating surface is controlled. One or more hardware processors can provide deterministic control of humidity levels based on the absolute pressure of the gas at the inlet or atmospheric pressure. One or more hardware processors can provide deterministic control of humidity levels based on the dew point temperature of the gas at the inlet. One or more hardware processors can provide deterministic control of humidity levels based on the heat content provided by the heating surface. One or more hardware processors can provide deterministic control of humidity levels based on the temperature of the gas before interacting with the heating system. One or more hardware processors can provide deterministic control of humidity levels based on the relative humidity of the gas before interacting with the heating system. One or more hardware processors can provide deterministic control of humidity levels based on the effective heating surface area of ​​the heating surface. One or more hardware processors can provide deterministic control of humidity levels based on the pressure of the gas. One or more hardware processors can provide deterministic control of humidity levels as a function of gas velocity. One or more hardware processors can provide deterministic control of humidity levels based on the temperature of the liquid in a controlled liquid flow. The breathing humidification system may include a water temperature sensor. The breathing humidification system may include a gas flow rate sensor. The breathing humidification system may include a gas flow rate sensor located at the inlet of the gas passage. The breathing humidification system may include a liquid flow rate determined by a model. The breathing humidification system may include a gas flow rate determined by a model. The breathing humidification system may include an ambient pressure sensor. The breathing humidification system may include an ambient dew point temperature sensor or an ambient humidity sensor located upstream of the humidification zone. The breathing humidification system may include an ambient dew point temperature sensor located upstream of the gas preheater. The breathing humidification system may include an ambient dew point temperature sensor located downstream of the gas preheater. The breathing humidification system may include an ambient dew point temperature sensor located downstream of the gas preheater and a temperature sensor located at the inlet of the gas passage. The breathing humidification system may include at least one temperature sensor forming part of a heating system. At least one temperature sensor can be used to determine the proportion of the heater permeated by liquid. The breathing humidification system may include a gas preheater. The temperature of the gas at the gas inlet is controlled in an open-loop manner by controlling the power of the preheater. The breathing humidification system may include a liquid preheater. One or more liquid sensors may be used to prevent liquid overflow onto the heated surface.One or more liquid sensors can be used by one or more hardware processors to determine the humidity level of gases delivered through the respiratory system. One or more liquid sensors can be used by one or more hardware processors to adjust the evaporation area of ​​a heated surface. One or more liquid sensors can be temperature sensors. One or more liquid sensors can be resistive or capacitive sensors.

[0018] According to another aspect of this disclosure, a heater plate for a respiratory humidification system includes a printed circuit board (PCB) or etched foil molded over a surface comprising microchannels. The surface may have microchannels extending only in a single direction. The microchannels may include a first set of distribution channels connected to a second set of main channels. The number of distribution channels may be less than the number of main channels. The microchannels may be radially distributed from a single point. The heating system can be used with any respiratory humidification system described herein.

[0019] According to another aspect of this disclosure, a respiratory humidification system for humidifying gas before it is delivered to a patient's airway via a gas passage includes a liquid flow controller providing a controlled liquid flow; a heating system including a heating surface configured to receive the controlled liquid flow and humidify the gas delivered through the humidification system, wherein the heating surface is configured to wick liquid across its surface; and a gas preheater arranged in the gas passage upstream of the heating system. The respiratory humidification system may include a coupling configured to receive the controlled liquid flow from the liquid controller and distribute the liquid onto the heating surface. The respiratory humidification system may be configured to be in line with the inhalation tubing used to deliver gas to the patient. The respiratory humidification system may be configured to be located within the inhalation tubing used to deliver gas to the patient. The liquid may be water. The respiratory humidification system may include a filter. The filter may be located in the liquid delivery line. The filter may be positioned downstream of the pump. The filter may be positioned at the inlet leading to the heating surface. The filter may be a biofilter. Breathing humidification systems may include a UV source to achieve sterility.

[0020] The liquid flow controller may include a metering system. The liquid flow controller may be a pump. The pump may be a positive displacement pump. A positive displacement pump may be a piezoelectric pump, a diaphragm pump, or a peristaltic pump. The liquid flow controller may include a pressure supply (such as gravity supply) and a control valve. The liquid flow controller may include a check valve configured to maintain the operation of the liquid flow controller. The liquid flow controller may be configured to use wicking or capillary action. The humidification system may further include a safety valve for preventing liquid flow in the event of a liquid controller failure. The humidification system may further include a reservoir. The humidification system may further include a flow restrictor located between the reservoir and the liquid flow controller and configured to prevent gravity-driven flow from affecting the delivered liquid flow. The flow restrictor may be a resilient protrusion that limits the flow path. The liquid flow controller may be an open-loop pump. The liquid flow controller may be a closed-loop pump or a flow actuator connected in series with a flow sensor. The liquid flow actuator can provide a continuous liquid flow in the range of 0 mL / min to approximately 10 mL / min. Liquid flow actuators can provide a continuous liquid flow in the range of 0 mL / min to approximately 7 mL / min. Liquid flow actuators can provide a continuous liquid flow in the range of 0 mL / min to approximately 5 mL / min. Liquid flow actuators can provide a continuous liquid flow in the range of 40 μL / min to approximately 4 mL / min, or approximately 70 μL / min to approximately 2.5 mL / min. Liquid flow controllers can provide controlled liquid flow with the following accuracy: approximately ±15% of the desired liquid flow rate, approximately ±10% of the desired liquid flow rate, approximately ±6.5% of the desired liquid flow rate, or approximately ±5% of the desired liquid flow rate.

[0021] The heating system may include a heater plate comprising a printed circuit board (PCB) or etched foil molded with a surface including microchannels. The surface may have microchannels extending only in a single direction. The microchannels may include a first set of distributed channels connected to a second set of main channels. The number of distributed channels may be less than the number of main channels. The microchannels may be radially distributed from a single point. The connector may be a fiber polymer, a porous polymer, or a sintered polymer. The heating surface may be immersed in a gas flow. The heating surface may include modular areas.

[0022] According to another aspect of this disclosure, a breathing humidification system includes a liquid flow controller providing a controlled liquid flow; a heating system including a heating surface, the heating system being configured to be located in a gas passage and to provide humidification to the gas passing through the passage, wherein the heating system receives the controlled liquid flow, the heating system being configured to maintain the heating surface at a predetermined temperature between approximately 30°C and approximately 99.9°C; and the heating surface may be configured to be maintained at a temperature between approximately 30°C and approximately 99.9°C, and wherein approximately 80%–99.9% of the system's power output is converted into heat in the liquid. The heating surface may be configured to be maintained at temperatures between approximately 35°C and approximately 90°C, between approximately 45°C and approximately 70°C, between approximately 45°C and approximately 60°C, between approximately 50°C and approximately 60°C, or approximately 50°C. In some configurations, approximately 85%–99.99% of the system's power output is converted into heat in the liquid, approximately 90%–99.99% of the system's power output is converted into heat in the liquid, approximately 95%–99.99% of the system's power output is converted into heat in the liquid, or approximately 98% of the system's power output is converted into heat in the liquid. The liquid can be water. The breathing humidification system can be configured as any breathing humidification system as described herein.

[0023] According to another aspect of this disclosure, a respiratory humidification system for humidifying gas before it is delivered to a patient's airway via a gas passage includes means for heating the gas flow and positioned upstream of a humidification zone; a liquid flow generator; and a heating system including a heating surface, configured to be located in the gas passage and to humidify the gas delivered through the passage, wherein the heating system is configured to maintain the heating surface at a predetermined temperature between approximately 30°C and approximately 99.9°C. The heating system is configured to maintain the heating surface at a predetermined temperature between approximately 35°C and approximately 90°C. The heating system is configured to maintain the heating surface at a predetermined temperature between approximately 40°C and approximately 80°C. The heating system is configured to maintain the heating surface at a predetermined temperature between approximately 45°C and approximately 70°C. The heating system is configured to maintain the heating surface at a predetermined temperature between approximately 45°C and approximately 60°C. The heating system is configured to maintain the heating surface at a predetermined temperature between approximately 50°C and approximately 60°C. The heating system is configured to maintain the heated surface at a predetermined temperature of approximately 50°C. The device may be a preheater. The preheater may include a gas heating element. The gas heating element may be one of the following: a resistive element, an etched foil, a heating coil, or a PTC element. The humidification system may include a temperature sensor located downstream of the preheater. The power supplied to the gas heating element can be controlled based on the measurement results obtained from the downstream temperature sensor. The humidification system may also include a temperature sensor located upstream of the preheater. The power supplied to the gas heating element can be controlled based on the airflow rate and measurement results obtained from the upstream temperature sensor. Characteristics of the gas heating element can be used as a temperature sensor. The desired downstream temperature after preheating can be set according to the evaporation rate of the heated surface. The desired downstream temperature can be set to ensure that approximately all sensible heat is supplied by the preheater. The desired downstream temperature can be set between 0°C and approximately 5°C, above the output temperature. The desired downstream temperature can be set to obtain a given output relative humidity. The desired downstream temperature can be set to obtain a given output absolute humidity. The desired downstream temperature can be set to approximately 25°C to approximately 43°C, or approximately 31°C to approximately 43°C, or approximately 31°C to approximately 41°C, or approximately 31°C to approximately 37°C, or approximately 37°C. The humidification system may include a device for preheating the liquid flow. This preheating device can be integrated into the heating structure by increasing the number of resistance heating rails through which the liquid is introduced. The preheating device can be located within the liquid supply line.

[0024] According to another aspect of this disclosure, deterministic control of humidity in a breathing humidification system is described by controlling the flow of water to a heating source. Deterministic control of humidity levels can be based on gas flow rate. Deterministic control of humidity levels can be based on the evaporation rate of water from the heating surface. Deterministic control of humidity levels can be based on the temperature of the heating surface, wherein the temperature of the heating surface is maintained at a constant temperature. Deterministic control of humidity levels can be based on the temperature of the heating surface, wherein the temperature of the heating surface is controlled. Deterministic control of humidity levels can be based on the absolute pressure of the gas at the inlet or atmospheric pressure. Deterministic control of humidity levels can be based on the dew point temperature of the gas at the inlet. Deterministic control of humidity levels can be based on the heat content provided by the heating surface. Deterministic control of humidity levels can be based on the temperature of the gas before interacting with the heating system. Deterministic control of humidity levels can be based on the relative humidity of the gas before interacting with the heating system. Deterministic control of humidity levels can be based on the effective heating surface area of ​​the heating surface. Deterministic control of humidity levels can be based on gas pressure. Deterministic control of humidity levels can be based on a function of gas velocity. Deterministic control of humidity levels can be based on the temperature of the liquid in a controlled liquid flow. Deterministic control can be based on a combination of two or more of the above inputs, and all combinations of the above inputs are within the scope of this disclosure. Deterministic control can be based on a combination of controls on the water flow rate and gas flow rate to the heating source. Deterministic control can be based on a combination of controls on the water flow rate, gas flow rate, and dew point temperature of the gas at the inlet. Deterministic control can be based on a combination of controls on the water flow rate, gas flow rate, and absolute pressure or atmospheric pressure of the gas at the inlet. Deterministic control can be based on a combination of controls on the water flow rate, gas flow rate, absolute pressure or atmospheric pressure of the gas at the inlet, and dew point temperature of the gas at the inlet. The breathing humidification system may include a water temperature sensor. The breathing humidification system may include a gas flow rate sensor. The breathing humidification system may include a gas flow rate sensor located at the inlet of the gas passage. The breathing humidification system may include a liquid flow rate determined by a model. The breathing humidification system may include a gas flow rate determined by a model. The breathing humidification system may include an ambient pressure sensor. The breathing humidification system may include a pressure sensor located at or near the heating surface. The breathing humidification system may include a heating surface temperature sensor. A breathing humidification system may include an ambient dew point temperature sensor or an ambient humidity sensor located upstream of the humidification zone. A breathing humidification system may include an ambient dew point temperature sensor located upstream of the gas preheater. A breathing humidification system may include an ambient dew point temperature sensor located downstream of the gas preheater. A breathing humidification system may include an ambient dew point temperature sensor located downstream of the gas preheater and a temperature sensor located at the gas passage inlet. A breathing humidification system may include at least one temperature sensor forming part of a heating system.At least one temperature sensor can be used to determine the proportion of the heater surface area that is permeated (or covered) by liquid. The breathing humidification system may include a gas preheater. The temperature of the gas at the gas passage inlet is controlled in an open-loop manner via power control of the preheater. The breathing humidification system may include a liquid preheater. The heating surface may include a wicking surface. Heat can be supplied to the heating surface via a PCB with resistive traces or resistive strips. Heat can be supplied to the heating surface via etched foil or a flexible PCB. Heat can be supplied via a heating wire. Heat can be supplied via PTC ceramic. Heat can be supplied by a Peltier device or a thermoelectric device. The heating surface may be a cladding mold, including microchannels configured to conduct liquids such as water within the cladding mold. The surface temperature of the heating surface can be at least partially determined by using the resistance or other characteristics of the heating system. The resistance can indicate the average heating system temperature. In some configurations, the heating system is arranged such that a higher density of heat is provided in designated areas of the heater, thus giving these areas a higher power density. The higher density of heat can be located near the outlet of the water supply system. Higher density heat can be provided in the water preheating zone. The breathing humidification system may include a temperature sensor located at the outlet of the gas passage.

[0025] According to another aspect of this disclosure, a respiratory humidification system is provided that provides embedded humidification. Embedded humidification allows humidification to occur in the gas flow path, thus enabling the humidification system to be positioned, for example, inside the inhalation tube, partially inside the inhalation tube, or at the end of the inhalation tube.

[0026] According to another aspect of this disclosure, a breathing humidification system is provided, comprising a gas passage through which gas can flow, the gas passage extending between an inlet position and an outlet position, the gas passage including a humidification position between the inlet position and the outlet position; a heating surface in fluid communication with the gas passage, the heating surface being configured to be maintained within a temperature range; and a water flow controller configured to control the flow of water to the heating surface; wherein, in use, the humidity level of the gas at the outlet position is deterministically controlled by controlling the flow rate of the water to the heating surface.

[0027] The water flow controller may include a metering arrangement. The metering arrangement may further include a pump. The pump may be a positive displacement pump, such as a piezoelectric diaphragm pump, peristaltic pump, micropump, or progressive cavity pump. The pump may also be a pressure supply connected in series with a control valve. The pressure source may be gravity. The breathing humidification system may have a conduit in fluid communication with the metering arrangement, configured to carry water to the metering arrangement. The conduit may have a check valve configured to maintain the operation of the metering arrangement. The conduit may also have a check valve configured to maintain the operation of the pump. The metering arrangement may include a wicking structure that uses capillary action to controllably and quantitatively supply water to a wicking element and / or a heated surface. The conduit may also have a safety valve, such as a pressure relief valve, in the conduit leading to the metering arrangement. The breathing humidification system may have a reservoir configured to hold water. The breathing humidification system may also have a flow restrictor positioned between the reservoir and the metering arrangement to prevent gravity-driven flow from affecting the water flow path. The flow restrictor may be a resilient protrusion that squeezes or otherwise restricts the flow path. A water flow controller can be an open-loop pump. A water flow controller can be a closed-loop pump or flow actuator connected in series with a flow sensor. A water flow controller can provide a continuous water flow rate in the range of 0 mL / min to approximately 5 mL / min. A water flow controller can provide a continuous water flow rate in the range of 0 mL / min to approximately 7 mL / min. A water flow controller can provide a continuous water flow rate in the range of 0 mL / min to approximately 5 mL / min. A water flow controller can provide a continuous water flow rate in the range of approximately 40 μL / min to approximately 4 mL / min, or approximately 70 μL / min to approximately 2.5 mL / min. A water flow controller can provide a continuous water flow rate in the range of approximately 40 μL / min to approximately 4 mL / min. A water flow controller can provide a continuous water flow rate in the range of approximately 70 μL / min to approximately 2.5 mL / min. A water flow controller can provide a water flow rate with an accuracy of approximately ±15%. A water flow controller can provide a water flow rate with an accuracy of approximately ±10%. A water flow controller can provide a water flow rate with an accuracy of approximately ±6.5%. Water flow controllers can provide water flow rate accuracy of approximately ±5%.

[0028] The heated surface can have a flow sensor. The flow sensor can be a thermal mass meter. The flow sensor can be a drop-by-drop counter. The flow sensor can be a differential pressure flow sensor.

[0029] The flow rate control of water to the heating surface can be based on the gas flow rate in the gas channel. The flow rate control of water to the heating surface can be based on the evaporation rate of water from the heating surface. The flow rate control of water to the heating surface can be based on the temperature of the heating surface, where the temperature of the heating surface is maintained at a constant temperature. The flow rate control of water to the heating surface can be based on the absolute pressure or atmospheric pressure of the gas at or near the inlet location. The flow rate control of water to the heating surface can be based on the dew point temperature of the gas at the inlet location. The flow rate control of water to the heating surface can be based on the heat content provided by the heating surface. The flow rate control of water to the heating surface can be based on the power level provided by the heating surface. The flow rate control of water to the heating surface can be based on the temperature of the gas at the inlet location. The dew point temperature of the gas at the inlet location can be derived by processing information provided by temperature and humidity sensors. The flow rate control of water to the heating surface can be based on the dew point temperature of the gas at the inlet location. The flow rate control of water to the heating surface can be based on the relative humidity level of the gas at the inlet location. The flow rate control can also be based on the effective heating surface area of ​​the heating surface. Alternatively, the flow rate control can be based on the pressure level of the gas in the gas channel. The flow rate control can also be based on the velocity of the gas flowing in the gas channel. The flow rate control can also be based on the temperature of the water flow. The breathing humidification system may include a water temperature sensor. The breathing humidification system may include a gas flow rate sensor. The breathing humidification system can determine the water flow rate based on a model. The breathing humidification system can determine the gas flow rate based on a model. The breathing humidification system may include an ambient pressure sensor. The pressure sensor may be located at or near the heating surface. The breathing humidification system may include a temperature sensor configured to measure the temperature of the heating surface. The breathing humidification system may include an ambient dew point temperature sensor located within the gas channel and upstream of the humidification location. The breathing humidification system may include an ambient humidity sensor located within the gas channel and upstream of the humidification location. The breathing humidification system may include a gas preheater. A gas preheater can be arranged within the gas channel, between the inlet and the humidification location. An ambient dew point sensor can be positioned within the gas channel, upstream of the gas preheater. An ambient humidity sensor can be positioned within the gas channel, upstream of the gas preheater. An ambient dew point temperature sensor can be positioned within the gas channel, downstream of the gas preheater. The ambient humidity sensor can also be positioned within the gas channel, downstream of the gas preheater, in conjunction with a temperature sensor positioned at the inlet of the gas channel. The breathing humidification system may include at least one temperature sensor configured to measure at least one temperature of a heated surface.At least one temperature sensor can be configured to determine the proportion of water permeable to the heated surface. The breathing humidification system can control the gas temperature at the inlet of the gas passage by controlling the power level leading to the gas preheater in an open-loop manner. The breathing humidification system may include a water preheater.

[0030] The heating surface can be configured to be maintained within a temperature range. The temperature range can be between approximately 30°C and approximately 99.9°C. The temperature range can be between approximately 35°C and approximately 90°C. The temperature range can be between approximately 40°C and approximately 80°C. The temperature range can be between approximately 45°C and approximately 70°C. The temperature range can be between approximately 45°C and approximately 60°C. The temperature range can be between approximately 50°C and approximately 60°C. The heating surface can be configured to maintain a temperature of approximately 50°C. The heating surface can include a wicking surface. The heating surface can include a heating element configured to provide heat to the heating surface. The heating element can be a circuit board. The circuit board can be a printed circuit board. The circuit board can be a flexible circuit board. The flexible circuit board can be made of a polymer, such as silicone, polyester, or polyimide. The circuit board can have multiple resistance bars (strips or traces). The resistance bars can be copper. The heating element can be an etched foil. The heating element can be a heating wire. The heating wire can be a nickel-chromium-iron alloy. The heating element can be a positive thermal resistance coefficient (PTC) ceramic. The PTC ceramic can be barium titanate. The heating element can be a thermoelectric device. The thermoelectric device can be a Peltier device. The wicking surface can be provided by a coating mold on a circuit board, the coating mold containing microchannels. The temperature of the heated surface can be measured at least in part by determining the resistance level or other characteristics of the heating element. The resistance level of the heating element can be used to indicate the average temperature of the heated surface. The heating element can be arranged to deliver a higher power density in a designated area of ​​the heating element compared to the power density delivered to other areas of the heating element. The designated higher-density area of ​​the heating element can be located at the water supply outlet to the heated surface. The designated higher-density area of ​​the heating element can be located in a water preheating area on the heated surface. The breathing humidification system can include a temperature sensor located at the outlet of the gas channel.

[0031] According to another aspect of this disclosure, a breathing humidification system is provided, the breathing humidification system including a gas passage through which gas can flow, the gas passage extending between an inlet position and an outlet position, the gas passage including a humidification position between the inlet position and the outlet position; a gas preheater disposed within the gas passage, located between the inlet position and the humidification position; and a heating surface in fluid communication with the gas passage at the humidification position, the heating surface having a wicking element configured to distribute water to the heating surface.

[0032] The breathing humidification system may include a gas flow generator adapted to propel, drive, or otherwise cause gas to move in a general direction from the inlet to the outlet of the gas channel. The gas preheater may include a gas heating element. The gas heating element may be a printed circuit board. The printed circuit board may have resistive elements. The gas heating element may be an etched foil. The gas heating element may be a heating coil. The gas heating element may be PTC ceramic. The breathing humidification system may include a temperature sensor. The temperature sensor may be located in the gas channel downstream of the gas preheater. The temperature sensor may be located in the gas channel upstream of the gas preheater. Characteristics of the gas heating element (e.g., resistance) may be used to determine the temperature of the gas. Control of the power level delivered to the gas heating element may be based on information provided by the temperature sensor located in the gas channel downstream of the gas preheater. Control of the power level delivered to the gas heating element may be based on information provided by a gas flow sensor and by a temperature sensor located in the gas channel upstream of the gas preheater. The desired downstream temperature of the gas may be determined based on the evaporation rate of water from the heating surface. The desired downstream temperature of the gas can be set to ensure that approximately all sensible heat is supplied by the gas preheater. The desired downstream temperature of the gas can be set to achieve the desired relative humidity level of the gas at the outlet location. The desired downstream temperature of the gas can be set between 0°C and approximately 5°C, higher than the desired temperature of the gas at the outlet location. The desired downstream temperature of the gas can be set to the desired dew point temperature at the outlet location. The desired downstream temperature of the gas can be set to approximately 25°C to approximately 43°C, or approximately 31°C to approximately 43°C, or approximately 31°C to approximately 41°C, or approximately 31°C to approximately 37°C, or approximately 37°C. The heating surface can include heating elements configured to provide heat to the heating surface. The heating element can include multiple resistance bars (strips or traces). The breathing humidification system can include a water flow generator configured to generate a flow of water toward the heating surface. The water flow generator can include a pump. The pump can be a positive displacement pump. The positive displacement pump can be a piezoelectric diaphragm pump, peristaltic pump, micropump, or progressive cavity pump. The breathing humidification system may include a device for preheating water. The device for preheating water can be incorporated into the heating element by increasing the density of resistance strips at one or more regions corresponding to the area on the heating surface where water is introduced, and thus increasing the power density delivered to the heating surface. The breathing humidification system may include a water supply line configured to deliver water to the heating surface. The device for preheating water can be incorporated into the water supply line.

[0033] The wicking element may include absorbent fabric. The wicking element may include absorbent paper. The wicking element may include microchannels. The wicking element may include a hydrophilic coated surface. The wicking element may include multiple capillary / contact wicks. The wicking element may include a thin porous medium, such as a fibrous polymer, a porous polymer, or a sintered polymer. The wicking element may include or be coupled to a connector that performs some form of water distribution to a heated surface. The connector may be a section of wicking medium bonded to or otherwise incorporated into contact with the wicking element or the heated surface. The connector may be a porous polymer. The connector may be fabric. The connector may be paper. The connector may be a hydrophilic coated section. The connector may be a second surface forming an acute angle with the wicking element. The second surface may be a glass plate. The connector may be a cavity in contact with the wicking element. The coupling may be performed by a line source. The coupling may be performed by multiple line sources. The coupling may be performed by a point source. The coupling may be performed by multiple point sources. The coupling may be performed by a radial source. The coupling may be performed by multiple radial sources. The connection can be implemented by a combination of linear, point, and / or radial sources. The heating surface can be adapted to maintain temperatures between approximately 30°C and approximately 99.9°C. The heating surface can be adapted to maintain temperatures between approximately 35°C and approximately 90°C. The heating surface can be adapted to maintain temperatures between approximately 40°C and approximately 80°C. The heating surface can be adapted to maintain temperatures between approximately 45°C and approximately 70°C. The heating surface can be adapted to maintain temperatures between approximately 45°C and approximately 60°C. The heating surface can be adapted to maintain temperatures between approximately 50°C and approximately 60°C. The heating surface can be adapted to be maintained at approximately 50°C. The breathing humidification system can be mechanically configured such that the wicking element, heating surface, and water flow generator are positioned within or integrated into the gas channel. The breathing humidification system can be mechanically configured such that the water flow generator, connection, wicking element, and heating surface are positioned within or integrated into the gas channel. The breathing humidification system may include a filter. The filter may be located in the water supply line. The filter can be located downstream of the pump. The filter can be located at the inlet leading to the heating surface. The filter can be a biological filter. The breathing humidification system can include multiple filters. The breathing humidification system can include a first filter in the water supply line located between the reservoir and the water flow generator, and a second filter in the water supply line located between the water flow generator and the heating surface. The breathing humidification system can include an electromagnetic radiation emitter to achieve sterility. The electromagnetic radiation emitter can be a UV light source. The UV light source can be a lamp or a light-emitting diode (LED).

[0034] According to another aspect of this disclosure, a breathing humidification system is provided, comprising: a gas passage through which gas can flow, the gas passage extending between an inlet position and an outlet position, the gas passage including a humidification position between the inlet and outlet positions; a water flow metering system configured to meter water at a flow rate; a heating surface in fluid communication with the gas passage at the humidification position, the heating surface configured to receive water supplied by the water flow metering system and to evaporate the received water; at least one temperature sensor configured to measure the temperature of the heating surface; two or more fluid sensors positioned at, on, adjacent to, or near one or more areas of the heating surface, the two or more fluid sensors configured to detect whether the heating surface is wetted in the two or more areas; and a water flow controller configured to control the flow rate of water toward the heating surface; wherein, in use, the breathing humidification system deterministically controls the humidity level of the gas at the outlet position by controlling the flow rate of water toward the heating surface.

[0035] The water flow metering system may include a pump. The pump may be a positive displacement pump. A positive displacement pump may be a piezoelectric diaphragm pump, peristaltic pump, micropump, or progressive cavity pump. The pump may be a pressure supply, such as gravity supply, connected in series with a control valve. The breathing humidification system may have a conduit in fluid communication with the water flow metering system, configured to carry water to the water flow metering system. The conduit may have a check valve configured to maintain the operation of the water flow metering system. The conduit may have a check valve configured to maintain the operation of the pump. The water flow metering system may include a wicking structure that uses capillary action to controllably and quantitatively supply water to a wicking surface on a heated surface. The conduit may have a safety valve, such as a pressure relief valve, in the conduit leading to the water flow metering system. The breathing humidification system may have a reservoir configured to hold water. The breathing humidification system may have a flow restrictor positioned between the reservoir and the water flow metering system to prevent gravity-driven flow from affecting the water flow path. The flow restrictor may be an elastic protrusion that squeezes or otherwise restricts the flow path. A water flow metering system can be an open-loop pump. A water flow metering system can also be a closed-loop pump or flow actuator connected in series with a flow sensor. A water flow metering system can provide a continuous water flow in the range of 0 mL / min to approximately 5 mL / min. A water flow metering system can provide a continuous water flow in the range of approximately 40 μL / min to approximately 4 mL / min. A water flow metering system can provide a continuous water flow in the range of approximately 70 μL / min to approximately 2.5 mL / min. A water flow metering system can provide a water flow rate with an accuracy of approximately ±15%. A water flow metering system can provide a water flow rate with an accuracy of approximately ±10%. A water flow metering system can provide a water flow rate with an accuracy of approximately ±6.5%. A water flow metering system can provide a water flow rate with an accuracy of approximately ±5%.

[0036] The flow rate control of water to the heating surface can be based on the gas flow rate in the gas channel. The flow rate control of water to the heating surface can be based on the evaporation rate of water from the heating surface. The flow rate control of water to the heating surface can be based on the temperature of the heating surface, where the temperature of the heating surface is maintained at a constant temperature. The flow rate control of water to the heating surface can be based on the absolute pressure or atmospheric pressure of the gas at or near the inlet location. The flow rate control of water to the heating surface can be based on the dew point temperature of the gas at the inlet location. The flow rate control of water to the heating surface can be based on the heat content provided by the heating surface. The flow rate control of water to the heating surface can be based on the power level provided by the heating surface. The flow rate control of water to the heating surface can be based on the temperature of the gas at the inlet location. The dew point temperature of the gas at the inlet location can be derived by processing information provided by temperature and humidity sensors. The flow rate control of water to the heating surface can be based on the dew point temperature of the gas at the inlet location. The flow rate of water to the heating surface can be controlled based on the relative humidity level of the gas at the inlet. It can also be controlled based on the effective heating surface area of ​​the heating surface, the pressure level of the gas in the gas channel, the velocity of the gas flowing in the gas channel, or the temperature of the water flow.

[0037] The breathing humidification system may include a water temperature sensor. The breathing humidification system may include a gas flow rate sensor. The breathing humidification system can determine the water flow rate based on a model. The breathing humidification system can determine the gas flow rate based on a model. The breathing humidification system may include an ambient pressure sensor. The pressure sensor may be located at or near the heating surface. The breathing humidification system may include an ambient dew point temperature sensor located upstream of the humidification location within the gas channel. The breathing humidification system may include an ambient humidity sensor located upstream of the humidification location within the gas channel. The breathing humidification system may include a gas preheater. The gas preheater may be arranged within the gas channel, between the inlet location and the humidification location. The ambient dew point temperature sensor may be located upstream of the gas preheater within the gas channel. The ambient humidity sensor may be located upstream of the gas preheater within the gas channel. The ambient dew point temperature sensor may be located downstream of the gas preheater within the gas channel. The ambient humidity sensor may be located downstream of the gas preheater within the gas channel. An ambient dew point temperature sensor can be positioned within the gas channel, downstream of the gas preheater, in conjunction with a temperature sensor positioned at the inlet of the gas channel.

[0038] At least one temperature sensor can be configured to determine the proportion of water permeable to the heated surface. The breathing humidification system can control the gas temperature at the inlet of the gas passage by controlling the power level leading to the gas preheater in an open-loop manner. The breathing humidification system may include a water preheater. Two or more fluid sensors can be used to prevent liquid from overflowing from the heated surface. The flow rate of water to the heated surface can be controlled based on information provided by two or more fluid sensors. Two or more fluid sensors can be used to control the evaporation area on the heated surface. Two or more fluid sensors can be specifically used to control the evaporation area on the heated surface. Two or more fluid sensors can be temperature sensors. Two or more fluid sensors can be resistive or capacitive sensors.

[0039] According to another aspect of this disclosure, a heater plate for a breathing humidification system is provided, the heater plate having multiple resistance strips, the heater plate being overmolded together with a surface including microchannels. The heater plate may include a printed circuit board (PCB). The heater plate may include etched foil. The microchannels may include an arrangement of parallel channels configured to guide water flow in one direction. The overmolded surface may include a set of distributed channels connected to a set of wicking channels, wherein the distributed channels are fewer than the wicking channels. The microchannels may be radially distributed from a single point.

[0040] According to another aspect of this disclosure, a respiratory therapy system is provided, comprising a gas channel through which gas can flow, the gas channel extending between an inlet and an outlet; a gas preheater disposed within the gas channel; and a humidification assembly disposed within and in fluid communication with the gas channel, the humidification assembly comprising: a heating surface in fluid communication with the gas, the heating surface having a wicking element configured to distribute water to the heating surface; a coupling configured to distribute water to the wicking element; and a water flow controller in fluid communication with the coupling, the water flow controller being configured to meter water supply to the coupling, the water flow controller including a pump and a flow sensor, the water flow controller being configured to control the water flow rate, wherein in use, the wicking element distributes metered water to at least a portion of the heating surface, and the heating surface causes the distributed water to evaporate into gas. The heating surface may have heat provided by a circuit board. The circuit board may be a printed circuit board. The circuit board may have multiple resistor strips. The resistor strips may be copper. The wicking surface may be provided by an overlay mold on the circuit board. The overcoating mold may contain microchannels. The overcoating mold may be made of thermoplastic material. The heating surface may have modular zones. The heating surface may have a first zone configured to preheat water and a second zone configured to evaporate water.

[0041] The water flow controller may include a metering arrangement. The metering arrangement may further include a pump. The pump may be a positive displacement pump, such as a piezoelectric diaphragm pump, peristaltic pump, micropump, or progressive cavity pump. The pump may also be a pressure supply, such as gravity supply, connected in series with a control valve. The breathing humidification system may have a conduit in fluid communication with the metering arrangement, configured to carry water to the metering arrangement. The conduit may have a check valve configured to maintain the operation of the metering arrangement. The conduit may also have a check valve configured to maintain the operation of the pump. The metering arrangement may include a wicking structure that uses capillary action to controllably and quantitatively supply water to a wicking element and / or a heated surface. The conduit may also have a safety valve, such as a pressure relief valve, in the conduit leading to the metering arrangement. The breathing humidification system may have a reservoir configured to hold water. The breathing humidification system may also have a flow restrictor positioned between the reservoir and the metering arrangement to prevent gravity-driven flow from affecting the water flow path. The flow restrictor may be a resilient protrusion that squeezes or otherwise restricts the flow path. A water flow controller can be an open-loop pump. A water flow controller can also be a closed-loop pump or flow actuator connected in series with a flow sensor. A water flow controller can provide a continuous water flow rate from 0 mL / min to approximately 5 mL / min. A water flow controller can provide a continuous water flow rate from approximately 40 μL / min to approximately 4 mL / min. A water flow controller can provide a continuous water flow rate from approximately 70 μL / min to approximately 2.5 mL / min. A water flow controller can provide a water flow rate with an accuracy of approximately ±15%. A water flow controller can provide a water flow rate with an accuracy of approximately ±10%. A water flow controller can provide a water flow rate with an accuracy of approximately ±6.5%. A water flow controller can provide a water flow rate with an accuracy of approximately ±5%.

[0042] The heating surface can be configured to be maintained within a temperature range. The temperature range can be between approximately 30°C and approximately 99.9°C. The temperature range can be between approximately 35°C and approximately 90°C. The temperature range can be between approximately 40°C and approximately 80°C. The temperature range can be between approximately 45°C and approximately 70°C. The temperature range can be between approximately 45°C and approximately 60°C. The temperature range can be between approximately 50°C and approximately 60°C. The heating surface can be configured to maintain a temperature of approximately 50°C. The heating surface can include a wicking surface. The heating surface can include a heating element configured to provide heat to the heating surface. The heating element can be a circuit board. The circuit board can be a printed circuit board. The circuit board can be a flexible circuit board. The flexible circuit board can be made of a polymer. The polymer can be silicone, polyester, or polyimide. The circuit board can have multiple resistance strips. The resistance strips can be copper. The heating element can be an etched foil. The heating element can be a heating wire. The heating wire can be a nickel-chromium-iron alloy. The heating element can be a positive thermal resistance coefficient (PTC) ceramic. The PTC ceramic can be barium titanate. The heating element can be a thermoelectric device. The thermoelectric device can be a Peltier device. The wicking surface can be provided by a coating mold on a circuit board, the coating mold containing microchannels. The temperature of the heated surface can be measured at least in part by determining the resistance level or other characteristics of the heating element. The resistance level of the heating element can be used to indicate the average temperature of the heated surface. The heating element can be arranged to deliver a higher power density in a designated area of ​​the heating element compared to the power density delivered to other areas of the heating element. The designated higher-density area of ​​the heating element can be located at the water supply outlet to the heated surface. The designated higher-density area of ​​the heating element can be located in a water preheating area on the heated surface. The breathing humidification system can include a temperature sensor located at the outlet of the gas channel.

[0043] The breathing humidification system may include a gas flow generator adapted to propel, drive, or otherwise cause gas to move in a general direction from the inlet to the outlet of the gas channel. The gas preheater may include a gas heating element. The gas heating element may be a printed circuit board. The printed circuit board may have resistive elements. The gas heating element may be an etched foil. The gas heating element may be a heating coil. The gas heating element may be PTC ceramic. The breathing humidification system may include a temperature sensor. The temperature sensor may be located in the gas channel downstream of the gas preheater. The temperature sensor may be located in the gas channel upstream of the gas preheater. Characteristics of the gas heating element (e.g., resistance) may be used to determine the temperature of the gas. Control of the power level delivered to the gas heating element may be based on information provided by the temperature sensor located in the gas channel downstream of the gas preheater. Control of the power level delivered to the gas heating element may be based on information provided by a gas flow sensor and by a temperature sensor located in the gas channel upstream of the gas preheater. The desired downstream temperature of the gas may be determined based on the evaporation rate of water from the heating surface. The desired downstream temperature of the gas can be set to ensure that all sensible heat is supplied by the gas preheater. The desired downstream temperature of the gas can be set to achieve the desired relative humidity level of the gas at the outlet location. The desired downstream temperature of the gas can be set between 0°C and approximately 5°C, higher than the desired temperature of the gas at the outlet location. The desired downstream temperature of the gas can be set to the desired dew point temperature at the outlet location. The desired downstream temperature of the gas can be set to approximately 25°C to approximately 43°C, or approximately 31°C to approximately 43°C, or approximately 31°C to approximately 41°C, or approximately 31°C to approximately 37°C, or approximately 37°C.

[0044] A breathing humidification system may include a filter. The filter may be located in the water supply line. The filter may be positioned downstream of the pump. The filter may be positioned at the inlet leading to the heating surface. The filter may be a biological filter. A breathing humidification system may include multiple filters. The system may include a first filter in the water supply line located between the reservoir and the water flow generator, and a second filter in the water supply line located between the water flow generator and the heating surface. The breathing humidification system may include an electromagnetic radiation emitter to achieve sterility. The electromagnetic radiation emitter may be a UV light source. The UV light source may be a lamp or an LED.

[0045] According to another aspect of this disclosure, a breathing humidification system is provided, configured to cause water evaporation, and configured to output power, wherein the output power is converted into heat in the water. The breathing humidification system can be configured such that approximately 80% to approximately 99.9% of the power output is converted into heat in the water. The breathing humidification system can be configured such that approximately 85% to approximately 99.9% of the power output is converted into heat in the water. The breathing humidification system can be configured such that approximately 90% to approximately 99.9% of the power output is converted into heat in the water. The breathing humidification system can be configured such that approximately 98% of the power output is converted into heat in the water. A heating surface can be adapted to maintain a temperature of approximately 30°C to approximately 99.9°C. A heating surface can be adapted to maintain a temperature of approximately 35°C to approximately 90°C. A heating surface can be adapted to maintain a temperature of approximately 40°C to approximately 80°C. A heating surface can be adapted to maintain a temperature of approximately 45°C to approximately 70°C. The heating surface can be adapted to maintain temperatures of approximately 45°C and approximately 60°C. The heating surface can be adapted to maintain temperatures of approximately 50°C and approximately 60°C. The heating surface can be adapted to maintain temperatures of approximately 50°C.

[0046] According to another aspect of this disclosure, a breathing humidification system is provided, comprising a gas passage through which gas can flow, the gas passage extending between an inlet position and an outlet position, the gas passage including a humidification position between the inlet position and the outlet position; a gas preheater disposed within the gas passage, located between the inlet position and the humidification position; a heating surface in fluid communication with the gas passage at the humidification position; and a water flow generator in fluid communication with the heating surface, the water flow generator being configured to meter water supply to the heating surface.

[0047] The heating surface can be adapted to maintain temperatures of approximately 30°C and approximately 99.9°C. The heating surface can be configured to maintain temperatures of approximately 35°C and approximately 90°C. The heating surface can be configured to maintain temperatures of approximately 40°C and approximately 80°C. The heating surface can be configured to maintain temperatures of approximately 45°C and approximately 70°C. The heating surface can be configured to maintain temperatures of approximately 45°C and approximately 60°C. The heating surface can be configured to maintain temperatures of approximately 50°C and approximately 60°C. The heating surface can be adapted to maintain temperatures of approximately 50°C.

[0048] The breathing humidification system may include a gas flow generator adapted to propel, drive, or otherwise cause gas to move in a general direction from the inlet to the outlet of the gas channel. The gas preheater may include a gas heating element. The gas heating element may be a printed circuit board. The printed circuit board may have resistive elements. The gas heating element may be an etched foil. The gas heating element may be a heating coil. The gas heating element may be PTC ceramic. The breathing humidification system may include a temperature sensor. The temperature sensor may be located in the gas channel downstream of the gas preheater. The temperature sensor may be located in the gas channel upstream of the gas preheater. Characteristics of the gas heating element (e.g., resistance) may be used to determine the temperature of the gas. Control of the power level delivered to the gas heating element may be based on information provided by the temperature sensor located in the gas channel downstream of the gas preheater. Control of the power level delivered to the gas heating element may be based on information provided by a gas flow sensor and by a temperature sensor located in the gas channel upstream of the gas preheater. The desired downstream temperature of the gas may be determined based on the evaporation rate of water from the heating surface. The desired downstream temperature of the gas can be set to ensure that all sensible heat is supplied by the gas preheater. The desired downstream temperature of the gas can be set to achieve the desired relative humidity level of the gas at the outlet location. The desired downstream temperature of the gas can be set between 0°C and approximately 5°C, higher than the desired temperature of the gas at the outlet location. The desired downstream temperature of the gas can be set to the desired dew point temperature at the outlet location. The desired downstream temperature of the gas can be set to approximately 25°C to 43°C, or approximately 31°C to 43°C, or approximately 31°C to 41°C, or approximately 31°C to 37°C, or approximately 37°C. The heating surface may include heating elements configured to provide heat to the heating surface. The heating elements may include multiple resistance bars.

[0049] The water flow generator may include a pump. The pump may be a positive displacement pump. A positive displacement pump may be a piezoelectric diaphragm pump, a peristaltic pump, a micropump, or a progressive cavity pump. The breathing humidification system may include a device for preheating water. The device for preheating water can be incorporated into the heating element by increasing the density of resistance strips (traces or bars) at one or more regions of the heating element corresponding to the area where water is introduced onto the heating surface, and thus increasing the power density delivered to the heating surface. The breathing humidification system may include a water supply line configured to deliver water to the heating surface. The device for preheating water may be incorporated into the water supply line.

[0050] According to another aspect of this disclosure, a breathing humidification system is provided, comprising a gas passage through which gas can flow, the gas passage extending between an inlet location and an outlet location; a heating surface in fluid communication with the gas passage; and a water flow controller configured to control the flow rate of water delivered to the heating surface; wherein, in use, the humidity level of the gas at the outlet location is deterministically controlled by controlling the water flow rate. The breathing humidification system may include a water flow sensor. Water flow rate control may be based on the gas flow rate in the gas passage. Water flow rate control may be based on the evaporation rate of water from the heating surface. Water flow rate control may be based on the temperature of the heating surface, wherein the temperature of the heating surface is maintained at a constant temperature. Water flow rate control may be based on the temperature of the heating surface, wherein the temperature of the heating surface is controlled. Water flow rate control may be based on the absolute pressure or atmospheric pressure of the gas at or near the inlet location. Water flow rate control may be based on the dew point temperature of the gas at the inlet location. The dew point temperature of the gas at the inlet location can be derived by processing information provided by a temperature sensor and a humidity sensor. Water flow rate control can be based on the heat content provided by the heating surface. Water flow rate control can be based on the power level provided by the heating surface. Water flow rate control can be based on the gas temperature at the inlet location. Water flow rate control can be based on the relative humidity level of the gas at the inlet location. Water flow rate control can be based on the effective heating surface area of ​​the heating surface. Water flow rate control can be based on the gas pressure level in the gas channel. Water flow rate control can be based on the gas flow velocity in the gas channel. Water flow rate control can be based on the water temperature. The breathing humidification system may include a water temperature sensor. The breathing humidification system may include a gas flow rate sensor. The breathing humidification system can determine the water flow rate based on a model. The breathing humidification system can determine the gas flow rate based on a model. The breathing humidification system may include a pressure sensor. The breathing humidification system may include an ambient pressure sensor. The pressure sensor may be located at or near the heating surface. The breathing humidification system may include a temperature sensor configured to measure the temperature of the heating surface. The breathing humidification system may include an ambient dew point temperature sensor located within the gas channel, upstream of the humidification location. The breathing humidification system may include an ambient humidity sensor positioned within the gas passage and upstream of the humidification location. The breathing humidification system may also include a gas preheater. The gas preheater may be positioned within the gas passage, near the inlet. An ambient dew point temperature sensor may be positioned within the gas passage and upstream of the gas preheater. An ambient humidity sensor may be positioned within the gas passage and upstream of the gas preheater. An ambient dew point temperature sensor may be positioned within the gas passage and downstream of the gas preheater. An ambient humidity sensor may be positioned within the gas passage and downstream of the gas preheater.An ambient dew point temperature sensor may be positioned within the gas passage, downstream of the gas preheater, in conjunction with a temperature sensor positioned at the inlet of the gas passage. The breathing humidification system may include at least one temperature sensor configured to measure at least one temperature of a heated surface. The at least one temperature sensor may be configured to determine the proportion of water permeable to the heated surface. The breathing humidification system can control the gas temperature at or near the inlet of the gas passage by controlling the power level supplied to the gas preheater in an open-loop manner. The breathing humidification system may include a water preheater.

[0051] According to another aspect of this disclosure, a humidification system is provided, which is positioned within the inhalation tube of a respiratory therapy system. Brief description of the attached figures

[0052] Different embodiments of this disclosure will now be described by way of illustrative examples only, with reference to the accompanying drawings. In the drawings, similar elements have the same reference numerals.

[0053] Figure 1A-1E These are schematic diagrams of different embodiments of a respiratory therapy system.

[0054] Figure 2A This is a functional block diagram of the overall control system according to an embodiment of the present disclosure.

[0055] Figure 2B This is a functional block diagram of the entry and preheating control subsystem according to an embodiment of this disclosure.

[0056] Figure 2C This is a functional block diagram of a water flow control subsystem according to an embodiment of this disclosure.

[0057] Figure 2D This is a functional block diagram of a heated surface control subsystem according to an embodiment of this disclosure.

[0058] Figure 2E This is a functional block diagram of the overall controller according to an embodiment of the present disclosure.

[0059] Figure 3A This is a schematic perspective view of an exemplary integrated humidification system according to one embodiment of this disclosure.

[0060] Figure 3B It shows Figure 3A A schematic vertical cross-sectional view of the airflow in the humidification system.

[0061] Figure 3C It shows Figure 3A A schematic vertical cross-sectional view of water flow in a humidification system.

[0062] Figure 3D yes Figure 3AA schematic horizontal cross-sectional view of the humidification system.

[0063] Figure 3E-3F A humidification system 300 is shown installed for use with a flow generation system.

[0064] Figure 4A This is a schematic perspective view of a printed circuit board heating element according to an embodiment of this disclosure.

[0065] Figure 4B This is a schematic top view of a printed circuit board heating element according to an embodiment of this disclosure.

[0066] Figure 4C This is a partial schematic top view of a printed circuit board heating element according to an embodiment of the present disclosure.

[0067] Figure 4D A schematic top view of an etched foil heating element according to an embodiment of this disclosure is shown.

[0068] Figure 4E An embodiment of an etched foil heating element in a rolled configuration is shown.

[0069] Figure 5A This is a schematic diagram illustrating a grid-structured microchannel water distribution pattern according to an embodiment of the present disclosure.

[0070] Figure 5B This is a schematic diagram illustrating a radial microchannel water distribution pattern according to an embodiment of the present disclosure.

[0071] Figure 6A This is a schematic perspective axial cross-sectional view of a portion of an example of a respiratory humidification system including a connector, according to an embodiment of the present disclosure.

[0072] Figure 6B It includes exemplary connectors. Figure 6A A schematic perspective cross-sectional side view of a breathing humidification system.

[0073] Figure 6C It includes exemplary connectors. Figure 6A A schematic side view of the humidification system.

[0074] Figure 6D yes Figure 6A A schematic perspective axial view of the humidification system assembly.

[0075] Figure 7 This is a schematic perspective view of a distribution pipe connector wound around the edge of a heating surface according to an embodiment of this disclosure.

[0076] Figure 8 This is a schematic diagram of a porous media connector according to an embodiment of the present disclosure.

[0077] Figure 9A This is a schematic perspective view of a radial coupling according to an embodiment of the present disclosure.

[0078] Figure 9B yes Figure 9A A schematic perspective cross-sectional view of the radial connecting member.

[0079] Figure 10A This is a schematic perspective view of a multilayer connector according to an embodiment of the present disclosure.

[0080] Figure 10B yes Figure 10A A schematic perspective cross-sectional view of a multi-layered connector.

[0081] Figure 10C It is attached to the humidifying housing according to an embodiment of this disclosure. Figure 10A A schematic cross-sectional view of a multi-layered connector.

[0082] Figure 10D It is attached to the humidifying housing according to an embodiment of this disclosure. Figure 10A A schematic cross-sectional view of the multi-layered connector, the humidifying housing including a printed circuit board heating element.

[0083] Figure 11A This is a drawing showing the dew point temperature accuracy of a respiratory humidification system according to an embodiment of this disclosure.

[0084] Figure 11B This is a plot of the dew point temperature error on the airflow rate of the breathing humidification system according to an embodiment of this disclosure.

[0085] Figure 12A This is a schematic perspective view of an alternative embodiment of a humidification system according to the embodiments of this disclosure.

[0086] Figure 12B yes Figure 12A A schematic cross-sectional view of the humidification system.

[0087] Figure 12C It shows Figure 12A A schematic cross-sectional view of the top layer of the humidification system.

[0088] Figure 12D It shows Figure 12A A schematic cross-sectional view of the bottom layer of the humidification system.

[0089] Figure 13 This is a schematic diagram of an embedded humidification system according to an embodiment of the present disclosure. Detailed description

[0090] The following description is illustrative in nature and is not intended to limit this disclosure, its application, or its uses. For the sake of brevity, the same reference numerals will be used in the accompanying drawings to identify similar elements. However, for convenience, some features shown in some figures of this disclosure, or those represented by reference numerals, are not shown or are not labeled by reference numerals in other figures of this disclosure. Unless the context otherwise explicitly requires, these omissions should not be construed as meaning that a feature omitted from one figure may not be equivalently incorporated or implemented in the configuration of the disclosed methods, apparatus, and systems involved in or embodied in other figures. Rather, unless the context otherwise explicitly requires, it should not be assumed that the presence of certain features in some figures of this disclosure means that the disclosed methods, apparatus, and systems involved in or embodied in such figures must necessarily include those features.

[0091] Certain features, aspects, and advantages of this disclosure include the realization of an open-loop and deterministic configuration of an on-demand humidifier, wherein a necessary amount of water (or other humidifying fluid) is metered onto a heated surface, evaporated, and mixed with a preheated gas source to produce a desired humidity level. Advantageously, rather than immediately heating the entire fluid supply system or heating an additional excess volume of liquid (such as a chamber liquid), by employing the disclosed humidification control system, apparatus, and method, dispensed water can be deposited on demand onto a heating element in fluid communication with a gas passage. Illustratively, by measuring the inlet gas flow rate, inlet gas dew point temperature, and / or gas passage pressure level, the fluid flow rate of the liquid to the heated surface can be determined and controlled to achieve the desired output humidity and temperature level (or outlet dew point temperature) of the gas to be delivered to the patient.

[0092] refer to Figure 1A A non-limiting exemplary configuration of a respiratory therapy system 100 is shown. In the illustrated configuration, the respiratory therapy system 100 includes a flow generator 120. The flow generator 120 may have, for example, a blower 121 adapted to propel gas through the respiratory therapy system 100. The gas propelled using the blower 121 may, for example, include air received from the external environment of the respiratory therapy system 100 (e.g., “ambient air” or “ambient gas”) and / or from a gas container in communication with the respiratory therapy system 100 (see, for example...). Figure 1EThe gas is stored in a gas reservoir 137. Gas from the flow generator 120 is directed to and / or through a respiratory humidification system 101, which is adapted to add moisture to the gas. The respiratory humidification system 101 includes a gas passage 102 (which may also be referred to herein as a "breathing tube" or "inhalation tube") adapted to receive gas from the flow generator 120 and / or another gas source and to direct the gas to an outlet, such as a patient interface 122. (As used...) (or Figure 1A Top As indicated by the vector, in use, gas can generally flow downstream from the flow generator 120 to the respiratory humidification system 101 (e.g., through the gas channel 102), and from the respiratory humidification system 101 to the outlet or patient interface 122 (e.g., through the gas channel 102).

[0093] Further reference Figure 1A The non-limiting exemplary configuration shown includes a respiratory humidification system 101 comprising a fluid reservoir 106 that holds fluid during use. In this context, "fluid" can refer to a liquid or liquid entity suitable for humidifying respiratory gases and may include, for example, water. The fluid may be water containing additives that are more volatile than water. The fluid reservoir 106 is fluidly or otherwise physically linked to a metering arrangement (also referred to herein as a liquid flow controller or water flow controller) 110. The metering arrangement 110 is configured to meter fluid from the fluid reservoir 106 to a humidification housing 115 located within or outside the gas passage 102 but in pneumatic communication with it. The metering arrangement 110 may further include a pump. The pump may be a positive displacement pump, such as a piezoelectric diaphragm pump, peristaltic pump, micropump, or progressive cavity pump. The pump may also be connected to a control valve (e.g., such as...) Figure 1D (As shown and described below) pressure supply in series, such as gravity supply. The metering arrangement may include a wicking structure that uses capillary action to controllably and quantitatively supply water to the wicking element and / or heating surface.

[0094] The metering arrangement 110 can be controlled by a water flow controller. The water flow controller can be an open-loop pump. It can also be a closed-loop pump or flow actuator connected in series with a flow sensor. In some configurations, an open-loop pump is preferred because it is simpler and requires only one component (the pump). However, an open-loop pump may not deliver water precisely, but it may still be useful where accuracy is not critical. Therefore, in other configurations where greater accuracy is desired, a closed-loop pump or flow actuator connected in series with a flow sensor can be used. In this configuration, the choice of pump may be less critical as it may not be precise, and a dedicated flow sensor is used to control accuracy. Another advantage of a closed-loop pump or flow actuator connected in series with a flow sensor is that the pump or flow actuator provides two independent flow indications (pump setting and sensed flow), thus adding a layer of security to the system (e.g., the pump and sensor can be compared to each other to verify that they are operating correctly).

[0095] The water flow controller can provide a continuous water flow rate from 0 mL / min to approximately 10 mL / min. The water flow controller can provide a continuous water flow rate from 0 mL / min to approximately 7 mL / min. The water flow controller can provide a continuous water flow rate from 0 mL / min to approximately 5 mL / min. The water flow controller can provide a continuous water flow rate from approximately 40 μL / min to approximately 4 mL / min. The water flow controller can provide a continuous water flow rate from approximately 70 μL / min to approximately 2.5 mL / min. The water flow controller can provide a water flow rate with an accuracy of approximately ±15%. The water flow controller can provide a water flow rate with an accuracy of approximately ±10%. The water flow controller can provide a water flow rate with an accuracy of approximately ±6.5%. The water flow controller can provide a water flow rate with an accuracy of approximately ±5%.

[0096] The water flow controller, including the metering system 110, can be configured to ensure that the surface of the heating element 114 is completely wetted (saturated). A fully wetted surface allows for improved deterministic control of humidity. A wetted surface also means that humidity can increase more rapidly when water travels more quickly on a wet surface than on a dry surface.

[0097] Any positive displacement pump can be used in a water controller or metering arrangement 110. Positive displacement pumps operate by displacing a fixed volume of water and generally produce good accuracy. Any of a variety of positive displacement pumps is suitable, such as peristaltic pumps, diaphragm pumps, impeller pumps, piston pumps, etc., and most of these can be scaled up to operate at the flow rates desired herein. However, piezoelectric micropumps (small diaphragm pumps using piezoelectric elements as actuators) and peristaltic pumps (peristaltic pumps using rollers to squeeze water through a pipe at a constant rate) can be particularly advantageous because many piezoelectric micropumps and peristaltic pumps are commercially available in sizes, prices, operating ranges, and power suitable for the systems described herein. Additionally, in series with a control valve (see...) Figure 1D Pressure supply (such as gravity supply) and / or wicking / capillary action can be used instead of a pump. In some configurations, an electric pump / magnetic hydrodynamic pump can be used.

[0098] When a water flow controller includes a flow sensor, in some configurations the flow sensor may be a thermal mass meter. These sensors operate by heating the liquid and measuring the power required for heating (e.g., a heated droplet) or the introduced temperature gradient, or some variation thereof. Alternatively, the flow sensor may be replaced or supplemented by: droplet-by-drop supply (e.g., counting droplets as is common in measuring flow rate in IV droplets); differential pressure sensors that measure the pressure drop across a restriction to calculate the flow rate; and / or positive displacement sensors that use the same principles as positive displacement pumps to sense the flow. By way of non-limiting example, a suitable pump is the mp6 micropump, available from Bartels Mikrotechnik. An exemplary liquid flow sensor is the LG16, available from Sinsiron. The datasheet for the LG16 is available at http: / / www.sensirion.com / fileadmin / user_upload / customers / sensirion / Dokumente / LiquidFlow / Sensirion_Liquid_Flow_LG16_Datasheet_V3.pdf and is incorporated herein by reference.

[0099] Fluid reservoir 106 is connected to metering arrangement 110 via a first fluid conduit 108. The first conduit 108 may have a check valve configured to maintain the metering arrangement in operation. The first conduit 108 may also have a check valve configured to maintain the pump in operation. The first conduit 108 may also have a safety valve, such as a pressure relief valve, located in the conduit leading to the metering arrangement to prevent fluid flow in the event of a pump or water controller failure. The breathing humidification system 101 may also have a flow restriction device positioned between reservoir 106 and metering arrangement 110 to prevent gravity-driven flow from affecting the water flow path. The flow restriction device may be a resilient protrusion that squeezes or otherwise restricts the flow path. Metering arrangement 110 metered fluid to humidification housing 115 via a second fluid conduit 112. Specifically, metered fluid may enter and reach humidification housing 115 through inlet 116.

[0100] The heating device 114 may be present in, at, or near the humidifying housing 115. The heating device 114 may have a wicking element configured to distribute a metered fluid to the heating device 114. In some configurations, the wicking element is configured to uniformly wick the metered fluid across the surface of the heating device 114. The heating device 114 may be configured to evaporate the metered fluid, thereby entraining the metered fluid in the gas stream used by the respiratory therapy system 100. The heating device 114 may be configured to maintain the heated surface within a certain temperature range. The temperature range may be between approximately 30°C and approximately 99.9°C. The temperature range may be between approximately 35°C and approximately 90°C. The temperature range may be between approximately 40°C and approximately 80°C. The temperature range may be between approximately 45°C and approximately 70°C. The temperature range may be between approximately 45°C and approximately 60°C. The temperature range may be between approximately 50°C and approximately 60°C. The heating surface can be configured to maintain a temperature of approximately 50°C. "Approximately" should be understood herein as being within a specified acceptable tolerance, such as ±3°C. The heating surface may include a wicking surface. The heating surface may include a heating element configured to provide heat to the heating surface. The heating element may be a circuit board. The circuit board may be a printed circuit board (e.g., as referenced below). Figures 4A-4C (As shown and described). The circuit board can be a flexible circuit board. The flexible circuit board can be made of aluminum-polyimide. The circuit board can have multiple resistor strips. The resistor strips can be copper. The heating element can be etched foil (e.g., as referenced below). Figure 4D-4E(As shown and described). The heating element can be a heating wire. The heating wire can be a nickel-chromium-iron alloy. The heating element can be a positive thermal resistance coefficient (PTC) ceramic. The PTC ceramic can be barium titanate. The heating element can be a thermoelectric device. The thermoelectric device can be a Peltier device. The wicking surface can be provided by a coating mold on a circuit board having microchannels. The temperature of the heated surface can be measured at least in part by determining the resistance level or other characteristics of the heating element. The resistance level of the heating element can be used to indicate the average temperature of the heated surface. The heating element can be arranged to deliver a higher power density in a designated area of ​​the heating element compared to the power density delivered to other areas of the heating element (e.g., as referenced). Figure 4C (As explained). A designated higher density zone of the heating element may be located at the water supply outlet to the heating surface. A designated higher density zone of the heating element may be located in the water preheating area on the heating surface.

[0101] The components of the respiratory therapy system 100 of the respiratory humidification system 101 may include a controller 118, which can control the operation of the respiratory therapy system 100 or the components of the respiratory humidification system 101, including but not limited to a flow generator 120, a metering arrangement 110, and / or a heating device 114.

[0102] The metering arrangement 110 can be configured to meter fluid to or distribute to the humidification housing 115 and / or the heating device 114 at a rate that increases the metering rate of the moisture content of the gas passing through the gas channel 102, thereby achieving a predetermined, calculated, or estimated humidity level that represents the required or desired level of gas humidification for a patient using the respiratory humidification system 101, while taking care to reduce or eliminate the possibility of excessive moisture accumulation in the gas channel 102. To achieve this, in one example, the controller 118 can control the metering rate of the metering arrangement 110 based on: (a) the measured flow rate of the gas passing through the gas channel 102, (b) the measured moisture content corresponding to the humidity of the upstream gas of the humidification housing 115, (c) the measured pressure level corresponding to the pressure level in the gas channel 102, or (d) a combination thereof. The controller 118 can control the metering rate of the metering arrangement 110 based on a combination of one or more of the measured inputs (a)–(c), such as based on (a) the measured flow rate of the gas passing through the gas passage 102 and (b) the measured moisture value corresponding to the humidity of the upstream gas of the humidifying housing 115, or (a) the measured flow rate of the gas passing through the gas passage 102 and (c) the measured pressure level corresponding to the pressure level in the gas passage 102.

[0103] In some configurations, the metering rate of metering arrangement 110 can be directly calculated by controller 118. Illustratively, by way of a non-limiting example, if the flow rate of the gas passing through flow channel 102 is determined to be 20 L / min and the desired output humidity of the gas leaving the breathing humidification system 101 is determined to be 44 mg / L, then if we assume that the humidity of the gas entering the system is zero (that is, if the gas is completely dry), then 0.88 g / min of fluid (20 L / min * 0.044 g / L) will need to be added to the gas in gas channel 102. A correction factor corresponding to the (hypothetical, estimated, calculated, or measured) humidity of the gas entering the breathing humidification system 101 can then be calculated. Therefore, especially when the fluid can be rapidly evaporated, the metering rate of the metering arrangement 110 can be set to 0.88 g / min, adjusted by a correction factor derived from the assumed, estimated, calculated or measured humidity of the upstream gas of the humidifying housing 115 or the ambient gas present outside the respiratory therapy system 100.

[0104] The desired output humidity of the gas (e.g., relative humidity (RH) = 100% or absolute humidity (AH) = 44 mg / L) and / or the desired output temperature (e.g., 37°C or 98.6°F) can be input by the user of the respiratory humidification device 101 via, for example, a user interface 105 located on the housing 103 of the respiratory therapy system 100 or using a remote control module. The user interface 105 may include, for example, one or more buttons, knobs, dials, keyboards, switches, levers, touch screens, speakers, displays, and / or other input or output modules, enabling the user to view data and / or input commands to control components of the respiratory therapy system 100 or the respiratory humidification system 101.

[0105] The respiratory therapy system 100 or the respiratory humidification system 101 may include deterministic control or open-loop control. The following will refer to... Figures 2A-2EThe different control systems are described in more detail. Generally, deterministic control allows for on-demand humidification by controlling certain input variables, such as the flow of water to a heated surface. In some configurations, the flow rate control of water to the heated surface can be based on the gas flow rate in the gas channel. The flow rate control of water to the heated surface can be based on the evaporation rate of water from the heated surface. The flow rate control of water to the heated surface can be based on the temperature of the heated surface, where the temperature is maintained at a constant temperature. The flow rate control of water to the heated surface can be based on the temperature of the heated surface, where the temperature of the heated surface is controlled. The flow rate control of water to the heated surface can be based on the absolute pressure or atmospheric pressure of the gas at or near the inlet location. The flow rate control of water to the heated surface can be based on the dew point temperature of the gas at the inlet location. The flow rate control of water to the heated surface can be based on the heat content provided by the heated surface. The flow rate control of water to the heated surface can be based on the power level provided by the heated surface. The flow rate control of water to the heated surface can be based on the temperature of the gas at the inlet location. The dew point temperature of the gas at the inlet can be derived by processing information provided by temperature and humidity sensors. The flow rate control of water to the heating surface can be based on the dew point temperature of the gas at the inlet. The flow rate control of water to the heating surface can be based on the relative humidity level of the gas at the inlet. The flow rate control of water to the heating surface can be based on the effective heating surface area of ​​the heating surface. The flow rate control of water to the heating surface can be based on the pressure level of the gas in the gas channel. The flow rate control of water to the heating surface can be based on the velocity of the gas flowing in the gas channel. The flow rate control of water to the heating surface can be based on the temperature of the water flow. See the following reference... Figure 1E As shown and described, the respiratory therapy system 100 and / or its components (including the respiratory humidification system 101) may include multiple sensors for measuring these variables.

[0106] The configurations shown should not be considered limiting, and many other configurations of the respiratory therapy system 100 and its components (including the respiratory humidification system 101) are considered. Additional details regarding the configurations of the components of the respiratory therapy system 100 are described below.

[0107] The first fluid conduit 108 and the second fluid conduit 112 can be configured to deliver fluid to different components of the respiratory humidification system 101. For example... Figure 1AAs shown, a first fluid conduit 108 can be configured to fluidly deliver fluid from a fluid reservoir 106 to a metering arrangement 110, and a second fluid conduit 112 can be configured to fluidly deliver fluid from the metering arrangement 110 to a humidification housing 115. In some configurations, the first fluid conduit 108 and / or the second fluid conduit 112 are optional. For example, if the fluid reservoir 106 is in direct fluid communication with the metering arrangement 110, the first fluid conduit 108 is not required. Similarly, if the metering arrangement 110 is in direct fluid communication with the humidification zone 115, the second fluid conduit 112 is not required.

[0108] like Figure 1E As shown, the first fluid conduit 108 and / or the second fluid conduit 112 may additionally include one or more filters 128 configured to remove contaminants, impurities, or other unwanted materials from the fluid delivered from the fluid reservoir 106. Filters 128 may include any structure configured to perform such behavior, including permeable or semi-permeable membranes positioned in the fluid flow path of the first conduit 108 and / or the second conduit 112 and / or configured for use in microfiltration, ultrafiltration, or reverse osmosis. The presence of one or more filters 128 in the first conduit 108 and / or the second conduit 112 helps ensure to the user of the breathing humidification system 101 that the quality of the fluid introduced into the humidification housing 115 is at an acceptable level. If one or more of the filters 128 have been used for an extended period, the filters 128 and / or the first conduit 108 and / or the second conduit 112 may be replaced. The lifespan of filter 128 can be indicated to the user, for example, by a chemical color change indicator located in or on the first conduit 108 and / or the second conduit 112, or by the color of filter 128 changing over time due to prolonged exposure to gases and / or fluids. Filter 218 can be used as a preliminary distributor of humidifying liquids.

[0109] As described above, metering arrangement 110 can be used to meter fluid from fluid reservoir 106 to humidification housing 115. Metering arrangement 110 may include, for example, a positive displacement pump that can actively deliver fluid from fluid reservoir 106 to humidification housing 115 along, for example, a first conduit 108 and / or a second conduit 112. In some embodiments, metering arrangement 110 may operate in reverse or act to draw fluid from humidification housing 115. The fluid displacement pump may include, for example, a positive displacement pump, such as a piezoelectric diaphragm pump, peristaltic pump, micropump, or progressive cavity pump.

[0110] like Figure 1BAs shown, the system can be embodied as an embedded humidifier. In this embodiment, the humidification system 101 can be an add-on to the breathing circuit for use with any flow generating system, or the humidification system can be a stand-alone humidifier that uses ambient air and relies on normal patient breathing to generate a gas flow.

[0111] like Figure 1C As shown, in some configurations, the heating element 114 can be positioned outside the gas passage 102. For example, the heating element 114 can reside in a separate compartment 124. The compartment 124 can be physically linked to the gas passage 102 but can be fluidly isolated from it. The compartment 124 can be fluidly isolated from the gas passage 102 by using a semi-permeable membrane 126 positioned between the compartment 124 and the gas passage 102. In some configurations, the semi-permeable membrane 126 may not allow fluid transfer but may allow evaporated fluid to transfer (and thus allow evaporated fluid to merge into the gas passing through the gas passage 102). Examples of suitable materials for use with a semipermeable membrane include perfluorinated polymers or polymers with fine pores, and include materials such as those described in co-owned U.S. Patent No. 6,769,431, filed May 8, 2001, entitled "Expiratory Limit for a Breathing Circuit," and U.S. Patent Application No. 13 / 517,925, filed December 22, 2010, entitled "Components for Medical Circuits," both of which are incorporated herein by reference in their entirety. In use, fluid can be metered into compartment 124 through outlet 116, the fluid is evaporated using heating device 114 (which may also be positioned in compartment 124), and the evaporated fluid is forced through semipermeable membrane 126 to merge with gas moving downstream through gas passage 102. Fluidly isolating outlet 116 from gas passage 102 can, for example, reduce the possibility of liquid water being present in gas passage 102.

[0112] It should be understood that the metering arrangement 110 may not necessarily include a pump and may simply include a structure configured to distribute fluid to the humidification housing 115 in a predetermined, desired, or specified amount. For example, and as... Figure 1D As shown, the fluid reservoir 106 can be vertically suspended above the gas passage 102 and / or the humidification housing 115. The fluid reservoir 106 can be connected to an electromechanical valve 150, which can be partially or fully opened or closed in response to a signal generated by the controller 118 to control the flow of fluid from the fluid reservoir 106 through the second fluid conduit 112 to the humidification housing 115.

[0113] In some configurations, the second fluid conduit 112 may be absent and the fluid reservoir 106 may cooperate with the electromechanical valve 150 to directly deliver fluid to the humidification zone 115 (and / or the location at or near the heating device 114). Fluid flow sensors (such as, but not limited to, microelectromechanical systems or MEMS sensors) may be used to determine fluid flow through the electromechanical valve 150 or the second fluid conduit 112. Signals from the fluid flow sensors, or values ​​derived from these signals, may be used, for example, to control the operation of the electromechanical valve 150 via closed-loop control. Although in Figure 1D The fluid reservoir 106 is shown vertically above the gas passage 102. In some configurations, the fluid reservoir 106 may be at the same level as or below the gas passage 102. Other forces may be applied to the fluid reservoir 106 to provide a metered supply of fluid in conjunction with the electromechanical valve 150. For example, the respiratory humidification system 101 may be configured to propel fluid from the reservoir 106 using the force of gas transmitted through the respiratory therapy system 100 and / or the respiratory humidification system 101. In some configurations, the gas may act directly on the fluid in the fluid reservoir 106. In some configurations, the fluid reservoir 106 may be pressurized by a fluid-filled bag (filled with gas, for example, from a flow generator 120 or from a separate gas source) from which fluid is expelled. The pressure applied by the bag may be controlled using a biasing force generated by, for example, a spring or other mechanical arrangement.

[0114] In some embodiments, the heating device 114 may be configured to transfer heat to a fluid metered and supplied to or near the heating device 114, thereby stimulating fluid evaporation and entrainment into the gas flow passing through the gas passage 102. The specific form of the heating device 114 is not limited, and many types of heating devices are conceivable for use with the respiratory humidification system 101. In some configurations, the heating device 114 may include a heating plate or heating element that can be heated resistively when electrical energy is applied. The resistance heating plate may be constructed of a conductive metallic material, but may also be made of conductive plastic.

[0115] Controller 118 may include a microprocessor or some other architecture configured to direct the operation of controllable components of systems 100, 101. In some configurations, a controller 118 may control the operation of each controllable component of the respiratory therapy system 100 and / or the respiratory humidification system 101, including but not limited to metering arrangement 110, heating device 114, and / or flow generator 120. Controller 118 may be physically located in, on, or near components of the respiratory therapy system 100, including but not limited to flow generator 120, respiratory humidification system 101, housing 103, and / or gas passage 102. In some configurations, controller 118 may be physically separate from the respiratory therapy system 100. For example, controller 118 may be located on a remote computer, tablet, mobile phone, smartwatch, or other device, and controller 118 may remotely direct the operation of controllable components of the respiratory therapy system 100. In some configurations, multiple controllers may be used to control the operation of controllable components of the respiratory therapy system 100 and / or the respiratory humidification system 101. Multiple controllers can be individually directed to mutually exclude one or more controllable components of one or both of systems 100 and 101. In some configurations, control of one or more controllable components of one or both of systems 100 and 101 can be handled by multiple controllers. The multiple controllers can be configured to communicate with each other.

[0116] In order for the controller 118 to control the metering rate of the metering arrangement 110 according to the functions described above or elsewhere in this specification (e.g., by using measured flow values, moisture values, and / or pressure values; see, for example, the following) Figures 2A-2E (as described below), it is possible to determine hypothetical, estimated, calculated, or measured signals and values. In some configurations, signals and / or values ​​can be determined as described below.

[0117] A predetermined value can be chosen to represent the flow rate of gas passing through gas channel 102. By way of non-limiting example, the flow rate of gas passing through gas channel 102 can be assumed to be 40 L / min.

[0118] The gas flow rate (equivalent to the gas velocity passing through gas channel 102) can be estimated or roughly estimated using various methods. In some cases, the flow generator 120 includes a mechanical blower 121. An electric motor sensing module 130 (e.g., ...) can be used. Figure 1E(As shown) The motor sensing module 130 determines the motor speed, motor torque, and / or motor current of the electric motor of the blower 121. This motor sensing module includes, for example, one or more associated transducers. One or more of the signals output by the motor sensing module 130, or the values ​​derived from these signals, can be input into a lookup table or lookup equation, either of which can then return an estimated or coarsely estimated gas flow rate value based on, for example, a set of inputs and outputs determined experimentally.

[0119] A flow signal indicating the velocity of gas passing through gas channel 102 can be obtained from a gas flow sensor 134 positioned in gas channel 102 (see [link]). Figure 1E The signal generated by the gas flow sensor 134 can be processed and converted into a gas flow rate value.

[0120] A predetermined value can be selected to represent the relative humidity or absolute humidity of the gas upstream of the humidifying housing 115. Illustratively, by way of non-limiting example, the relative humidity of the gas upstream of the humidifying housing 115 can be assumed to be 50%, or the absolute humidity of the gas upstream of the humidifying housing 115 can be assumed to be 15 mg / L.

[0121] If the temperature and relative humidity of the gas passing through gas channel 102 can be sensed or otherwise estimated or determined, the dew point temperature of the gas can be derived using, for example, the Clausius-Clapeyron equation. If the temperature and pressure of the gas upstream of humidifying housing 115 can be sensed or otherwise estimated or determined, the relative humidity value can be converted into an absolute humidity value.

[0122] A moisture signal indicating the relative or absolute humidity of the gas upstream of the humidifying housing 115 or the ambient gas outside the respiratory therapy system 100 can be obtained from a humidity sensor 136 located upstream of the humidifying housing 115 or outside the respiratory therapy system 100 (e.g., such as...). Figure 1E (As shown). The signal generated by the humidity sensor 136 can be processed and converted into a moisture value.

[0123] Different sensor modules can also be positioned within the gas channel 102, downstream of the humidification housing 115. For example... Figure 1EAs shown, the sensor module may include, for example, a flow sensor 138, a humidity sensor 140 (e.g., including an absolute humidity sensor and / or a relative humidity sensor), a temperature sensor 141, and / or a pressure sensor 142. One or more of these sensors may be used by the controller 118 to facilitate the control of components of the respiratory therapy system 100 and / or the respiratory humidification system 101, including the gas flow generator 120 (including, for example, the motor speed of the blower 121), the heat output of the heating device 114, the metering rate of the metering arrangement 110, and / or the operational control of some other component.

[0124] And, as Figure 1E As shown, a gas concentration sensor 135 can be positioned in a gas passage 102. The gas concentration sensor 135 can be configured to sense the concentration of one or more gases in a gas stream. The gas concentration sensor 135 may include an ultrasonic sensor adapted to sense, for example, oxygen. The sensed gas may include, for example, oxygen, nitric oxide, carbon dioxide, and / or a helium-oxygen mixture introduced into the gas passage 102 from a gas reservoir 137 via a gas concentration regulating valve 139. The gas concentration sensor 135 can use the gas concentration signal generated by the gas concentration sensor 135 to control the gas concentration regulating valve 139 (e.g., via closed-loop control) based on a predetermined desired gas concentration (e.g., input by a user through a user interface 105).

[0125] In some configurations, and as Figure 1EAs demonstrated, as a safety measure to help avoid burns to patients from overheated gas, the flow sensor 117 can communicate with the humidification housing 115 and / or the heating device 114. Illustratively, the flow sensor 117 can be configured to generate a signal when fluid is detected in or on the humidification housing 115 and / or the heating device 114. The controller 118 can use the signal emitted by the flow sensor 117 to control the operation of the metering arrangement 110 and / or the heating device 114. For example, the metering rate of the metering arrangement 110 and / or the heat output of the heating device 114 can be set as a function of the signal generated by the flow sensor 117. If the signal does not indicate the presence of fluid in or near the humidification housing 115 or on a modular area of ​​the heating device, the metering rate of the metering arrangement 110 can be increased because the heating device is designed to be covered by a humidifying fluid film. Similarly, if the signal does not indicate the presence of fluid in or near the humidification housing 115 or on a modular area of ​​the heating device, the heat output of the heating device 114 can be reduced or set to zero to avoid heating the gas to unsafe temperatures. If it is determined that there is no fluid in such a location when fluid is expected to be present in the humidification zone 115 and / or on the heating surface of the heating device 114 (e.g., if the metering arrangement 110 attempts to meter the fluid at a positive rate), the flow sensor 117 can therefore be used to assist in the control of the metering arrangement 110 and / or the heating device 114. In some configurations, the respiratory therapy system 100 or its components (including the respiratory humidification system 101) may be configured to generate a warning or convey a message to the user (e.g., via the user interface 105) when it is determined that the situation should be corrected (e.g., by refilling the fluid reservoir 106).

[0126] However, in some configurations, the humidification system may include a separate sensor for measuring surface temperature and other sensors for measuring whether the surface is wetted (e.g., fluid sensors 117, preferably located at / near the edge of heating element 114, which may be temperature sensors but also any other water detectors, such as resistive or capacitive sensors). In other configurations, it is possible to use a control algorithm to set the surface temperature to achieve the desired evaporation (wetting) area. The algorithm may be based on system measurements (gas flow rate, water flow rate, etc., as described below) and models (e.g., Dalton's law of evaporation). The fluid sensor 117 can therefore act as a safety mechanism to prevent spills and as a means of correcting / regulating the algorithm (by providing a calibration point at which the surface is known to be wetted). The system can therefore be configured to provide a modular arrangement such that individual areas or selected areas can be wetted and that these individual areas or selected areas can be energized. Furthermore, the modular system can be controlled using a control algorithm based on system measurements. A separate sensor can be used to measure surface temperature and other sensors to measure whether the surface is wetted. Fluid sensor 117 can be used in closed feedback control to control the metered supply of water to one or more selected areas, or alternatively, the control algorithm can use a model to control the metered supply of water to one or more selected areas, thus allowing fluid sensor 117 to act as a safety mechanism to prevent spills and as a means of correction / regulation algorithms (by providing a calibration point at which the surface is known to be saturated).

[0127] In some configurations, fluid sensor 117 may include a capacitive fluid sensor. If a heating surface of heating device 114 is present, the capacitive fluid sensor may, for example, include a pair of conductive sensing electrodes positioned on opposite sides of the heating surface. If the conductive sensing electrodes are connected in a circuit and a voltage is applied, the capacitance of the circuit will change depending on the presence or absence of water. The capacitance of the circuit can be measured using, for example, a standard AC measuring circuit. Many other sensing systems, including ultrasonic or optical level sensing systems, can also be used to determine the presence of fluid.

[0128] Different sensor modules can be utilized by controller 118 to control different components of respiratory therapy system 100 and / or respiratory humidification system 101. Sensor modules may include one or more sensors for detecting different characteristics of gas in gas passage 102 or in, around, or nearby locations within or near respiratory therapy system 100 (including gas inlet 123, gas outlet 127, patient interface 122, or located upstream and / or downstream of humidification housing 115). These different characteristics include pressure, gas flow rate, temperature, absolute humidity, relative humidity, calorific value, gas composition, oxygen concentration, carbon dioxide concentration, ambient temperature, and / or ambient humidity. One or more of these sensors and / or sensor modules may, for example, facilitate control of flow generator 120 (including pressure and / or flow rate control of gas propelled downstream by flow sensor 120), heat output control of heating device 114 (including temperature control of heating device), and / or metering rate control of metering arrangement 110 (including power and / or current control applied to metering arrangement 110).

[0129] In some configurations, one or more of the sensors or sensing modules described above or elsewhere in this disclosure can be used to determine, estimate, or calculate the respiratory activity of a patient using the respiratory therapy system 100 and / or the respiratory humidification system 101. The controller 118 can control different components of the respiratory therapy system 100 and / or the respiratory humidification system 101, such that the components operate based on determined respiratory activity or respiratory state. Illustratively, by non-limiting example, the heating device 114 can be configured to be energized or to evaporate a significant amount of fluid only when a positive inhalation of the patient is determined. The metering arrangement 110 can be configured to meter the fluid only when a positive inhalation of the patient is determined. The flow generator 120 can be configured to generate flow or increase the generated flow only when a positive inhalation of the patient is determined.

[0130] Additionally, components can be controlled to act synchronously with a determined patient's transient respiratory activity or respiratory state, rather than being limited to a binary operating state. For example, heating device 114 can be configured to have a relatively low heat output at the start of inspiration, increasing towards a maximum heat output at the peak of inspiration, and subsequently decreasing towards the end of inspiration. Metering arrangement 110 can meter a relatively small amount of fluid at the start of inspiration, gradually increasing the metering rate towards a maximum at the peak of inspiration, and subsequently decreasing towards the end of inspiration. Flow generator 120 can be configured to generate or propagate gas at a relatively low flow rate at the start of inspiration, gradually increasing the flow rate towards a maximum at the peak of inspiration, and subsequently decreasing towards the end of inspiration. Other components of one or both of systems 100, 101 can be similarly controlled.

[0131] In some configurations, the flow generator 120 may include, for example, a source or container of compressed gas (e.g., air, oxygen, etc.). If a container is used, it may include a valve that can be adjusted to control the flow of gas leaving the container. In some configurations, the flow generator 120 may use such a compressed gas source and / or another gas source instead of the blower 121. In some configurations, the flow generator 120 may use such a compressed gas source and / or another gas source in conjunction with the blower 121. The blower 121 may include a motorized blower or a bellows arrangement or some other structure adapted to generate a gas flow. In some configurations, the flow generator 120 may draw in atmospheric gas through a gas inlet 123. In some configurations, the flow generator 120 may be adapted to draw in atmospheric gas through a gas inlet 123 and may be adapted to accept other gases (e.g., oxygen, nitric oxide, carbon dioxide, etc.) through the same gas inlet 123 or through different gas inlets (not shown). In some configurations and as... Figure 1B As shown, the flow generator 120 may be absent and the respiratory therapy system 100 may be configured such that only unpressurized ambient air is humidified and directed to the outlet / patient interface 122.

[0132] In some configurations and such Figure 1E As shown, the respiratory therapy system 100 and / or the respiratory humidification system 101 may include an electromagnetic radiation emitter 151 (located, for example, in a gas passage 102). The emitter 151 may include an ultraviolet light source (e.g., a UV LED), a microwave emitter, or some other radiator configured to sterilize the gas flow path. Means for sterilizing the passage (through which gas is delivered via the respiratory therapy system 100 and / or the respiratory humidification system 101) can reduce concerns about patient infection due to the introduction of unwanted pathogens.

[0133] In some configurations and such Figure 1EAs shown, the respiratory therapy system 100 and / or respiratory humidification system 101 may include a gas heating zone 132. The gas heating zone 132 can preheat the gas before it reaches the humidification housing 115 after being passed through the gas passage 102. Preheating the gas before humidification can improve humidification efficiency. The gas heating zone 132 may include, for example, one or more heating wires present in, above, around, or near, the inner and / or outer walls of the gas passage 102. The gas heating zone 132 may be controlled and electrically connected to a controller 118, which may use sensor signals to control the heat output of the gas heating zone 132 in a manner similar to, for example, controlling the heat output of the heating device 114 as described elsewhere in this disclosure. The controller 118 may control the temperature and / or heat output of the gas heating zone 132 such that the temperature of the gas reaching the gas outlet 127, the patient interface 122, or the patient is between approximately 31°C and approximately 43°C. In some cases, if the gas heating zone 132 is located away from the gas outlet 127 or the patient interface 122, the gas heating zone 132 can heat the gas to a temperature above approximately 37°C to approximately 43°C, so that the gas reaches the gas outlet 127, the patient interface 122, or the patient at the desired temperature (due to temperature loss of the gas as it travels along, for example, the gas channel 102). To determine the correct temperature, the temperature loss of the gas transmitted through the respiratory therapy system 100 can be modeled theoretically or experimentally. Gases in the range of approximately 25°C to approximately 43°C, or approximately 31°C to approximately 43°C, or approximately 31°C to approximately 41°C, or approximately 31°C to approximately 37°C are generally considered comfortable for patient use.

[0134] Gas heating zone 132 may include a gas preheater, which may include a gas heating element. The gas heating element may be a printed circuit board. The printed circuit board may have resistive elements. The gas heating element may be an etched foil (see example...). Figure 4D and Figure 4EThe gas heating element can be a heating coil. The gas heating element can be PTC ceramic. The breathing humidification system 100 can have a temperature sensor. The temperature sensor can be located in the gas passage, downstream of the gas preheater. Alternatively, the temperature sensor can be located in the gas passage, upstream of the gas preheater, in place of a temperature sensor located downstream of the gas preheater, or in any other way. Characteristics of the gas heating element can be used to determine the gas temperature. Control of the power level delivered to the gas heating element can be based on information provided by the temperature sensor located in the gas passage, downstream of the gas preheater. Control of the power level delivered to the gas heating element can be based on information provided by a gas flow sensor and by the temperature sensor located in the gas passage, upstream of the gas preheater. The desired downstream temperature of the gas can be determined based on the evaporation rate of water from the heating surface. The desired downstream temperature of the gas can be set to ensure that substantially all sensible heat is supplied by the gas preheater. The desired downstream temperature of the gas can be set to obtain the desired relative humidity level of the gas at the outlet location. The desired downstream temperature of the gas can be set between 0°C and approximately 5°C, higher than the desired gas temperature at the outlet location. The desired downstream temperature of the gas can be set to the desired dew point temperature at the outlet location. The desired downstream temperature can be set to approximately 25°C to approximately 43°C, or approximately 31°C to approximately 43°C, or approximately 31°C to approximately 41°C, or approximately 31°C to approximately 37°C, or approximately 37°C. The heating surface can include heating elements configured to provide heat to the heating surface. The heating element can include multiple resistance bars. The heating element can be a printed circuit board. The printed circuit board can have resistive elements. The gas heating element can be an etched foil (see example...). Figure 4D and Figure 4E ).

[0135] Figures 2A-2EThis is a functional block diagram illustrating different control features disclosed herein. In some configurations, the control features described herein allow for deterministic or open-loop control of the humidification system. That is, it is possible to calculate the water flow rate required to achieve a specific humidity level and deliver that amount of water to the heater. The heater can then evaporate the water delivered thereto to achieve the desired dew point temperature. Deterministic control eliminates the need to measure the output humidity or some other indirect variable and subsequently feed back the output humidity or some other indirect variable through a closed-loop controller to achieve a specific dew point temperature (a need present in many conventional humidification systems). In some configurations, the control features described herein allow the humidification system to evaporate only the correct amount of water or other humidifying liquid at the correct time to precisely produce the correct humidity. The control features described herein can be combined or otherwise modified to be included in any breathing humidification system described herein. In some configurations, deterministic control of humidity by controlling the water flow to the heater surface collectively allows for heating of the heater surface at relatively low temperatures.

[0136] To achieve deterministic control, the flow rate of water supplied to the surface to produce the desired dew point temperature can be calculated using the following equation.

[0137] Refer to Table 1 for the symbols used in the following equations. Table 1 also provides the associated units for each variable. Additionally, symbols with subscripts a and b indicate component a at location b. Subscripts a, i, s, and o refer to the surrounding area, inlet, surface (heater plate), and outlet, respectively; subscripts w, wv, and air refer to water, water vapor, and dry air, respectively. Therefore, for example, Q... air，i Indicates the mass flow rate of the air at the inlet. Note that equations 1-6 are written in steady state (or equivalently, assuming instantaneous responses from all variables).

[0138] Table 1: Naming

[0139]

[0140] To achieve deterministic control, the flow rate of water delivered to the surface to produce the desired dew point can be calculated using the following equation:

[0141]

[0142]

[0143] Q w =Q air，i [h s (T d，o ,p)-h s (T d，iEquation 3 (p)

[0144] Where hs is the specific humidity. The evaporation rate of water from the surface is modeled by the following equation:

[0145] Q w =kAf(v)[p sat (T s )-φp sat (T d，i Equation 4

[0146] Where A is the surface area, k is a constant to be determined for any specific surface, and f(v) is a function of the gas velocity, determined primarily empirically. The power P required for evaporation... l And the power P required to heat the water w The following is given:

[0147] P l =l(T s )Q w Equation 5

[0148] P w =c p，w Q w (T s -T a Equation 6

[0149] Power P required by air air And the power P required by water vapor wv The following is given:

[0150] P air =c p，air Q air，i (T o -T i Equation 7

[0151] p wv =c p，wv [Q w [T o -T s )+(Q in -Q air，i (T) o -T i Equation 8

[0152] Equations 1-3 represent the general concept of deterministic or open-loop control of a system: the amount of water required to achieve a specific dew point temperature. In the given expression, the provided Q can be sufficiently determined. air，i Q w T d，i And p, the dew point temperature T at the outlet d，o The measurement results.

[0153] It is possible to perform substitutions or rearrangements to use different inputs or outputs (e.g., absolute or relative humidity at the outlet, or volumetric flow rate at the inlet or different locations). It is possible to avoid measuring some of the input variables. T d，i If appropriate assumptions can be made (e.g., the calculated height p is known), it is entirely possible not to measure p, or if the introduced error is acceptable (e.g., if T...). d，i <<T d，o The impact of error will be relatively small if Q is not measured. air，i Or Q w In some cases, it might be impossible to continue because they are dominant factors. It's possible that some measurements are not performed directly. For example, it's not necessary to directly measure T. d，i Conversely, the sensor measurement result T i and φ i (RH at the entrance) can be used to calculate T. d，i The same applies to other variables.

[0154] Equations 1-6 assume that the pressure throughout the system is constant, although it is possible to modify the equations to avoid this assumption. While the pressure throughout the system can vary significantly (e.g., pressure drop across the tube), the pressures near the evaporation surface and the sensor are typically very close to constant, making such corrections unnecessary in some configurations.

[0155] Equation 4 can be used to calculate the required area and temperature of the evaporation surface and to model the control response of the system. Equation 4 is based on Dalton's law of evaporation and, unlike previous equations, is semi-empirical. Therefore, other equations that are not entirely equivalent can be used. Specifically, Equation 4 can be used to calculate T for a given A. s Or vice versa (both are used to design and control systems), or to calculate related Q. w Individual verification. Generally, Equation 4 implies that the temperature of the inflow gas does not significantly affect the evaporation rate. However, there are two mechanisms that do affect the evaporation rate, and these mechanisms may be important in some cases. First, the inflow temperature changes the relative humidity φ. If T d，o Close to T s This change can be significant. Secondly, and more importantly, the mechanism is heat exchange. If T i <T d，o Water vapor must heat the air, and if the water vapor does not contain enough sensible heat to raise the gas temperature above T... d，oSome water vapor must condense to release latent heat. This is likely the main complexity when considering the net evaporation rate; although surfaces can easily drive evaporation, cold air causes the vapor to condense rapidly. This can be avoided by increasing the surface temperature. The problem is further exacerbated by the nature of evaporation. Because a boundary layer exists near the surface, water cannot immediately evaporate into all of its gaseous form; it must evaporate completely and then diffuse through the gas (in a laminar manner) or be mixed (in a turbulent manner). Vapor in the boundary layer can be permeated at the surface temperature, thus inhibiting further evaporation. Therefore, one of the main limiting factors is not the evaporation rate at the surface, but the rate at which vapor diffuses or is transported from the boundary layer. Thus, heat exchange between the vapor and the air occurs at the boundary, and the vapor must be hotter to prevent condensation (because most of the latent heat is unavailable). These effects not only interfere with the system's physical ability to evaporate water but also compromise the validity of evaporation models.

[0156] Equations 5 and 6 can be used to calculate power requirements and to model the control response of the system. These equations make an assumption of 100% efficiency, which may not be entirely accurate, but experiments have shown that the system disclosed herein is highly efficient. In systems where this assumption is incorrect, appropriate corrections will have to be made at the expense of accuracy and simplicity. Equations 5 and 6 can be used to calculate separate checks on the power input (e.g., to limit heat content). Equations 5 and 6 can also be used for control (e.g., for open-loop control) or as corrective feedback.

[0157] While acceptable results have been obtained using these equations, achieving healthy and stable systems may require further consideration, as equations 1-6 are only accurate under steady-state conditions. For example, consider the flow rate of water: a finite volume of water must remain on the evaporation surface, therefore the rate of evaporation is not immediately equal to the flow rate, and for this reason, a hidden “buffer variable” may lead to temporary discrepancies.

[0158] Consider a finite water film thickness as a heuristic example, if the mass of water on the surface is m w =Aρ w t w , where t w Given the thickness of the water (assuming it's constant), then for the first approximate estimate (assuming the heater plate only supplies power for evaporation):

[0159]

[0160]

[0161] Equation 9 is derived by considering the difference between the water reaching the surface and the water evaporating, and Equation 10 is similarly derived by considering that the power delivered to the surface is less than the power consumed by evaporation. Therefore, surface temperature and evaporation area are linked in a time-varying and nonlinear manner, and a simplified controller relying solely on the principles of Equations 1-3 will only produce the desired humidity if and when the above systems stabilize. This highlights the significant possibility of instability; even though these systems are merely first-order systems when considered individually, when considered in combination, they may oscillate or become unstable.

[0162] Assuming that for water, ρ w =1000kg m ---3 And l = 2.26 MJ kg ---1 If we assume (based on reasonable figures obtained through testing the prototype system) k = 1 μL min ---1 cm ---2 kPa ---1 t w =10μm, Q w =0.9mL min ---1 T d，i =15℃, φ=75%, f(v)=1, m s =0.025, c p，s =400J kg ---1 K ---1 And at point A = 30cm ---2 P of the next operation s =34W and T s =70℃, then it is possible to make p sat (T s ) and 1.353T s -63.28 linearization, according to which the system can be represented as:

[0163]

[0164]

[0165] Then the Jacobian determinant of the system is:

[0166]

[0167] Alternatively, at the operation point:

[0168]

[0169] The eigenvalues ​​of J0 are -18.3 and 0.0006, indicating that the system is unstable. This instability stems from the fact that the system can be driven with constant power—any mismatch will result in either excess or insufficient water, leading to either complete surface saturation or complete drying, respectively. By introducing proportional feedback in terms of power, the expression for surface temperature becomes:

[0170]

[0171] So:

[0172]

[0173] Then the characteristic polynomial is λ. 2 +λ(α+18.31)+3.015(α+15.29)-46.11=0, deriving the eigenvalues:

[0174]

[0175] This shows that for λ < 0 (stability), α > 0.0033. Therefore, even a small amount of feedback will make the system stable at least at this operating point.

[0176] Since the area is difficult to measure directly, it is worth checking whether this is an observable state. Because the system is nonlinear, this is difficult to evaluate, but equation T... s It can be restated as:

[0177]

[0178] Then rearrange to obtain:

[0179]

[0180] This simply means that the area is observable, and all other measurements are known, rather than trying to sense the area at certain limits. The equations can be integrated over time to continuously calculate A. Of course, it may still be desirable to design a system capable of sensing when a surface is saturated, but this model allows for smooth control of the area rather than jumping back to a hard limit.

[0181] Numerous factors limit the control response time. The most fundamental limitation is the dynamics of the evaporating surface during transients. This is important primarily due to heat content considerations, and equally important when achieving sequential humidity control.

[0182] If the surface temperature remains constant, the evaporation area can be varied to control humidity. Humidity can be actively increased (by pumping water) but only passively decreased (by evaporation), thus limiting the downward response to the time spent evaporating water in the "reservoir." For example, if the airflow rate increases from 20 L / min... ---1 Decrease to 10L min ---1 For nominal conditions (37°C dew point temperature, etc.), the initial evaporation rate will be 0.7 mL / min. ---1 If the initial area is 20cm² -2 And it dropped to 10cm -2 (To maintain the dew point temperature), and with a water film thickness of 10 μm, an additional 0.1 mL of water must evaporate to allow the area to shrink. Even with the pump off, it will take at least 8.6 seconds to shrink (at a rate of 0.7 mL / min). ---1 Shrink to a minimum of 0.1 mL, because the evaporation rate drops to zero when the area shrinks, and if the pump is turned on during this time, the response will be further delayed.

[0183] If the evaporation area remains constant, the surface temperature must change, and passive cooling remains the limitation. A 40cm layer with a 10μm film... 2 Place 0.4g of water in a plate; cook at 10L / min ---1 The potential power required for evaporation will be approximately 13W, and the potential power required to lower the water temperature by 20°C is 33.5J, equivalent to 2.6s, similar to the previous assumption, assuming that the heater plate will shut off during this time and ignoring the fact that the evaporation rate will decrease as the surface cools.

[0184] Even when using microchannels, 10 μm may be an unattainable water thickness; for wicking paper or wicking fabric, a more reasonable figure would be in the range of 0.1 mm or larger, resulting in a proportionally extended response time.

[0185] In some configurations, designing a humidifier with a sequential breathing pattern requires a thin water film; otherwise, the surface temperature must be traded off for the response time (higher surface temperatures to generate a smaller evaporation area). In extreme cases, this trade-off results in a very hot surface (>100°C), which vaporizes the water and raises patient safety and material compatibility issues.

[0186] Another factor affecting response time is the thermal mass and resistance of the heater plate. The thermal mass of the heater plate contributes in the same way as water, thus requiring time for passive cooling through evaporation. Increased thermal resistance means higher heating element temperatures, which exacerbate the effect of thermal mass (by requiring larger temperature changes).

[0187] Equations 1-3 calculate the water flow rate based on the assumption that all water evaporates. In some configurations, the goal of the control system is to ensure that all water does indeed evaporate in order to improve transient response and other aspects of the system. In some configurations, this may require as many individual inputs as possible, as the individual outputs, otherwise the system will not be controllable. In the most basic scenario, where controlling the humidity at the outlet is not desired, a single relevant control input (such as the water flow rate) will suffice. However, if it is also desired to control the temperature at the outlet, another control input is needed—for example, the power delivered to the heater plate. However, if it is desired to maintain the heater plate temperature within certain limits, another control input will be required. An additional input could be the addition of a secondary heater to preheat the incoming air.

[0188] In some configurations, the concept of preheating air can be important. While the goal of the system is to determine the humidity at the outlet, being able to determine the temperature to prevent condensation is equally desirable. As explained above, the power delivered to the heater plate will allow for temperature determination, but using heat from the evaporation surface entangles two problems (evaporating water and heating air). Preheating the air separates these two problems and provides several advantages, including:

[0189] Easier to control: Since latent heat and sensible heat are added independently, they can be controlled almost independently. Combined control systems would be more complex and less stable.

[0190] Improved evaporation: As explained in the reference evaporation equation above, water evaporates into a warm gas (i.e., T). i >T d，o ) than evaporating into a cooling gas (i.e., T) i <T d，o (Easier to evaporate and model).

[0191] Lower surface temperature: Following improved evaporation, warm gas allows for lower surface temperatures, and the surface temperature / area can be controlled independently.

[0192] Power: When air is preheated, the pressure on the heater plate will decrease, which will produce a shock effect that requires a lower temperature to drive the heating and requires better efficiency (because the temperature is lower).

[0193] Heat content / safety: Since most of the heat content in the system is supplied as latent heat in the water vapor, it is easier to ensure that the heat content is kept within extreme limits when heat is added independently, while still ensuring that the gas at the outlet is not impregnated (to prevent condensation). In systems without preheating, the only way to limit the heat content is to limit the total power, without directly controlling whether this reduces sensible heat rather than latent heat (and thus leads to condensation).

[0194] In similar veins, the system may also include preheating of the water flow. This can be done by heating the water source, heating the water supply line, or designating special zones on the heater plate (e.g., water is wicked above the water preheater before reaching the evaporation zone, or the initial zone has a higher power density).

[0195] In some configurations, preheating the gas allows latent and sensible heat to be supplied to the system separately. Sensible heat can be provided by a preheater, while latent heat can be provided by steam. As a result, the heater plate can be kept at a lower temperature, which has advantages such as patient safety. More precisely, the lower temperature enhances safety as excess heat in the delivered heat content is reduced; a surface at 37°C will not generate steam at a dew point temperature greater than 37°C, and therefore patients have never suffered burns.

[0196] A byproduct of separating latent and sensible heat is that it becomes desirable to keep the heated portion of the evaporating surface saturated—if the unheated portion of the heated surface is exposed, it will facilitate heating of the air, thus enabling control tasks to proceed. Therefore, methods including sensing when water reaches the edge of the surface via physical means (temperature drop, short-circuiting conductors, capacitance) or existing models are desirable. This is also useful as a safety mechanism to prevent the system from being flooded.

[0197] Figure 2A The overall control topology of the breathing humidification system 101 is shown, illustrating the basic control principle in a simplified form, where a known amount of air plus a known amount of water produces a known humidity. By controlling the water and temperature, it is possible to effectively control the evaporation rate of water from the heated surface into gas. In some configurations, since the evaporation rate is only a function of other input variables, it is not necessary to measure the evaporation rate. For example, it is possible to set the water flow rate based on the desired evaporation rate. In some configurations, it is possible to calculate the actual evaporation as a verification based on the surface temperature and power. In the control topology shown, water is input into a liquid flow regulator and directed to a heater plate controller. Air and / or gas are received at the inlet for conditioning and testing before being directed to the heater plate controller. The heater plate controller controls the dew point temperature T based on known (e.g., directly determined or indirectly determined by sensors) parameters of the incoming water and air and / or gas. d,o .

[0198] Figure 2AThe inlet conditioning and testing described herein may include an inlet subsystem at or near the gas supply location, including one or more inlet sensors configured to measure the humidity around the inlet gas, the inlet gas flow, the inlet gas temperature, and the pressure level of the gas passage. An inlet gas heater may also be located at or near the gas supply location to preheat the gas to a desired (predetermined) temperature as it enters and passes through the gas passage, so that the gas arrives at the humidification location at the desired temperature. By separately preheating the gas, the energy delivered to the heating element in the humidification zone can be used to evaporate the humidifying fluid, thereby separating the functions of heating the gas in the gas passage (by supplying sensible heat from the gas preheater) and humidifying the gas (by providing latent heat from the heating element). Advantageously, this functional separation allows the heating element to operate at a lower power level corresponding to a lower temperature level, thus making the breathing humidification system safer and more efficient to operate. Furthermore, the temperature of the heated gas can be changed rapidly, making the system more responsive to changes than systems that heat the entire fluid reservoir or a fluid reservoir exceeding the required significant volume.

[0199] Figure 2A The liquid flow controller described herein may include a humidifying fluid flow control subsystem that monitors and controls the rate at which fluid is metered into the humidification zone, and more specifically, into the heating element. A fluid flow sensor measures the flow of the humidifying fluid and provides the measurement to the fluid flow controller. The controller compares the measured fluid flow rate with a desired fluid flow rate (which may be predefined, estimated, or deterministically derived) and adjusts the power level leading to the metering arrangement accordingly. In some embodiments, the humidifying fluid is preheated before being delivered to the heating element to facilitate evaporation, thereby reducing the amount of latent heat required for the heating element to evaporate the humidifying fluid. Different modes of preheating the humidifying fluid may be used, including heating the fluid reservoir, heating the fluid supply line, or designating a specific fluid preheating zone on the heating element before reaching the evaporation zone. According to some embodiments, a check valve is arranged in the fluid supply line prior to the metering arrangement to prevent backflow of the humidifying fluid. In some embodiments, a safety valve is arranged in the fluid supply line prior to the metering arrangement to release pressure in the line due to pump failure and other possible causes.

[0200] Figure 2AThe heater plate controller, as shown, may include a heated surface subsystem that monitors and controls the temperature of the heating element. The heating surface includes an area on which a humidifying fluid is distributed and evaporated by the heat energy provided by the heating surface. A wicking element is disposed above at least a portion of the heating surface. The wicking element is configured to receive and distribute a layer of humidifying fluid having a thickness above one or more portions of the heating surface that delivers heat to cause the fluid to evaporate. The wicking element may include paper, fabric, microfibers, or microstructures, including microfluidic channels. The heating surface may include a heating plate, a resistance heating plate, or a circuit board with resistance strips, to name just a few. In some embodiments, the heating surface is a circuit board overmolded with a thermoplastic material. In some embodiments, multiple heating surfaces or zones may be used. Each heating surface may be maintained at the same or different temperature levels. A heating surface temperature sensor is in thermal contact with the heating surface and communicates with a heating surface temperature controller. A surface heater (which also communicates with the surface temperature controller) is configured to control the temperature of the heating surface or multiple heating surfaces or heating zones according to the configuration of the heating surface.

[0201] Figure 2B-2D It shows the relationship with Figure 2E The overall controller configuration works together to deterministically control the different control subsystems of the humidification system as described herein.

[0202] Figure 2B This is a functional block diagram of the inlet and preheating control subsystem according to embodiments of this disclosure. A preheater is not mandatory but may be included in some configurations. The inlet sensor may be replaced by equivalent measurements or appropriate assumptions and / or calculations as explained above. In some configurations, T may also be controlled in an open-loop manner using a power equation. i In some configurations, the ambient humidity T d，i The humidification can be sensed at any time before humidification, although sensing before the preheater is preferred. If sensing occurs after the preheater, the preheater can be connected to the inlet sensor T. i merge.

[0203] Figure 2B The inlet and preheating control subsystems can use inlet sensors (e.g., the above reference). Figure 1E Those described measure the air and / or gas entering the system in order to determine the ambient humidity T. d，i Inflow air velocity Q i And the inflow air pressure P. As mentioned above, the gas can then be heated by a preheater, although this is not necessary in all embodiments. An inlet temperature sensor downstream of the preheater measures the temperature T of the heated gas. iThe measurement results are then provided to the preheating controller. The preheating controller can then... i With the following Figure 2E The calculated temperature T determined by the overall controller i,set The comparison is made, and a signal is sent to the preheater accordingly to adjust the temperature.

[0204] Figure 2C This is a functional block diagram of a water flow control subsystem according to an embodiment of this disclosure. In some configurations, flow sensors and feedback (liquid flow controllers) may be omitted if a sufficiently well-characterized and stable pump is used. The subsystem may also include a water preheater as described herein and elsewhere. A check valve may also be used before the pump to prevent backflow of water. If the pump is prone to failure, a safety valve may also be used before the pump. The system may also include passive water meters and flow sensors, such as pressure supplies (e.g., gravity supplies), and proportional valves instead of a pump.

[0205] exist Figure 2C In this configuration, water enters the pump from a water source. The pump delivers the water into the system. The pump can be any of the pumps described above. A water flow sensor is positioned downstream of the pump and measures the water flow velocity Q. w The water flow velocity Q w The output is sent to the liquid flow controller. The liquid flow controller provides a feedback loop, and the water pump is powered by the feedback loop based on Q. w With the calculated water flow velocity Q w,set Adjustments are made based on the comparison results. The calculated water flow velocity Q is then used. w,set As described below Figure 2E The overall system controller is determined.

[0206] Figure 2D This is a functional block diagram of a heated surface control subsystem according to an embodiment of this disclosure. Although only one surface is shown, multiple surfaces can be used. Multiple surface heating zones and multiple temperature sensors can exist. In some configurations, two heating zones and temperature sensors are present. An outlet temperature sensor may also be included to assist in control. The surface temperature sensor can be replaced or supplemented by using the resistance or other characteristics of the surface heater. For example, in the present implementation, the resistance of the copper strip represents the average heating temperature. In some configurations, it may be preferred that the surface temperature sensor provides a measurement as close as possible to the true surface temperature, which will be beneficial for the evaporation model described above.

[0207] exist Figure 2D In the configuration shown, water flow and gas flow, for example Figure 2B and Figure 2CThe output of the subsystem is directed above the surface. As described throughout this application, the surface may be a heating source. The surface may include one or more surface temperature sensors, which will transmit the measured surface temperature T. s Provided to the surface temperature controller. The surface temperature controller provides feedback and control mechanisms, and the surface heater, which is in thermal communication with the surface, is regulated by the feedback and control mechanisms. The surface temperature controller can control the temperature of the surface heater. s With the calculated surface temperature T s,set Compare the results. Calculate the surface temperature T. s,set From the following Figure 2E The overall system controller is determined.

[0208] Figure 2E This is a functional block diagram of the overall controller according to an embodiment of the present disclosure. Figure 2E The above is shown Figure 2B-2D An instance of a monolithic controller that binds the three controllers together. For example... Figure 2E As shown, in some configurations, because the digital indication control is based solely on the open-loop setpoint of the input, there is no closed-loop feedback regarding the outlet dew point temperature. The input variables are divided into two groups to represent a set of T. d，i Q i p and T d，o，set This is fundamental for the controller, while the other set can be omitted in simpler controllers. In the most basic controller, three output variables can be set according to the basic system equations; in other words, Q... w，set T can be determined by equation 1-3. i，set It can be set to the desired output at the desired gas inlet temperature, and T s，set It can be determined by Equation 4. In some configurations, P is not used. air P s And any other additional variables or used solely for system validation.

[0209] Figure 3A This is a schematic perspective view of an exemplary integrated humidification system 300 according to one embodiment of this disclosure. Figure 3B This is a schematic vertical cross-sectional view showing the airflow of the humidification system 300. Figure 3C This is a schematic vertical cross-sectional view showing the water flow in the humidification system 300. Figure 3D This is a schematic horizontal cross-sectional view of the humidification system 300. In some configurations, the humidification system 300 may be a stand-alone humidifier that uses ambient air and relies on normal patient breathing to generate a gas flow. In some configurations, the humidification system 300 may be an add-on to a breathing circuit for use with any flow generation system, such as a ventilator. Figure 3E-3FA humidification system 300 is shown installed for use with a flow generation system in an integrated system.

[0210] like Figure 3A As shown, the humidification system 300 includes a housing 303, a gas inlet 331, and a gas outlet 333. The gas inlet 331 is configured to receive gas into the humidification system 300. In some configurations, the gas inlet 331 is adapted to connect to a gas inlet tube, a flow generation system, or other gas source. The gas outlet 333 is configured to deliver humidified gas out of the humidification system 300 and to a patient. In some configurations, the gas outlet 333 is adapted to connect to a gas outlet tube, for example, to a breathing tube (e.g., an intubation tube) connected to a patient interface. The humidification system 300 also includes one or more water inlets 308 configured to allow water received from a water flow controller to enter the humidification system 300. In some embodiments, the humidification system 300 includes both an inlet and an outlet. In some embodiments, the humidification system 300 includes only an inlet because all water input into the system is evaporated to humidify the gas. The humidification system 300 also includes an electrical connector 351 for supplying power to the system and for communicating with different components of the system. The humidification system can also be used to supply power to heated breathing tubes and embedded sensors, thus enabling the design to act as a conduit for downstream system components that require power or communication.

[0211] Figure 3B It shows Figure 3A A schematic vertical cross-sectional view of the airflow in the humidifying shell. (See diagram below.) Figure 3B As shown, housing 303 defines a gas flow path 338. In this configuration, gas enters the humidification system 300 at gas inlet 331 and is guided downward by inner wall 337. An opening 338 at the bottom of inner wall 337 allows gas to pass to the other side of inner wall 337, where it is guided upward and exits the humidification system 300 at gas outlet 333. Housing 303 may include internal baffles 305. The gas is humidified along flow path 335 by evaporated water that has evaporated from heating element 314. Figure 3A The heating element 314 can be partially seen through the gas inlet 331, and the cross-sectional view of the heating element 314 is shown in... Figure 3C and Figure 3D It is visible in the middle. See below for reference. Figures 4A-4C An exemplary configuration of heating element 314 is described as heating element 400.

[0212] Figure 3C It shows Figure 3AA schematic vertical cross-sectional view of the water flow in the humidifying housing. In the configuration shown, water entering at inlet 308 is distributed through channel 318 to contact the heating element 314. In the configuration shown, channel 318 is partially located within the inner wall 337.

[0213] Figure 3D yes Figure 3A A schematic horizontal cross-sectional view of the humidifying casing. (See diagram below.) Figure 3D As shown, the heating element 314 separates the housing 303 in a first direction, and the inner wall 337 separates the housing 303 in a second direction orthogonal to the first direction. Therefore, the heating element 314 is immersed in the flow path. In some configurations, this is preferred because it effectively doubles the surface area, provides a sharp increase in power efficiency, allows for more accurate readings of the surface temperature, and allows the housing 303 to be kept relatively cooled (and therefore safe). Figure 3D In one embodiment, the baffle 305 is included in the airflow path.

[0214] Figure 3E-3F A humidification system 300 is shown installed for use with an embodiment of a flow generation system 390. The flow generation system 390 may include a gas inlet 391 for connection to an external gas source and a gas outlet 393 that can be adapted to connect to a gas inlet 331 of the humidification system 300. In the illustrated configuration, the flow generation system 390 includes a plurality of input controls 395. In some configurations, the flow generation system 390 may be Airvo, available from Fisher & Paykel Healthcare of Auckland, NZ.

[0215] Figure 4A This is a schematic perspective view of a heating element 400 according to an embodiment of the present disclosure. Figure 4B This is a schematic top view of the heating element 400. Figure 4C This is a partial schematic top view of the heating element 400. In some configurations, a printed circuit board heating element 400 can be used as a reference above. Figures 3A-3F The heating device 314 of the humidification system 300 described herein, or any other heating device used herein (e.g., Figure 1A-1E Heating device 114).

[0216] The heating device 400 may include a printed circuit board 401 to provide heating. The printed circuit board 401 may have multiple resistor strips 411. The resistor strips 411 may be copper. The outer surface of the heating element 400 may include a wicking surface. The wicking surface may be provided by an overlay mold on the printed circuit board 401. The overlay mold may have microchannels (described in more detail below). The overlay mold may be a thermoplastic material. The heating element 400 may have modular regions. For example, in the illustrated embodiment, the resistor strips 411 are divided into three modular regions 403, 405A, and 405B. In some configurations, modular regions 404A and 405B are connected in series. In some configurations, the heating element 400 may have a first region configured to preheat water and a second region configured to evaporate water, as will be referred to... Figure 4C As described. A single zone can be moist, and that single zone can be powered. This gives the controller flexibility. Alternatively, the entire heating surface can be powered, and the entire heating surface can be kept moist instead of operating in the separated zones.

[0217] like Figure 4B As shown, the heating element 400 may include electrical contacts 457 (for power conversion or communication) that can be used to power additional components of the breathing humidification system. For example, electrical contacts 457 may power a heated breathing tube (HBT). As another example, electrical contacts 457 may be used to power or communicate with additional sensors (e.g., temperature sensors, pressure sensors, or other sensors as described herein).

[0218] Microchannels can provide wicking surfaces. These wicking surfaces can work in conjunction with preheating of the gas to allow the heated surface to be maintained at a relatively low temperature. This is because lower temperatures require a larger surface area to generate the necessary vapor flow, and the larger area requires a more efficient mechanism to disperse the liquid so that more heated surface is available for evaporation.

[0219] In some configurations, microchannels can be small-scale (e.g., micro-scale) grooves formed on a surface. The surface can be flat or curved. In some configurations, the microchannels can be highly ordered. In some configurations, the microchannels are arranged in a pattern (see, for example...). Figure 5A and Figure 5B , Figure 5A An example of a grid structure pattern is shown. Figure 5BAn example of a radial pattern is shown; these examples are non-limiting and other patterns are possible. In some configurations, the purpose of microchannels is to disperse liquid across a surface, thereby increasing the surface area for a given volume. In some configurations, the microchannels have a roughly uniform cross-sectional profile along their length. For example, microchannels can have circular or semi-circular, elliptical or semi-elliptical, rectangular, triangular (V-shaped), or trapezoidal cross-sections. In some configurations, microchannels may include rounded edges and / or corners. In some configurations, microchannels can have a variable cross-sectional profile that changes along the length of the microchannel. For example, microchannels can become deeper and / or wider along their length. Microchannels can be “open” microchannels, which include at least one side open to the environment. For example, a microchannel can be a V-shaped groove formed into a surface, and liquid in or on the microchannel can be exposed to the environment on at least one open side of the V. Because the open side of the microchannel provides a destination for the evaporating fluid, such microchannels can facilitate liquid evaporation. For example, the open side of an open microchannel can lead to a gas passage. Liquid in or on the microchannel can evaporate, and the evaporated liquid can be entrained in the gas flowing through the gas passage. In some configurations, the microchannel can have a depth in the range of 1-1000 μm (depth can also be considered as height). In some configurations, the depth of the microchannel is between 20-200 μm. In some configurations, the width of the microchannel can be between 1-1000 μm. In some configurations, the width of the microchannel is between 20-200 μm. In some configurations, the inclination of the sidewalls of the microchannel can be in the range of 0-45 degrees. As used herein, the inclination of the sidewalls is measured between the wall and a vertical line (in other words, between the wall and an axis perpendicular to the surface forming the microchannel). That is, a 0-degree wall inclination indicates a completely vertical wall. For example, if the sidewalls of the microchannel include a 0-degree wall inclination, the microchannel can be approximately square, and the top of the square can be open. As another example, if the sidewalls of the microchannel include a 45-degree inclination, the microchannel can be approximately V-shaped when the incised walls intersect directly, or approximately trapezoidal when the sidewalls intersect the horizontal, flat bottom surface of the microchannel, and the top of the microchannel can be open. In some configurations, the inclination of the sidewalls of the microchannel can range from 5 to 20 degrees. The microchannel can disperse liquid by wicking (capillary action), or in some cases by gravity flow of liquid through the channel. In some configurations, the microchannel can be defined by protrusions extending beyond the surface, wherein the microchannel is formed by the space between the protrusions.

[0220] In some configurations, heating element 400 includes one or more sensors for measuring the surface temperature of heating element 400. One or more sensors may be thermistors 421. In some configurations, the heated surface temperature may be calculated at least in part by determining the resistance level or other characteristics of heating element 400. The resistance level of the heating element may be used to indicate the average temperature of the heated surface. The heating element may be arranged to deliver a higher power density in a designated area of ​​the heating element compared to other areas delivered to the heating element. The designated higher density area of ​​the heating element may be located at the water supply outlet to the heated surface. The designated higher density area of ​​the heating element may be located in a water preheating area on the heated surface. The breathing humidification system may include a temperature sensor located at the outlet of the gas passage, which may act as a safety valve.

[0221] The resistor strip 411 and / or the sensor (e.g., thermistor 421) can be electrically connected to electrical contacts 452 located on contact area 451 of printed circuit board 401. Contact area 451 can be positioned to mate with electrical connector 351 of humidification system 300.

[0222] In some configurations, the heating element 400 is configured to provide some form of "preheating" to the water. In some configurations, this can be achieved simply by increasing the stripe (and therefore power) density of the area where water is introduced. This increase in power density will allow for the additional amount of power required to heat the water within a small area. For example, as... Figure 4C As shown, if water is introduced into the heating element 400 at position 408 and the surface of the heating element is configured to wick water across the heating element 400 in the direction of the arrow, the heating element 400 may include a higher density of resistance strips 411 at and around position 418 (in other words, closer to position 408 where water is introduced) and a lower density of resistance strips 411 at and around position 428 (in other words, farther from position 418).

[0223] The power required for latent heat and sensible heat is approximately and (where L is the latent heat of vaporization, c) p It is the specific heat capacity of water. It is the water flow rate, T s It is the surface temperature, and T w (This refers to the temperature of the water). The ratio of sensible heat to latent heat is therefore... Because the water flow rate cancels out the flow, it is sufficient to design a power density zone that is consistently higher than the remaining portion of the plate by a certain fixed ratio and achieve the desired effect. Due to T s -T w It may change significant quantities, which is not always precise, but in some configurations, excessive precision is not necessary.

[0224] Preheating the water is generally less important than preheating the air in a system because it requires a smaller fraction of the total heat (about half that of air) and has little impact on evaporation and exhaust conditions. Furthermore, in some configurations, heating the water consumes up to 9% of the system's power, so it is not insignificant. Without preheating, the effect is that a temperature gradient will exist across the surface as the water heats up, which reduces the evaporation rate in these areas and complicates the evaporation model.

[0225] Another option for preheating the water is to include a heater in the water supply line (i.e., between the pump / flow sensor and the surface connection). The heater can be a PTC (positive temperature coefficient) element, a heating coil, or any other heater that is in thermal contact with the water flow. The heater heats the water to the same temperature as the surface of the heating element 400.

[0226] Although the above reference describes heating element 400 for heating water, a similar heating element 400 can also be used to heat gas, for example as a gas preheater.

[0227] Figure 4D Schematic top views of two alternative embodiments of heating elements 400A and 400B according to embodiments of the present disclosure are shown. Heating elements 400A and 400B may include etched foils 401A and 401B. Etched foils 401A and 401B may include multiple resistance strips 411A and 411B. Heating elements 400A and 400B may also each include electrical connections 451A and 451B.

[0228] Figure 4E An embodiment of the heating element 400A in a rolling configuration is shown.

[0229] In some configurations, the humidification system includes various components (e.g., distribution and / or wicking systems) to deliver humidifying fluid to the heating element. In some configurations, it is preferable to deliver water to the entire surface of the heating element, in other words, to saturate the surface of the heating element. It is important to recognize that the distribution / wicking system needs to be able to maintain a flow rate. In some configurations, if the distributor cannot wick water fast enough to keep the heating element saturated, it is insufficient to distribute water above the surface. In some configurations, the liquid flow rate is maintained at up to 5 mL / min. ---1 It is the preferred option.

[0230] A distribution and / or wicking system may include two parts: a wicking surface that distributes water across the surface; and a connector that attaches the water supply system to the surface at one or more points. The connector may also perform partial water distribution (e.g., by connecting water in zones or lines rather than at points). Technologies that can be used for connecting and wicking include, but are not limited to: fabrics / paper (e.g., Kimberly-Clark Hydroknit); microchannels; hydrophilic coatings (e.g., lotus leaf-coated HydroPhil); capillary / contact wicks (custom-designed); and / or porous polymers (e.g., Porex fibers).

[0231] The requirements for connectors are primarily based on the properties of the surface. If the surface is isotropic (with the same wicking in all directions), then the connector only needs to bind water to the surface at a single point. If the surface is anisotropic (depending on the direction), some additional features will be needed to account for this; that is, the water will need to be effectively guided above a certain area to ensure uniform wicking. Anisotropy also depends on the hydrophobicity of the surface—hydrophilic surfaces readily absorb water, so the connector only needs to impede water contact with the surface, while hydrophobic surfaces require a connector that "forces" the water against the surface to prevent it from merely "rolling" away, or provides an intermediate mechanism with greater affinity to the humidifying fluid when it comes into contact with the surface.

[0232] For example, the fabric of the wicking surface can be very close to anisotropic and substantially hydrophilic, making a point source sufficient. Simply placing a tube to deliver liquid into contact with the surface can be sufficient to generate flow (up to a given surface size and depending on orientation). In some configurations, and on some matrices such as silicone, the wicking surface includes microchannels that can wick only in the channel direction and have poor hydrophilicity. When using a surface that wicks and / or is less hydrophilic in one direction, having a distributor can be beneficial, as it retains water in place until it is drawn away by the microchannels and can also guide water in another (e.g., vertical) direction.

[0233] In some configurations, the wicking surface can be a microchannel surface, which may include parallel channels in only one direction; a small group of distributed channels connected to a larger number of main channels; and / or channels radially distributed from a single point, among other possible configurations. The wicking surface can also be absorbent fabric or absorbent paper, a superhydrophilic coated surface, or a thin porous medium.

[0234] In some configurations, the connector may be a segment of wicking medium attached to a surface, which may include a porous polymer or a fibrous polymer, fabric / paper, and / or a hydrophilic segment. The connector may also be a second surface forming an acute angle with the wicking surface, the second surface drawing water through capillary action. The second surface may include a flat slider (such as a glass slider) abutting the surface at a low angle, or alternatively, a round bar abutting the surface, the bar forming a low contact angle at the contact point. The wicking surface may also include a cavity in contact with the surface, the cavity including a plane directly facing and pressed against the water supply cavity, the surface having a C-shaped tube connected along the edge of the surface. In some configurations, any of these connection methods can be a line source (useful when the surface is anisotropic, such as microchannels, in which case the line source is perpendicular to the main wicking direction of the surface; for example, thin segments of porous polymers placed across channels); a point source (useful when the surface is isotropic or contains embedded water distribution devices); a radial source; or multiple line / point / radial sources (useful when there are two separate wicking surfaces (e.g., the side of a heater plate) or the wicking velocity of the surface is insufficient for the surface to be permeated by a single source).

[0235] Specific examples of wicking surfaces and / or couplings will now be described by way of example rather than limitation.

[0236] Figure 5A This is a schematic diagram illustrating a mesh-structured microchannel water distribution pattern 500a according to an embodiment of the present disclosure. The distribution pattern 500a includes a water input region 501a, a first microchannel 502a, and a second microchannel 503a. The first microchannel 502a can act as a distribution channel for distributing water to the second microchannel 503a. The second microchannel 503a distributes water across the surface. The mesh-structured microchannel water distribution pattern 500a can be applied to the surface of a heating element 400. The mesh-structured microchannel water distribution pattern 500a is an example of a wicking element as described herein. In some configurations, the first microchannel 502a moves water in a first direction and the second microchannel 503a moves water in a second direction orthogonal to the first direction. However, the mesh-structured microchannel water distribution pattern 500a can be modified to include the first microchannel 502a positioned at a different location relative to the second microchannel 503a. In some configurations, the mesh-structured microchannel water distribution pattern 500a includes only a first microchannel 502a or only a second microchannel 503a. Generally, the mesh-structured microchannel water distribution pattern 500a is a system for distributing water through microchannels: water is supplied to several distribution channels, which are divided into many channels that wick across most of the surface.

[0237] Figure 5BA radial microchannel water distribution pattern 500b according to an embodiment of this disclosure is shown. Figure 5B This is a still image captured from a video showing radial microchannels for wicking fluorescent dye. The fluorescent dye is dropped onto a central point 501b and wicked outwards through the channels. The radial microchannel water distribution pattern 500b includes microchannels that radially diverge from the central point 501b where water is introduced. In some configurations, the microchannels may split as they radiate from the central point 501b to maintain a uniform channel density. The radial microchannel water distribution pattern 500b may also include circumferentially extending microchannels.

[0238] Figure 6A This is a schematic perspective axial cross-sectional view of a humidification system 600 including a glass sliding connector 631 according to an embodiment of this disclosure. Figure 6B yes Figure 6A A schematic perspective cross-sectional side view of the 600 breathing humidification system. Figure 6C Figure 6A A schematic side view of the 600 breathing humidification system. Figure 6D yes Figure 6A A schematic perspective axial view of the assembly of the breathing humidification system 600. The glass sliding connector 631 can be considered as a contact angle / capillary distributor.

[0239] In the illustrated embodiment, the breathing humidification system 600 includes a gas inlet 601 and a gas outlet 603, and has a gas flow channel 605 extending between the gas inlet and the gas outlet. As gas moves from the inlet 601 to the outlet 603, the gas is humidified in the flow channel 605. The breathing humidification system 600 also includes a micropump 621 adapted to supply water from a water source into the system. Water is delivered from the micropump 621 into the flow channel 605 through the water inlet 621. The breathing humidification system further includes a glass sliding coupling 631, the surface 633 of which abuts against the heating element 614 being held at an acute angle 625 (see [link to documentation]). Figure 6C Surface 633 includes microchannels extending in the direction of the arrow and perpendicular to the glass slider 631. A water supply pipe 623 is positioned at the intersection of the glass slider 631 and surface 633. Due to the acute angle 625 between the glass slider 631 and surface 633 (see...), Figure 6C Water is wicked along the confluence and subsequently wicked by microchannels throughout surface 633. Notably, the coupling 600 exposes the heating element 614 only on one side; however, in some configurations, the design can be modified to expose the heating element 614 on both sides. The breathing humidification system 600 may also include a honeycomb gas diffuser 645 in the gas flow path 605.

[0240] Figure 7This is a schematic perspective view of a distribution pipe connector 700 wound over the edge of a heating element 714 according to an embodiment of this disclosure. The drawing shows a pipe 701 used as a connector or distributor. The pipe 701 is clamped above the heating element 714, and water is subsequently pumped into the pipe 701. When the pipe 714 is full, water is drawn across the heating element 714. Notably, the pipe connector 700 can distribute water onto the top surface 714a and the bottom surface 714b of the heating element 714.

[0241] Figure 8 This is a schematic diagram of a porous media connector 800 according to an embodiment of the present disclosure. The connector 800 is shown as a scatter strip extending along the surface of the heating element 814. The connector may be, for example, a fabric. Water is supplied onto the fabric to allow the water to distribute along the μ channels. In some configurations, the connector 800 may be a thin porous medium, such as a porous polymer or a sintered polymer.

[0242] Figure 9A This is a schematic perspective view of a radial coupling 900 according to an embodiment of the present disclosure. Figure 9B yes Figure 9A A schematic perspective cross-sectional view of the radial connector 900. The radial connector 900 can be considered as a cavity / face connector. Generally, the connector 900 pushes water against the surface of the heating element. In some configurations, the connector 900 is configured to work with a fully hydrophilic or absorbent surface. In some configurations, the connector 900 is adapted such that when multiple outlets are present, the outlets are balanced, for example, so that the water does not simply favor one path and flow entirely in that direction.

[0243] The connector 900 receives the supplied water at the inlet 901 and supplies water radially to both sides from the center of the heating element. For example... Figure 9B As shown, water flows downward from inlet 901 through a series of channels 903 to a heating element (not shown). The coupling 900 may include multiple outlets 905. In some configurations, the coupling 900 also delivers water through a central channel 907 that extends through a hole in the heating element to a similar system on the other side. Figure 9B In the image, arrows are added to indicate the flow of water.

[0244] Figure 10A This is a schematic perspective view of a multilayer connector 1000 according to an embodiment of the present disclosure. Figure 10B yes Figure 10A A schematic perspective cross-sectional view of a multi-layered connector 1000. The connector 1000 includes a body 1001 having one or more protruding sections 1003. An outlet 1005 may be positioned on one or each of the inward surfaces of the protruding sections 1003. Figure 10B As shown, the connector 1000 includes an inlet 1011 and an internal channel for delivering water to an outlet 1005. Arrows have been added. Figure 10B In order to show the flow of water. Heating element (such as...) Figure 10C and Figure 10D (As shown) can be positioned between the protruding sections 1003 and receive water from the outlet 1005.

[0245] Figure 10C It is attached to the humidifying housing 303 according to an embodiment of this disclosure. Figure 10A A schematic cross-sectional view of the multi-layer connector 1000. Figure 10D It is attached to the humidifying housing 303 according to an embodiment of this disclosure. Figure 10A A schematic cross-sectional view of the multi-layer connector 1000, the humidifying housing 303 including a printed circuit board heating element 400. The housing 303 may be similar to the reference... Figures 3A-3D The housing 303 and heating element 400 of the described humidification system 300 can be similar to those in the reference. Figures 4A-4C The heating element 400 is described.

[0246] An embodiment of the humidification system described herein has been tested and satisfactory results have been obtained regarding the achievable dew point temperature and control accuracy. For example, gas flow rates up to approximately 45 L / min... ---1 Furthermore, a dew point temperature T can be achieved below sea level. d =37℃, at 60L min ---1 The flow drops to approximately T d =35℃. This is consistent with the maximum power achievable using a specific PCB design.

[0247] Figure 11A and Figure 11B The accuracy performance of a respiratory humidification system according to an embodiment of this disclosure is illustrated. The system operates across a range of flow rates and dew points under open-loop control as described above, wherein the dew point temperature at the outlet is measured individually and calculated from the system's predicted dew point temperature using transformation equation 3:

[0248]

[0249] Figure 11A This is a graph showing the accuracy of the dew point temperature for tested breathing humidification, and also shows the measured dew point temperature plotted based on the predicted dew point temperature. Two points where the heater plate is soaked due to low power are not visible on the graph, but can be ignored because this condition is detectable. Most points are within ±2°C of the measured dew point temperature. Figure 11B This is a graph showing the dew point temperature error across the gas flow rate of the tested breathing humidification system.

[0250] Figure 12A This is a schematic perspective view of an alternative embodiment of the humidification system 1200 according to the embodiments of this disclosure. Figure 12B yes Figure 12A A schematic cross-sectional view of the humidification system 1200. (See diagram below.) Figure 12B As shown, the humidification system 1200 includes a top layer and a bottom layer. Figure 12C It shows Figure 12A A schematic cross-sectional view of the top layer of the humidification system 1200. Figure 12D It shows Figure 12A A schematic cross-sectional view of the bottom layer of the humidification system 1200.

[0251] The humidification system 1200 includes a gas inlet 1201 and a gas outlet 1202. The humidification system may include a blower 1231 configured to move gas from the gas inlet 1201 to the gas outlet 1202. The inlet 1201 and outlet 1202 may be connected by a channel. A flow sensor 1251 and a gas sensor 1281 may be located within the channel. The humidification system 1200 includes a power / communication connector 1203.

[0252] The humidification system 1200 may include a heating surface cavity 1211 configured to receive a heating element as described elsewhere. The heating surface cavity also includes a water supply section 1261, which may be configured with a connector for applying water to the heating element. The water supply section 1261 may be in fluid communication with a liquid flow module 1241, a water inlet 1242, a check valve 1243, and a micropump 1244. The humidification system 1200 may also include an electronic cavity 1271 accessible via port 1272.

[0253] Figure 13 This is a schematic diagram of an embedded humidification system according to an embodiment of the present disclosure. Figure 13 The embedded humidification system includes a preheater and a heater (represented by a heated surface) in the gas passage between the inlet and outlet. A heater controller is connected to the preheater and the heater. The preheater heats the gas before it reaches the heater. The heater is also connected to a water controller that distributes water onto the heated surface. The amount of water applied by the water controller and the heat applied by the heater controller can be deterministically controlled according to the principles described herein to evaporate the water and humidify the gas. The system outlet can be connected to a heated breathing tube (HBT) (i.e., a delivery inhalation tube). The power and sensing systems necessary for the HBT can be provided as a whole by the humidification system, or separately, or externally. The advantages of including the humidification system as part of the delivery tube are simplicity, cost reduction, and quality control by ensuring replacement as needed.

[0254] The foregoing description details certain embodiments of the systems, apparatus, and methods disclosed herein. However, it should be understood that the systems, apparatus, and methods can be practiced in many ways, regardless of how detailed the foregoing description is in the context. As also stated above, the use of specific terminology in describing certain features or aspects of the invention should not be construed as implying that the term is redefined herein as limited to any specific feature of the art associated with that term. The term "about" or similar terms used herein should be understood to mean within acceptable tolerances of the specified item (e.g., by reference, about can mean within acceptable tolerances, such as ±3°C).

[0255] It will be understood by those skilled in the art that various modifications and variations can be made without departing from the scope of this technology. Such modifications and improvements are intended to fall within the scope of the embodiments. It will also be understood by those skilled in the art that parts included in one embodiment are interchangeable with other embodiments; one or more parts from a depicted embodiment may be included in any combination with other depicted embodiments. For example, any of the different components depicted herein and / or in the figures may be combined with other embodiments, interchanged with other embodiments, or excluded from other embodiments.

Claims

1. A heater element for evaporating liquid in a respiratory humidification system to obtain humidified gas to be delivered to a patient, the heater element comprising a printed circuit board (PCB) or etched foil overmoulded with a surface comprising a wicking element, the wicking element comprising microchannels configured to distribute liquid throughout the wicking element, wherein the microchannels comprise open sides that open into a gas passageway, wherein the heater element is configured such that, in use, gas to be humidified flows substantially parallel to the surface and in contact with the wicking element to pick up evaporated liquid from the microchannels and be humidified.

2. The heater element of claim 1, wherein, The microchannels comprise a hydrophilic coating surface.

3. A heater element according to claim 1 or 2, wherein, The microchannels comprise a highly ordered microscale groove disposed on the overmoulded surface of the printed circuit board (PCB) or etched foil.

4. The heater element of claim 1 or 2, wherein the surface has microchannels extending in only a single direction.

5. The heater element of claim 1 or 2, wherein the microchannels comprise a first set of distribution channels connected to a second set of main channels.

6. The heater element of claim 5, wherein the number of distribution channels is less than the number of main channels.

7. The heater element of claim 1 or 2, wherein the microchannels are radially distributed from a single point.

8. The heater element of claim 1 or 2, wherein the microchannels have a depth of about 1-1000 pm.

9. The heater element of claim 1 or 2, wherein the microchannels have a width of about 1-1000 pm.

10. The heater element of claim 1 or 2, wherein the overmoulded surface of the printed circuit board (PCB) or etched foil comprises a thermoplastic material.

11. The heater element of claim 1 or 2, wherein the heater element comprises modular zones.

12. The heater element of claim 1 or 2, wherein the heater element comprises a first zone configured to pre-heat liquid and a second zone configured to evaporate liquid.

13. The heater element of claim 1 or 2, wherein the heater element comprises a resistive trace.

14. The heater element of claim 13, wherein the heater element comprises a greater density of resistive trace proximate to where liquid is introduced and a lower density of resistive trace around an area where liquid is evaporated.

15. The heater element of claim 13, wherein the printed circuit board comprises the resistive trace.

16. The heater element of claim 1 or 2, wherein the heater element comprises one or more sensors for measuring the temperature of the surface of the heater element.

17. The heater element of claim 16, wherein the one or more sensors are thermistors.

18. A respiratory humidification system, comprising: a housing; a gas inlet configured to receive gas into the respiratory humidification system; a gas outlet configured to deliver humidified gas out of the respiratory humidification system and to a patient; one or more liquid inlets configured to allow liquid to enter the respiratory humidification system; an electrical connector configured to supply power to the respiratory humidification system and to communicate with different components of the respiratory humidification system; and a heater element comprising a printed circuit board (PCB) or etched foil overmoulded with a surface comprising a wicking element comprising microchannels configured to distribute liquid throughout the wicking element and configured to evaporate the liquid to humidify a gas, wherein the microchannels comprise open sides that open into a gas passageway, wherein the heater element is configured such that, in use, a gas to be humidified flows generally parallel to the surface and in contact with the wicking element to pick up evaporated liquid from the microchannels and be humidified.

19. The respiratory humidification system of claim 18, wherein the housing defines a gas flow path along which gas enters the respiratory humidification system at a gas inlet and is directed downward by an inner wall, an opening at the bottom of the inner wall allowing gas to pass to the other side of the inner wall, gas being directed upward at the other side and out of the respiratory humidification system at a gas outlet.

20. The respiratory humidification system of claim 18 or 19, wherein the heater element comprises a contact region positioned to mate with a contact region of the respiratory humidification system.

21. The respiratory humidification system of claim 18 or 19, wherein the housing comprises an internal baffle in the gas flow path.

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