Area heating for breathing circuits

Abstract

A humidification system for providing humidified gas to a user is provided. The inspiratory limb for a breathing circuit includes a first section including a first heater wire circuit and a second section including a second heater wire circuit. The inspiratory limb includes an intermediate connector including a connection circuit that electrically couples the first heater wire circuit to the second heater wire circuit. The inspiratory limb can be configured to operate in two modes: in a first mode, power travels through a first electrical connection to provide power to the first heater wire circuit but not to the second heater wire circuit; and in a second mode, power travels through the first electrical connection to provide power to both the first heater wire circuit and the second heater wire circuit.

Description

[Technical field]

[0001] Incorporation by Reference This application is a continuation of U.S. Provisional Patent Application No. 61 / 726,532, filed November 14, 2012, entitled "ZONE HEATING FOR RESPIRATORY CIRCUITS"; U.S. Provisional Patent Application No. 61 / 786,141, filed March 14, 2013, entitled "ZONE HEATING FOR RESPIRATORY CIRCUITS"; U.S. Provisional Patent Application No. 61 / 877,736, filed September 13, 2013, entitled "ZONE HEATING FOR RESPIRATORY CIRCUITS"; U.S. Provisional Patent Application No. 61 / 877,784, filed September 13, 2013, entitled "CONNECTIONS FOR HUMIDICATION SYSTEM"; U.S. Provisional Patent Application No. 61 / 877,784, filed September 13, 2013, entitled "MEDICAL TUBES AND METHODS OF No. 61 / 877,622, entitled "HUMIDIFICATION SYSTEM," filed on September 13, 2013; and U.S. Provisional Patent Application No. 62 / 216,232, entitled "ZONE HEATING FOR RESPIRATORY CIRCUITS," filed on September 9, 2015; and U.S. Provisional Patent Application No. 62 / 380,195, entitled "ZONE HEATING FOR RESPIRATORY CIRCUITS," filed on August 26, 2016, each of which is incorporated herein by reference in its entirety.

[0002] Additionally, PCT Application No. PCT / IB2012 / 001786, filed May 30, 2012, and entitled "MEDICAL TUBES AND METHODS OF MANUFACTURE"; PCT Application No. PCT / NZ2013 / 000222, filed December 4, 2013, and entitled "MEDICAL TUBES AND METHODS OF MANUFACTURE"; and PCT Application No. PCT / NZ2013 / 000208, filed November 14, 2013, and entitled "ZONE HEATING FOR RESPIRATORY CIRCUITS" are also incorporated by reference in their entireties herein.

[0003] The present disclosure relates generally to humidification systems for providing humidified gas to a user, and more particularly to heating gas in a breathing circuit for use with a humidification system. [Background technology]

[0004] Many gas humidification systems deliver heated and humidified gases for various medical procedures, including respiratory therapy, laparoscopy, and the like. These systems can be configured to control temperature, humidity, and flow rate using feedback from sensors. To maintain desired characteristics during delivery to the user, the breathing circuit can have a heater associated with the gas line, where the heater provides heat to the gas as it flows to and / or from the user. The line heater can be controlled to provide heat to the gas so that it arrives at the user with desired characteristics, such as temperature and / or humidity. The humidification system can include a temperature sensor and provide feedback to a humidification controller, which can adjust and / or modify the power sent to the line heater to achieve a target temperature at a location along the associated line. Summary of the Invention [Means for solving the problem]

[0005] The systems, methods, and devices described herein have innovative aspects, none of which are essential or solely responsible for their desirable attributes. Without limiting the scope of the claims, some of the advantageous features are summarized below.

[0006] Some embodiments provide an inspiratory limb for a breathing circuit. The inspiratory limb described herein is particularly useful in situations where heated and humidified gas must pass through two different environments. This can be problematic, for example, in an infant incubator, where the temperature is significantly higher than the surrounding environment or where a portion of the ductwork delivering gas to the patient is under a blanket. However, the embodiments disclosed herein can be used in any environment where heated and / or humidified gas is delivered to a patient and are not limited to applications where the inspiratory limb passes through two different environments.

[0007] The inspiratory limb can include a first section of the inspiratory limb comprising a first structure forming a conduit configured to transport the humidified gas, the first section of the inspiratory limb comprising a first heater wire circuit. The inspiratory limb can include a second section of the inspiratory limb comprising a second structure forming a conduit configured to transport the humidified gas, the second structure configured to mechanically couple to the first structure of the first section to form an extended conduit for the humidified gas, the second section of the inspiratory limb comprising a second heater wire circuit. The inspiratory limb can include an intermediate connector including a connection circuit electrically coupling the first heater wire circuit to the second heater wire circuit, the intermediate connector can be coupled to a patient end of the first section of the inspiratory limb and a chamber end of the second section of the inspiratory limb to form a single conduit for the humidified gas. The intermediate connector may be covered by a portion of the first segment of the inspiratory limb, a portion of the second segment of the inspiratory limb, or a portion of both the first and second segments of the inspiratory limb such that the intermediate connector is internal to the inspiratory limb.

[0008] The inspiratory limb can be configured to operate in two heating modes. In a first heating mode, power passes through the intermediate connector to provide power to the first heater wire circuit and not to the second heater wire circuit. In a second heating mode, power passes through the intermediate connector to provide power to both the first heater wire circuit and the second heater wire circuit. For example, the intermediate connector can include electrical components configured to route power along different paths based at least in part on a direction of current and / or a polarity of voltage. The intermediate connector can include a conductive track, which can provide a short circuit (e.g., a direct electrical connection without an intervening electrical component) between one or more wires in the first heater wire circuit and one or more wires in the second heater wire circuit. The intermediate connector can include a conductive track, which can electrically couple one or more wires in the first heater wire circuit to one or more wires in the second heater wire circuit, where the conductive track includes electrical components such as, for example, but not limited to, diodes, transistors, capacitors, resistors, logic gates, integrated circuits, etc. In certain embodiments, the intermediate connector includes a diode electrically coupled to both the first heater wire circuit and the second heater wire circuit. In certain embodiments, the inspiratory limb can further include a first sensor circuit having a first sensor positioned at the intermediate connector. In certain embodiments, the inspiratory limb can further include a second sensor circuit having a second sensor positioned at the patient-end connector, the patient-end connector being positioned at a patient-end of the second section of the inspiratory limb. The inspiratory limb can be configured to operate in two sensing modes. In the first sensing mode, a signal from the first sensor is received and a signal from the second sensor is not received. In the second sensing mode, a signal from the second sensor is received and a signal from the first sensor is not received. In some embodiments, the sensing includes receiving signals in parallel from both the first sensor and the second sensor.In such an embodiment, the algorithm may determine a parameter measured by the first sensor based at least in part on signals received in parallel from both the first sensor and the second sensor. In certain embodiments, the intermediate connector includes a diode electrically coupled to both the first sensor circuit and the second sensor circuit. The patient-end connector may be configured to provide an electrical connection for the second sensor circuit. Similarly, the patient-end connector may also be configured to provide an electrical connection for the second heater wire circuit. The sensor may be a temperature sensor, a humidity sensor, a flow sensor, or the like. The first and second sensors may be sensors configured to measure one or more parameters, such as temperature, humidity, flow, oxygen content, or the like. In some embodiments, the first and second sensors are configured to measure at least one similar parameter (e.g., temperature, humidity, flow, or the like). In some embodiments, three or more sensors may be included and may be positioned in the intermediate connector and / or the patient-end connector.

[0009] Some embodiments provide a respiratory humidification system comprising an inspiratory limb and a controller. The inspiratory limb may include a first segment having a first heater wire circuit, a second segment having a second heater wire circuit, an intermediate connector having a connector circuit configured to electrically couple the first heater wire circuit to the second heater wire circuit, a first sensor positioned at a patient end of the first segment, and a second sensor positioned at a patient end of the second segment. The controller may be adapted to selectively switch between a first mode and a second mode, where in the first mode the controller provides power to the first heater wire circuit through the connector circuit and in the second mode the controller provides power to the first and second heater wire circuits. In certain embodiments, the respiratory humidification system switches modes based at least in part on input from one or both sensors. In certain embodiments, the switching is based at least in part on parameters including one or more of temperature, flow rate, humidity, power, or any combination thereof. The parameters may be derived or obtained directly from the first sensor, the second sensor, or a combination of both sensors. In certain embodiments, the first and second modes are defined by the direction of current or polarity of voltage provided by the power source. In some embodiments, the respiratory humidification system may include three or more sensors, which provide inputs used to control the heating of the inspiratory limb.

[0010] Some embodiments provide a dual limb circuit that can include an inspiratory limb. Such an inspiratory limb can include a first segment having a first heater wire circuit, a second segment of the inspiratory limb having a second heater wire circuit, an intermediate connector having a connector circuit configured to electrically couple the first heater wire circuit to the second heater wire circuit, a first sensor positioned at a patient end of the first segment, and a second sensor positioned at a patient end of the second segment. The dual limb circuit can also include an expiratory limb with an expiratory heater wire circuit. The dual limb system can further include an interface connected to the inspiratory limb and the expiratory limb. The dual limb system can further include a controller adapted to selectively switch between a first mode and a second mode, where in the first mode the controller provides power to the first heater wire circuit through the connector circuit and in the second mode the controller provides power to the first and second heater wire circuits. In certain embodiments, the heating of the expiratory limb is performed using an expiratory heater wire circuit separate from the heating of the inspiratory limb using the first and second heater wire circuits. In certain embodiments, the expiratory limb is powered in parallel with the first heater wire circuit in the first section of the inspiratory limb and / or in parallel with the first and second heater wire circuits. In certain embodiments, the expiratory limb can be designed to be powered in only the first mode, only the second mode, or in both the first and second modes. In certain embodiments, the interfaces are connected by a Y-piece. Any suitable patient interface can be incorporated. Patient interface is a broad term and should be interpreted in its ordinary and customary sense to those skilled in the art (i.e., should not be limited to a special or specialized sense), including, but not limited to, masks (such as tracheal masks, face masks, and nasal masks), cannulas, and nasal pillows.

[0011] In some embodiments, a segmented inspiratory limb is provided, where the segment structure comprises an elongated tube. The elongated tube can include a first elongated member having a hollow body helically wound to at least partially form a conduit having a longitudinal axis, a lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen. The elongated tube can include a second elongated member helically wound and joined between adjacent turns of the first elongated member, the second elongated member forming at least a portion of the lumen of the elongated tube. In certain implementations, the first elongated member forms a plurality of bubbles in the lumen having a flattened surface in a longitudinal cross section. In certain implementations, adjacent bubbles are separated by a gap above the second elongated member. In certain implementations, adjacent bubbles are not directly connected to each other. In certain implementations, the plurality of bubbles have perforations.

[0012] Some embodiments provide a respiratory humidification system comprising two control circuits. The respiratory humidification system may include an inspiratory limb including a first section comprising a first heater wire and a second section comprising a second heater wire. The respiratory humidification system may also include a sensor positioned at a patient-end of the second section to measure a patient-end parameter. The first and second heater wires are electrically coupled, the first heater wire forming a first heater circuit and the first and second wires forming a second heater circuit. The respiratory humidification system may include a hardware controller configured to receive an output of the sensor. The hardware controller may be further configured to provide power to the first heater circuit when a difference between an output of the sensor and a patient-end parameter set point is less than a predetermined threshold, and to provide power to the second heater circuit when a difference between an output of the sensor and a patient-end parameter set point is equal to or greater than a predetermined threshold. The hardware controller may be configured to provide maximum power to the first heater circuit when the hardware controller provides power to the first heater circuit. In some embodiments, the respiratory humidification system may further include an intermediate connector having a connector circuit configured to electrically connect the first and second heater wires. In some embodiments, the patient-end parameter may be temperature. In some embodiments, the first and second heater wires may be exposed to different ambient environments. In some embodiments, the first and second heater wires may be exposed to different ambient temperatures. In some embodiments, the power supplied to the first and / or second heater circuits may be determined by a PID control scheme.

[0013] Some embodiments provide a respiratory humidification system with two control circuits. The respiratory humidification system can include an inspiratory limb including a first section with a first heater wire, a second section with a second heater wire, and a temperature sensor positioned at a patient end of the second section to measure a patient end parameter. The first and second heater wires can be electrically coupled, the first heater wire forming a first heater circuit and the first and second wires forming a second heater circuit, the first and second heater wires configured to heat respiratory gas passing through the inspiratory limb. The respiratory humidification system can include a flow sensor in a flow path of the system and configured to measure a flow rate of the respiratory gas. The respiratory humidification system can include a hardware processor in electrical communication with the first and second heater wires and the temperature sensor and the flow sensor. The hardware processor can be configured to execute software instructions that can cause the processor to control the first and second heater circuits. The processor can be configured to heat the respiratory gas using a first heater circuit until a maximum temperature is reached at the first heater wire when the difference between the output of the sensor and the patient-end parameter set point is less than a predetermined error threshold. The processor can be configured to heat the respiratory gas using a second heater circuit when the difference between the output of the sensor and the patient-end parameter set point is equal to or greater than a predetermined error threshold. The maximum power provided to the first heater circuit can be a first maximum or a second maximum based on the flow rate, the first maximum being greater than the second maximum.

[0014] In some embodiments, the maximum power can be a first maximum when the measured flow rate is greater than the flow rate threshold and a second maximum when the measured flow rate is less than the flow rate threshold. In some embodiments, the flow rate threshold can be between about 2.4 lpm and about 5 lpm. In some embodiments, the flow rate threshold can be about 3.5 lpm. In some embodiments, the flow rate threshold can be about 3 lpm.

[0015] In other embodiments, a first maximum power may be provided to the first heater circuit and when the measured flow rate decreases to a high-low flow threshold, the maximum power provided to the first heater circuit may switch to a second maximum power. A second maximum power may be provided to the first heater circuit and when the flow rate increases to a low-high flow threshold, the maximum power provided to the first heater circuit may switch to the first maximum power, the high-low flow threshold being lower than the low-high flow threshold. In some embodiments, the high-low flow threshold may be between about 2.4 lpm and about 5 lpm. In some embodiments, the low-high flow threshold is about 6.5 lpm.

[0016] In some embodiments using a flow sensor, a portion of a first segment of the inspiratory limb adjacent to the second segment can be exposed to the same ambient environment as the second segment. In some embodiments, the portion of the first segment and the second segment can be inside the incubator, and the remaining portion of the first segment can be outside the incubator.

[0017] Reference numbers may be repeated throughout the drawings to indicate a general correspondence between referenced elements. The drawings are provided to illustrate example embodiments described herein and are not intended to limit the scope of the present disclosure. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 illustrates an exemplary respiratory humidification system for delivering humidified gas to a user, the respiratory humidification system having a breathing circuit that includes a segmented inspiratory limb having a sensor within each segment. [Diagram 2] FIG. 1 illustrates a segmented inspiratory limb for use with a humidification system having an intermediate connector configured to join heater wires and sensors in the two segments. [Figure 3A]FIG. 1 is an exemplary circuit diagram including an active rectifier power supply for providing power to heater wires in a segmented inspiratory limb of a breathing circuit, the circuit being configured to power the heater wires in a first segment of the inspiratory limb in a first mode and to power the heater wires in both segments in a second mode. [Figure 3B] FIG. 1 is an exemplary circuit diagram including an active rectifier power supply for providing power to heater wires in a segmented inspiratory limb of a breathing circuit, the circuit being configured to power the heater wires in a first segment of the inspiratory limb in a first mode and to power the heater wires in both segments in a second mode. [Figure 4A] FIG. 1 illustrates an exemplary humidification system having an inspiratory limb and an expiratory limb, the humidification system configured to control heater wires in both limbs. [Figure 4B] FIG. 1 illustrates an exemplary humidification system having an inspiratory limb and an expiratory limb, the humidification system configured to control heater wires in both limbs. [Figure 4C] FIG. 1 illustrates an exemplary humidification system having an inspiratory limb and an expiratory limb, the humidification system configured to control heater wires in both limbs. [Figure 4D] FIG. 1 illustrates an exemplary humidification system having an inspiratory limb and an expiratory limb, the humidification system configured to control heater wires in both limbs. [Diagram 5] FIG. 1 is a block diagram of an exemplary system configured to detect the presence of an inspiratory limb extension and provide power to heater wires in the inspiratory limb, the inspiratory limb extension, and the expiratory limb. [Figure 6A] FIG. 2 illustrates an exemplary circuit diagram in a humidification system, where the circuit is configured to read data from two sensors. [Figure 6B] FIG. 2 illustrates an exemplary circuit diagram in a humidification system, where the circuit is configured to read data from two sensors. [Figure 7]FIG. 1 is an exemplary circuit diagram in a humidification system, where the circuit is configured to read temperature data using two transistors. [Figure 8A] FIG. 1 is an example diagram of a hardware configuration for a breathing circuit with an inspiratory limb and an expiratory limb, the inspiratory limb having a first section and a second section. [Figure 8B] FIG. 1 is an example diagram of a hardware configuration for a breathing circuit with an inspiratory limb and an expiratory limb, the inspiratory limb having a first section and a second section. [Figure 9] FIG. 13 shows an exemplary embodiment of a respiratory humidification system that utilizes a microcontroller in the intermediate connector to measure data for controlling heating and reading sensor values ​​at the inspiratory limb. [Figure 10] FIG. 13 is a block diagram of an intermediate connector for the inspiratory limb, the intermediate connector using a microcontroller. [Figure 11] FIG. 11 is a circuit diagram for an exemplary power module and data line converter included in the intermediate connector shown in FIG. [Figure 12] FIG. 11 is a circuit diagram of an exemplary dual optocoupler circuit used with the intermediate connector shown in FIG. 10 to provide bidirectional data communication between the control side and AC side on a circuit board. [Figure 13] FIG. 1 is a circuit diagram of an exemplary humidification system incorporating a digital temperature sensor for use with a breathing circuit having an inspiratory limb with at least two sections. [Figure 14A] FIG. 1 illustrates an exemplary printed circuit board ("PCB") of an intermediate connector. [Figure 14B] FIG. 1 illustrates an exemplary printed circuit board ("PCB") of an intermediate connector. [Figure 14C] 1 illustrates an exemplary embodiment of an intermediate connector. [Figure 14D] 1 illustrates an exemplary embodiment of an intermediate connector. [Figure 15A] FIG. 1 illustrates an exemplary PCB for a patient-end connector. [Figure 15B]1 illustrates an exemplary embodiment of a patient end connector. [Figure 15C] 1 illustrates an exemplary embodiment of a patient end connector. [Figure 15D] 1 illustrates an exemplary embodiment of a patient end connector. [Figure 15E] 1 illustrates an exemplary embodiment of a patient end connector. [Figure 16A] FIG. 13 illustrates an exemplary embodiment of a placement limiter for a segmented inspiratory limb. [Figure 16B] FIG. 13 illustrates an exemplary embodiment of a placement limiter for a segmented inspiratory limb. [Figure 16C] FIG. 13 illustrates an exemplary embodiment of a placement limiter for a segmented inspiratory limb. [Figure 16D] FIG. 13 illustrates an exemplary embodiment of a placement limiter for a segmented inspiratory limb. [Figure 16E] FIG. 13 illustrates an exemplary embodiment of a placement limiter for a segmented inspiratory limb. [Figure 17A] FIG. 2 is a side view of a section of an exemplary composite pipe. [Figure 17B] 17B is a longitudinal cross-sectional view of the upper portion of a tube similar to the exemplary composite tube of FIG. 17A. [Figure 17C] FIG. 11 is another longitudinal cross-sectional view showing a first elongated member within a composite tube. [Figure 17D] FIG. 2 is another longitudinal cross-sectional view of the upper part of the tube. [Figure 17E] FIG. 2 is another longitudinal cross-sectional view of the upper part of the tube. [Figure 18A] FIG. 13 is a transverse cross-sectional view of a second elongated member within a composite tube. [Figure 18B] FIG. 11 is another transverse cross-sectional view of the second elongated member. [Figure 18C] FIG. 13 illustrates another exemplary second elongated member. [Figure 18D] FIG. 13 illustrates another exemplary second elongated member. [Figure 18E] FIG. 13 illustrates another exemplary second elongated member. [Figure 18F]FIG. 13 illustrates another exemplary second elongated member. [Figure 18G] FIG. 13 illustrates another exemplary second elongated member. [Figure 19A] 11A-11C illustrate examples of first elongated member shapes configured to improve thermal efficiency. [Figure 19B] 11A-11C illustrate examples of first elongated member shapes configured to improve thermal efficiency. [Figure 19C] 11A-11C illustrate examples of first elongated member shapes configured to improve thermal efficiency. [Figure 19D] FIG. 1 illustrates an example of a filament configuration configured to improve thermal efficiency. [Figure 19E] FIG. 1 illustrates an example of a filament configuration configured to improve thermal efficiency. [Figure 19F] FIG. 1 illustrates an example of a filament configuration configured to improve thermal efficiency. [Figure 20A] FIG. 13 is a diagram showing an example of a stack of first elongated members. [Figure 20B] FIG. 2 is a diagram showing an example of a stack of first elongated members. [Figure 20C] FIG. 13 is a diagram showing an example of a stack of first elongated members. [Figure 21A] FIG. 1 is an exemplary circuit diagram configured to independently control two heaters. [Figure 21B] FIG. 1 is an exemplary circuit diagram configured for gating two heaters. [Figure 21C] FIG. 13 is an example circuit diagram configured to switch between independent and gated control of two heaters. [Figure 22A] FIG. 13 is an example circuit diagram including a logic module and mode relay configured to enable control of two heaters or a sectionalized heater. [Figure 22B] FIG. 1 is a block diagram of a mode relay configured to control two heaters. [Figure 22C] FIG. 1 is a block diagram of a mode relay configured to control a sectionalized heater. [Diagram 23] FIG. 22B is an example circuit diagram configured to switch between independent control of two heaters and gated control of two heaters and to provide the functionality described with respect to the example circuit diagram shown in FIG. 22A. [Figure 24A] FIG. 1 is an exemplary circuit diagram configured to control two heaters in parallel. [Figure 24B] 24B illustrates an example configuration of the heater module shown in FIG. 24A in which both heaters include diodes for controlling current flow. [Figure 24C] FIG. 24B illustrates an exemplary circuit diagram shown in FIG. 24A configured to control a segmented heater by using a heater module. [Figure 24D] FIG. 24D illustrates an exemplary configuration of the heater module shown in FIG. 24C. [Figure 25A] FIG. 13 is another example circuit diagram configured to control two heaters in parallel using an active commutation circuit. [Figure 25B] FIG. 13 is another example circuit diagram configured to control two heaters in parallel using an active commutation circuit. [Figure 25C] FIG. 13 is another example circuit diagram configured to control two heaters in parallel using an active commutation circuit. [Figure 26] 4 is a flow chart of an exemplary method for controlling a segmented heater. [Figure 27] FIG. 1 illustrates a target temperature profile. [Figure 28] FIG. 2 is a functional block diagram illustrating the relationship between the processing components of the control module, the demands associated with the heater sections, and the application of the control module's decisions. [Figure 29] 4 is a flow chart of an exemplary control algorithm. [Diagram 30] 4 is a flow chart of an exemplary PID control scheme. [Diagram 31] 4 is a flow chart of another exemplary control algorithm. [Figure 32A] FIG. 1 illustrates an exemplary intermediate connector. [Figure 32B] FIG. 1 illustrates an exemplary intermediate connector. [Figure 32C] FIG. 1 illustrates an exemplary intermediate connector. [Figure 33A] 1 illustrates an exemplary cover for an intermediate connector. [Figure 33B] 1 illustrates an exemplary cover for an intermediate connector. [Figure 33C] 1 illustrates an exemplary cover for an intermediate connector. [Diagram 34] FIG. 13 illustrates an exemplary embodiment of inspiratory and extension limbs with heater wires directly bonded to each other with diodes. [Diagram 35] 4 is a flow chart of another exemplary control algorithm. [Diagram 36] 4 is a flow chart of another exemplary control algorithm. [Figure 37] 4 is a flow chart of another example PID control scheme. [Figure 38] FIG. 13 illustrates another exemplary embodiment of an intake line for use with a humidification system. [Figure 39A] FIG. 1 illustrates an exemplary configuration of inspiratory and extension limbs for an incubator. [Figure 39B] FIG. 1 illustrates an exemplary configuration of inspiratory and extension limbs for an incubator. [Diagram 40] 11 is a flow chart of another exemplary control algorithm with a low flow control component. [Diagram 41] 5 is a flow chart of another example low flow control component. [Diagram 42] FIG. 13 illustrates another exemplary PCB of the intermediate connector. [Diagram 43] FIG. 13 illustrates another exemplary PCB for the patient end connector. [Figure 44A] FIG. 1 illustrates an exemplary PCB for the chamber edge connector. [Figure 44B] FIG. 1 illustrates an exemplary PCB for the chamber edge connector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Specific embodiments and examples of segmented inspiratory limb, multi-zone heating, and inspiratory and / or expiratory limb heating are described herein. Those skilled in the art will appreciate that the present disclosure encompasses the specifically disclosed embodiments and / or uses, as well as obvious modifications and equivalents thereof. Thus, it is not intended that the scope of the present disclosure disclosed herein be limited by any specific embodiments described herein.

[0020] Described herein are systems and methods for providing heat to a segmented inspiratory limb or to the inspiratory and / or expiratory limb in a breathing circuit of a respiratory humidification system. While most of the description herein is in the context of a segmented inspiratory and / or expiratory limb in a breathing circuit, it should be understood that one or more features of the present disclosure may also be implemented in other scenarios where it is desirable to provide differential heating within segmented gas delivery lines or independent heating of separate gas delivery lines, for example in respiratory, surgical, or other applications.

[0021] The present disclosure refers to heater wires, heating elements, and / or heaters in the context of providing heat to a conduit. For example, heater wire is a broad term and should be interpreted in its ordinary and customary sense to one of ordinary skill in the art (i.e., not limited to a special or specialized sense), including, but not limited to, heater strips and / or heat transfer elements that generate heat when power is provided. Examples of such heating elements include wires formed from conductive metals (e.g., copper), conductive polymers, conductive inks printed on the surface of a conduit, conductive materials used to create tracks in a conduit, and the like. Additionally, the present disclosure refers to conduits, limbs, and medical tubing in the context of gas delivery. For example, tubing is a broad term and should be interpreted in its ordinary and customary sense to one of ordinary skill in the art, including, but not limited to, passages having various cross sections, such as cylindrical and non-cylindrical passages. Certain embodiments may incorporate composite tubing, which may be generally defined as a tube comprising two or more sections, or in particular, in some embodiments, two or more components, as described in more detail below. The segmented limbs with the disclosed medical tubing can also be used within breathing circuits, such as continuous, variable, or bilevel positive airway pressure (PAP) systems, or other forms of respiratory therapy. The terms "conduit" and "limb" should be construed as equivalent to tubing.

[0022] When a heated and humidified breathing tube is used for an incubator or temperature controlled environment (or any area with temperature changes, such as around a radiant warmer used for burn patients or under a blanket used by the patient), the breathing tube passes through at least two different zones: a cooler zone (such as an area outside the incubator) and a hotter zone (such as an area inside the incubator). If the tube is heated with a single heater along its entire length, one of the zones will tend to be at an undesirable, inappropriate, or suboptimal temperature, depending on which zone is sensed (e.g., which zone contains a temperature sensor). If the heater is controlled by a sensor inside the incubator (such as a patient end temperature sensor), the section outside the incubator will tend to be too cold, which can result in condensation. Conversely, if the heater is controlled by a sensor outside the incubator, the section inside the incubator may be too hot, which can result in gas being delivered to the patient that is too hot. Thus, the present disclosure describes systems and methods that allow for control of heat in a segmented breathing tube. Here, each section has an associated sensor that provides feedback to the control module. Although some embodiments are described herein with respect to two sections, such systems may be expanded to accommodate applications with additional sections, sections, or regions. For example, in one embodiment with three temperature sections, a section of the breathing tube may be heated based at least in part on three different temperature sensors within the section. Additionally, embodiments disclosed herein may control heat delivered to the breathing tube based at least in part on parameters at the patient end, bypassing or ignoring one or more of the sensors at midpoints along the tube. Additionally, embodiments disclosed herein may control heat delivered to the breathing tube using parameters provided by sensors including, for example, but not limited to, temperature sensors, humidity sensors, flow sensors, oxygen sensors, and the like.

[0023] The control module can monitor and control the heating temperature in multiple zones or sections. The control module can be configured to provide heat to a first section of the breathing tube in a first mode and to the entire breathing tube in a second mode using some embodiments of the connector assembly described herein. Some embodiments described herein can be used without flying leads, exposed connectors, and / or patient-end electrical connections. The term "flying leads" as used herein includes electrical connections that extend external to the breathing tube, electrical connections that extend internally through the breathing tube, and electrical connections that are incorporated, molded, or otherwise formed or included as part of the breathing tube. The control module can be located inside the humidifier or outside the humidifier. In some embodiments, the control module is located inside the humidifier to control heater wires associated with the first section of the inspiratory limb, the second section of the inspiratory limb, and the expiratory limb, and to read parameters from sensors associated with the first and second sections of the inspiratory limb and / or the expiratory limb. In some embodiments, the control module is configured to independently control a heater wire associated with the inspiratory limb and a heater wire associated with the expiratory limb.

[0024] The control module may also adaptively change temperatures associated with the segments. For example, the control module may monitor temperature sensors associated with one or more segments. The monitoring may be continuous, periodic, interrupt or event-based, or other manner. For example, the monitoring of the temperature sensors may be based on reading values ​​from an analog-to-digital converter, determining a voltage or current, sensing a logical condition, reading a thermostat device, measuring a thermistor value, measuring a resistance temperature detector, measuring a thermocouple voltage, or other methods for sensing temperature, such as, but not limited to, using a semiconductor junction sensor, an infrared or thermal radiation sensor, a thermometer, an indicator, etc. In some embodiments, the temperature sensor is a thermistor.

[0025] In some embodiments, the ratio of power delivered to a first section of the inspiratory limb and a second section of the inspiratory limb can be varied during use based at least in part on feedback from sensors associated with each section. For example, the ratio of power can be varied such that each section is heated to a temperature that reduces or prevents condensation. As a further example, the ratio of power can be varied such that too hot gas is not provided to the patient. In some embodiments, the ratio of power can be varied continuously based on feedback from sensors (e.g., temperature sensors, humidity sensors, oxygen sensors, flow sensors, etc.). The ratio of power can be varied in a variety of ways. For example, the ratio of power can be varied by modifying the amplitude (including but not limited to voltage and / or current) of the power signal, the duration of the power signal, or the duty cycle of the power signal, or by other suitable modifications to the power signal. In one embodiment, the ratio of power is varied by changing the magnitude of the current provided. Similarly, in some embodiments, the ratio of power delivered to the inspiratory limb and the expiratory limb can be varied during use based at least in part on feedback from sensors associated with each limb.

[0026] Some embodiments provide an inspiratory limb with heater wires that are not internal to the gas path, but rather are contained within a material that separates the heater wires from the gas path and insulates them from the external environment. In some embodiments, the circuitry used to provide power to the heater wires in the section and to read the sensors is internal to the inspiratory limb so that it is not exposed to the external environment. In some embodiments, the heater wires are molded into the inspiratory or expiratory tubing such that the ends of the heater wires in the complementary section of the tubing contact an intermediate connector such that the heater wires are electrically coupled to the intermediate connector, where the intermediate connector can be configured to provide circuitry for heater wire control and / or sensor reading. In some embodiments, the duty cycle of the power source applied to the heater wires can be adjusted, modified and / or changed to vary the amount of heat delivered to the gas as it flows along the associated section or limb.

[0027] Some embodiments described herein provide a respiratory humidification system configured to deliver warm humidified gas to a patient or other user. The gas is passed through a liquid chamber filled with liquid (e.g., water) that is heated using a heater plate. The liquid evaporates in the chamber and mixes with the gas flowing over it, thereby heating and / or humidifying the gas. The humidified gas can be delivered to an inspiratory limb having one or more heater wires associated therewith. The heater wires can be selectively powered to provide a predetermined, desired, suitable, or selected amount of heat to the humidified gas. In some embodiments, the respiratory humidification system can be used with an incubator or radiant warmer or a temperature-controlled environment. The temperature-controlled environment can be a substantially sealed environment in which the temperature within the environment is tightly controlled within predetermined temperature limits. The temperature-controlled environment referred to defines a sealed enclosure that includes strict temperature control. The inspiratory limb can be compartmentalized such that a first compartment is outside the incubator and a second compartment is inside the incubator. Further, a first heater wire set can be associated with the first section and a second heater wire set can be associated with the second section. The humidification system can be configured to provide power to the first heater wire set in a first mode and to the second heater wire set in a second mode. In some embodiments, the humidification system can be configured to provide power to the first heater wire set in a first mode and to the second heater wire set in a second mode. In some embodiments, the first section or first set of heater wires is heated and both the first and second sets of heater wires are heated only when there is a sudden change in the temperature controlled environment or in the incubator, such as due to ventilation or a fan or a blanket placed over a sensor of a tube in the incubator. The inspiratory limb can include a sensor at the end of each section to provide feedback to the humidification system for use in selecting power to deliver to the set of heater wires in the section. In some embodiments, the sensor may be located only at the end of the entire tube, and the sensor may be located within a temperature controlled environment or incubator or radiant warmer.In some embodiments, the humidification system may include an expiratory limb having an associated heater wire that is also selectively controlled by the humidification system. In this disclosure, the segmented limb is described with reference to the inspiratory limb, however, the features described may also be applied to the expiratory limb.

[0028] Respiratory Humidification Systems 1 illustrates an exemplary respiratory humidification system 100 for delivering humidified gas to a user, the respiratory humidification system 100 having a breathing circuit 200 including a segmented inspiratory limb 202 having sensors 204a, 204b in each segment. The segmented inspiratory limb 202 may be used with an incubator 208 as shown, or may be used with another system in which there are different temperatures along various segments of the inspiratory limb 202, such as a radiant warmer or a temperature controlled environment. The segmented inspiratory limb 202 may be used to provide different levels of heat to various segments 202a, 202b of the inspiratory limb to reduce or prevent condensation and / or control the temperature of the gas delivered to the user.

[0029] The illustrated respiratory humidification system 100 includes a pressurized gas source 102. In some implementations, the pressurized gas source 102 includes a fan, blower, or the like. In some implementations, the pressurized gas source 102 includes a ventilator or other positive pressure generating device. In some implementations, the gas source may be a pressurized gas storage vessel, and the gas may be provided by an outlet, such as a wall gas source in a hospital. The pressurized gas source 102 includes an inlet 104 and an outlet 106.

[0030] The pressurized gas source 102 provides a flow of fluid (e.g., oxygen, anesthetic gas, air, a mixture of air and oxygen, a gas mixture, etc.) to the humidification unit 108. The flow of fluid proceeds from an outlet 106 of the pressurized gas source 102 to an inlet 110 of the humidification unit 108. In the illustrated configuration, the humidification unit 108 is separate from the pressurized gas source 102 and is removably connectable to the pressurized gas source 102. In the illustrated configuration, the humidification unit 108 is shown independent of the pressurized gas source 102, with the inlet 110 of the humidification unit 108 connected to the outlet 106 of the pressurized gas source 102 by a conduit 112. In some implementations, the pressurized gas source 102 and the humidification unit 108 can be integrated into a single housing.

[0031] Although other types of humidification units may be used to obtain certain features, aspects, and advantages described in this disclosure, the illustrated humidification unit 108 is a pass-over humidifier that includes a humidification chamber 114 and an inlet 110 to the humidification chamber 114. In some implementations, the humidification chamber 114 includes a body 116 to which a base 118 is attached. A compartment may be defined within the humidification chamber 116, the compartment adapted to hold a volume of liquid that may be heated by heat transferred or provided through the base 118. In some implementations, the base 118 is adapted to contact a heater plate 120. The heater plate 120 may be controlled by a controller 122 or other suitable component to vary and control the heat transferred into the liquid.

[0032] The controller 122 of the humidification unit 108 can control the operation of the various components of the respiratory humidification system 100. Although the illustrated system is shown as using a single controller 122, multiple controllers can be used in other configurations. The multiple controllers can communicate or can provide separate functions, and thus the controllers do not need to communicate. In some implementations, the controller 122 can comprise a microprocessor, processing unit, or logic circuitry with associated memory or storage media that includes software code for a computer program. In such implementations, the controller 122 can control the operation of the respiratory humidification system 100 according to instructions contained in, for example, a computer program, and also in response to internal or external inputs. The controller 122, or at least one of the multiple controllers, can be located with the breathing circuit, attached to the breathing circuit, or incorporated as part of the breathing circuit.

[0033] The body 116 of the humidification chamber 114 includes a port 124 that defines an inlet 110 of the humidification chamber 114, and a port 126 that defines an outlet 128. When a liquid contained within the humidification chamber 114 is heated, liquid vapor is mixed with gas introduced into the humidification chamber 114 through the inlet port 124. The gas and vapor mixture exits the humidification chamber 114 through the outlet port 126.

[0034] The respiratory humidification system 100 includes a breathing circuit 200 with an inspiratory limb 202 connected to an outlet 128 that defines an outlet port 126 of the humidification unit 108. The inspiratory limb 202 carries the mixture of gas and water vapor exiting the humidification chamber 114 toward the user. The inspiratory limb 202 can include a heating element 206 positioned along the inspiratory limb 202 that is configured to reduce condensation along the inspiratory limb 202 to control the temperature of the gas reaching the user, maintain the humidity of the gas, or any combination thereof. The heating element 206 can increase or maintain the temperature of the mixture of gas and water vapor carried by the inspiratory limb 202. In some implementations, the heating element 206 can be a wire that defines a resistive heater. By increasing or maintaining the temperature of the mixture of gas and water vapor exiting the humidification chamber 114, water vapor is less likely to condense from the mixture.

[0035] The respiratory humidification system 100 may be used with an incubator 208. The incubator 208 may be configured to maintain a desired environment for a user, such as a selected, predetermined, or desired temperature, inside the incubator 208. Thus, inside the incubator 208, the internal ambient temperature may be different than the temperature outside the incubator 208. Thus, the incubator 208 generates, defines, creates, or maintains zones of different temperatures along the inspiratory limb 202, where the internal temperature is typically higher than the external temperature. Having at least two different temperature zones along the inspiratory limb 202 may create problems during delivery of gas to the user, such as condensation along the inspiratory limb 202, delivery of gas at too high a temperature, or both.

[0036] The respiratory humidification system 100 may include an expiratory limb 210 having an associated heating element 212. In some embodiments, the expiratory limb 210 and the inspiratory limb 202 may be connected using a suitable attachment (e.g., a Y-piece). In some embodiments, the respiratory humidification system 100 may be used with radiant warmers, under blankets, or other systems or situations that create two or more temperature zones. The systems and methods described herein may be used with such systems and are not limited to implementations incorporating incubators.

[0037] The inspiratory limb 202 can be divided into sections 202a and 202b, where the first section 202a can be the portion of the inspiratory limb 202 that is outside the incubator 208 and the second section 202b (e.g., an incubator extension) can be the portion of the inspiratory limb 202 that is inside the incubator 208. The first section 202a and the second section 202b can be of different lengths or the same length. In some embodiments, the second section 202b can be shorter than the first section 202a, and in certain implementations, the second section 202b can be about half the length of the first section 202a. The first section 202a can have a length of, for example, at least about 0.5 m and / or no more than about 2 m, at least about 0.7 m and / or no more than about 1.8 m, at least about 0.9 m and / or no more than about 1.5 m, or at least about 1 m and / or no more than about 1.2 m. The second section 202b can have a length of, for example, at least about 0.2 m and / or no more than about 1.5 m, at least about 0.3 m and / or no more than about 1 m, at least about 0.4 m and / or no more than about 0.8 m, or at least about 0.5 m and / or no more than about 0.7 m.

[0038] The inspiratory limb sections 202a, 202b can be coupled together to form a single gas delivery conduit. In some embodiments, the first section 202a can include one or more first heater wires 206a and one or more first sensors 204a, and can be used without the second section 202b. The controller 122 can be configured to control the first heater wires 206a and read the first sensor 204a even when the second section 202b is not coupled to the first section 202a. Additionally, when the second section 202b is coupled to the first section 202a, the controller 122 can be configured to control the first and second heater wires 206a, 206b in the respective sections and read the first and second sensors 204a, 204b. In some embodiments, the controller 122 can be configured to control the respective first and second heater wires 206a, 206b and read the respective first and second sensors 204a, 204b when the second section 202b is attached, and can be configured to control the first heater wire 206a and read the first sensor 204a when the second section 202b is not attached, without requiring modification of the controller 122 or the humidification unit 108. Thus, the same controller 122 and / or humidification unit 108 can be used regardless of whether the inspiratory limb 202 includes both the first and second sections 202a and 202b, or only the first section 202a. In some embodiments, the controller 122 can be further configured to control the heater wires 212 in the expiratory limb 210 without modification of the controller 122 or the humidification unit 108. Thus, the respiratory humidification system 100 can operate with or without the second section 202b attached, and / or with or without the expiratory limb 210 attached. It should be appreciated that without the second section 202b, the first section 202a of the inspiratory limb 202 can function as a standalone inspiratory limb, such as when a patient interface is attached to the end of the first section to provide gas to a patient.In some configurations, the controller 122 may control both the first and second segments 202a, 202b, or only the first segment 202a or only the second segment 202b.

[0039] In one configuration, the controller 122 is configured to control the first and second segments 202a, 202b, or just the first segment 202a, based solely on readings from the sensor 204b. In this configuration, the intake pipe 202 may include only one sensor 204b located at the end of the second segment, without the intermediate sensor 204a.

[0040] In some embodiments, the first section 202a and the second section 202b are permanently joined together to form a single gas delivery conduit. As used herein, "permanently joined" means that the sections 202a, 202b are joined together such that it is difficult to separate them, for example, by using adhesives, friction fits, overmolding, mechanical connectors, etc. In some embodiments, the first section 202a and the second section 202b are configured to be releasably coupled. For example, the first section 202a can be used for gas delivery without the second section 202b, or the first section 202a and the second section 202b can be coupled together to form a single gas delivery conduit. In some embodiments, the first section 202a and the second section 202b can be configured to be coupled together in a unique configuration. For example, the first section 202a can have a predetermined chamber end (e.g., an end closest to the chamber 114 or the humidification unit 108 along the direction of flow of humidified gas to the patient) and a predetermined patient end (e.g., an end closest to the patient along the direction of flow of humidified gas to the patient), where the chamber end is configured to couple to components at the chamber 114 and / or the humidification unit 108. The second section 202b can have a predetermined chamber end and a predetermined patient end, where the chamber end is configured to couple only to the patient end of the first section 202a. The chamber end of the first section 202a can be configured not to couple to either end of the second section 202b. Similarly, the patient end of the first section 202a can be configured not to couple to the patient end of the second section 202b. Similarly, the patient end of the second section 202b can be configured not to couple to either end of the first section 202a. Thus, the first section 202a and the second section 202b can be configured to couple in only one direction to form a single gas delivery conduit. In some embodiments, the first section 202a and the second section 202b can be configured to couple in a variety of configurations.For example, the first and second segments 202a and 202b can be configured to not include a predetermined patient end and / or a predetermined chamber end. As another example, the first and second segments 202a and 202b can be configured such that the patient end and / or chamber end of the first segment 202a can be coupled to the chamber end or patient end of the second segment 202b. Similarly, the first and second segments 202a and 202b can be configured such that the chamber end and / or patient end of the second segment 202a can be coupled to the patient end or chamber end of the second segment 202b.

[0041] The respiratory humidification system 100 includes an intermediate connector 214 that can be configured to electrically couple elements of the first and second segments 202a and 202b of the inspiratory limb 202. The intermediate connector 214 can be configured to electrically couple the heater wires 206a of the first segment 202a to the heater wires 206b of the second segment 202b to enable control of the heater wires 206a, 206b with the controller 122. The intermediate connector 214 can be configured to electrically couple the second sensor 204b of the second segment 202b to the first sensor 204a of the first segment to enable the controller 122 to obtain the outputs of each of the sensors. The intermediate connector 214 can include electrical components that enable selective control of the heater wires 206a, 206b and / or selective reading of the sensors 204a, 204b. For example, the intermediate connector 214 may include electrical components that transmit power through the first heater wire 206a in a first mode and through the first and second heater wires 206a, 206b in a second mode. Electrical components included in the intermediate connector 214 may include, for example, but are not limited to, resistors, diodes, transistors, relays, rectifiers, switches, capacitors, inductors, integrated circuits, microcontrollers, microprocessors, RFID chips, wireless communication sensors, and the like. In some embodiments, the intermediate connector 214 may be configured within the inspiratory limb 202 such that it is substantially shielded from external elements (e.g., less than 1% of water, particulates, contaminants, and the like from the environment outside the inspiratory limb 202 contacts the intermediate connector 214). In some embodiments, some of the electrical components in the intermediate connector 214 may be configured to be physically isolated from the humidified gases within the inspiratory limb 202 to reduce or prevent damage that may occur due to exposure to moisture. In some embodiments, the intermediate connector 214 may include relatively inexpensive passive electrical components to reduce cost and / or increase reliability.

[0042] The inspiratory limb 202 may include sensors 204a, 204b in each section 202a, 202b of the inspiratory limb. The first sensor 204a may be positioned near the end of the first section 202a, near the incubator 208, such that a parameter derived from the first sensor 204a corresponds to a parameter of the humidified gas entering the second section 202b. The second sensor 204b may be positioned near the end of the second section 202b, such that a parameter derived from the second sensor 204b corresponds to a parameter of the humidified gas delivered to the patient or user. The output of the sensors 204a, 204b may be sent to the controller 122 as feedback for use in controlling the power delivered to the heating elements 206a, 206b of the inspiratory limb sections 202a, 202b. In some embodiments, one or both of the sensors 204a, 204b may be a temperature sensor, a humidity sensor, an oxygen sensor, a flow sensor, etc. The temperature sensor may be any suitable type of temperature sensor including, for example, without limitation, a thermistor, a thermocouple, a digital temperature sensor, a transistor, etc. Parameters provided by or derived from the sensor may include, for example, without limitation, temperature, humidity, oxygen content, flow rate, or any combination thereof, etc.

[0043] The controller 122 can be configured to control the heater wires 206a and 206b, receive feedback from the sensors 204a and 204b, provide logic for controlling power to the heater wires 206a and 206b, adjust control of the heater wires 206a and 206b in response to readings from the sensors 204a and 204b, detect the presence of the second segment 202b of the inspiratory limb 202, derive parameters from readings from the sensors 204a and 204b, and the like. In some embodiments, the controller 122 includes a power source configured to send power to the heater wires. The power source may be an AC or DC power source. In some embodiments, the controller 122 can receive input from a heater plate sensor 130. The heater plate sensor 130 can provide the controller 122 with information regarding the temperature and / or power usage of the heater plate 120. In some embodiments, the controller 122 can receive input from a flow sensor 132. Any suitable flow sensor 132 may be used, and the flow sensor 132 may be positioned between the ambient air and the humidification chamber 114, or between the pressurized gas source 102 and the humidification chamber 114. In the illustrated system, the flow sensor 132 is positioned at the inlet port 124 of the humidification chamber 114.

[0044] Segmented inspiratory limb 2 illustrates a portion of a segmented inspiratory limb 202 for use with the respiratory humidification system 100, the segmented inspiratory limb 202 comprising a first segment 202a and a second segment 202b, and having an intermediate connector 214 configured to couple a first heater wire 206a to a second heater wire 206b and a first sensor 204a to a second sensor 204b within segments 202a and 202b, respectively. Coupling the two segments 202a and 202b may include mechanically coupling the segments to form a single conduit through which humidified gas can be delivered to a user, where the mechanical coupling of segments 202a and 202b allows the respective heater wires 206a, 206b to be electrically coupled to the respective sensors 204a, 204b by the intermediate connector 214.

[0045] The segmented inspiratory limb 202 can comprise a structure 216 that forms a lumen through which the humidified gas can pass. The structure 216 can include a passage formed in a wall of the structure 216 configured to accommodate the heater wire 206a or 206b, such that the heater wire 206a or 206b is covered by an outer surface of the structure 216 so as to be shielded from and / or not exposed to the humidified gas traveling through the lumen. For example, the structure 216 can be a spiral bubble tube, and the heater wire passage is a coil molded within the tube. The structure 216 can comprise any type of suitable material, and can include insulating and / or flexible materials. In some embodiments, the structure 216 and intermediate connector 214 can be configured to wrap around the intermediate connector 214 such that the heater wires 206a and 206b are electrically coupled to the intermediate connector 214 when the first section 202a and the second section 202b are mechanically coupled. In some embodiments, the first section 202a and / or the intermediate connector 214 may eliminate flying leads for connecting to the second section 202b, thereby facilitating connection of the second section 202b to the first section 202a.

[0046] Structures 216 at the complementary ends of the first and second segments 202a, 202b can be configured to receive the intermediate connector 214. Thus, the intermediate connector 214 can be internal to the inspiratory limb 202. In some embodiments, the complementary ends of the first and second segments 202a, 202b can be configured to shield the intermediate connector 214 from humidified gas traveling through the inspiratory limb 202. In some embodiments, the intermediate connector 214 is internal to the inspiratory limb 202 and is shielded from humidified gas in the lumen, thereby reducing or preventing exposure of electrical connections at the intermediate connector 214. In an exemplary configuration, the intermediate connector, or at least the portion of the intermediate connector 214 that is internal to the lumen, is overmolded with a silicone or plastic material to form a protective layer or coating.

[0047] In some embodiments, the first heater wire 206a can comprise two wires 218 and 220, and the second heater wire 206b can comprise two wires 222 and 224. The two wires 218 and 220 of the first section 202a can be electrically coupled to each other via an electrical component 228, the electrical coupling creating an electrical path through the wire 218, at least a portion of the electrical component 228, and the wire 220. Similarly, the two wires 222 and 224 of the second section 202b can be electrically coupled to each other via the electrical component 228 and / or electrically shorted to each other at an end of the section 202b opposite the intermediate connector 202b, e.g., via a patient end connector (not shown) described in more detail herein with reference to Figures 3A, 3B, 8A, 8B, 9, and 13. By joining the wires 222 and 224 of the second section 202b at the intermediate connector 214, electrical connections at the patient end of the inspiratory limb 202 are reduced or eliminated, which can reduce cost, system complexity, and / or risk to the patient.

[0048] The intermediate connector 214 can be configured to allow a single controller to control power to the heater wires 206a, 206b, which can be the humidifier controller 122 described herein with reference to FIG. 1. In some embodiments, the humidifier controller 122 controls the heater wires without additional control functionality located in the intermediate connector 214. For example, the intermediate connector 214 can include passive components without logic circuitry, which send power to the heater wires 206a and / or 206b selected by the controller 122. This can allow the intermediate connector 214 to be designed using relatively inexpensive components, reducing design complexity.

[0049] In some embodiments, heating of sections 202a and 202b can be accomplished using up to four wires in each section 202a, 202b. For example, in the first section 202a, the four wires can include a first heater wire 218, a second heater wire 220, a signal sensor wire 228, and a return sensor wire 230. In the second section 202b, the four wires can include a first heater wire 222, a second heater wire 224, a signal sensor wire 232, and a return sensor wire 234. By coupling the second heater wires 222, 224 to the first heater wires 218, 220 at connection points 226, and by coupling the second sensor wires 232, 234 to the first sensor wires 228, 230 at connection points 226, the controller can be configured to provide power to the first heater wires 206a and the second heater wires 206b individually and read sensor data from the sensors 204a and 204b individually, without including more than four wires in the segments 202a or 202b. In some embodiments, control of the heater wires 206a and 206b, and reading of the sensors 204a and 204b can be accomplished using three or fewer wires in each segment (e.g., using three wires, or using two wires), or using five or more wires in each segment (e.g., using five wires, using six wires, using seven wires, using eight wires, or using nine or more wires).

[0050] The intermediate connector 214 may include electrical components 228 configured to allow the controller 122 to selectively control the heater wires 206a, 206b. The controller 122 may be configured to control the heating of the inspiratory limb 202 using two modes, a first control mode including providing power to the heater wires 206a in the first section and a second control mode including providing power to the heater wires 206a and 206b in the first and second sections 202a and 202b. Thus, the controller 122 may be configured to control the heater wire sections individually. This feature allows the controller 122 to control the heating of the inspiratory limb 202 by only controlling the heating of the inspiratory limb according to the first control mode when the second section 202b is not present, thereby allowing the respiratory humidification system 100 to be used in a variety of situations without modifying the controller 122 or the humidification unit 108. In some embodiments, the control mode can include a mode in which power is sent only to the heater wires 206b in the second section 202b. In some embodiments, the controller 122 includes a power source that provides a current. The first and second control modes can be based at least in part on the voltage provided by the power source, where a positive voltage or a positive current can trigger the first control mode and a negative voltage or a negative current can trigger the second control mode. In some embodiments, the power source provides rectified AC or DC power to the heater wires 206a, 206b, and a change in rectification or polarity triggers a change in control mode. By switching between control modes, control of heating in the breathing circuit 200 can be achieved with any power source that can switch the polarity of its output signal. In some embodiments, the amount of power provided to the heater wires 206a, 206b can be adjusted by adjusting the duty cycle of the power applied to the heater wires 206a, 206b. For example, pulse width modulation (PWM) can be used to power the heater wires 206a, 206b, and the duty cycle of the PWM can be adjusted to control the power delivered.In another example, the amount of power provided to the heater wires 206a, 206b can be adjusted by controlling the amplitude of the power signal.

[0051] The intermediate connector 214 can include electrical components 230 configured to allow the controller 122 to selectively read the sensors 204a, 204b. As described herein with reference to Figures 6A, 6B, and 7, selective reading can be accomplished through the use of a current source, where a positive current across wires 228-230 causes the controller 122 to measure a signal from the first sensor 204a, and a negative current across wires 228 and 230 causes the controller 122 to measure a signal from the second sensor 204b, or from both the first and second sensors 204a, 204b. The controller 122 can use the readings from the sensors 204a, 204b to adjust power to the heater wires 206a, 206b, for example, using pulse width modulation. A first sensor 204a may be positioned near the junction or intersection of the first and second sections 202a, 202b and provides the controller 122 with parameters of the gas entering the second section 202b (which may correspond to entering an incubator or other such area having a different ambient temperature). A second sensor 204b may be positioned at the patient end of the second section 202b and provides the controller 122 with parameters of the gas being delivered to the patient or before the final piece upstream of the patient, such as a Y-piece. The controller 122 can use these readings to adjust the power to the heater wires 206a, 206b to maintain the temperature of the gas at the patient end of the inspiratory limb 202 at a target or appropriate temperature. The target or suitable temperature may vary, at least in part, depending on the application and environment in which it is used, and may be about 37° C., about 40° C., at least about 37° C. and / or about 38° C. or less, at least about 36.5° C. and / or about 38.5° C. or less, at least about 36° C. and / or about 39° C. or less, at least about 35° C. and / or about 40° C. or less, at least about 37° C. and / or about 41° C. or less, or at least about 39.5° C. and / or about 40.5° C. In some embodiments, the second sensor 204b may be positioned inside the incubator, but not attached to the breathing circuit.For example, the temperature of the second section 202b can be calculated by measuring a parameter inside the incubator.

[0052] The controller 122 can independently control the amount of power delivered in the first and second control modes, as described herein. Based at least in part on feedback from the sensors 204a and / or 204b, the controller 122 can independently adjust the power delivered in the first and second control modes, thereby varying the ratio of heater power to the first segment 202a and the second segment 202b.

[0053] In some embodiments, the first sensor 204a is positioned in the gas flow within the inspiratory limb 202. In some embodiments, the intermediate connector 214 or the first section 202a can include mechanical components that reduce turbulence in the gas flow across the first temperature sensor 204a, which can increase the accuracy of the sensor 204a reading. For example, the mechanical connector can have an aerodynamic cross-section, some examples of which are described for the patient end connector with reference to Figures 15B-15E. In some embodiments, the mechanical components that reduce turbulence (e.g., cross-members within the inspiratory line) also secure the sensor 204a in the gas flow. In some embodiments, the intermediate connector 214 and mechanical components are configured to insulate the sensor 204a from electrical components in the intermediate connector 214, which can be advantageous, for example, when the sensor 204a is a temperature sensor.

[0054] In some embodiments, the intermediate connector 214 includes additional connection points in addition to the connection points 226 shown in Figure 2. The additional connection points can be used to incorporate additional functionality into the breathing circuit, such as a memory device (PROM) or (EPROM), a microcontroller, additional circuitry, etc.

[0055] Intermediate Connector Circuit 3A shows a circuit diagram of an exemplary intermediate connector 214, which includes an active rectifying power supply for providing power to heater wires in a segmented inspiratory limb of a breathing circuit, the circuit being configured to power heater wires R1 and R2 in a first segment of the inspiratory limb in a first mode, and heater wires R1, R2, R3, R4 in both segments in a second mode. Alternatively, power can be applied through heater wires R1 and R2 (where resistors are heater wires) or through heater wires R1, R2, R3, and R4 by providing diodes D1 and D2 and switches S1 and S2 in the intermediate connector 214.

[0056] The power source is indicated in the figures with the labels VP and VN, which correspond to the terminals of the power source. In one embodiment, the voltage supply is an alternating current (AC) power source. Alternatively, the power source may be a direct current (DC) power source. Although described as diodes in this embodiment, D1 and D2 may include any of a number of different types of flow control devices, such as, for example, but not limited to, rectifiers, transistors, relays, switches, triacs, MOSFETs, thyristors (SCRs), thermostats, etc.

[0057] Switches S1 and S2 switch between the VP and VN terminals of the power supply. In one embodiment, switches S1 and S2 are switched every half cycle of the AC power cycle, so that approximately equal currents are drawn from the power supply during each half cycle. Using the circuit shown in FIG. 3A, heaters R1, R2, R3, and R4 can be controlled in two control modes, a first control mode corresponding to providing power only to R1 and R2, and a second control mode corresponding to providing power to R1, R2, R3, and R4. To provide power only to heaters R1 and R2 in the first section 202a (which corresponds to the first control mode), during a positive cycle from the power supply, switch S1 connects to VP and switch S2 connects to VN, and during a negative cycle from the power supply, switch S1 connects to VN and switch S2 connects to VP. In the first control mode, current flows through R1, R2, and D1, and D2 prevents current from flowing through R3 and R4. To provide power to the heaters R1, R2, R3, and R4 in the first and second sections 202a, 202b (which corresponds to a second control mode), during a positive cycle from the power source, switch S1 connects to VN and switch S2 connects to VP, and during a negative cycle from the power source, switch S1 connects to VP and switch S2 connects to VN. In the second control mode, current flows through R1, R2, R3, R4, and D2, and D1 prevents current from flowing through the wires and shorting out the heaters R3 and R4. As described herein with reference to FIG. 5, the switching of switches S1 and S2 can be accomplished by hardware or software that adds logic to the system. In some embodiments, the switching of S1 and S2 occurs at the zero crossings of the AC power circuit. In some embodiments, the falling and rising edges of the zero crossing circuit are not delayed by the same amount, and the circuit is not active near the zero crossings. Thus, the switching of switches S1 and S2 can be done with or without zero-crossing switching detection and / or logic.

[0058] Diodes D1 and D2 may dissipate power in the circuit and therefore generate heat. In some embodiments, Schottky diodes may be used when it is desirable to reduce power loss in relatively hot environments. Schottky diodes may be operated near their maximum junction temperature to reduce or minimize power loss, which may be desirable in certain implementations of the respiratory humidification systems described herein. In some embodiments, heat generated by the diodes may affect the temperature readings of the sensor 204a. To reduce this effect, the diodes may be thermally connected to the airflow path of the circuit. To reduce this effect and to dissipate heat generated by the diodes, the intermediate connector 214 may include a heat sink or pad thermally coupled to the ambient environment. To reduce this effect, and the effect of other components on the intermediate connector 214, the sensor 204a (e.g., a thermistor or other temperature sensor) may be insulated from those components and physically located relatively far from the other components, as described with reference to FIGS. 14A-B and 15.

[0059] FIG. 3B shows another circuit diagram of an exemplary intermediate connector 214, which includes an active rectifying power source for providing power to heater wires in a segmented inspiratory limb of a breathing circuit, the circuit being configured to power heater wires R1 and R2 in a first segment of the inspiratory limb in a first mode, and heater wires R1, R2, R3, R4 in both segments in a second mode. As shown in FIG. 3B, only diode D1 can be provided, and the path of power through heater wires R1 and R2 or through heater wires R1-R4 can still be controlled in a manner similar to that described above with respect to FIG. 3A. Diode D2 shown in the circuit of FIG. 3A has been omitted. The circuit shown in FIG. 3B with only one diode D1 can reduce heat generated by the circuit, reduce component costs, and allow for a smaller circuit board. The remainder of the circuit shown in FIG. 3B operates in a manner similar to that described in FIG. 3A. In an embodiment without D2 as shown in Figure 3B, most of the current flows through R1, R2, and D1, and only the residual current flows through R3 and R4. The residual current through R3 and R4 can be neglected and therefore does not affect the performance of the humidification system.

[0060] In addition to the AC operation described with respect to Figures 3A and 3B, a similar circuit can also be operated with a DC power supply. Switches S1 and S2 can be switched based at least in part on, for example, time, the output current of the power supply, feedback from a sensor, or other control input. Also, in such an embodiment, the circuit shown in Figure 3A or 3B can be used to control heaters R1, R2, R3, and R4 in two control modes, where a first control mode corresponds to providing power only to R1 and R2, and a second control mode corresponds to providing power to R1-R4. To provide power only to heaters R1 and R2 in the first section 202a (which corresponds to the first control mode), switch S1 connects to VP and switch S2 connects to VN. In the first control mode, current flows through R1, R2, and D1. D2 prevents current from flowing through R3 and R4 in the circuit shown in Figure 3A. However, as shown in Figure 3B, D2 is an optional component. To provide power to the heaters R1, R2, R3, and R4 in the first and second sections 202a, 202b (which corresponds to a second control mode), switch S1 connects to VN and switch S2 connects to VP. In the second control mode, current flows through R1, R2, R3, R4, and D1 prevents current from flowing through the wires and shorting out the heaters R3 and R4. As previously mentioned, switching can be accomplished by hardware or software that adds logic to the system, as described herein with reference to FIG.

[0061] Inspiratory and expiratory limb heater control 1 further illustrates an exemplary respiratory humidification system 100 having an inspiratory limb 202 and an expiratory limb 210, the humidification system 100 configured to control heater wires 206, 212 in both limbs. In some embodiments, the expiratory heater wires 212 in the expiratory limb 210 can be electrically coupled to the inspiratory heater wires 206 external to the humidification unit 108 and the controller 122, such that control of the expiratory heater wires 212 can be performed without affecting other control modes and without additional switching transistors. Similarly, the expiratory heater wires 212 can also be electrically coupled to the inspiratory heater wires 206 internal to the humidification unit 108. The connection of the expiratory heater wires 212 to the inspiratory heater wires 206 can be made within the humidification system 108, on an intermediate connector 214, in a sensor cartridge in the humidification system 108, or the like. Thus, the controller 122 can control the exhalation heater wires 212 without additional electrical connections at the patient end. The presence of such electrical connections can increase hazards, system complexity, and cost. Examples of electrical couplings between the exhalation heater wires 212 and the inhalation heater wires 206 inside the humidification unit 108 are shown in Figures 4A-4D, 8A, and 8B.

[0062] 4A, the humidification unit 108 may incorporate switches or relays S3 and S4 to select between independent and dependent control of the inspiratory and expiratory heater wires. In some embodiments, the switches or relays are activated when a tube having the appropriate identification (e.g., inspiratory limb or expiratory limb) is connected to the humidification unit 108, for example, by detecting and / or measuring an identification resistor by the humidification unit 108. For example, when the switches are not activated (e.g., both switches S3, S4 are open), the heater wire in the inspiratory limb and / or the heater wire in the expiratory limb may be controlled separately and / or independently.

[0063] When the appropriate tubing is connected or the system determines that the tubing is appropriate, switches S3 and S4 can be closed to simultaneously control the inspiratory and expiratory limbs. The humidification unit 108 can include an inspiratory power supply INSP and an expiratory power supply EXP, where the system can implement switching of each power supply as described herein with reference to FIGS. 3A and 3B. For example, with reference to FIG. 3A, the inspiratory power supply can have switches S1 and S2 configured to selectively send positive and negative cycles to heaters R1-R4. Similarly, with reference to FIG. 4A, the expiratory power supply EXP can include switches configured to selectively send power to the expiratory limb having heaters R5 and R6. In some embodiments, when switches S3 and S4 are closed, both switches in the expiratory power supply EXP can be opened, whereby power is provided to the inspiratory heater wires and the expiratory heater wires by the inspiratory power supply INSP. In some embodiments, the humidification unit 108 does not include an expiratory power supply EXP. In such an embodiment, the inspiratory power supply INSP is used to provide power to the inspiratory heater wires when switches S3 and S4 are open, and to provide power to both the inspiratory and expiratory heater wires when switches S3 and S4 are closed. Thus, the inspiratory limb heater wires 206 can be controlled similarly as described above, but now the system can use switches S3, S4 to simultaneously control power to the expiratory heater wires 212 and the inspiratory heater wires 206 using a unified electrical circuit and / or control system. For example, the humidification unit 108 may operate in two modes for the inspiratory limb 202 (e.g., a first mode in which the humidification unit 108 provides power to heaters R1 and R2 and a second mode in which the humidification unit 108 provides power to heaters R1-R4) while selectively controlling power to heaters R5 and R6 in the expiratory limb, such that the humidification unit 108 may provide power to heaters R5 and R6 or may not provide power to heaters R5 and R6 while operating in the first mode, the second mode, or both modes. As previously discussed, the connection between the inspiratory limb 202 and the expiratory limb 210 may be internal or external to the humidification unit 108.In one embodiment, the connection is made within the sensor cartridge, at the intermediate connector 214, or at another location.

[0064] In some embodiments, an expiratory circuit configured to connect the expiratory heater wires 212 to the controller 122 can be implemented in the intermediate connector 214 shown in FIG. 1. The expiratory circuit can be connected in one or more of several ways. For example, the expiratory circuit can be connected in parallel with the heater wires 206a in the first section 202a or in parallel with the heater wires 206b in the second section 202b. In some embodiments, the intermediate connector 214 can include an internal fly or flying lead that makes the expiratory circuit available at the intermediate connector 214. In some embodiments, the intermediate connector 214 can be connected to an added third channel, thereby eliminating the flying lead between the inspiratory and expiratory circuits. To accommodate such embodiments, a heater wire driver control circuit can be added to the controller 122.

[0065] FIG. 4B illustrates an exemplary embodiment of a humidification system incorporating a power source 405 to provide power to both the inspiratory heater wires R1-R4 and the expiratory heater wires R5 and R6 through a combination of switches or relays S1-S6 and diode D1. In an exemplary embodiment, the humidification system is configured to provide power to the expiratory heater wires when only the inspiratory heater wires R1, R2 in a first section of the inspiratory limb are receiving power (e.g., in a first mode of operation) or when the inspiratory heater wires R1-R4 in both sections are receiving power (e.g., in a second mode of operation). The power source 405 may be any suitable power source, including a power source providing alternating current, for example, in a sine wave, sawtooth wave, square wave, or other form. In some embodiments, the power source 405 may be a transformer providing an alternating current signal at a voltage of at least about 22 VAC, at least about 5 VAC or less than about 30 VAC, at least about 10 VAC or less than about 25 VAC, at least about 12 VAC or less than about 22 VAC.

[0066] With continued reference to FIG. 4B, the humidification system can be configured to provide power to the expiratory heater wires R5, R6 in a first operating mode while the power supply 405 is providing power in the negative cycle. To do so, switches S1, S2, S5, S6 are closed and switches S3, S4 are opened. Current flows from the negative terminal of the power supply 405 through switch S2 and branches to provide power to the heater wires of both the inspiratory and expiratory limbs. In the inspiratory limb, the current flows to the inspiratory heater wire R2, then through D1 to the inspiratory heater wire R1, then through switch S1 back to the positive terminal of the power supply 405. In the expiratory limb, the current flows through switch S6 to the expiratory heater wire R5, then through expiratory heater wire R6, then through switches S5 and S1 back to the positive terminal of the power supply 405.

[0067] Similarly, with continued reference to FIG. 4B, the humidification system can be configured to provide power to the expiratory heater wires R5, R6 in a first operating mode while the power supply 405 is providing power in a positive cycle. To do so, switches S3, S4, S5, S6 are closed and switches S1, S2 are opened. Current flows from the positive terminal of the power supply 405 through switch S3 and branches to provide power to the heater wires of both the inspiratory and expiratory limbs. In the inspiratory limb, current flows through switch S6 to the inspiratory heater wire R2, then through diode D1 to the inspiratory heater wire R1, then through switches S5 and S4 back to the negative terminal of the power supply 405. In the expiratory limb, current flows to the expiratory heater wire R5, then through expiratory heater wire R6, then through switch S4 back to the negative terminal of the power supply 405.

[0068] With continued reference to FIG. 4B, the humidification system can be configured to provide power to the expiratory heater wires R5, R6 in a second operating mode while the power supply 405 is providing power in a positive cycle. To do so, switches S1, S2, S5, S6 are closed and switches S3, S4 are opened. Current flows from the positive terminal of the power supply 405 through switch S1 and branches to provide power to the heater wires of both the inspiratory and expiratory limbs. In the inspiratory limb, the current flows to the inspiratory heater wire R1, then to the inspiratory heater wire R3 without passing through diode D1, then to the inspiratory heater wire R4, then to the inspiratory heater wire R2, then back to the negative terminal of the power supply 405 through switch S2. In the expiratory limb, the current flows through switch S5 to the expiratory heater wire R6, then to the expiratory heater wire R5, then back to the negative terminal of the power supply 405 through switches S6 and S2.

[0069] Similarly, with continued reference to FIG. 4B, the humidification system can be configured to provide power to the expiratory heater wires R5, R6 in a second operating mode while the power supply 405 is providing power in the negative cycle. To do so, switches S3, S4, S5, S6 are closed and switches S1, S2 are opened. Current flows from the negative terminal of the power supply 405 through switch S4 and branches to provide power to the heater wires of both the inspiratory and expiratory limbs. In the inspiratory limb, the current flows through switch S5 to the inspiratory heater wire R1, then to the inspiratory heater wire R3 without passing through diode D1, then to the inspiratory heater wire R4, then to the inspiratory heater wire R2, then back to the positive terminal of the power supply 405 through switches S6 and S3. In the expiratory limb, the current flows to the expiratory heater wire R6, then to the expiratory heater wire R5, then back to the positive terminal of the power supply 405 through switch S3.

[0070] 4C illustrates an exemplary embodiment of a humidification system incorporating a power source 405 to provide power to both the inspiratory heater wires R1-R4 and the expiratory heater wires R5 and R6 through a combination of switches or relays S1-S6 and diodes D1, D2. In an exemplary embodiment, the humidification system is configured to provide power to the expiratory heater wires when only the inspiratory heater wires R1, R2 in a first segment of the inspiratory limb are receiving power (e.g., in a first mode of operation).

[0071] With continued reference to FIG. 4C, the humidification system can be configured to provide power to the expiratory heater wires R5, R6 in a first operating mode while the power supply 405 is providing power in the negative cycle. To do so, switches S1, S2, S5, S6 are closed and switches S3, S4 are opened. Current flows from the negative terminal of the power supply 405 through switch S2 and branches to provide power to the heater wires of both the inspiratory and expiratory limbs. In the inspiratory limb, the current flows to the inspiratory heater wire R2, then through D1 to the inspiratory heater wire R1, then through switch S1 back to the positive terminal of the power supply 405. In the expiratory limb, the current flows through switch S6 and diode D2 to the expiratory heater wire R5, then through expiratory heater wire R6, then through switches S5 and S1 back to the positive terminal of the power supply 405.

[0072] Similarly, with continued reference to FIG. 4C, the humidification system can be configured to provide power to the expiratory heater wires R5, R6 in a first operating mode while the power supply 405 is providing power in a positive cycle. To do so, switches S3, S4, S5, S6 are closed and switches S1, S2 are opened. Current flows from the positive terminal of the power supply 405 through switch S3 and branches to provide power to the heater wires of both the inspiratory and expiratory limbs. In the inspiratory limb, current flows through switch S6 to the inspiratory heater wire R2, then through diode D1 to the inspiratory heater wire R1, then through switches S5 and S4 back to the negative terminal of the power supply 405. In the expiratory limb, current flows through diode D2 to the expiratory heater wire R5, then through expiratory heater wire R6, then through switch S4 back to the negative terminal of the power supply 405.

[0073] With continued reference to FIG. 4C, the humidification system can be configured to provide power only to the inhalation heater wires R1-R4 (and not to the exhalation heater wires R5, R6) in a second mode of operation while the power supply 405 is providing power in the positive cycle. To do so, switches S1, S2, S5, S6 are closed and switches S3, S4 are opened. Current flows from the positive terminal of the power supply 405 through switch S1 to the inhalation heater wire R1, then to the inhalation heater wire R3, inhalation heater wire R4, inhalation heater wire R2 without passing through diode D1, and back to the negative terminal of the power supply 405 through switch S2. Current does not flow through the exhalation heater wires due to diode D2. Diode D2, in conjunction with a switch configured as described above, blocks current flow through the circuit in the positive cycle.

[0074] With continued reference to FIG. 4C, the humidification system can be configured to provide power only to the inhalation heater wires R1-R4 (and not to the exhalation heater wires R5, R6) in a second mode of operation while the power supply 405 is providing power on the negative cycle. To do so, switches S3, S4, S5, S6 are closed and switches S1, S2 are opened. Current flows from the positive terminal of the power supply 405 through switches S4 and S5 to the inhalation heater wire R1, then to the inhalation heater wire R3, the inhalation heater wire R4, the inhalation heater wire R2 without passing through diode D1, and back to the negative terminal of the power supply 405 through switches S6 and S3. Current does not flow through the exhalation heater wires due to diode D2. Diode D2, together with a switch configured as described above, blocks current flow through the circuit on the negative cycle.

[0075] FIG. 4D illustrates an exemplary embodiment of a humidification system incorporating a power source 405 that provides power to both the inspiratory heater wires R1-R4 and the expiratory heater wires R5 and R6 through a combination of switches or relays S1-S6 and diode D1, with the expiratory heater wires R5, R6 electrically coupled to the inspiratory heater wires R1-R4 at the patient ends of the heater wires in the first section of the inspiratory limb, which may result in an intermediate connector, such as any of the intermediate connectors described herein. As described with reference to FIG. 4D, the expiratory heater wires R5, R6 are coupled to the inspiratory heater wires R1-R4 at an intermediate connector, although any suitable location after the inspiratory heater wires in the first section may be used to couple the heater wires of the inspiratory and expiratory limbs. In an exemplary embodiment, the humidification system is configured to provide power to the expiratory heater wires only when the inspiratory heater wires R1-R4 in both sections of the inspiratory limb are receiving power (e.g., only in the second mode of operation).

[0076] With continued reference to FIG. 4D, the humidification system can be configured to provide power to the inspiratory heater wires R1-R4 and the expiratory heater wires R5, R6 in a second mode of operation while the power supply 405 is providing power in a positive cycle. To do so, switches S1, S2, S5, S6 are closed and switches S3, S4 are opened. Current flows from the positive terminal of the power supply 405 through switch S1 to the inspiratory heater wire R1 and then branches to provide power to the heater wires of both the second section of the inspiratory limb and the expiratory limb without passing through diode D1. In the second section of the inspiratory limb, the current flows to the inspiratory heater wire R3 and then to the inspiratory heater wire R4 and back to the intermediate connector. In the expiratory limb, the current flows to R5 and then to R6 and back to the intermediate connector. The current then flows through the inspiratory heater wire R2 and then back through switch S2 to the negative terminal of the power supply 405.

[0077] Similarly, with continued reference to FIG. 4D, the humidification system can be configured to provide power to the expiratory heater wires R5, R6 in a second operating mode while the power supply 405 is providing power in the negative cycle. To do so, switches S3, S4, S5, S6 are closed and switches S1, S2 are opened. Current flows from the negative terminal of the power supply 405 through switches S4 and S5 to the inspiratory heater wire R1, and then branches to provide power to the heater wires of both the second section of the inspiratory limb and the expiratory limb without passing through diode D1. In the second section of the inspiratory limb, the current flows to the inspiratory heater wire R3, then to the inspiratory heater wire R4, and back to the intermediate connector. In the expiratory limb, the current flows to R5, then to R6, and back to the intermediate connector. The current then flows through the inspiratory heater wire R2, and then through switches S6 and S3 to return to the positive terminal of the power supply 405.

[0078] 4D, the humidification system can be configured to provide power only to the inspiratory heater wires R1 and R2 in the first section of the inspiratory limb (and not to the expiratory heater wires R5, R6) in a first mode of operation while the power supply 405 is providing power on the negative cycle. To do so, switches S1, S2, S5, S6 are closed and switches S3, S4 are opened. Current flows from the negative terminal of the power supply 405 through switch S2 to the inspiratory heater wire R2, then through diode D1 to the inspiratory heater wire R1, and then back through switch S1 to the positive terminal of the power supply 405.

[0079] Similarly, with continued reference to FIG. 4D, the humidification system can be configured to provide power only to the inspiratory heater wires R1 and R2 in the first section of the inspiratory limb (and not to the expiratory heater wires R5, R6) in a first mode of operation while the power supply 405 is providing power in a positive cycle. To do so, switches S3, S4, S5, S6 are closed and switches S1, S2 are opened. Current flows from the positive terminal of the power supply 405 through switches S3 and S6 to the inspiratory heater wire R2, then through diode D1 to the inspiratory heater wire R1, and back to the negative terminal of the power supply 405 through switches S5 and S4.

[0080] Other circuit designs and configurations for controlling the inlet heater, the sectioned inlet heater, and / or the outlet heater are possible. The control of power to the various heaters can be controlled by a controller or control module, such as the controller 122 described with reference to FIG. 1. The control module can be configured to coordinate the opening and closing of switches to selectively control the power to one or more heaters. For example, the switches can be opened and closed to control the amount of power delivered to the heaters. In certain embodiments, the power source provides alternating current and the switches can be controlled to modulate the amount of power to one or more heaters using, for example, pulse width modulation techniques. As another example, the control module can coordinate the operation of the switches to control which heater or heater section is delivered power. In some embodiments, each heated section or heater wire can include a dedicated power source. This may allow for the omission of diodes configured to regulate the current in the heater wire circuit. In some embodiments, the control algorithm can use the flow information to directly control the fixed duty cycle of the first heater section. In some embodiments, the control algorithm may use an ambient temperature reading or measurement to directly control the fixed duty cycle of the first heater section to an adjusted value.

[0081] In some embodiments, a midpoint temperature measurement, i.e., between the patient end and the chamber end, may be used by the control module. For example, the control module may utilize such midpoint temperature measurement to adapt a duty cycle of the first heater section to maintain a target midpoint temperature. The duty cycle of the first heater section may be adapted to maintain a target temperature difference relative to the chamber output dew point (humidity) related to the chamber output temperature. The duty cycle of the first heater section may be adapted to continuously maintain a target temperature difference relative to the patient end measured temperature. If the duty cycle remains at 100% for the adjusted time period and the flow is determined to be non-zero while the patient end temperature is below the target set point by the adjustment, the chamber output temperature may be advantageously reduced to a calculated target level based at least in part on the combined duty cycle of the first and second heater sections (as determined by the patient end temperature).

[0082] In some embodiments, at least a single measurement point in the system for temperature feedback control can be implemented, and the measurement point can be located at the system outlet. Such a configuration can be sufficient to achieve the target gas conditions. In certain embodiments, the dual zone system can be equipped with no temperature sensor if a priori knowledge of the heat transfer characteristics of each zone is established for known environmental operating conditions. In such a system, individual power levels can be established for each zone such that the target gas output conditions can be derived from accurate measurement of mass flow through the system and knowledge of the gas conditions entering the gas delivery system.

[0083] FIG. 21A shows an example circuit diagram 2000a configured to independently control two heaters H1, H2 (e.g., inhalation heater, exhalation heater, segmented heater, etc.). As used herein, independent control means that the delivery of power to one of the two heaters does not determine whether power is delivered to the other heater. For example, to deliver power only to heater H1, switches S1 and S3 can be closed and switches S2 and S4 can be opened, to deliver power only to heater H2, switches S1 and S3 can be opened and switches S2 and S4 can be closed, or to deliver power to both heaters H1, H2, switches S1-S4 can be closed.

[0084] The circuit 2000a can include a power source 2002 configured to provide electrical power. The power source 2002 can be an AC or DC power source. The power source 2002 can be a voltage or current source. The circuit 2000a can include a main relay 2004 configured to control the delivery of electrical power to the components of the circuit 2000a. The main relay 2004 can be opened (e.g., placed in a state that does not allow electrical current to flow) when a fault condition is detected by the system or when the system decides to cut off electrical power to the heater and / or other electrical components of the breathing circuit.

[0085] In some embodiments, the system can be configured to detect possible shorts between the low power circuit and the high power circuit (e.g., a short between the heater and the sensor wire) when they occur. Shorts can occur when the high power circuit and the low power circuit receive power from a common power source and / or receive power from a common circuit. In certain embodiments, the high power circuit and the low power circuit receive power from a transformer that rectifies the power (e.g., from an AC power source), reduces (or increases) the output voltage to the high power circuit (e.g., using a voltage divider), and reduces the output voltage to the low power circuit (e.g., using a voltage divider). For example, the high power circuit can be configured to provide about 22V and the low power circuit can be configured to provide about 3.3V. Other voltages are possible. For example, the high power circuit can provide a voltage of at least about 50V, at least about 30V and / or less than about 50V, at least about 20V and / or less than about 30V, or at least about 10V and / or less than about 25V. As another example, the low power circuit may provide a voltage of at least about 5V, at least about 3V and / or less than about 5V, at least about 2V and / or less than about 3.5V, or at least about 1.5V and / or less than about 2V. The actual voltage of the low power circuit may depend on the temperature measured by one or more temperature sensors coupled to the low power circuit. For example, in a low power circuit providing about 3.3V, a thermistor measuring a temperature of about 50°C may output a voltage of about 0V, and a thermistor measuring a temperature of about 20°C may output a voltage of about 1.2V.

[0086] The system may include a first comparator referenced to an output of a series of voltage dividers electrically coupled to a transformer output configured to provide a voltage to a low power circuit. The first comparator may provide an out-of-range signal when the voltage exceeds an expected voltage (e.g., a voltage that the comparator is configured to detect). For example, if the expected range is 0-1.2V or 1.5V, the comparator may be configured to provide a signal indicative of a possible short circuit when the voltage exceeds 1.2V or 1.5V. The system may include a second comparator referenced to ground configured to provide a signal indicative of a possible short circuit when the voltage is negative. The system may be configured to provide a signal indicative of a potential short circuit immediately (e.g., in real time or near real time) upon detecting a voltage outside of the expected range. In some embodiments, the system may include logic configured to ignore the short circuit signal, initiate an alert, and / or turn off or reduce power to the high power circuit and / or the low power circuit. If the system receives an out-of-range signal, the system may open a main relay 2004 to cut off power to electrical components (e.g., heater wires, sensors, etc.). A short circuit can occur if there is voltage leakage from the high power circuit to the low power circuit that can cause the voltage on the low power circuit to increase outside of the expected range. Similarly, if a negative bias voltage supplied to the high power circuit leaks onto the low power circuit, the voltage on the low power circuit can go negative.

[0087] The circuit 2000a may include switches S1-S4 for controlling power to the heaters H1, H2. As used herein, the term "switch" may be used to refer to an electrical switch and / or any other combination of electrical and / or electromechanical components configured to control the flow of current. For example, the switches may include MOSFETs, diodes, transistors, or combinations thereof, etc. The heaters H1, H2 may be any of the heaters described herein.

[0088] The circuit 2000a may include a control module 2006 configured to control the switches S1-S4. The control module 2006 may be configured to provide signals to the switches to indicate a desired state of the receiving switch. For example, the control module may send a signal (e.g., a voltage above a threshold voltage) to the switches S1 and S3 or the switches S2 and S4 to control the switches S1 and S3 or the switches S2 and S4 to close. The control module 2006 may be configured to control the switches S1 and S3 using one signal and to control the switches S2 and S4 using another signal. In this manner, the switch pairs (e.g., switches S1, S3 and / or switches S2, S4) may synchronize their operation (e.g., open and close at or near the same time). The circuit 2000a is configured to independently control the heaters H1, H2 by independently controlling the opening and closing of the switch pair S1, S3 and the switch pair S2, S4.

[0089] FIG. 21B shows an example circuit diagram 2000b configured to gate heaters H1, H2. Circuit 2000b is similar to circuit 2000a, except that the flow of power to the lines controlled by switches S2 and S4 is controlled by switches S1 and S3, respectively. In this manner, the control module 2006 can gate heaters H1, H2. As used herein, gated control can mean that the flow of power to heater H1 is controlled by switches S1 and S3, whereas the flow of power to heater H2 is controlled to a first level by switches S1 and S3 and to a second level by switches S2 and S4. For example, power can flow to heater H2 when switches S1 and S3 are closed depending on the state of switches S2 and S4. However, if switches S1 and S3 are open, no power flows to heater H2, so the state of switches S2 and S4 is irrelevant. In this manner, the hardware can control the operation of heaters H1, H2. This provides gating control of heater H2, as the control module 2006 can control power to heater H2 using switches S1 and S3 (e.g., provide gating of power to heater H2). This can be useful when hardware control of heaters H1, H2 is desired to provide an additional control mechanism in addition to software control of the heaters. For example, control software in a humidifier may require heater H2 to be powered on, but that requirement can be overridden by hardware configuration.

[0090] 21C shows an example circuit diagram 2000c configured to switch between independent and gated control of heaters H1, H2. A control module 2006 can control switches S5, S6 to selectively place circuit 2000c in an independent control configuration, similar to circuit 2000a described herein with reference to FIG. 21A, or in a gated control configuration, similar to circuit 2000b described herein with reference to FIG. 21B. Circuit 200c provides the benefits of both circuits 2000a, 2000b to select a desired, appropriate, and / or preferred configuration for control module 2006.

[0091] FIG. 22A shows an example circuit diagram 2100a including a logic module 2008 and a mode relay 2010 configured to enable control of two heaters (e.g., an inlet heater and an outlet heater) or a segmented heater (e.g., a heater in a segmented inlet line). The circuit diagram 2100a includes a power supply 2002, a main relay 2004, and a control module 2006 similar to the circuit diagrams 2000a, 2000b, and 2000c described herein with reference to FIGS. 21A-21C. The switches S1-S4 are configured similarly to the circuit diagram 2000a. However, the logic module 2008 interfaces with the control module 2006 to control the switches S1-S4. Additionally, the mode relay 2010 provides dynamic configuration for different heater configurations.

[0092] The logic module 2008 receives control signals SW1, SW2 from the control module 2006 and processes these control signals SW1, SW2 based at least in part on a mode signal MODE from the control module 2006. The mode signal MODE may indicate an intended, selected, or desired mode for the circuit 2100a. For example, the mode signal MODE may be used to indicate to the logic module 2008 whether the operation of the circuit 2100a is for independent control of the heaters or for a sectioned heater. Based on the control signals SW1, SW2 and the mode signal MODE, the logic module 2008 outputs switch signals HW1 and HW2 to control the pairs of switches S1, S3 and S2, S4, respectively.

[0093] In certain implementations, the mode signal MODE can be used to indicate a heater independent control mode to the logic module 2008. In this case, the logic module 2008 can be configured to pass the control signals SW1, SW2 to the output switch signals HW1, HW2 with little or no modification. In this manner, the control module 2006 can control the two heaters independently. In some embodiments, the mode relay 2010 receives an indication of an operating mode similar to the indication provided by the mode signal MODE. In response to the received indication, the mode relay 2010 can provide electrical connection to lines 1-4 (corresponding to the lines controlled by the switches S1-S4). For example, as shown in FIG. 22B, the mode relay 2010 can provide electrical passage to lines 1-4 to enable independent control of the heaters H1, H2, similar to the operation of the circuit 2000a described herein with reference to FIG. 21A.

[0094] In certain implementations, the mode signal MODE can be used to indicate a sectionalized heater control mode to the logic module 2008. In this case, the logic module 2008 can be configured to output switch control signals HW1, HW2 to selectively control the control switches S1-S4 to provide a rectified electrical signal to the sectionalized heater. In this manner, the control module 2006 can control the sectionalized heater as described elsewhere herein. In some embodiments, the mode relay 2010 receives an indication of an operating mode similar to the indication provided by the mode signal MODE. In response to the received indication, the mode relay 2010 can provide an electrical connection to lines 1-4 (corresponding to the lines controlled by the switches S1-S4). For example, as shown in FIG. 22C, the mode relay 2010 can electrically couple lines 1 and 4 and electrically couple lines 2 and 3 to enable control of a sectionalized heater comprising heater sections H1 and H2 similar to the operation of other circuits configured to control sectionalized heaters described herein. In this mode, the mode relay 2010 provides the ability to turn on heater section H1 or both heater sections H1 and H2 based at least in part on the configuration of switches S1-S4 and the polarity of the voltage / current.

[0095] For example, in a sectionalized heater mode, the control module 2006 can use the control signal SW1 to indicate a desire or request to provide power to both heater sections H1, H2. In response to the control signal SW1, the logic module 2008 can provide a switch control signal HW1 that controls switches S1 and S3 to close upon receiving a positive polarity signal from the power source 2002, and a switch control signal HW2 that controls switches S2 and S4 to close upon receiving a negative polarity signal from the power source 2002. Similarly, the control module 2006 can use the control signal SW2 to indicate a desire or request to provide power to only the heater section H1. In response to the control signal SW2, the logic module 2008 can provide a switch control signal HW2 that controls switches S2 and S4 to close upon receiving a positive polarity signal from the power source 2002, and a switch control signal HW1 that controls switches S1 and S3 to close upon receiving a negative polarity signal from the power source 2002. In this manner, the logic module 2008 enables rectification of voltage / current to the sectionalized heaters H1, H2.

[0096] The logic module 2008 allows for a safety latch that may be implemented when operating with sectionalized heater control. The logic module 2008 may be configured to set both switch control signals HW1, HW2 to control switches S1-S4 to open if both control signals SW1, SW2 indicate a request to operate in their requested mode. The logic module may be used to reduce or prevent malfunctions associated with providing power to the sectionalized heaters. For example, the power supply 2002 may be used to provide alternating voltages, i.e., alternating positive and negative bias voltages. These currents and / or bias voltages may be controlled by the switches S1-S4. By closing all switches S1-S4, both directions of current or both positive and negative bias voltages may be provided to the heater circuit 2100a simultaneously, which may damage the system. The logic module 2008 may include a latch that opens the main relay 2004 when the control module 2006 activates incompatible heater drives (e.g., when both pairs of switches S1, S3 and S2, S4 are activated or closed) (e.g., due to a software or hardware malfunction).

[0097] FIG. 23 shows an example circuit diagram 2100b configured to switch between independent control (e.g., circuit diagram 2000a described herein with reference to FIG. 21A) and gated control (e.g., circuit diagram 2000b described herein with reference to FIG. 21B) of two heaters and to provide the functionality described with respect to example circuit diagram 2100a shown in FIG. 22A. Circuit diagram 2100b provides the switching functionality of circuit diagram 2000c described herein with reference to FIG. 21C along with the functionality provided by circuit diagram 2100a described herein with reference to FIG. 22A. To enable this functionality, control module 2006 can provide an additional control signal SW3 that logic module 2008 can use to provide switch control signal HW3 to operate switches S5 and S6. Switches S5 and S6 can be configured such that switches S1 and S2 are in parallel and switches S3 and S4 are in parallel when operating in heater independent control mode and when operating in sectioned heater control mode. Switches S5 and S6 may be configured such that switches S1 and S2 are in series and switches S3 and S4 are in series when operating in a heater gated control mode. Logic module 2008 may perform additional checks to ensure that control signal SW3 is appropriate based at least in part on a mode signal MODE, where the mode signal may be configured to provide an indication of a selection, request, or desire to operate in a heater independent control mode, a heater gated control mode, or a sectioned heater control mode.

[0098] 24A shows an example circuit diagram 2200 configured to control two heaters H1, H2 in parallel. The circuit 2200 can be configured to couple to a heater module 2012a, which includes heaters H1, H2. The circuit 2200 can be configured to provide electrical connections to the heater module 2012a, similar to those provided by the mode relay 2010 when configured as described herein with reference to FIG. 22C. Otherwise, the circuit 2200 can be configured to the circuit 2100a, described herein with reference to FIG. 22A.

[0099] Referring to FIG. 24A, the circuit 2200 can be configured to provide power in parallel to heaters H1, H2 in a heater module 2012a. In some embodiments, the heater module 2012a can include one or more diodes to direct or limit the flow of current to one or more of the heaters in the heater module 2012a. For example, FIG. 24B shows an example configuration of a heater module 2012a in which heaters H1, H2 both include diodes to control the flow of current. Diodes D1, D2 can be used to control when power flows through the associated heater H1, H2 to provide additional control capabilities.

[0100] 24B also shows a simplified circuit diagram demonstrating the functionality of the circuit 2200 with the heater module 2012a configured to include diodes D1, D2. When the switches S1 and S3 are closed (and the switches S2 and S4 are open), a positive current provided by the power supply 2002 flows through the heater H1 but not through the heater H2, and a negative current provided by the power supply 2002 flows through the heater H2 but not through the heater H1. Similarly, when the switches S2 and S4 are closed (and the switches S1 and S3 are open), a positive current provided by the power supply 2002 flows through the heater H2 but not through the heater H1, and a negative current provided by the power supply 2002 flows through the heater H1 but not through the heater H2. In this manner, the control module can regulate the opening and closing of the switch pairs S1, S3 and S2, S4 according to the polarity of the voltage or current provided by the power supply 2002 to selectively energize the heaters H1, H2. In some implementations, diodes D1, D2 can be configured to have different biases so that current flows through heaters H1, H2 opposite to that described above. In certain implementations, either one of diodes D1 or D2 can be removed so that current is limited in one of heaters H1, H2 but not the other.

[0101] FIG. 24C shows an example circuit diagram 2200 configured to control a sectionalized heater by using a heater module 2012b. In this configuration, the circuit 2200 with the heater module 2012b operates in the same manner as the circuit 2100a when the mode relay 2010 in the circuit 2100a is configured to electrically couple lines 1 and 4 and electrically couple lines 2 and 3 to enable control of a sectionalized heater with heater sections H1 and H2, as described herein with reference to FIG. 22C. FIG. 24D shows an example configuration of the heater module 2012b and a simplified schematic diagram of the circuit 2200 to demonstrate the functionality of the circuit when the switches are in various configurations. As described elsewhere herein, both heater sections H1, H2 can be powered when a positive current is provided by the power supply 2002 and switches S1, S3 are closed, or when a negative current is provided by the power supply 2002 and switches S2, S4 are closed. Heater section H1 can be powered when a negative current is provided by power supply 2002 and switches S1, S3 are closed, or when a positive current is provided by power supply 2002 and switches S2, S4 are closed.

[0102] The circuit diagram 2200 can advantageously allow connectivity with different heater modules to allow a single circuit design to operate different heater configurations, which can simplify control system design, software design, and also increase interoperability of components for different respiratory devices.

[0103] 25A-C show an example circuit diagram 2500 for controlling a sectioned heater by using an active rectifier circuit that uses back-to-back MOSFETs to rapidly and finely control the direction of current from an A / C power source 2502. To facilitate the explanation of how the example circuit 2500 controls the sectioned heater, FIGS. 25B and 25C show switches S1-S4 as diodes to facilitate understanding of the resulting current flow in the circuit for particular control modes and particular configurations of open and closed switches, as described below. However, it should be understood that switches S1-S4 are electrical switches, such as MOSFETs, as shown in FIG. 25A.

[0104] The active rectifier circuit 2500 can serve to provide current to the target heater sections H1 and / or H2 by selectively switching MOSFETs S1, S2, S3, and S4. For example, FIG. 25B shows a circuit configuration for providing power to heater sections H1 and H2. When a positive current is provided by the power supply 2502, MOSFETs S1 and S3 can be closed (e.g., switched on) and MOSFETs S2 and S4 can be opened (e.g., switched off), and when a negative current is provided by the power supply 2502, MOSFETs S1 and S3 can be opened (e.g., switched off) and MOSFETs S2 and S4 can be closed (e.g., switched on). FIG. 25C shows a circuit configuration for providing power to heater section H1. When a positive current is provided by the power supply 2502, MOSFETs S1 and S3 may be open (e.g., switched off) and MOSFETs S2 and S4 may be closed (e.g., switched on), and when a negative current is provided by the power supply 2502, MOSFETs S1 and S3 may be closed (e.g., switched on) and MOSFETs S2 and S4 may be open (e.g., switched off).

[0105] In some embodiments, the breath heater is electrically coupled to the first heater section H1. In such embodiments, the breath heater receives power when the first heater section H1 receives power.

[0106] Circuit diagram 2500 advantageously allows for controlling a sectioned heater using a single power supply and a patient-end temperature sensor (e.g., a thermistor). For example, circuit diagram 2500 can be implemented in a system that does not include a temperature sensor in the intermediate connector connecting the first heater section H1 to the second heater section H2. Circuit diagram 2500 can be implemented using a control system configured to vary the switching of MOSFET pairs to heat either the first heater section H1 (e.g., the inner loop HW1 of the inspiratory limb) or the first or second heater section H1, H2 (e.g., the outer loop HW2 of the inspiratory limb comprising the inspiratory limb and the extension limb), as described in more detail below. HW2 can include both H1 and H2, i.e., the entire heating circuit along the entire tube.

[0107] Detection of the articulated extension of the inspiratory limb FIG. 5 illustrates a block diagram of an exemplary system 500 configured to detect the presence of an inspiratory limb extension using an extension detection module 502 and provide power to a heater wire in the inspiratory limb (e.g., a first section of the inspiratory limb), an inspiratory limb extension (e.g., a second section of the inspiratory limb), and / or an expiratory limb. As described with reference to FIGS. 3A, 3B, 4, 8A, and 8B, for example, a logic module 504 (which may comprise hardware, software, or some combination of both) may be configured to provide logic to enable the switching described with respect to the various control modes. The logic module 504 may receive signals from an integrated circuit 506 that is part of the respiratory humidification system 100. In some embodiments, the logic module 504 is software embedded in whole or in part in the integrated circuit 506 and converts signals from the integrated circuit 506. The combination of the logic module 504 and the integrated circuit 506 may be configured to detect zero level crossings, i.e., points at which a voltage or current transitions from positive to negative or vice versa, and change the state of a switch according to the control module. The logic module 504 can output PWM signals 508a, 508b according to a desired, selected, or predetermined power output, where the PWM signals are delivered to the inhalation heater wires (INSP HW), the exhalation heater wires (EXP HW), or both.

[0108] In some embodiments, the system 500 can include an extension detection module 502 configured to detect whether the second section 202b is connected to the breathing circuit 200. The extension detection module 502 can generate an "enable signal" if the second section 202b is connected. The logic module 504 can receive the "enable signal" and adjust the switching accordingly. In some embodiments, the "enable signal" indicates to the logic module 504 that the system 500 does not control the inspiratory and expiratory circuits independently and simultaneously.

[0109] In some embodiments, the extension detection module 502 can be configured to detect the presence of the second section 202b by switching on both the inhalation and exhalation circuits and detecting whether a hardware overcurrent event is detected. When no overcurrent event is detected when each is switched on individually, but an overcurrent event is detected when both are switched on simultaneously, the extension detection module 502 can generate an "enable signal" indicating that the second section 202b is connected. In some embodiments, the extension detection module 502 can detect the presence of the second section 202b by detecting the resistance of an identification resistor or heater wire in each section using current measurements. Based at least in part on the current measurements of the various sections, the extension detection module 502 can generate an "enable signal" when the current measurements for the various cycles in which the various control modes are implemented are different as described above with reference to Figures 3A, 3B, 4, 8A, and 8B.

[0110] Sensor Circuit 6A and 6B show an exemplary circuit diagram in the respiratory humidification system 100, where a circuit 600 is configured to read data from two sensors R1 and R2. With reference to FIGS. 6A and 6B, the sensors R1 and R2 are represented using resistors, but any suitable type of sensor can be used, such as, for example, but not limited to, a temperature sensor, a humidity sensor, a flow sensor, an oxygen sensor, etc. In some embodiments, the sensor can be a temperature sensor, such as a thermistor. In such an embodiment, the sensors R1 and R2 respectively represent a first thermistor at the intermediate connector 214 and a second thermistor at the patient end (e.g., the patient end connector) of the breathing circuit 200. The two thermistors R1 and R2 can be measured using two wires in the breathing circuit 200 using the circuit 600 with a current or voltage source and a switch in the humidifier controller 122. Although this description with reference to Figures 6A and 6B is in terms of a thermistor, other suitable sensors that affect the voltage and / or current provided to an associated circuit are also applicable.

[0111] To selectively read sensors R1 and R2, current is provided in either polarity via lines 602 and 604. To measure patient-end sensor R2, the humidifier controller 122 sets a switch to ground the top current source. Current then flows from the bottom current source through R2, through the switch to ground. Diode D1 prevents current from passing through R1. The humidifier controller 122 can be configured to measure the voltage drop from the bottom current source to ground and derive the resistance of sensor R2 based at least in part on the current provided and the measured voltage. To measure sensor R1 positioned at the middle connector 214, the humidifier controller 122 can read the patient-end sensor R2 and record the results. The humidifier controller 122 can then set a switch to ground the bottom current source. Current then flows from the top current source through R1 and R2, through the switch to ground. The humidifier controller 122 can be configured to measure the voltage drop from the upper current supply to ground and derive the resistance of the sensor R1 based at least in part on the current supplied, the measured voltage, and the recorded results from measuring the resistance of R2. In some embodiments, the voltage drop across D1 is taken into account when deriving the resistance of R1. In the embodiment shown in FIG. 6A, by placing D1 close to R1, the temperature of the diode D1 can be calculated, and this temperature can be used to calculate the voltage drop across D1. One possible advantage of the configuration shown in FIG. 6A is that the measurement of the sensor R2 at the patient end can be more accurate because the measurement is made without passing through a diode as illustrated in the embodiment of FIG. 6B. Passing through a diode can introduce uncertainty or error.

[0112] In some embodiments, an additional diode D2 can be added to the intermediate connector 214, as shown in FIG. 6B. In such an embodiment, the humidifier controller 122 can be configured to measure sensors R1 and R2 similar to the embodiment shown in FIG. 6A and described above. The difference is that when measuring sensor R1, current flows through R1 and D1, but not through R2, as diode D2 prevents current flow through R2. In this way, the measurement of sensor R1 can be substantially isolated or separated from the measurement of sensor R2. Similar to the derivation of the resistance of sensor R1, the voltage drop across diode D2 can be taken into account when deriving the resistance of sensor R2. By placing D1 and D2 close to R1, the temperature of the diodes can be calculated, which can be used when calculating the voltage drop across D1 and D2, respectively.

[0113] In a particular embodiment, the measurement of the sensors R1, R2 is performed by software running on a controller connected to the circuit of FIG. 6A or FIG. 6B. The direction and amount of current supplied to the circuit can be controlled by such software. An accurate measurement of the resistance of the sensors R1, R2 can be obtained by measuring the voltage, for example, using an analog-to-digital converter. To minimize or prevent the effect of the changes caused by the diodes D1 and / or D2, the software can supply two different currents (I1 and I2) in the same direction. This results in two different voltage readings (V1 and V2) corresponding to the two different currents (I1 and I2). Using these two voltages and currents, the software can determine the voltage drop of the diodes D1, D2 and the resistance for the sensors R1, R2. For the sensor R1, for example, the voltage drop can be determined by the following formula: Vdrop=((V1*I2-V2*I1) / ((V1-V2) / R2+I2-I1)). The resistance of sensor R1 can be calculated using the following formula: R1=(V2-Vdrop) / (I2-V2 / R2). In one embodiment, the calculated Vdrop has a certain error from the measured Vdrop, and this error is corrected in software. In one embodiment, Vdrop is increased by about 15% as error compensation.

[0114] In some embodiments, sensors R1 and R2 (e.g., thermistors) may be omitted. In such embodiments, more precise sensors may be included in the system. This may allow for the use of symmetric intermediate connectors (e.g., mechanically and electrically independent connectors). For example, the intermediate connector may be physically connected in two ways and may operate to mechanically couple the inspiratory limb sections and to direct power to the target sections of the segmented heater. In some of the embodiments described herein, diodes and other electrical components may be configured such that the control algorithm provides power to undesired portions of the segmented heater if the connector is plugged in backwards.

[0115] FIG. 7 shows an exemplary circuit diagram in the respiratory humidification system 100, where the circuit 700 is configured to read temperature data using two transistors Q1 and Q2 acting as temperature sensors. The temperature measurement may be based at least in part on the temperature effect of the pn junction of the base and emitter terminals of the transistors. The switching of the current in the humidifier controller 122 may be the same as for the circuit described with reference to FIGS. 6A and 6B, or may be an alternating configuration as shown. For example, the switching configuration shown uses two switches with two power sources and two grounds to selectively provide power to the wires. In a first configuration, the top switch electrically connects the top power source to the wire 702, and the bottom switch electrically connects the ground to the wire 704. In a second configuration, the top switch electrically connects the ground to the wire 702, and the bottom switch electrically connects the bottom power source to the wire 704. By using transistors Q1 and Q2 as temperature sensors, the diodes can be omitted since the transistors provide the function of the temperature sensor and the diode.

[0116] Breathing circuit hardware configuration FIG. 8A shows an example diagram of a hardware configuration 800 for a breathing circuit 200 having a first section 202a of the inspiratory limb, a second section 202b of the inspiratory limb, and an expiratory limb 210. The hardware configuration 800 can include a humidifier 108 configured to couple the wiring of heater wires HW1 and HW2 via switches or relays S3 and S4, and to couple wiring for sensors 204a, 204. In some embodiments, a sensor cartridge 802 can be configured to couple the wiring of heater wires HW1, HW2 and wiring for sensors 204a, 204. Switches S3, S4 can be used to selectively control power to the heater wire HW2 of the expiratory limb 210, as described with reference to FIG. 4A, with similar functionality as described with reference to FIGS. 4B-4D. In some embodiments, both switches S3 and S4 are in an open position by default and are closed when the appropriate tube (e.g., inspiratory limb or expiratory limb with the appropriate discrimination resistor) is connected to the humidifier 108. In this manner, the hardware configuration 800 can be used to provide power to the heater wire HW1 and / or heater wire HW2. Regardless of whether the heater wire HW2 is receiving power, the heater wire HW1 can be controlled in two modes. In the first mode, the first heater wire 206a receives power and the second heater wire 206b does not. In the second mode, the first and second heater wires 206a, 206b receive power. In the illustrated embodiment, the heater wire HW2 can be powered when the heater wire HW1 is controlled in either the first or second mode. It should be understood that the heater wire HW2 of the expiratory limb can be selectively controlled and the heater wire HW1 of the inspiratory limb is single mode. For example, when the inspiratory limb heater wire HW1 is controlled in a first mode (or a second mode), the expiratory limb heater wire HW2 can alternate between receiving and not receiving power based at least in part on the operation of switches S3 and S4 without changing the control mode of the heater wire HW1.Similarly, the heater wire HW2 in the expiratory limb may remain receiving power while the heater wire HW1 in the inspiratory limb is changed between the first and second modes.

[0117] The hardware configuration 800 may include an intermediate printed circuit board (PCB) 214 that includes two diodes, one of which is a power diode D1 and the other is a signal diode D3. The intermediate PCB 214 may include a heat pad to dissipate heat generated by the diodes D1, D3 and reduce the effect on the sensor 204a. The hardware configuration 800 may include a patient-end PCB 804 with two heater wires and one sensor 204b, with the heater wire 206b electrically directly coupled. In a first mode of operation, power may be provided to HW1 such that current flows through the heater wire 206a and the diode D1, while substantially no current flows through the heater wire 206b (e.g., less than 1% of the current through the heater wire 206a flows through the heater wire 206b). In a second mode of operation, power may be provided to HW1 such that current flows through the heater wires 206a and 206b. The first and second modes of operation can be controlled at least in part by the direction of current through the heater wire HW1.

[0118] In certain embodiments, diodes D2 and D4 can be added to the hardware configuration 800 as shown in FIG. 8B. In such embodiments, the software for the sensing circuit can be modified to take into account the increase in heat. In some embodiments, the signal diodes D3, D4 are positioned close to each other so that they experience the same or similar ambient conditions, reducing differences in effects caused by different ambient temperatures. Otherwise, the circuit 200 operates similarly to the circuit shown in FIG. 8A.

[0119] In some embodiments, comparing Figures 8A and 8B, omitting diode D4 improves sensing reliability at the patient end. For example, the diode may fail in an open position. If diode D4 fails open, a patient end temperature reading may not be possible. In the circuit shown in Figure 8A, if diode D3 fails, the patient end sensor 204b can still be read. Omitting diode D2 may have similar advantages.

[0120] In some embodiments, the sensor cartridge 802 can be located internal to the humidification system 100 or external to the system.

[0121] Exemplary Segmented Inspiratory Limb with Connector Having a Microcontroller FIG. 9 shows an exemplary embodiment of a respiratory humidification system 100 that utilizes a microcontroller at the intermediate connector 214 to measure data for controlling heating and reading sensor values ​​at the inspiratory limb 202. In some embodiments, one or more microcontrollers can be incorporated into the sensor cartridge, the humidifier, the intermediate connector 214, or any combination thereof. When incorporated into the sensor cartridge, for example, the microcontroller provides similar functionality as described herein. The exemplary embodiment shown uses one heater wire connected to VN as a common reference and connects the two heater wires HW1, HW2 and the sensor wires to the common reference. The exemplary embodiment also converts the readings of both sensors 204a, 204b to digital signals at the signal intermediate connector 214 and sends them to the humidifier controller 122. This can reduce or prevent isolation issues by providing a common reference point for the sensors 204a, 204 and sending digital parameter readings. The readings can be passed through an optocoupler in the controller 122, which isolates the signals as described herein with reference to Figure 12. Use of this exemplary embodiment allows two independent control channels to heat only the first section 202a or the first and second sections 202a, 202b of the inspiratory limb to provide desired, selected, or predetermined heating control.

[0122] FIG. 10 shows a block diagram of the intermediate connector 214 for the inspiratory limb 202, where the intermediate connector 214 uses a microcontroller. The microcontroller can be used to measure analog signals from thermistors 204a and 204b and convert the analog signals to digital signals using an analog-to-digital converter (ADC). The converted digital signal can be sent to the humidifier controller 122 on a single data line. The data line can be used to enable communication between the microcontroller and the humidifier controller 122 to provide temperature data. The data line can be used to provide power to the microcontroller by pulling the data line high at the humidifier controller 122 when no data is being transmitted. The power module and data line converter can include a capacitor and a diode, so that the capacitor is charged when the data line is high. The charged capacitor can be used to power the microcontroller when the data line is being used for communication. A circuit diagram for an exemplary power module and data line converter is shown in FIG. 11.

[0123] Temperature sensing using this configuration can be accomplished using a current or voltage source at the intermediate connector 214 to drive a thermistor, which can then be read by the microcontroller. This can be done using transistors or op-amps, for example. Data line communication can be accomplished using a time slot based approach, where each logic level can be sent and read within a given time slot. In this way, a single wire can be used to enable bidirectional communication between the humidifier controller 122 and the microcontroller.

[0124] The humidifier controller 122 may include a DC power supply referenced to VN. A capacitor may be included that may charge when the heater wires are on and provide power to the microcontroller while the heater wires are switched off. The humidifier controller 122 may include a dual optocoupler circuit 1200 as shown in FIG. 12. The dual optocoupler circuit may be used to isolate signals and provide bidirectional data communication between the controller 122 and the power supply.

[0125] In some embodiments, calibration data can be stored in the microcontroller, which can be read out when a breathing circuit is connected. In some embodiments, a part identification number or serial number can be stored to identify the manufacturer of the connected circuit.

[0126] Segmented inspiratory limb with digital temperature sensor 13 shows a circuit diagram of an exemplary respiratory humidification system 100 incorporating digital temperature sensors 204a, 204b for use with a breathing circuit 200 having a first section 202a and an intermediate connector 214 joining a second section 202b to form an inspiratory limb 202. As with the design described with reference to FIG. 9, the digital temperature sensors 204a, 204b can utilize a single line for communication and power supply, simplifying the circuit design and reducing the amount of wires used in the system 100. The design shown in FIG. 13 allows the temperature sensor and data communication to be implemented as a single chip rather than a combination of circuit elements, which may be desirable.

[0127] Intermediate Connector Board 14A and 14B show an example intermediate PCB 250 of the intermediate connector 214, with each view showing one of two sides of the intermediate PCB 250. The intermediate PCB 250 includes connection pads 252, 254 for the heater wires and the sensor connection lines. The connection pads 252, 254 are configured on both sides of the intermediate PCB 250 to facilitate connection with the heater wires spirally wrapped around the inspiratory limb.

[0128] The intermediate PCB 250 includes a sensor connection pad 256 for a sensor, such as a thermistor or other temperature measuring component, or a humidity sensor, or a flow sensor. The sensor can be coupled to a diode (e.g., diode D3 described with reference to FIG. 8B) via a signal connection pad 258 on the intermediate PCB 250. As shown, the intermediate PCB 250 includes a gap 262 configured to insulate the sensor from other electrical components and tracks. In some embodiments, the gap 262 can be filled with an insulating material to further insulate the sensor connected to the sensor connection pad 256. Additionally, the intermediate PCB 250 can be configured to position the sensor away from other active and / or passive electrical components, such as by a protrusion 257.

[0129] The intermediate PCB 250 includes a power connection pad 260 for a diode that is electrically coupled to the heater wires via electrical tracks on the intermediate PCB 250. The diode may be diode D1 as described with reference to Figures 3B, 6B, or 8B. The power connection pad 260 may be electrically and thermally coupled to a heat sink 264 to help dissipate heat and reduce or minimize the effect on the accuracy of parameter readings of the sensor coupled to the sensor connection pad 256.

[0130] 14C and 14D show an exemplary embodiment of an intermediate connector 214 comprising an intermediate PCB 250 and an intermediate connection element 263. The intermediate connection element 263 can be configured to route a portion of the humidified gas flowing through the inspiratory limb through a conduit formed by the intermediate connection element 263. A sensor on the intermediate PCB 250 can then provide a signal corresponding to a parameter of the gas flowing through the intermediate connection element 263, the parameter representing at least one characteristic (e.g., temperature, humidity, flow rate, oxygen content, etc.) of the humidified gas in the inspiratory limb at that time. In some embodiments, the intermediate connection element 263 is configured to provide mechanical support for the intermediate PCB 250 to position the intermediate PCB 250 within the inspiratory limb. In some embodiments, the intermediate connection element 263 is configured to provide mechanical support for joining two sections of the inspiratory limb at or near the intermediate connector 214.

[0131] The intermediate connector 214 includes a first connection pad 252 on a first side of the intermediate PCB 250 and a second connection pad 254 on a second side of the intermediate PCB 250 (the opposite side of the intermediate PCB 250). As described herein, the first and second connection pads 252, 254 can be configured to provide electrical contacts for heater wires in first and second sections of the segmented inspiratory limb, respectively. In some embodiments, the heater wires in the sections of the inspiratory limb are spirally wound. The intermediate PCB 250 is configured to electrically couple the spirally wound heater wires and / or signal wires (e.g., temperature sensor wires) in the first section to the spirally wound heater wires and / or signal wires in the second section.

[0132] In some embodiments, the intermediate PCB 250 includes a first portion that extends across the lumen formed by the intermediate connection element 263 along a diameter or chord line, such that a portion of the intermediate PCB 250 generally crosses at least a portion of the flow path of the gas. The first portion of the intermediate PCB 250 can be overmolded with an overmolding composition. The intermediate PCB 250 can include a second portion 251 adjacent to the first portion, the second portion 251 projecting outwardly from the outside of the intermediate connection element 263 in a direction away from the lumen. The second portion 251 of the intermediate PCB 250 includes one or more connection pads 252 configured to receive one or more wires from the first segment of the inspiratory limb. The intermediate PCB 250 can include a third portion 253 adjacent to the first portion, the third portion 253 projecting outwardly from the outside of the intermediate connection element 263 in a direction away from the lumen and opposite the second portion 251. The third portion 253 may include one or more connection pads 254 on the intermediate PCB 250 configured to receive one or more wires from the second segment of the inspiratory limb. The intermediate PCB 250 includes one or more conductive tracks configured to electrically couple the one or more connection pads 252 of the second portion 251 to the one or more connection pads 254 of the third portion 253 and to provide an electrical connection between the wires in the first and second segments of the inspiratory limb.

[0133] In some embodiments, the intermediate PCB 250 may limit the number of contact pads for the wires to four. In such embodiments, the wires may overlap the tubes to maintain the continuity of the tubes. In such embodiments, it may be beneficial to maintain the orientation and / or order of the wires.

[0134] FIG. 34 illustrates an exemplary embodiment of an inspiratory limb 3405 and an extension limb 3410 with heater wires 3402, 3404 directly coupled to each other with a diode 3420. In some embodiments, the intermediate connector 214 can be configured to include a diode to directly connect the wires 3402, 3404. For example, the wires 3402, 3404 can be laser ablated so that the wires 3402, 3404 are exposed. The diode 3420 can be configured to cross the heater wires 3402, 3404 and contact the wires where there is no sensor and no intermediate PCB, as described herein. In such a configuration, the inspiratory limb and the extension limb can be advantageously configured to be free of unheated sections. Similarly, this configuration can reduce or eliminate condensation, dendrite growth, electrical shorting of the heater wires or sense wires, printed circuit boards in the intermediate connector, circuit breakdown, and / or flow resistance.

[0135] Patient End Connector Board FIG. 15A illustrates an exemplary patient-end PCB 270 of the patient-end connector 804. The patient-end PCB 270 includes connection pads 272 for the heater wires and the sensor connection wires. The connection pads 272 are configured to be on only one side of the patient-end PCB 270 to connect to the spirally wound heater wires and the signal wires from the inspiratory limb. Two of the connection pads 272 can be electrically directly coupled to each other as an electrical pathway. The heater wires can be coupled to the electrically directly coupled connection pads 272. The remaining two connection pads 272 can be electrically coupled to a sensor connection pad 274. The electrical tracks 278 to and from the sensor connection pads 274 can be configured to reduce or minimize the trace width and increase or maximize the track length to insulate the sensors connected to the sensor connection pads 274. The patient-end PCB 270 can include a protrusion 276 similar to that described with reference to the PCB 250 illustrated in FIGS. 14A and 14B. The protrusion 276 can be configured to further insulate the sensor from the effects of currents and components on the patient-end PCB 270.

[0136] Figures 15B-15E show an exemplary embodiment of the patient-end connector 804. Figures 15B and 15D show an exemplary embodiment of a patient-end PCB 270 that is overmolded as part of the inspiratory limb 202. The cross-sections of the patient-end PCB 270 shown in Figures 15C and 15E, respectively, can be aerodynamically configured to reduce or minimize turbulence in the gas delivered to the patient.

[0137] Segmented Inspiratory Limb Placement Limiter 16A-16E illustrate an exemplary embodiment of a placement limiter 280 for a segmented inspiratory limb 202. FIG. 16A illustrates an exemplary placement limiter 280 configured to have a larger chamber end 282 (e.g., the end closer to the gas source), a smaller patient end 284, and a sharp corner 286 with a groove 288 into which a grommet 294 can be placed. The placement limiter 280 can be configured to prevent or reduce the possibility of an intermediate connector or segment connection point of the inspiratory limb 202 (e.g., where the intermediate PCB 250 is located) from entering the incubator 290 through an opening 292. The smaller end 284 can be configured to enter the incubator 290, while the larger end 282 can be configured to prevent or block entry through the incubator opening 292 by contacting the grommet 294. In some embodiments, the position limiter 280 is configured to substantially fix the position of the intermediate PCB 250 within a target or desired distance from the incubator, or other such point that defines a different temperature environment. The target or desired distance may be about 20 cm or less, about 10 cm or less, about 5 cm or less, or about 0 cm. FIG. 16B illustrates an exemplary position limiter 280 for use with a bubble tube 202, where the position limiter is located a distance d1 from an entrance 292 to an incubator 290.

[0138] FIG. 16C illustrates an exemplary embodiment of a position limiter 280 configured to be clipped or secured to an object such as clothing, a blanket, or other object separate from the patient. The position limiter 280 is configured to be secured to the inspiratory limb 202 and capable of moving along the inspiratory limb 202 to adjust the position of the inspiratory limb 202. FIG. 16D illustrates the inspiratory limb 202 with the position limiter 280 in use with an incubator 290 to block or prevent entry of the intermediate PCB connector 250 into the incubator 290. FIG. 16E illustrates the inspiratory limb 202 with the position limiter 280 in use with a patient, where the position limiter 280 is secured to the patient's blanket to block or prevent movement of the inspiratory limb 202 relative to the patient and / or blanket. The position limiter 280 may also be used with an expiratory limb or other medical tubing used in connection with a gas delivery system.

[0139] Sectionalized medical tubing for use with respiratory humidification systems FIG. 17A shows a side view of a section of an exemplary composite tube 1201 that can be used with the respiratory humidification system 100 described with reference to FIG. 1. The composite tube 1201 can be used as the inspiratory limb 202 and can be configured to provide thermally beneficial properties that help prevent condensation of gas along the tube as described herein. The composite tube 1201 includes multiple elongated members wrapped and joined to form a pathway, where the multiple elongated members can include one or more of the heater wires described herein. Based at least in part on the heater wires being embedded in the wall of the composite tube 1201, the use of the composite tube 1201 as the inspiratory limb 202 can reduce condensation and rainout and maintain a more desirable or targeted temperature profile along the length of the inspiratory limb 202. The walls of the composite tube can provide a greater thermal mass, which is more resistant to temperature changes and increases the insulating effect of the wall against the ambient temperature outside the limb 202. As a result, the temperature along the length of the limb 202, including any number of different temperature environments, can be more precisely controlled, and less power or energy can be lost in controlling the temperature of the gas delivered to the patient. In some embodiments, a composite tube 1201 can also be used as the expiratory limb 210.

[0140] In general, the composite tube 1201 comprises a first elongated member 1203 and a second elongated member 1205. Member is a broad term and should be interpreted in its ordinary and customary sense to one of ordinary skill in the art (i.e., not limited to a special or specialized sense), including, but not limited to, an integral portion, an integral component, and a distinct component. Thus, while FIG. 17A illustrates an embodiment formed from two distinct components, it should be understood that in other embodiments, the first elongated member 1203 and the second elongated member 1205 can represent regions within a tube formed from a single material. Thus, the first elongated member 1203 can be a hollow portion of the tube, and the second elongated member 1205 is a structural support or reinforcing portion of the tube that adds structural support to the hollow portion. As described herein, the hollow portion and the structural support portion can have a helical configuration. Composite tube 1201 may be used to form the inspiratory limb 202 and / or expiratory limb 210 described herein, the coaxial tubes described below, or any other tubes described elsewhere in this disclosure.

[0141] In this example, the first elongated member 1203 comprises a helically wound hollow body at least partially forming an elongated tube having a longitudinal axis LA-LA and comprises a lumen 1207 extending along the longitudinal axis LA-LA. In at least one embodiment, the first elongated member 1203 is a tube. Preferably, the first elongated member 1203 is flexible. Additionally, the first elongated member 1203 is preferably transparent, or at least translucent or semi-opaque. A degree of translucency allows a caregiver or user to inspect the lumen 1207 for blockages or contaminants, or to identify the presence of moisture. A variety of plastics, including medical grade plastics, are suitable for the body of the first elongated member 1203. Examples of suitable materials include polyolefin elastomers, polyether block amides, thermoplastic copolymer elastomers, EPDM-polypropylene blends, and thermoplastic polyurethanes.

[0142] The hollow body structure of the first elongated member 1203 contributes insulating properties to the composite tube 1201. An insulated tube 1201 is desirable because it prevents or reduces heat loss as described herein. This allows the tube 1201 to deliver gas from the heater-humidifier to the patient while substantially maintaining the gas in a conditioned state with less or minimal energy loss.

[0143] In at least one embodiment, the hollow portion of the first elongated member 1203 is filled with a gas. The gas can be air, which has a low thermal conductivity (2.62×10 at 300 K). -2 W / m K) and very low cost. Also, advantageously, gases more viscous than air can be used, since higher viscosity reduces convective heat transfer. Thus, argon (17.72×10 at 300 K) -3 W / m K), krypton (9.43 × 10 at 300 K) -3 W / m K), and xenon (5.65 × 10 at 300 K). -3 Gases such as 1200 W / m·K can enhance the thermal insulation. Each of these gases is non-toxic, chemically inert, flame-resistant, and commercially available. The hollow portion of the first elongated member 1203 can be sealed at both ends of the tube, substantially stagnating the gas therein. Alternatively, the hollow portion can be a secondary pneumatic connection line, such as a pressure sample line for transmitting pressure feedback from the patient end of the tube to a controller. The first elongated member 1203 can be optionally perforated. For example, a surface of the first elongated member 1203 can be perforated on the outward facing surface opposite the lumen 1207. In another embodiment, the hollow portion of the first elongated member 1203 is filled with a liquid. An example of the liquid can be water or other biocompatible liquid with a high heat capacity. For example, a nanofluid can be used. An exemplary nanofluid with suitable heat capacity includes water and nanoparticles of a material such as aluminum.

[0144] The second elongated member 1205 is also helically wound and joined to the first elongated member 1203 between adjacent turns of the first elongated member 1203. The second elongated member 1205 forms at least a portion of the lumen 1207 of the elongated tube. The second elongated member 1205 serves as structural support for the first elongated member 1203.

[0145] In at least one embodiment, the second elongate member 1205 is wider at the base (proximal to the lumen 1207) and narrower at the top. For example, the second elongate member may be generally triangular, generally T-shaped, or generally Y-shaped. However, any shape that matches the contour of the corresponding first elongate member 1203 is suitable.

[0146] Preferably, the second elongated member 1205 is flexible to facilitate bending of the tube. Desirably, the second elongated member 1205 is less flexible than the first elongated member 1203. This improves the ability of the second elongated member 1205 to structurally support the first elongated member 1203. For example, the elastic modulus of the second elongated member 1205 is preferably 30-50 MPa (or about 30-50 MPa). The elastic modulus of the first elongated member 1203 is less than the elastic modulus of the second elongated member 1205. The second elongated member 1205 may be solid or nearly solid. Additionally, the second elongated member 1205 may encapsulate or house a conductive material, such as a filament, particularly a heating filament, or a sensor (not shown). The heating filament may minimize cold surfaces on which condensation from moist air may occur. A heating filament may also be used to change the temperature profile of the gas within the lumen 1207 of the composite tube 1201. A variety of polymers and plastics, including medical grade plastics, are suitable for the body of the second elongated member 1205. Examples of suitable materials include polyolefin elastomers, polyether block amides, thermoplastic copolymer elastomers, EPDM-polypropylene blends, and thermoplastic polyurethanes. In certain embodiments, the first elongated member 1203 and the second elongated member 1205 may be formed from the same material. The second elongated member 1205 may also be formed from a material of a different color than the first elongated member 1203, and may be transparent, translucent, or opaque. For example, in one embodiment, the first elongated member 1203 may be formed from a transparent plastic and the second elongated member 1205 may be formed from an opaque blue (or other color) plastic.

[0147] This spirally wound structure with a flexible hollow body and integral supports can provide compression resistance while allowing the tube walls to be flexible enough to allow short radius bending without buckling, plugging, or collapsing. Preferably, the tube can be bent around a 25 mm diameter metal cylinder without buckling, plugging, or collapsing as defined in the test for increase in flow resistance with bending according to ISO 5367:2000(E). This structure can also provide a smooth lumen 1207 surface (tube bore), which helps keep the tube free of deposits and improves gas flow. The hollow body has been found to improve the insulating properties of the tube while keeping it lightweight.

[0148] As explained above, the composite tube 1201 can be used as an expiratory and / or inspiratory tube in a breathing circuit, or as part of a breathing circuit. Preferably, the composite tube 1201 is used at least as an inspiratory tube.

[0149] FIG. 17B shows a longitudinal cross-section of the top of the exemplary composite tube 1201 of FIG. 17A. FIG. 17B has the same orientation as FIG. 17A. This example further illustrates the hollow body shape of the first elongated member 1203. As can be seen in this example, the first elongated member 1203 forms a plurality of hollow air bubbles in the longitudinal cross-section. A portion 1209 of the first elongated member 1203 overlaps an adjacent turn of the second elongated member 1205. A portion 1211 of the first elongated member 1203 forms the wall of the lumen (lumen).

[0150] It has been surprisingly discovered that having gaps 1213 between adjacent turns of the first elongated member 1203, i.e., between adjacent bubbles, improves the overall thermal insulation properties of the composite tube 1201. Thus, in certain embodiments, adjacent bubbles are separated by gaps 1213. Additionally, certain embodiments include the realization that providing gaps 1213 between adjacent bubbles increases the heat transfer resistance (R-value) and therefore decreases the thermal conductivity of the composite tube 1201. This gap configuration has also been found to improve the flexibility of the composite tube 1201 by allowing for shorter radius bends. As shown in FIG. 17B, the T-shaped second elongated member 1205 can help maintain the gaps 1213 between adjacent bubbles. Nevertheless, in certain embodiments, adjacent bubbles are in contact. For example, adjacent bubbles can be bonded together.

[0151] One or more conductive materials may be disposed within the second elongated member 1205 to heat or sense the gas flow. In this example, two heating filaments 1215 are encapsulated within the second elongated member 1205, one on each side of the vertical portion of the "T". The heating filaments 1215 include conductive materials such as alloys of aluminum (Al) and / or copper (Cu) and conductive polymers. Preferably, the material forming the second elongated member 1205 is selected so that it does not react with the metals in the heating filaments 1215 when the heating filaments 1215 reach their operating temperature. The filaments 1215 may be positioned away from the lumen 1207 so that they are not exposed to the lumen 1207. At one end of the compound tube, several pairs of filaments may be formed as connected loops.

[0152] In at least one embodiment, multiple filaments are disposed within the second elongated member 1205. The filaments can be electrically connected to each other and share a common rail. For example, a first filament, such as a heating filament, can be disposed on a first side of the second elongated member 1205. A second filament, such as a sensing filament, can be disposed on a second side of the second elongated member 1205. A third filament, such as a ground filament, can be disposed between the first and second filaments. The first, second, and / or third filaments can be connected to each other at one end of the second elongated member 1205.

[0153] FIG. 17C shows a longitudinal cross section of the foam in FIG. 17B. As shown, the portion 1209 of the first elongate member 1203 that overlaps the adjacent turn of the second elongate member 1205 is characterized by some bond area 1217. The larger bond area improves the resistance of the tube to delamination at the interface of the first and second elongate members. Additionally or alternatively, the shape of the bead and / or foam can be adapted to increase the bond area 1217. For example, FIG. 17D shows a relatively small bond area on the left side. Also, FIG. 19B shows a smaller bond area. In contrast, FIG. 17E has a much larger bond area than that shown in FIG. 17D due to the size and shape of the bead. FIGS. 19A and 19C also show larger bond areas. Each of these figures is discussed in more detail below. It should be understood that while the configurations in Figures 17E, 19A, and 19C may be preferred in certain embodiments, other configurations, including the configuration in Figure 17D, the configuration in Figure 19B, and other variations, may be utilized in other embodiments, if desired.

[0154] Figure 17D shows a longitudinal cross section of the top of another composite tube. Figure 17D has the same orientation as Figure 17B. This example further illustrates the hollow body shape of the first elongated member 1203 and how the first elongated member 1203 forms multiple hollow air bubbles in the longitudinal cross section. In this example, the bubbles are completely separated from each other by gaps 1213. A generally triangular second elongated member 1205 supports the first elongated member 1203.

[0155] FIG. 17E shows a longitudinal cross section of the top of another composite tube. FIG. 17E has the same orientation as FIG. 17B. In the example of FIG. 17E, the heating filaments 1215 are spaced farther apart from each other than the filaments 1215 in FIG. 17B. It has been discovered that increasing the space between the heating filaments can improve the heating efficiency. Certain embodiments include this realization. Heating efficiency represents the ratio of the amount of heat entering the tube to the amount of energy exiting or recoverable from the tube. In general, the more energy (or heat) dissipated from the tube, the lower the heating efficiency. For improved heating performance, the heating filaments 1215 can be evenly (or nearly evenly) positioned along the bore of the tube. Alternatively, the filaments 1215 can be positioned at the end of the second elongated member 1205, which may allow for simpler manufacturing.

[0156] Reference is now made to Figures 18A-18G, which illustrate exemplary configurations for the second elongated member 1205. Figure 18A illustrates a cross-section of a second elongated member 1205 having a shape similar to the T-shape shown in Figure 17B. In this exemplary embodiment, the second elongated member 1205 does not have a heating filament. Other shapes for the second elongated member 1205 may also be utilized, including variations of the T-shape as described below, and a triangular shape.

[0157] FIG. 18B illustrates another exemplary second elongated member 1205 having a T-shaped cross section. In this example, the heating filament 1215 is embedded in notches 1301 in the second elongated member 1205 on each side of the vertical portion of the “T”. In some embodiments, the notches 1301 can be formed in the second elongated member 1205 during extrusion. Alternatively, the notches 1301 can be formed in the second elongated member 1205 after extrusion. For example, a cutting tool can form the notches in the second elongated member 1205. Preferably, the notches are formed by the heating filament 1215 as it is pushed or pulled (mechanically secured) into the second elongated member 1205 immediately after extrusion while the second elongated member 1205 is relatively soft. Alternatively, one or more heating filaments can be attached (e.g., glued, bonded, or partially embedded) to the bottom of the elongated member such that the filaments are exposed to the lumen of the tube. In such embodiments, it may be desirable to contain the filaments with insulation to reduce the risk of ignition when a flammable gas, such as oxygen, is passed through the lumen of the tube.

[0158] 18C illustrates in cross section yet another exemplary second elongate member 1205. The second elongate member 1205 has a generally triangular shape. In this example, heating filaments 1215 are embedded on either side of the triangle.

[0159] FIG. 18D illustrates yet another exemplary second elongated member 1205 in cross section. The second elongated member 1205 includes four grooves 1303. The grooves 1303 are depressions or indentations in the cross-sectional shape. In some embodiments, the grooves 1303 can facilitate the formation of a notch (not shown) for embedding a filament (not shown). In some embodiments, the grooves 1303 facilitate the positioning of a filament (not shown) so that the filament is pushed or pulled into the second elongated member 1205 and thereby embedded. In this example, the four starting grooves 1303 facilitate the placement of up to four filaments, e.g., four heating filaments, four sensing filaments, two heating filaments and two sensing filaments, three heating filaments and one sensing filament, or one heating filament and three sensing filaments. In some embodiments, the heating filaments can be located on the outside of the second elongated member 1205. The sensing filament can be located on the inside.

[0160] 18E illustrates in cross-section yet another exemplary second elongate member 1205. The second elongate member 1205 has a T-shaped cross-sectional shape and a number of grooves 1303 for positioning heating filaments.

[0161] FIG. 18F illustrates yet another exemplary second elongated member 1205 in cross section. Four filaments 1215 are encapsulated within the second elongated member 1205, two on each side of the vertical portion of the “T”. The filaments are encapsulated within the second elongated member 1205 because the second elongated member 1205 was extruded around the filaments, as described in more detail below. No notches were formed to embed the heating filaments 1215. In this example, the second elongated member 1205 also includes a number of grooves 1303. Because the heating filaments 1215 are encapsulated within the second elongated member 1205, the grooves 1303 are not used to facilitate the formation of notches to embed the heating filaments. In this example, the grooves 1303 can facilitate separation of the embedded heating filaments, which, for example, facilitates stripping of the individual cores when terminating the heating filaments.

[0162] 18G illustrates yet another exemplary second elongate member 1205 in cross section. The second elongate member 1205 has a generally triangular shape. In this example, the shape of the second elongate member 1205 is similar to that of FIG. 18C, but four filaments 1215 are encapsulated within the second elongate member 1205, all of which are centrally located in the lower third of the second elongate member 1205 and disposed along a generally horizontal axis.

[0163] As explained above, it may be desirable to increase the distance between the filaments to improve heating efficiency. However, in some embodiments, when the heating filament 1215 is incorporated into the composite pipe 1201, the filament 1215 may be positioned relatively centrally in the second elongated member 1205. The centralized location provides robustness to the composite piping for reuse, in part because such a location reduces the likelihood of the filament breaking during repeated bending of the composite pipe 1201. Centering the filament 1215 may also reduce the risk of fire hazards, since the filament 1215 is coated with a thermal barrier and away from the gas path.

[0164] As discussed above, some of the above examples show suitable arrangements of the filaments 1215 within the second elongated member 1205. In the aforementioned examples with multiple filaments 1215, the filaments 1215 are aligned generally along a horizontal axis. Alternative configurations are suitable. For example, two filaments could be aligned along a vertical axis or along a diagonal axis. Four filaments could be aligned along a vertical axis or along a diagonal axis. Four filaments could be aligned in a cross configuration, with one filament disposed at the top of the second elongated member, one filament disposed at the bottom of the second elongated member (near the lumen of the tube), and two filaments disposed at the left and right bars of a "T" or "Y" shape, or at the ends of the base of a triangle.

[0165] Tables 1A and 1B show some preferred dimensions of the medical tubing described herein, as well as some preferred ranges for these dimensions. The dimensions represent the transverse cross-section of the tubing. In these tables, lumen diameter represents the inner diameter of the tubing. Pitch represents the distance between two repeating points measured axially along the tubing, i.e., the distance between the tips of adjacent vertical portions of the "T" of the second elongated member. Bubble width represents the width (maximum outer diameter) of the bubble. Bubble height represents the height of the bubble from the lumen of the tubing. Bead height represents the maximum height of the second elongated member from the lumen of the tubing (e.g., the height of the vertical portion of the "T"). Bead width represents the maximum width of the second elongated member (e.g., the width of the horizontal portion of the "T"). Bubble thickness represents the thickness of the bubble wall.

[0166] [Table 1A]

[0167] [Table 1B]

[0168] Tables 2A and 2B provide exemplary ratios between dimensions of tube geometries for the tubes set forth in Tables 1A and 1B, respectively.

[0169] [Table 2A]

[0170] [Table 2B]

[0171] The following table shows some exemplary properties of a composite tubing (designated "A") having a heating filament embedded within the second elongated member as described herein. For comparison, properties of a Fisher & Paykel model RT100 disposable corrugated tubing (designated "B") having a heating filament helically wound within the bore of the tubing are also shown.

[0172] Resistance to flow (RTF) measurements were performed according to ISO5367:2000(E), Annex A. The results are summarized in Table 3. As can be seen below, the RTF for the composite pipe is less than the RTF for the model RT100 pipe.

[0173] [Table 3]

[0174] Condensation or "rainout" inside the tube represents the weight of condensate collected per day at a room temperature of 18°C ​​with a gas flow rate of 20 L / min. Humidified air is continuously flowed from the chamber through the tube. The weight of the tube is recorded before and after each day of testing. Three consecutive tests are performed, allowing the tube to dry between each test. The results are shown in Table 4. These results showed that rainout was significantly lower on the composite tube than on the model RT100 tube.

[0175] [Table 4]

[0176] The power requirements represent the power consumed during the condensation test. In this test, the ambient air was kept at 18°C. The humidification chamber (see, for example, humidification chamber 114 in FIG. 1) was powered by an MR850 heater base. A heating filament in the tube was powered separately from the DC power supply. Various flow rates were set and the chamber was maintained at 37°C at the chamber output. The DC voltage to the circuit was then changed to produce a temperature of 40°C at the circuit output. The voltage required to hold the output temperature was recorded and the resulting power was calculated. The results are shown in Table 5. These results show that composite tube A uses significantly more power than tube B. This is because tube B uses a helical heating filament within the tube bore to heat the gas from 37°C to 40°C. The composite tube does not tend to heat the gas as quickly because the heating filament is within the tube wall (embedded in the second elongated member). Rather, the composite tube is designed to hold the gas temperature and prevent rainout by keeping the tube bore at a temperature above the dew point of the humidified gas.

[0177] [Table 5]

[0178] The tubes were tested for flexibility using a three-point bend test. The tubes were placed in a three-point bend test jig and used with an Instron 5560 Test System instrument to measure load and elongation. Each tube sample was tested three times. The elongation of the tubes with respect to the applied load was measured to obtain an average stiffness constant for each. The average stiffness constants for Tube A and Tube B are shown in Table 6.

[0179] [Table 6]

[0180] As mentioned above, heated wires 206 can be placed inside the inspiratory limb 202 and / or expiratory limb 210 to keep the wall temperature above the dew point temperature, thereby reducing the risk of rainout within the tube.

[0181] thermal properties In embodiments of the composite tube 1201 incorporating a heating filament 1215, heat may be lost through the wall of the first elongated member 1203, resulting in uneven heating. As explained above, one method to compensate for these heat losses is to apply an external heating source at the wall of the first elongated member 1203, which helps to regulate the temperature and prevent heat loss. However, other methods for optimizing thermal properties may also be used.

[0182] Reference is now made to Figures 19A-19C, which illustrate example configurations for bubble height (i.e., the cross-sectional height of the first elongate member 1203 measured from the lumen-facing surface to the surface defining the maximum outer diameter) for improving thermal properties.

[0183] The dimensions of the bubbles can be selected to reduce heat loss from the composite tube 1201. In general, increasing the bubble height also increases the effective thermal resistance of the tube 1201 because a larger bubble height allows the first elongated member 1203 to hold more insulating air. However, it has been discovered that at some bubble height, changes in air density cause convection currents inside the tube 1201, thereby increasing heat loss. Also, at some bubble height, the surface area becomes so large that heat lost through the surface exceeds the benefit of a larger bubble height. Certain embodiments include these realizations.

[0184] The radius of curvature and the curvature of the bubble can be useful in determining the desired bubble height. The curvature of an object is defined as the inverse of the radius of curvature of the object. Thus, the greater the radius of curvature an object has, the less curved the object is. For example, a flat surface has an infinite radius of curvature and therefore a curvature of 0.

[0185] FIG. 19A shows a longitudinal cross section of the top of the composite tube. FIG. 19A shows one embodiment of the composite tube 1201 where the bubble has a large height. In this example, the bubble has a relatively small radius of curvature and therefore a large curvature. Also, the bubble is about 3-4 times as tall as the height of the second elongated member 1205.

[0186] Figure 19B shows a longitudinal cross section of the top of another composite tube. Figure 19B shows an embodiment of a composite tube 1201 where the bubble is flattened at the top. In this example, the bubble has a very large radius of curvature and a small curvature. Also, the bubble is about the same height as the second elongated member 1205.

[0187] FIG. 19C shows a longitudinal cross section of the top of another composite tube. FIG. 19C shows an embodiment of a composite tube 1201 where the width of the bubble is greater than the height of the bubble. In this example, the bubble has a radius and curvature between those of FIG. 19A and FIG. 19B, with the center of radius for the top of the bubble being on the outside of the bubble (as compared to FIG. 19A). The inflection points on the left and right sides of the bubble are approximately in the middle (heightwise) of the bubble (as opposed to being at the bottom of the bubble as in FIG. 19A). Also, the height of the bubble is approximately twice that of the second elongate member 1205, resulting in a bubble height between the heights of FIG. 19A and FIG. 19B.

[0188] The configuration of FIG. 19A had the least heat loss from the tubes. The configuration of FIG. 19B had the most heat loss from the tubes. The configuration of FIG. 19C had intermediate heat loss between the configurations of FIG. 19A and 19B. However, the large external surface area and convective heat transfer in the configuration of FIG. 19A resulted in inefficient heating. Thus, of the three bubble configurations of FIG. 19A-FIG. 19C, the configuration of FIG. 19C was determined to have the best overall thermal properties. With the same thermal energy input to the three tubes, the configuration of FIG. 19C produced the greatest temperature rise along the length of the tubes. The bubbles of FIG. 19C are large enough to increase the insulating air volume, but not so large as to cause significant heat loss by convection. The configuration of FIG. 19B was determined to have the worst thermal properties. That is, the configuration of FIG. 19B produced the least temperature rise along the length of the tubes. The configuration of FIG. 19A had intermediate thermal properties and produced a lower temperature rise than the configuration of FIG. 19C.

[0189] It should be understood that while the configuration of FIG. 19C may be preferred in certain embodiments, other configurations, including the configuration of FIG. 19A, the configuration of FIG. 19B, and other variations, may be utilized in other embodiments, if desired.

[0190] Table 7 shows the bubble height, tube outer diameter, and radius of curvature for the configurations shown in Figures 19A, 19B, and 19C, respectively.

[0191] [Table 7]

[0192] 19C-19F, which show example positioning of heating elements 1215 in similar bubble shapes to improve thermal properties. The position of the heating elements 1215 can change the thermal properties of the interior of the composite tube 1201.

[0193] Figure 19C shows a longitudinal cross section of the top of another composite tube. Figure 19C shows an embodiment of a composite tube 1201 where the heating elements 1215 are centrally located within the second elongate member 1205. This example shows the heating elements 1215 close to each other but not close to the bubble wall.

[0194] Figure 19D shows a longitudinal cross section of the top of another composite tube. Figure 19D shows an embodiment of a composite tube 1201 in which the heating elements 1215 are positioned further apart within the second elongate member 1205 than in Figure 19C. These heating elements are closer to the bubble wall, allowing for better regulation of the heat inside the composite tube 1201.

[0195] Figure 19E shows a longitudinal cross section of the top of another composite tube. Figure 19E shows an embodiment of a composite tube 1201 in which heating elements 1215 are spaced above and below the vertical axis of the second elongate member 1205. In this example, the heating elements 1215 are equally close to each bubble wall.

[0196] Figure 19F shows a longitudinal cross section of the top of another composite tube. Figure 19F shows an embodiment of a composite tube 201 in which heating elements 1215 are spaced apart on either end of the second elongate member 1205. The heating elements 1215 are closer to the bubble wall, particularly in comparison to Figures 19C-19E.

[0197] Of the four filament configurations of Figures 19C-19F, Figure 19F was determined to have the best thermal performance. All configurations produced similar heat loss from the tube due to their similar bubble shape. However, when the same heat energy was input into the tube, the filament configuration of Figure 19F produced the greatest temperature rise along the length of the tube. The configuration of Figure 19D was determined to have the second best thermal performance, producing the second greatest temperature rise along the length of the tube. The configuration of Figure 19C produced the next best results. The configuration of Figure 19E had the worst performance, producing the smallest temperature rise along the length of the tube when the same amount of heat was input.

[0198] It should be understood that while the configuration of FIG. 19F may be preferred in certain embodiments, other configurations, including the configurations of FIGS. 19C, 19D, 19E, and other variations, may be utilized in other embodiments, if desired.

[0199] Reference is now made to Figures 20A-C, which show exemplary configurations for stacking the first elongated member 1203. In certain embodiments, it has been discovered that stacking multiple foam bodies can improve heat distribution. These embodiments may be more beneficial when using an internal heating filament 1215. Figure 20A shows a longitudinal cross section of the top of another composite tube. Figure 20A shows a cross section of the composite tube 1201 without stacking.

[0200] FIG. 20B shows a longitudinal cross section of the top of another composite tube. FIG. 20B shows another exemplary composite tube 1201 with stacked bubbles. In this example, two bubbles are stacked on top of each other to form a first elongated member 1203. Compared to FIG. 20A, the overall bubble height remains the same, but the bubble pitch is half that of FIG. 20A. Also, the embodiment in FIG. 20B has only a slight reduction in air volume. The stacking of bubbles reduces natural convection and heat transfer in the gaps between the bubbles 1213, lowering the overall thermal resistance. The heat flow path is increased within the stacked bubbles, allowing heat to be more easily distributed through the composite tube 1201.

[0201] FIG. 20C shows a longitudinal cross section of the top of another composite tube. FIG. 20C shows another example of a composite tube 1201 with stacked bubbles. In this example, three bubbles are stacked on top of each other to form a first elongated member 1203. Compared to FIG. 20A, the overall bubble height remains the same, but the bubble pitch is one third of that in FIG. 20A. Also, the embodiment in FIG. 20B has only a slight reduction in air volume. The stacking of bubbles reduces natural convection and heat transfer in the gaps between the bubbles 1213.

[0202] Additional Exemplary Intermediate Connectors 32A-32C show another example of an intermediate connector 3200 comprising an intermediate PCB 3205 and an intermediate connection element 3210. The intermediate PCB 3205 can include a conformal coating configured to protect the intermediate PCB 3205 from water ingress. For example, water can follow the contours of the intermediate PCB 3205. The intermediate connector 3200 can include features configured to position beads in suitable locations for attaching wires, such as for heating or sensing elements of the circuits described herein. The intermediate PCB 3205 can extend partially through the intermediate connection element 3210. For example, a portion of the intermediate PCB 3205 can extend outside the tube of the intermediate connection element 3210 and a portion can extend partway through the lumen portion of the intermediate connection element 3210. In some implementations, the portion of the intermediate PCB 3205 that extends into the lumen penetrates about one-third of the lumen. This can provide a relatively low flow resistance for the intermediate PCB that extends through the entire lumen.

[0203] In some embodiments, the intermediate PCB 3205 generates heat during operation due at least in part to diodes in the intermediate PCB 3205. The heat generated by the intermediate PCB 3205 can help evaporate excess condensation.

[0204] The intermediate connector 3200 may be overmolded to securely hold the components in place and seal the part. In some embodiments, a clamshell may be applied, which may increase the insulation of the intermediate connector 3200.

[0205] The intermediate connector 3200 can include a tube stopper 3220 configured to prevent the tube from rotating excessively as the tube stopper 3220 can be configured to capture between the foam and the bead. The tube stopper 3220 can be configured to be positioned 180 degrees and / or 270 degrees from the PCB to properly align the tube. The tube stopper 3220 can be configured to provide an attachment point for the tube. The intermediate connector 3200 can include one or more bridges 3222 configured to lift the bead to allow polymer to flow under the bead to reduce water ingress. In some embodiments, one or more bridges 3222 can be located on each side of the intermediate connector 3200. The intermediate connector 3200 can include a comb 3224 configured to hold the wire (e.g., heater wire) in place within the slot. The intermediate connector 3200 can include an indicator, such as an arrow 3226, configured to indicate the orientation of the intermediate connector 3200 so that the diode is oriented in the correct direction. The arrow 3226 may also help reduce or prevent water ingress. The intermediate connector 3200 may include a waterproof ring 3228 that forms a complete loop around the intermediate connector 3200. The waterproof ring 3228 may be configured to inhibit or eliminate water ingress into exposed areas of the PCB 3205.

[0206] In some embodiments, the intermediate connecting element 3210 can have a wall thickness of about 1-2 mm and a diameter of 4-15 mm. In some embodiments, the inner diameter of the intermediate connecting element 3210 can be about 8-9 mm and the outer diameter can be about 11.5 mm. The outer diameter of the intermediate connecting element 3210 can be configured to be large enough to reduce flow resistance. Smaller passages in the intermediate connecting element 3210 can mean gas passes through the passages faster, which can reduce condensation.

[0207] The intermediate connector 3200 can include a process aid 3230 configured to properly align the tube so that the foam engages and holds the tube in place. The intermediate connector 3200 can include pins 3232 configured to position a cover (e.g., clamshell 3300 as described herein with reference to FIG. 33) and hold the cover by friction fit (e.g., the pins 3232 can engage with mating recesses in the cover). The intermediate connector 3200 includes three or four pins in some implementations. The pins 3232 can be configured to have a sufficient length to protrude through the overmolded portion for alignment and / or positioning purposes. The pins 3232 can be positioned on either side of the intermediate connector 3200, for example, to be positioned 90 degrees from the position shown. In some embodiments, the intermediate connector 3200 includes slots 3234 that act as machined keyway features to reduce the chance of being placed in an incorrect orientation.

[0208] Figures 33A-C show an example of a clamshell 3300 that can be applied to an intermediate connector, such as the intermediate connector 3200 described herein with reference to Figure 32. The clamshell 3300 can be configured to provide an aesthetic cover for an overmolded intermediate connector, such as the intermediate connector 3200. The clamshell 3300 can also be configured to protect the PCB from damage.

[0209] The clamshell 3300 comprises two halves 3305a, 3305b that mate with each other. In some embodiments, the two halves 3305a, 3305b are permanently attached to each other (e.g., separating the two halves involves at least partially damaging or breaking the clamshell 3300, or in which case a force of at least about 30 N is required to separate the two halves 3305a, 3305b of the clamshell 3300). Each half 3305a, 3305b can be formed from the same integral tool and can be symmetrical such that one half can be rotated to snap into the other half. The clamshell 3300 can include a snap-fit ​​connection comprising a clip 3309a and a clip receiving mechanism 3309b. The clip 3309a can be a pair of protruding clips extending diagonally opposite each other from the two covers of the clamshell 3300. The clip 3309a can be configured to interact with a complementary clip receiving feature 3309b to reduce the gap between the halves 3305a, 3305b, keep the gap closed, and hold the ends closed to form the primary mating feature of the clamshell 3300. The clamshell 3300 can include a female locating slot 3307a configured to engage with a male locating pin 3307b. In some embodiments, the female locating slot 3307a can include a slight inward taper that requires force to insert the male locating pin 3307b. The male locating pin 3307b can be configured to be press-fit into a corresponding female locating slot 3307a in the other half of the clamshell 3300. This can act as a back-up connection if the snap-fit ​​connection does not work.

[0210] The clamshell 3300 includes features such as ribs 3310a, 3310b to ensure the clamshell is assembled correctly. Correct assembly may occur at least in part due to the two halves 3305a, 3305b being configured such that they cannot be fully engaged with one another if assembled incorrectly. The cover 3300 may include horizontal ribs 3310b to reduce vertical movement of the middle connector and vertical ribs 3310a to reduce horizontal movement of the middle connector. The vertical ribs 3310b may be configured such that the middle rib is longer so that it can be closer to the overmolded portion and reduce rotation of the overmolded portion. The ribs 3310a, 3310b may be generally configured to receive and position pins from the overmolded middle connector. For example, the ribs 3310a, 3310b can be configured to prevent or impede incorrect positioning by pushing a pin of an overmolded intermediate connector (e.g., pin 3232 of intermediate connector 3200 described herein with reference to FIG. 32) off-center, and the ribs 3310a, 3310b may also prevent or impede engagement of a second pin.

[0211] The clamshell 3300 may include a mating region 3315 comprising a protrusion and a cutout region. The mating region 3315 may be configured to interact with a corresponding region on the other half of the clamshell 3300. The mating region 3315 may be configured to prevent rough edges between the two halves 3305a, 3305b resulting in a better overall finish and may help guide proper alignment of the halves. The mating region 3315 may be configured to be symmetrical with a corresponding mating region on the other half of the clamshell. The clamshell 3300 may include an internal cutout region 3320 configured to allow space for an overmolded protruding PCB to fit within the region 3320.

[0212] In some embodiments, the overmolded intermediate connector 3200 can be configured to fit within the clamshell 3300 in at least four different positions. The intermediate connector 3200 can include, for example, three pins that are not centrally located relative to the intermediate connector 3200. The intermediate pins, in some embodiments, can be centrally located relative to the other pins rather than the intermediate connector 3200.

[0213] In some embodiments, the overmolded intermediate connector 3200 includes three or more pins 3220 for securely fastening the overmolded intermediate connector 3200 to the clamshell 3300. The pins 3220 can be configured to reduce horizontal and / or vertical translation and / or rotation about a horizontal axis, as described herein with reference to FIGS. 32A-32C. In some embodiments, four pins 3220 can be used to effectively position and locate the overmolded intermediate connector 3200 within the clamshell 3300. In such embodiments, the two halves 3305a, 3305b of the clamshell 3300 may not be symmetrical. Additionally, the fourth pin may push the wires outward, potentially increasing the possibility of exposing the wires due to the reduced amount of overmolded material covering the wires. The pins 3220 can be configured to be long enough so that they engage with the ribs 3310a, 3310b to reduce or prevent rotation of the overmolded intermediate connector 3200. In some embodiments, the center pin can be longer than the other pins. Additionally, the pins 3320 can be configured to be thick enough for mechanical robustness.

[0214] The clamshell 3300 and the overmolded intermediate connector may include components that reduce or prevent misalignment of the overmolded intermediate connector within the clamshell 3300 during installation or fabrication. In some embodiments, when the overmolded intermediate connector is incorrectly positioned within the clamshell 3300, the overmolded intermediate connector may move within the clamshell 3300, thereby preventing the two halves 3305a, 3305b from mating properly. This may cause the two halves 3305a, 3305b to become disconnected and the clamshell 3300 to come off the overmolded intermediate connector.

[0215] The clamshell 3300 can be sized based on the intended use. For example, the clamshell 3300 can be sized according to the size of the opening in the side of the incubator. The clamshell 3300 can be configured to fit into the opening of the incubator, allowing the tube to be positioned within the incubator. However, if the clamshell 3300 is too small, the material strength may be reduced below an acceptable level. This may be especially true with respect to the clip-on mechanism. In some embodiments, the clamshell 3300 is configured to seat snugly without touching the overmolded intermediate connector. As a result, it may be difficult to include additional structure or features in the clamshell 3300.

[0216] During fabrication, the tubes can be wrapped around either end of the intermediate connector before overmolding. The clamshell 3300 can be configured to seat close to the tubes but with little or no contact, as the tubes may exert pressure on the clamshell 3300. The clamshell 3300 can be made from materials including polypropylene, acetyl, or other materials with similar properties.

[0217] In some embodiments, the cover (e.g., clamshell 3300) can include a living hinge that can be used to join the two halves of the cover. This living hinge may provide a simple mechanism for assembling the cover. In some embodiments, an internal hinge can be integrated into the cover, where the hinge is combined with a clip to provide an effective joining mechanism.

[0218] In some embodiments, the cover may include pins that are used to replace the horizontal and vertical ribs of the clamshell 3300. These pins may be configured to provide the same locating function as the ribs 3310a, 3310b of the clamshell 3300. In certain embodiments, the cover may use fewer pins or no pins at all. This cover may allow rotation of the middle connector but resist sliding of the middle connector. In some embodiments, the ends of the locating pins may be thickened so that the insert forms a locating point.

[0219] In some embodiments, the overmolded portion of the intermediate connector can form an outer cover. In some embodiments, the cover can be shaped to match the shape of the overmolded intermediate connector. In such a configuration, the cover can be asymmetric. The shape can be configured to reduce contact between the cover and the intermediate connector.

[0220] In some embodiments, the cover halves can be joined using ultraviolet (UV) cured glue, adhesives, or using male and female locating pins on the cover to form a press-fit connection.

[0221] Sectionalized Heater Control 26 shows a flow chart of an exemplary method for controlling a segmented heater, such as in an inspiratory limb with a heater coupled to an extension limb also having a heater. The control method may be performed by a humidification system or other control module as described herein. As such, for ease of explanation, the following method is described as being performed by a control module, but one or more steps of the method, or portions of a single step of the method, may be performed by any combination of components in the humidification system. In some embodiments, method 2600 may be performed at least once per second to provide substantially continuous and fine control of the humidification system.

[0222] In step 2605, the control module determines a power demand for the first heater section (e.g., a heater in the inspiratory limb). This can be done, for example, using open loop control. A predefined duty cycle can be determined to be the power demand of the first heater section that is determined at least in part by the flow of gas through the humidification system. In some embodiments, this predefined duty cycle can be used for control of the first heater section and can be determined using a model configured to be applicable to a majority of situations. Advantageously, this can allow the control module to apply the same control parameters in most situations. For example, this can mean that the control module does not change its control parameters for different ambient conditions.

[0223] The power demand can be configured by the control module to maintain a target temperature profile, an example of which is shown in FIG. 27. In some embodiments, the target temperature profile utilizes a greater amount of heating in the first heater section to reduce condensation (e.g., relative to the second heater section of the extension limb). For example, the first heater section can be controlled to heat the inspiratory limb above a set point to impart a lower relative humidity to the gas. This can effectively control the cooling of the gas by the time it reaches the patient after flowing through the extension limb, allowing the gas to maintain a high absolute humidity.

[0224] In step 2610, the control module determines the temperature at the patient-end of the combined inspiratory and extension limbs, the temperature being determined using a patient-end temperature sensor. The control module can be configured to monitor this temperature sensor frequently (e.g., once per second, twice per second, etc.). In response to the determined temperature, the control module can modify the duty cycle to achieve a target temperature profile, a target absolute or relative humidity of the gas at the patient-end, and / or a target temperature of the gas at the patient-end.

[0225] In step 2615, the control module determines the difference between the setpoint temperature and the temperature measured at the patient end. For ease of reference, this difference value is referred to as the error, although it is not inferred or understood that this value represents an error or other unintended result.

[0226] In step 2620, the control module determines a power demand for a combination of a first heater section and a second heater section (e.g., an inspiratory limb and an extension limb coupled to the inspiratory limb). The power demand can be proportional to the length of the limb relative to the flow rate. For example, the control module can determine the power demand as power per unit length.

[0227] The power demand can be expressed as DC_12=Kp*e+Ki*∫e dt, where DC_12 is the control module output (e.g., power, duty cycle, etc.) for the first and second combinations, Kp is a proportional coefficient in a proportional-integral-derivative (PID) control scheme, Ki is an integral coefficient in the PID scheme, and e is the error (i.e., the current difference between the setpoint temperature and the measured temperature, as determined in step 2615). The control module can be configured to reduce or eliminate the error. For example, the control module can be configured to control the power to the heater sections to bring the current temperature to the setpoint, taking into account short-term and long-term effects on temperature responsive to the power delivered to each heater section.

[0228] In a PID control scheme, the value of Kp can be related to the rate of temperature change in the system. Kp can be modified to achieve a target or preferred rate of temperature change in the system with the objective of achieving a setpoint temperature, taking into account short-term and long-term effects. The product of Kp and e in the above equation can be referred to as the proportional term in the PID scheme.

[0229] In a PID control scheme, the value of Ki can relate to how quickly the system achieves the target set point as the system approaches steady state operation. The value of Ki can also relate to how fast the system heats up. The integral value of the error (e.g., ∫e de) represents the accumulated error over the time the system has been running. The product of Ki and the accumulated error in the above equation can be referred to as the integral term in the PID scheme.

[0230] In some embodiments, there is no derivative term in the PID control scheme.

[0231] In step 2625, the control module selectively heats the first and second heater sections to meet their respective power demands. In some embodiments, the power demand for the first heater section can be exceeded. In some implementations, the control module can implement an algorithm that allows the power demand for the first heater section to be exceeded depending on other control parameters, as described herein with reference to FIG.

[0232] The control module can be configured to consider the power demand for the first heater section to be met when at least one of the following conditions apply: (1) the power demand of the first heater section is met by heating the first heater section; (2) the power demand of the first heater section is met partially by heating the first heater section and partially by heating the second heater section, where the combined duty cycle of the first and second heater sections contributes to the total demand and any shortfall is met by heating the first heater section (an example of this is described with reference to FIG. 28 ); or (3) the demand of the first heater section is met by heating the combined first and second heater sections.

[0233] FIG. 28 illustrates a functional block diagram 2800 illustrating the relationship between the processing components of the control module, the demands associated with the heater sections, and the application of the resulting duty cycle determinations. For example, the control module can implement a PID controller 2802 as described herein with reference to FIG. 26 and / or FIG. 30. The PID controller 2802 can be configured to control a combination of the first and second heater sections 2806 (e.g., an outer loop of the inspiratory limb coupled to an extension of the inspiratory limb) based at least in part on the demands determined by the control module, as described herein with reference to FIG. 26. The control module can implement a control algorithm 2804 as described herein with reference to FIG. 26, FIG. 29, and / or FIG. 31. The control algorithm 2804 can be used to control the first heater section 2808 based at least in part on the demands determined by the control module. The control module can apply power to the first and second heater sections based on a duty cycle 2810 determined to meet the demand for the first and second heater sections 2806 using the PID controller 2802. Similarly, the control module can apply power to the first heater section based on a duty cycle 2812 determined to meet the demand for the first heater section 2808 using the control algorithm 2804. In some embodiments, the control algorithm can determine the duty cycle 2812 for the first heater section based at least in part on the demand for the combination of the first and second heater sections, since the power applied to the combination of heater sections affects the temperature and humidity of the gas in the first section. For example, as described herein with reference to FIG. 26, the demand for the first heater section can be met in part or in full by the demand for the combination of the first and second heater sections.In certain embodiments, the PID controller 2802 can be configured to be the primary means of controlling the heating of the combined inspiratory and extension limbs (e.g., first and second heater sections), and the control algorithm 2804 for the inspiratory limb (e.g., first heater section) can serve as a method of providing supplemental heating that may be particularly appropriate during certain stages of operation (e.g., during start-up, warm-up periods, temperature change periods, etc.).

[0234] 29 shows a flow chart of an example control algorithm 2900 implemented by the control module to control the sectioned heater. In step 2902, the control module operates in an open loop control mode by setting the power demand for the first heater section to be a fixed duty cycle value. In some implementations, the fixed duty cycle value may be initially set to 80%. The duty cycle value may be increased or decreased as determined by the steps of the control algorithm.

[0235] In step 2904, the control module determines whether the humidification system is in a standby state. In some embodiments, the control module may determine that the humidification system is in a standby state by examining a value stored in a local variable. If the humidification system is in a standby state, the control module proceeds to step 2906 and determines whether the patient end temperature (Tpe) has increased by more than a change threshold Tth (e.g., about 2° C.) within a time frame (e.g., about 1 minute). This may effectively determine whether flow has been added to the humidification system. If flow has been added as determined in step 2906, the control module exits the standby state in step 2908.

[0236] When the unit is not in standby as determined in step 2904 or after exiting from step 2908, the control module determines whether the heater plate temperature exceeds a heater plate temperature threshold Tth_hp (e.g., about 50° C.) in step 2910. This may correspond to a warm-up period. If the control unit determines that the heater plate temperature exceeds the heater plate temperature threshold, the control module determines in 2912 whether the duty cycle DC_12 of the combined first and second heater sections (e.g., outer section) is greater than about 99% and whether the patient end temperature Tpe is less than the setpoint temperature minus a temperature value Tnear (configured to determine when the patient end temperature approaches the setpoint temperature). In some embodiments, the value of Tnear may be about 2° C. If the control module determines that the combination of the first and second heater sections is greater than about 99% and the patient end temperature is less than the setpoint temperature minus Tnear, a no-flow condition may exist in the humidification system. For example, a no-flow condition may exist when the humidification system is applying a duty cycle of about 100% but the patient end temperature is not close enough to the setpoint. If this is true, the control module proceeds to step 2914 and waits an adjusted time t_wait (e.g., about 5 minutes) to account for potential disturbances in the system (such as putting something cold on the system). If it is longer than the time t_wait, the control module proceeds to step 2916 and enters a wait state until flow is applied or reapplied to the humidification system. In the wait state, the control mode sets the duty cycle of the first heater section to 0% and the combination of the first and second heater sections to about 40%.

[0237] If the outcome of the determination at any of steps 2910, 2912, or 2914 is "no," the control module proceeds to step 2918 and controls the combination of the first and second heater sections using a PID control scheme to achieve a target set point for the patient-end. In some embodiments, the PID control scheme is a method described herein with reference to FIG. 30. For example, the control module can control the combined first and second heater sections to achieve a target set point based on the difference between the current measured temperature at the patient-end and the set point. In certain embodiments, the control is proportional to the difference between the measured temperature and the temperature set point. The control module can monitor a timer in step 2920 to determine when an adjusted time threshold (e.g., 30 seconds) has elapsed. This adjusted time threshold can be set to allow sufficient time to elapse for the PID controller to become effective. The control module implements the PID control scheme to achieve a duty cycle that results in meeting the relevant demand, the demand determined in step 2922. For example, a PID control scheme can be implemented to achieve a duty cycle DC_12 for the combination of the first and second heater sections and / or a duty cycle DC_1 for the first heater section, where the duty cycle for the first heater section takes into account the demand of the combination of the first and second heater sections.

[0238] After the adjusted time threshold has elapsed, the control module proceeds to step 2924 and determines whether (a) the duty cycle for the combined first and second heater sections is equal to 0%, (b) the patient end temperature exceeds a set point (e.g., about 39° C.), or (c) the duty cycle for the first heater section is greater than a duty cycle threshold (e.g., about 40%). This test may be true if the combined first and second heater sections have stopped heating the gas, thus indicating that it is appropriate to reduce the temperature profile of the inspiratory limb. This may be accomplished, for example, by decreasing the duty cycle of the first heater section. Thus, if this is true, the computer module decreases the duty cycle for the heater section by a decrement value (e.g., 2%) in step 2926. If the test is not true, the control module proceeds to step 2928 and determines whether (a) the duty cycle for the combined first and second heater sections is greater than the duty cycle for the first heater section plus a constant c (e.g., tests whether DC_12>DC_1+c, where c may be about 20%) and (b) whether the duty cycle for the first heater section is less than an inner section threshold DC_1th (e.g., about 80%). The constant can be scaled so that the initial duty cycle value plus the constant is 100% (e.g., the initial duty cycle value can be 80% so that the constant can be 20%). This test may be true if it may be preferable to increase the duty cycle of the first heater section to maintain the temperature profile of the inspiratory limb. Thus, if the test is true, the control module proceeds to step 2930 and increases the duty cycle of the first heater section by an incremental value (e.g., about 2%). If the test is not true, the control module returns to step 2922, described above. If the control module increases or decreases the duty cycle of the first heater section, the control module resets the timer in step 2932. Control can then return to step 2922.

[0239] Figure 30 shows a flowchart of an exemplary PID control scheme 3000 configured to perform closed-loop control to achieve a target temperature setpoint at the patient end using a combined first and second heater section. The PID control scheme can be used to determine the duty cycle for the combined first and second heater sections.

[0240] In step 3002, the control module initializes the PID parameters by determining the difference between the measured temperature Tpe and the temperature setpoint Tset, which difference is referred to as the error e: e = Tset - Tpe. In step 3004, the control module sets the proportional term of the PID control scheme to the product of a constant Kp and the error e: P = Kp * e. In a particular implementation, the constant Kp is set to approximately 10. In step 3006, the control module sets the derivative term D of the PID control scheme to 0. Other values may be used.

[0241] In step 3008, the control module determines whether the error is less than or equal to a temperature difference threshold Tdiff (e.g., approximately 100). The control module can be used to determine when it is appropriate to set the integral term I of the PID control scheme to 0, as shown in step 3010. If the current temperature is within the temperature difference threshold of the temperature setpoint, the control module proceeds to step 3011 and can set the integral term I of the PID control scheme to the old or previous integral term plus a fraction Ki of the error e: I = Iprev + Ki * e. In a particular implementation, the fraction Ki may be approximately 0.05. The control module can further verify in step 3012 that the integral term I is within an acceptable or preferred boundary (e.g., -2 < I < 100), and the control module can set the integral term to the boundary value if the integral term is outside the preferred range.

[0242] In step 3014, the control module determines the duty cycle as the sum of proportional term P, integral term I, and derivative term D: DC=P+I+D. If the duty cycle is greater than 100% and the integral term is greater than the previous integral term (e.g., I>Iprev), as determined by the control module in step 3015, the control module resets the integral term to its previous value in step 3016 and recalculates the duty cycle in step 3018. In step 3020, the control module limits the range of values ​​of the duty cycle to 0-100 (e.g., if the duty cycle is less than 0, the control module sets the duty cycle to 0, and if the duty cycle is greater than 100, the control module sets the duty cycle to 100).

[0243] FIG. 31 shows a flow chart of another exemplary control algorithm 3100 that can be implemented by a control module in a humidification system. In step 3102, the control module determines a flow rate range for the humidification system. In step 3104, the control module determines a demand for the first heater section based on the determined flow rate range. In some embodiments, the flow rate range can be a level of flow rate for a corresponding demand. For example, the flow rate range can be a low flow rate range, a medium flow rate range, or a high flow rate range, and a low flow rate demand can be determined for the low flow rate range, a medium flow rate demand can be determined for the medium flow rate range, and a high flow rate range can be determined for the high flow rate range. In some embodiments, the flow rate ranges can overlap. In certain embodiments, the control module determines the flow rate range to determine an initial demand for the first heater section only at start-up. In such a case, the control module can use the demand for the combination of the first and second heater sections for the majority of the control of the humidification system. After this initial setting, the remaining control algorithm 3100 can adjust the demand for the first heater section.

[0244] In step 3106, the control module determines whether the humidification system is in a standby state. For example, the control module may determine that the humidification system is in a standby state by examining a value stored in a local variable. If the humidification system is in a standby state, the control module proceeds to step 3108 and determines whether the patient end temperature (Tpe) has increased by more than 2° C. in about one minute. This effectively determines whether flow has been added to the humidification system. If flow has been added as determined in step 3108, the control module exits the standby state in step 3110.

[0245] If the unit is not in standby as determined in step 3106, the control module determines in step 3112 whether the heater plate temperature is above about 50° C. This may correspond to a warm-up period. If the control unit determines that the heater plate temperature is above about 50° C., the control module determines in step 3114 whether the duty cycle of the first and second heater sections combined (e.g., the outer section) is greater than about 99% and whether the patient end temperature Tpe is less than the set point temperature minus a temperature value Tnear (e.g., about 2° C.). If the control module determines this to be true, a no-flow condition may exist in the humidification system. For example, a no-flow condition may exist if the humidification system is applying a duty cycle of about 100% but the patient end temperature is not close enough to the set point. If this is true, the control module proceeds to step 3116 to wait about 5 minutes to account for potential disturbances in the system (such as placing something cold on the system). If it is greater than about 5 minutes, the control module proceeds to step 3118 and enters a standby state until flow is applied or reapplied to the humidification system. In the standby state, the control mode sets the duty cycle of the first heater section to 0% and the combined first and second heater sections to about 40%.

[0246] If the outcome of the determination at any of steps 3112, 3114, or 3116 is "no," the control module proceeds to step 3120 and controls the combination of the first and second heater sections using a PID control scheme to achieve a target set point for the patient-end. In some embodiments, the PID control scheme is a method described herein with reference to FIG. 30. For example, the control module may control the combined first and second heater sections to achieve a target set point based on the difference between the current measured temperature at the patient-end and the set point. In certain embodiments, the control force is proportional to the difference between the measured temperature and the temperature set point. The control module implements the PID control scheme to achieve a duty cycle that results in meeting the relevant demand, the demand determined in step 3122. For example, a PID control scheme can be implemented to achieve a duty cycle DC_12 for the combination of the first and second heater sections and / or a duty cycle DC_1 for the first heater section, where the duty cycle for the first heater section takes into account the demand of the combination of the first and second heater sections.

[0247] The control module proceeds to step 3124 and determines whether (a) the duty cycle for the combined first and second heater sections is equal to 0%, (b) the patient end temperature exceeds a set point (e.g., about 39° C.), or (c) the duty cycle for the first heater section is greater than a duty cycle threshold (e.g., about 40%). This test may be true if the combined first and second heater sections have stopped heating the gas, thus indicating that it is appropriate to reduce the inspiratory limb temperature profile. This may be accomplished, for example, by decreasing the duty cycle of the first heater section. Thus, if this is true, the computer module in step 3126 decreases the duty cycle for the heater cycle by a decrement value (e.g., 2%) every 30 seconds while this is true. If the test is not true, the control module proceeds to step 3128 and determines whether (a) the duty cycle for the combined first and second heater sections is greater than the duty cycle for the first heater section plus a constant (e.g., tests whether DC_12>DC_1+c (where the constant may be about 20%)) and (b) whether the duty cycle for the first heater section is less than an inner section threshold (e.g., about 80%). The constant can be scaled so that the initial duty cycle value plus the constant is 100% (e.g., the initial duty cycle value can be 80% so that the constant can be 20%). This test may be true if it may be preferable to increase the duty cycle of the first heater section to maintain the temperature profile of the inspiratory limb. Thus, if the test is true, the control module proceeds to step 3130 and increases the duty cycle of the first heater section by an incremental value (e.g., about 2%). If the test is not true, the control module may return to step 3122 or step 3106 described above. If the control module increases or decreases the duty cycle of the first heater section, the control module may return to step 3122 or to step 3106.

[0248] Additional Control Systems Next, another exemplary control system for the circuit diagram 2500 of FIGS. 25A-25C will be described. As described above, the circuit diagram 2500 can be implemented in a system that does not include a temperature sensor in the intermediate connector that connects the first heater section H1 in the inspiratory limb to the second heater section H2 in the extension limb. The circuit diagram 2500 can be implemented using a control system configured to change the switching of the MOSFET pair to heat either the inner loop HW1 or the outer loop HW2. The loop HW1 (shown in FIG. 25C) can include the first heater section H1 of the inspiratory section. The loop HW2 (shown in FIG. 25B) can include the first and second heater sections H1, H2. Depending on the polarity of the voltage, power can be provided to the loop HW1 to heat H1 or to the loop HW2 to heat both H1 and H2. In this application, the power can include power, voltage and / or current. Loop HW1 can be activated by switching MOSFETs on and off in a switching configuration as shown in FIG. 25C. The diodes / switches can be MOSFETs. The polarity of the supply power can be switched to activate only loop HW2 as shown in FIG. 25B. The controller can be configured to operate the MOSFETS to switch polarity as needed to provide the appropriate duty cycle to the heater wires.

[0249] FIG. 35 illustrates an exemplary control algorithm 3500 for controlling loops HW1 and HW2. In an exemplary embodiment, loops HW1 and HW2 may be controlled sequentially, thereby allowing for smooth execution of algorithm 3500. The controller may continue to repeat all steps to determine whether and at what level the output of HW1 or HW2 duty cycles needs to be controlled. The controller may determine, in step 3502, an error between a patient-end temperature measured by a patient-end sensor, such as sensor 204b shown in FIG. 13, and a patient-end set point. The output of HW1 and HW2 duty cycles may each be controlled using a PID controller as known in the art based on the error. The controller may optionally perform one or more initial system readiness checks in step 3510. If the system is not ready, a system reset 3505 may be performed. If the system is ready, in step 3515, the output of HW1 duty cycle may be determined based on the error between the measured patient-end temperature and the patient-end temperature set point. The output of the HW1 duty cycle can optionally be based on a standard PID controller using a set of constants. In some embodiments, the PID controller can implement a PID control scheme 3700 shown in FIG. 37, which is described in more detail below. The controller can determine the output of each term (i.e., proportional, integral and derivative terms) based on the error and a set of constants. The constants can be pre-determined for the system and stored in memory or in a look-up table or in any other suitable format. The constants can be modified as conditions change, as the system can store multiple constants that may be relevant to multiple environments. One non-limiting example is when a portion of the conduit is or is not inside an incubator.

[0250] In one embodiment, the entire inhalation line, including the inhalation and extension limbs, is exposed to the same ambient environment along its length. In this embodiment, the controller can function as a normal PID controller controlling the output of the HW2 duty cycle in step 3515. The loop HW2 can be heated using a set of constants since the error between the measured patient end temperature and the patient end temperature set point can be large. The error can be large since the patient end of the inhalation line is exposed to the ambient temperature, which can be much lower than the patient end temperature set point. In this embodiment, the algorithm 3500 can output a large HW2 duty cycle in step 3520. The controller can then determine the output of the HW1 duty cycle in step 3625. In this embodiment, the HW1 duty cycle can be set to 0% since the output of the HW1 duty cycle can be inversely related to the output of the HW2 duty cycle. If the output of the HW2 duty cycle is high enough, the output of the HW1 duty cycle can be set to 0%. This can occur if there is a large error value between the patient end temperature and the patient end set point.

[0251] Power supplied to loop HW2 heats heater wires H1 and H2, thereby reducing the error to within an appropriate error threshold. As described above, the controller may continuously execute algorithm 3500 such that the error is continuously monitored. When the error is within an appropriate error threshold, in this embodiment loop HW1 may be activated to achieve temperature control. Further details of activated loop HW1 are provided below with reference to another embodiment.

[0252] In some embodiments, the inspiratory limb and the extension limb can be exposed to different ambient environments. For example, the extension section can be placed in a controlled environment, such as an incubator or other suitable device that is a closed system. The controlled environment can control at least the temperature and / or humidity in the environment. When the extension limb is inserted into the incubator, the patient end sensor can read a higher temperature value closer to the set point due to the temperature in the incubator being elevated above the ambient temperature. Therefore, the error can be smaller than when the extension limb is exposed to the ambient temperature. When the error is within a predetermined threshold, which is typically the case when the extension limb is placed inside the incubator. In a non-limiting example, the threshold error value can be 2.5° C. or less. The controller can determine the output of the HW1 duty cycle in step 3525. In some embodiments, the controller can perform PID control 3700 of the output of the HW1 duty cycle, as shown in FIG. 37. As the error is further reduced by heating H1, the output of the HW2 duty cycle determined in step 3515 is further reduced, so that the output of the HW1 duty cycle can be further increased.

[0253] Continuing with reference to the incubator embodiment, the controller is configured to control the power supplied to loop HW1 to energize H1 to maximum capacity until H1 reaches a predetermined surface temperature threshold. The surface temperature threshold can prevent the inspiratory limb from becoming too hot to safely handle or use the humidification system. In some embodiments, the surface temperature threshold can be mandated by regulatory standards. The predetermined surface temperature threshold can be related to a maximum power / voltage supplied to loop HW1. The maximum power / voltage can be set based on empirical data.

[0254] Additionally, when the controller provides power to loop HW1 in step 3530, because H2 is not energized and therefore does not heat up, there may be a temperature drop across the extension limb from the mid-connector to the patient-end. This temperature drop may be at a known decay rate due to known cooling characteristics within the incubator. The power provided to loop HW1 may be controlled to achieve an initial temperature in the extension limb such that a temperature drop across the extension limb may result in a desired patient-end temperature. FIG. 27 shows an exemplary heating profile of the inhalation line in this incubator embodiment. At the end where the inhalation line joins the humidification chamber, the temperature may be higher or lower than the patient-end temperature depending on the chamber outlet temperature set point. The controller may determine the difference between the chamber outlet temperature and the measured patient-end temperature and may adjust the output of the HW1 duty cycle accordingly. The temperature of the inhalation limb may rise along the length of the inhalation limb, which may terminate at the mid-connector, and may gradually drop from the mid-connector to the patient-end along the extension limb, which is not heated when loop HW1 is activated.

[0255] In the control algorithm 3500, loop HW1 can perform most of the heating of the humidification system. Loop HW2 can take over if the error exceeds a threshold. In addition, the controller can keep the output of HW2 duty cycle at a low value. On the one hand, the low output of HW2 duty cycle can advantageously reduce the possibility of overheating of the extension limb inside the incubator, thereby increasing the safety of the humidification system. For example, the low output of HW2 duty cycle can prevent the infant in the incubator or the caregiver handling the inhalation line from being burned. At the same time, H1 can heat up to a surface temperature threshold to advantageously prevent condensation in the inhalation limb. On the other hand, the low output of HW2 duty cycle can advantageously allow loop HW2 to rapidly respond to environmental changes to maintain the heating profile as shown in FIG. 27. The sudden environmental changes can include, but are not limited to, temperature changes inside the incubator, ventilation, low ambient temperature, etc. Moreover, by providing power to loop HW2, a more stable heating profile can be further advantageously provided. A more stable heating profile can be achieved by reducing or eliminating oscillations when loop HW2 is activated. Oscillations can occur when only loop HW1 is activated because it takes time for heat to be transferred and detected at the patient-end sensor by the heated gas moving from the inspiratory limb to the patient-end. Oscillations can be reduced when both heater sections H1 and H2 are activated because the patient-end sensor can detect a faster temperature change response at the patient-end than when only loop HW1 is activated.

[0256] Since the PID control scheme is configured to reduce the error, in some embodiments, the output of the HW2 duty cycle can reach a steady state at 0%, with loop HW2 activated to only react to rapid changes in the environment as described above. The steady state can result from the proportional and derivative terms for loop HW2 being reduced to substantially zero when the error is within a threshold. In other embodiments, the output of the HW2 duty cycle can have a low value, but not achieve a steady state. By way of example and not limitation, when the inspiratory line is in a cold ambient condition, cooling of the gas in the inspiratory limb outside the incubator can be enhanced. The rapid cooling can be due to a lower ambient temperature that can cause heating in the tubing and a higher rate of heat loss from the humidified gas to the surrounding environment. At 3530, the power provided to both H1 and H2 in the activated loop HW2 can compensate for the enhanced cooling of the gas in the inspiratory limb to achieve the desired patient end temperature.

[0257] 36 illustrates another example control algorithm 3600 for controlling the output of HW1 and HW2 duty cycles. Control algorithm 3600 may have the same features as control algorithm 3500, except as noted below. Thus, features of control algorithm 3600 may be incorporated into features of control algorithm 3500 and features of control algorithm 3500 may be incorporated into features of control algorithm 3600.

[0258] The controller may execute the algorithm 3600 continuously. The continuous execution of the algorithm 3600 may provide a substantially continuous fine control of the humidification system. The controller may begin 3602 by determining the error between the measured patient-end temperature and the patient-end set point. In some embodiments, the patient-end set point may be independent of the gas flow rate in the inlet line. The set point may be a function of the chamber outlet temperature set point. For example, the patient-end temperature set point may be set higher or lower than the chamber outlet temperature set point. The patient-end set point may be changed if the humidification system is in a very cold ambient environment. Additionally, the continuous execution of the algorithm 3600 may allow the system to be reset 3605 whenever significant overheating occurs. In an exemplary embodiment, the reset 3605 may reset the error term used in the PID control algorithm to zero and reset the output of both the HW1 and HW2 duty cycles to 0%.

[0259] As shown in FIG. 36, the controller can initiate algorithm 3600 with a series of checks 3610, 3615, 3620, 3625 to ensure that all sensors are working, all alarms are working, and the system is operational. These checks may be optional. Specifically, the controller can check whether a reset needs to occur (3610). In some embodiments, the controller can be programmed to determine whether a reset needs to occur based on a predefined algorithm. In other embodiments, the system may have a user interface to allow the user or caregiver to manually reset the system. For example, a reset can be performed by powering the device on and off using an on / off button, by unplugging the device, or automatically in software when the required conditions are met. If no reset is needed at step 3610, the controller can determine whether the system is ready to execute algorithm 3600 at step 3615. If the system is not ready, a reset 3605 can be performed. If the system is ready, the controller can determine the status of the patient end sensor and the sensor at the outlet of the humidification chamber (3620). The system may reset 3605 if the sensor is not responding or not functioning as designed. If the sensor condition is acceptable, the controller may determine if the high temperature control or high temperature alarm is enabled in step 3625. The reset 3605 may be actuated to prevent overheating of the intake line if the measured temperature is above the overheat temperature threshold. In some embodiments, a separate software module configured to control overheating may take over if the patient end temperature exceeds the overheat temperature threshold. This overheat module may set the output of both HW1 and HW2 duty cycles to 0. The reset 3605 may be performed to prevent accumulation of integral error terms of the PID control schemes 3630, 3680.

[0260] 36, after determining that the patient end temperature is below the set point and after an optional series of checks, the controller can determine the output of the HW2 duty cycle to bring the system to the desired set point temperature. The controller can implement a PID control scheme for the output of the HW2 duty cycle in step 3630. In an exemplary embodiment, the PID control step 3630 can be performed with a PID control scheme known in the art. In general, the output of the controller for HW1 or HW2 in a PID control scheme can be expressed as DC=Kp*e+Ki*∫e dt+Kd*de / dt, where DC is the output of the HW1 or HW2 duty cycle, Kp is the proportional coefficient, Ki is the integral coefficient, and Kd is the derivative coefficient. Furthermore, e is the error determined in step 3602. In addition, ∫e de is the error integral, i.e., the integral of the past error from time 0 to the current time t.de / dt is the rate of change of the current error (i.e., the derivative term). PID control schemes can be configured to reduce or eliminate the error.

[0261] FIG. 37 illustrates an example of a PID control scheme 3700. PID coefficients 3705, PID limits 3710, and an error term 3715 can be input to the PID control scheme 3700. As described above, the PID coefficients 3705 can include a proportional coefficient Kp, an integral coefficient Ki, a derivative coefficient Kd, and an error in introducing the integral term. In some embodiments, the proportional coefficient can be a system-based term determined by testing. In some embodiments, the derivative coefficient Kd can be determined for the system and / or the heater plates (not shown) of loops HW1 and HW2. For example, Kd can be determined experimentally. The PID control scheme 3700 including the derivative coefficient Kd can increase the stability of the system and reduce overshoot when correcting errors. In some embodiments, a PI control scheme can be used instead of the PID control scheme 3700, excluding the derivative term. The output of the controller in the PI control scheme can be expressed as DC=Kp*e+Ki*∫e dt. The PID limits 3710 may include minimum and maximum integral terms, as well as minimum and maximum output limits for the HW1 and HW2 duty cycles. The error terms 3715 may include a current error, an error integral, and a previous error.

[0262] From the above inputs, the controller can calculate the proportional term 3720, which is the product of the proportional coefficient Kp in the above equation and the current error of the system. The controller can also calculate the derivative term 3725, which is the product of the derivative coefficient Kd in the above equation and the rate of change of the current error de / dt. The controller can calculate the error integral in step 3735. The controller can then perform error term validation in step 3740. For example, the controller can validate the error term of any PID variable.

[0263] After error term validation 3740, the controller output may be calculated in step 3780 as DC=Proportional Term+Ki*Error Integral+Derivative Term. The controller may limit the range of the output value calculated from step 3780 to a maximum output limit of the controller to a minimum output limit of the controller in step 3795. The controller may provide the resulting controller output 3795 to step 3630 or to step 3680 in FIG. 37, described below.

[0264] Returning to Figure 36, the controller can output a limited HW2 duty cycle ranging from 0% to 100% in step 3635 based on the PID control in step 3630. The algorithm 3600 can use the output of the HW2 duty cycle to control the patient end temperature to maintain the heating profile shown in Figure 27. As mentioned above, the output of HW2 can be low, improving patient and caregiver safety by preventing overheating of the extension limb while allowing loop HW2 to respond quickly to sudden changes.

[0265] The algorithm 3600 can also use the output of the HW2 duty cycle to control the output of the HW1 duty cycle. Before providing the output of the HW2 duty cycle to step 3640 to calculate the PID limits of the output of the HW1 duty cycle, the controller can filter the raw output of the HW2 duty cycle in step 3645. The filtering can attenuate the output of the HW1 duty cycle. The filter can allow smoothing of noise from the loop HW2 being heated, which can allow attenuation of the output of the HW1 duty cycle. As shown in FIG. 36, the controller can sequentially control the outputs of the HW2 and HW1 duty cycles, which can advantageously provide a simple allocation of available power, voltage or current. Then, the PID control of the output of the HW2 duty cycle in step 3630 and the PID control of the output of the HW1 duty cycle in step 3680 can work together to provide a more stable control of the system. If the output of the HW1 duty cycle causes the patient end temperature to be too hot or too cold, the output of the HW2 duty cycle can compensate for the overheating or underheating. In some embodiments, the output of the HW2 duty cycle can be negative to effect a rapid change in the integral term of the PID control algorithm. The controller can limit the output of the HW2 duty cycle to zero in step 3635 when the output of the HW2 duty cycle is negative in step 3630. The controller can also rapidly reduce the output of the HW1 duty cycle in an overheating condition.

[0266] 36, the controller may determine a PID limit for the output of the HW1 duty cycle at step 3640. Specifically, the controller may calculate a maximum output of the HW1 duty cycle at step 3650. As also described above, the maximum output of the HW1 duty cycle may be capped to prevent the inspiratory limb from exceeding a surface temperature threshold and becoming unsafe to handle or use. In some embodiments, the maximum output of the HW1 duty cycle may be calculated using a function that includes a maximum upper limit output of the HW1 duty cycle and a range of limited output of the HW2 duty cycle. In one embodiment, the determination of the output of the HW1 duty cycle may also include a term to compensate for the difference in resistance of the two heater sections H1 and H2.

[0267] The controller may then determine whether the calculated maximum output of the HW1 duty cycle from step 3650 is negative. If the calculated maximum output of the HW1 duty cycle is negative, the controller may set the maximum output of the HW1 duty cycle to 0% in step 3660. If the calculated maximum output of the HW1 duty cycle is not negative, the controller may limit the range of the output of the HW1 duty cycle to 0% (or greater) to the maximum output limit of the HW1 duty cycle (or less), in step 3675. In some embodiments, the maximum output limit of the HW1 duty cycle may be calculated by subtracting the output of the HW2 duty cycle from 100%.

[0268] The PID limits calculated from step 3640 may cause the controller to PID control the output of the HW1 duty cycle in step 3680. The controller may output the HW1 duty cycle in step 3685. In one embodiment, the controller may use the PID control scheme of Figure 37 to PID control the output of the HW1 duty cycle. The controller may also reset 3605 the system after PID control of the output of the HW1 duty cycle in step 3680.

[0269] Figure 38 illustrates another exemplary embodiment of an intake line 3802 that can be controlled using the algorithms 3500, 3600. The intake line 3802 of Figure 35 can have the same characteristics as the intake line 202 of Figure 1, except as noted below. The characteristics of the intake line 3802 can be incorporated into the characteristics of the intake line 202, and the characteristics of the intake line 202 can be incorporated into the intake line 3802 of Figure 38.

[0270] As shown in FIG. 38, the inhalation conduit 3802 can be used with an incubator 3808 as shown, or with another system, such as a radiant warmer, where there are different temperatures along different sections of the inhalation limb 3802. The inhalation conduit 3802 can comprise two sections. A first section or inhalation limb 3802a can be outside the incubator 3808, and a second section or extension limb 3802b can be inside the incubator 3808. The first section 3802a can include one or more first inner heater wires 3806a, and the second section 3802b can include one or more second inner heater wires 3806b. The first and second inner heater wires 3806a, 3806b can have the same characteristics as the first and second heater wires 206a, 206b of FIG. 2. The inhalation conduit 3802 can have a gas lumen 3803. First and second inner heater wires 3806 a , 3806 b may be wrapped around the gas lumen 3802 .

[0271] 38, the inspiratory limb 3802 can include an intermediate connector 3814 having an intermediate circuit configured to couple elements of the first and second sections 3802a, 3802b of the inspiratory conduit 3802. In some embodiments, the intermediate connector 3814 can be configured to physically and electrically couple the first inner heater wire 3806a to the second inner heater wire 3806b. In addition, the inspiratory conduit 3802 can include one or more outer heater wires 3807. The outer heater wire 3807 can have the same or different characteristics as the first and second inner heater wires 3806a, 3806b. In some embodiments, the outer heater wire 3807 can be wrapped around the inspiratory conduit 3802. In some embodiments, the outer heater wire 3807 can be located outside the gas lumen 3803. In an exemplary embodiment, the outer heater wire 3807 can be in a helical configuration. However, one skilled in the art will appreciate that the number or configuration of the outer heater wires 3807 is not limiting.

[0272] A controller (shown in FIG. 9) can be configured to control the first inner heater wire 3806a forming an inner control loop (loop HW1). The controller can also be configured to control the outer heater wire 3807 forming an outer control loop (loop HW2). FIGS. 25A-25C show a circuit diagram 2500 for the intake line 3802, where H1 corresponds to the first inner heater wire 3806a and H2 corresponds to the outer heater wire 3807.

[0273] The inspiratory limb 3802 can include one or more sensors, and the controller can be configured to receive the output of the one or more sensors. As shown in FIG. 38, the sensor 3804b can be positioned near the patient end of the second section 3802b such that a parameter derived from the sensor 3804b (patient end temperature) can correspond to a parameter of the humidified gas delivered to the patient or user. In some embodiments, the sensor 3804b can function similarly to the sensors 204a, 204b described above. The output of the sensor 3804b can be sent to the controller as feedback used in controlling the power, voltage, and / or current delivered to the HW2 and HW1 loops.

[0274] Additional control system for low flow conditions As described herein, a humidification system incorporating the circuit diagram 2500 of FIGS. 25A-25C can be used with an incubator. A non-limiting exemplary use with an incubator can be when the humidification system is operating in a neonatal therapy mode and is connected to an infant patient inside the incubator. FIG. 39A shows an exemplary intended configuration of an inhalation line 3902 of the humidification system and an incubator 3908. The inhalation limb 3902a, comprising heater wire section H1 3906a, can remain outside the incubator 3908 and exposed to the ambient environment. The extension limb 3902b, comprising heater wire section H2 3906b, can be located inside the incubator 3908 and typically exposed to an elevated temperature compared to the ambient environment. In the intended configuration shown in FIG. 39A, an intermediate connector 3914 can be located at the interface between the incubator 3908 and the ambient environment.

[0275] However, the inspiratory conduit 3902 may be susceptible to movement. For example, the incubator 3908 may be moved while the inspiratory conduit 3902 is still connected to a patient inside the incubator 3908. In another example, an infant patient inside the incubator 3908, connected to a humidification system, may move around. As a result, the section 3902c of the inspiratory limb 3902a may inadvertently become displaced within the incubator 3908, as shown by the arrow in FIG. 39B. The sections 3902c may be of different lengths.

[0276] In both Figs. 39A and 39B, the control algorithms 3500, 3600 of Figs. 35-36 can heat loop HW1 (including H1 3906a) to a surface temperature threshold when the error is below a predetermined threshold. The control algorithms 3500, 3600 can heat loop HW2 (including H1 and H2 3906a, 3906b) to maintain the patient end set point when the error is greater than a predetermined threshold. The increased temperature inside the incubator 3908 can reduce the need to increase the HW2 duty cycle, resulting in loop HW1 having a higher duty cycle to do the majority of the heating. Section 3902c can have a higher surface temperature than extension limb 3902b because HW1 is primarily heated in the primary control scheme when section 3902c is part of loop HW1.

[0277] However, when the humidification system is in a low flow condition and section 3902c is inside the incubator as shown in FIG. 39B, the surface temperature difference between section 3902c and extension limb 3902b may be greater than when section 3902c is outside the incubator 3908 as shown in FIG. 39A. Low flow conditions may occur more frequently in neonatal therapy modes because gas may be delivered to infants at lower rates than adults. One skilled in the art will appreciate that gas may be delivered to other patients at lower rates. In some embodiments, low flow may occur when the flow rate is below a predetermined value. In some embodiments, low flow may occur when the flow rate is less than about 2.4 liters per minute (lpm) to about 5 lpm. In some embodiments, low flow may occur when the flow rate is less than about 5 lpm. In some embodiments, low flow may occur when the flow rate is less than about 3.5 lpm. In some embodiments, low flow may occur when the flow rate is less than about 3 lpm. The definition of a low flow condition is not limiting. Low flow conditions can increase heat loss from the gas as it takes longer for the gas to travel through the inspiratory line 3902. It can also take longer for the patient end sensor 3904b to sense the presence of heated gas. Greater heat loss and / or delay in detection of elevated patient end temperature can result in a larger error between the measured patient end temperature and the patient end set point. A large error can cause the controller to output a higher HW2 duty cycle than in normal or high flow conditions until a surface temperature threshold of the inspiratory limb 3902a, including the section 3902c inside the incubator 3908, is reached.

[0278] One concern with section 3902c inside the incubator 3908 when the system is in low flow conditions may be overheating of section 3902c. Overheating may be due to difficulties in dissipating heat inside the incubator 3908. Heat loss inside the incubator is proportional to the difference between the incubator temperature and the surface temperature of section 3902c. The increased temperature inside the incubator reduces the difference between the incubator temperature and the surface temperature of section 3902c. Therefore, the small amount of heat generated by the portion of loop HW1 in section 3902c due to the higher HW1 duty cycle at low flow conditions can be transferred to the inside of the incubator. Instead, the heat can accumulate on the surface of section 3902c. Because the heater wires 3906a, 3906b are embedded in the wall 3916 of the intake line 3902, heat accumulation on the surface of section 3902c may be significant. The accumulated heat may cause the surface temperature of section 3902c inside the incubator to exceed the surface temperature threshold.

[0279] Overheating of segment 3902c could be dangerous to the patient inside the incubator 3908 since segment 3902c is now in closer proximity to the patient than when it was outside the incubator 3908. Overheating of segment 3902c could also lead to non-compliance with regulatory or temperature standards set by a regulatory agency, if such surface temperature thresholds are mandated by such regulatory or temperature standards. Thus, it is important in low flow conditions to prevent segment 3902c from exceeding a surface temperature threshold when it is displaced inside the incubator 3908.

[0280] FIG. 40 illustrates a control algorithm 4000 for addressing overheating of section 3902c in low flow conditions. The control algorithm 4000 can reduce the likelihood that the surface temperature of section 3902c will exceed the surface temperature threshold even if section 3902c is moved inside the incubator 3908. The control algorithm 4000 can have the same features as the control algorithm 3600 of FIG. 36, except as described below. Thus, the features of the control algorithm 4000 of FIG. 40 can be incorporated into the features of the control algorithm 3600 of FIG. 36, and the features of the control algorithm 3600 of FIG. 36 can be incorporated into the features of the control algorithm 4000 of FIG. 40. Based on the control algorithm 4000, the duty cycle or power provided to either HW1 and / or HW2 is capped using a suitable upper limit or limit that prevents the surface temperature from exceeding a predetermined threshold. The duty cycle upper limit or limit is predefined in the control algorithm 4000. The duty cycle upper limit or limit may be defined as a percentage or a specific value. The limit or upper limit may be defined based on system parameters or based on a system model. In the example of FIG. 40, the upper limit or limit may be hard coded or predefined. In an alternative configuration, the system may include a temperature sensor located on a portion of the tube or at the intermediate connector. The system may include a first temperature sensor located on a portion of the first segment to determine a surface temperature of the first segment and a second temperature sensor located on the second segment to determine a surface temperature of the second segment. The control algorithm 4000 may be modified to determine the duty cycle upper limit or limit based on the measured surface temperature values.

[0281] As shown in Figure 40, a controller of the humidification system, such as the controller 122 shown in Figure 1, can determine the error between the measured patient end temperature and the patient end set point in step 4002 and perform a series of checks in steps 4010, 4015, 4020, 4025. The series of checks can ensure that all sensors and alarms are working and the system is in an operational state. These checks can be optional. A reset 4005 can be performed to clear the output and error integrals of both the HW1 and HW2 duty cycles if the controller detects any problems in any of steps 4010, 4015, 4020, 4025.

[0282] Continuing to refer to FIG. 40, after determining that the patient-end temperature is below the set point and after a series of optional checks, the controller may determine the output of the HW2 duty cycle required to bring the system to the patient-end set point temperature. The controller may implement a PID control scheme for the output of the HW2 duty cycle at step 4030. In an exemplary embodiment, the PID control step 4030 may be performed with a PID control scheme described herein and shown in FIG. 37. Based on the PID control at step 4030, the controller may output a HW2 duty cycle range-limited from 0% to 100% at step 4035. In one non-limiting example, the duty cycle of HW2 may be range-limited to an upper limit of 70%, i.e., 70% of the maximum power that can be delivered by the drive circuit. The 70% upper limit or limit is set to ensure that the surface temperature of the tube, i.e., both sections of the tube, do not exceed the surface temperature threshold.

[0283] The algorithm 4000 may also use the output of the HW2 duty cycle to control the output of the HW1 duty cycle after filtering the raw output of the HW2 duty cycle in step 4045 as described above. The controller may determine PID limits for the output of the HW1 duty cycle in step 4040. In an exemplary embodiment, the control algorithm 4000 may have a flow control component including steps 4050, 4050H, 4050L. Specifically, the controller may first determine whether the flow rate of the system is higher than a predetermined threshold in step 4050. In some embodiments, the flow rate may be measured using an integrated flow sensor located in the humidifier housing. In some embodiments, the flow sensor may be located at the outlet and / or inlet of the humidifier.

[0284] The controller may branch the calculation of the maximum output of the HW1 duty cycle based on comparing the measured flow rate to a predetermined threshold. The maximum output of the HW1 duty cycle may be calculated using a function including the high or low flow rate maximum upper limit output of the HW1 duty cycle and the range limited output of the HW2 duty cycle. The low flow rate maximum upper limit output of the HW1 duty cycle ("low flow rate upper limit") may be less than the high flow rate maximum upper limit output of the HW1 duty cycle ("high flow rate upper limit"). If the measured flow rate is higher than the predetermined threshold, the controller may calculate the maximum output of the HW1 duty cycle from the high flow rate upper limit in step 4050H. If the measured flow rate is equal to or less than the predetermined threshold, the controller may calculate the maximum output of the HW1 duty cycle from the low flow rate upper limit in step 4050L. In one embodiment, the determination of the output of the HW1 duty cycle may also include a term to compensate for the difference in resistance of the two heater wire sections H1 and H2. In one non-limiting example, the low flow upper limit of the HW1 duty cycle is capped at 37% of the maximum available power output expected from the drive circuit.

[0285] In some embodiments, the low flow cap may not affect the output of the HW2 duty cycle. The output of the HW2 duty cycle can reach 100% despite the low flow cap. In one embodiment, when the output of the HW2 duty cycle is between 0% and the low flow cap, the output of the HW1 duty cycle can be the difference between the low flow cap and the output of the HW2 duty cycle, and when the output of the HW2 duty cycle is equal to or greater than the low flow cap, the output of the HW1 duty cycle can be 0%. The low flow cap need not affect the output of the HW2 duty cycle since it can be controlled by the patient end temperature, which is much lower than the surface temperature threshold. Additionally, the elevated temperature inside the incubator 3908 can reduce the need for a very high HW2 duty cycle to maintain the patient end temperature.

[0286] In some embodiments, less gas flows through the inhalation line at a lower flow rate, which may result in less condensation forming in the inhalation line, even though the lower flow limit may result in less heat being available to minimize condensation. Additionally, better insulation may be provided to the inhalation limb to compensate for the less heat generated due to the lower flow limit.

[0287] The bifurcation at steps 4050H and 4050L can ensure that in high flow conditions, loop HW1 still heats to the surface temperature threshold, but in low flow conditions, to a lesser extent as determined by the low flow upper limit. In a non-limiting example, loop HW1 heats to the surface temperature threshold based on a duty cycle upper limit applied to the power provided to HW1. The bifurcation is advantageous because displacement of segment 3902c inside the incubator 3908 cannot result in overheating of segment 3902c in high flow conditions. However, the low flow upper limit is necessary to reduce the maximum HW1 duty cycle in low flow conditions so that the surface temperature of segment 3902c does not exceed the surface temperature threshold even if segment 3902c moves inside the incubator 3908.

[0288] After calculating the maximum power output of the HW1 duty cycle from either step 4050H or 4050L, the controller may determine whether the calculated maximum power output of the HW1 duty cycle is negative in step 4055. If the calculated maximum power output of the HW1 duty cycle is negative, the controller may set the maximum power output of the HW1 duty cycle to 0% in step 4060. If the calculated maximum power output of the HW1 duty cycle is not negative, the controller may limit the range of the power output of the HW1 duty cycle to 0% (or greater) to the maximum power output limit of the HW1 duty cycle (or less). In some embodiments, the maximum power output limit of the HW1 duty cycle may be calculated by subtracting the power output of the HW2 duty cycle from 100%.

[0289] The calculated PID limits from step 4040 allow the controller to PID control the output of the HW1 duty cycle in step 4080. The controller can then output the HW1 duty cycle in step 4085. In one embodiment, the controller can use the PID control scheme of Figure 37 to PID control the output of the HW1 duty cycle. The controller can reset 4005 the system after PID control of the output of the HW1 duty cycle in step 4080.

[0290] 41 , another exemplary flow control component 4150 may be implemented in the control algorithms described herein. The flow control component 4150 may be implemented in the control algorithm 3500 as part of step 3525, or in the control algorithm 3600 as part of step 3650. The flow control component 4150 may also replace steps 4045, 4050H, 4050L of the control algorithm 4000.

[0291] In the flow control component 4150, the controller can utilize different thresholds to determine whether the high flow upper limit or the low flow upper limit should be used to calculate the maximum output of the HW1 duty cycle. The controller can first determine in step 4152 whether the system is currently below the high flow upper limit or the low flow upper limit in order to calculate the maximum output of the HW1 duty cycle.

[0292] If the system is currently below the high flow upper limit, the controller may determine whether the measured flow is higher than a predetermined low flow threshold in step 4154. If the measured flow is higher than the predetermined low flow threshold, the controller may continue to calculate the maximum output of the HW1 duty cycle using the high flow upper limit in step 4150H. If the measured flow falls below the predetermined low flow threshold, the controller may switch to step 4150L to calculate the maximum output of the HW1 duty cycle using the low flow upper limit.

[0293] If the system is currently below the low flow upper limit, the controller may determine whether the measured flow is below a predetermined high flow threshold. If the measured flow is below the predetermined high flow threshold, the controller may continue to calculate the maximum output of the HW1 duty cycle using the low flow upper limit in step 4150L. If the measured flow reaches or exceeds the predetermined high flow threshold, the controller may switch to step 4150H to calculate the maximum output of the HW1 duty cycle using the high flow upper limit.

[0294] In some embodiments, the high flow threshold may be higher than the low flow threshold. The low and high flow thresholds may be determined empirically. In some embodiments, the thresholds may be device or sensor specific. In some embodiments, the low flow threshold may be about 2.4 lpm to about 5 lpm. In some embodiments, the low flow threshold may be about 3.5 lpm. In some embodiments, the low flow threshold may be about 5 lpm. In some embodiments, the high flow threshold may be about 6.5 lpm. By switching the duty cycle upper limit at different flow thresholds as the system transitions from low to high flow conditions, oscillations at the low / high flow boundary may be reduced.

[0295] Additional embodiments of mid-point / intermediate PCB designs FIG. 42 illustrates another exemplary intermediate PCB 4250 of the intermediate connector 214, 3514. A detailed description of how the intermediate PCB can be assembled within the inspiratory limb is provided above in connection with FIGS. 32A-32C. The intermediate PCB 4250 can include a diode 4265. The diode 4265 can allow for control of HW1 or HW2 as shown in FIGS. 25A-25C depending on the polarity of the voltage supplied. Unlike the PCB 250 of FIGS. 14A and 14B, the intermediate PCB 4250 can be free of a thermistor. Not having a thermistor can advantageously allow the controller to function more efficiently.

[0296] As shown in FIG. 42, the intermediate PCB 4250 can have a generally rectangular shape with two long sides 4254, 4256 and two short sides 4258, 4260. The diode 4265 can be located near the long side 4256 and near the midpoint of the long side 4256. The intermediate PCB 4250 can include connection pads 4252 for connection of heater wires and / or sensors. The connection pads 4252 can be configured to be located on the same side of the intermediate PCB 4250 and on both the front side (shown in FIG. 42) and back side (not shown) of the slot 4253. As shown in FIG. 42, the front side of the intermediate PCB 4250 can have two sets of four connection pads 4252 along the long side 4254 with two connection pads on each side of the diode 4265. The intermediate PCB 4250 can further have a positioning slot 4264 on each of the short sides 4258, 4260. The locating slots can help align the PCB during molding. By having two locating slots, rotation or movement of the PCB during molding can be reduced. The slots, the shape of the intermediate PCB 4250 and the configuration of the connection pads 4252 can advantageously allow for easier fabrication and assembly of the intermediate PCB 4250. The shape of the intermediate PCB 4250 and the configuration of the connection pads 4252 can reduce the possibility of short circuits and noise. The short sides 4258, 4260 of the intermediate PCB 4250 can each have a beveled edge 4262 where the short sides 4258, 4260 meet the long side 4256. The beveled edge 4262 can help maintain a good flow profile of the gas. Additionally, the intermediate PCB 4250 does not extend through the entire diameter of the inspiratory limb due to the reduced length of the short sides, but can extend over about 1 / 3 of the diameter. The short sides 4258, 4260 can advantageously reduce flow resistance (discussed above) in the inspiratory limb.

[0297] Additional Embodiments of Patient End Connector PCB Design FIG. 43 illustrates another exemplary patient-end PCB 4370 of the patient-end connector. The patient-end PCB 4370 can function in the same manner as the patient-end PCB 270 of FIG. 15A. However, the patient-end PCB 4370 can be longer than the patient-end PCB 270 of FIG. 15A for easier molding. The patient-end PCB 4370 can also have locating slots so that the PCB 4370 can only be mounted in one orientation on an assembly tool for easier assembly. As shown in FIG. 43, the patient-end PCB 4370 can have multiple top locating slots 4373 and bottom locating slots 4375. The locating slots can help align the PCB during molding. Portions of the PCB 4370 below the top locating slots 4373 or below the bottom locating slots 4375 can be broken off once the PCB 4370 is assembled.

[0298] The patient-end PCB 4370 may also include connection pads 4372 for the heater wires and the sensor connection lines. The connection pads 4372 may be configured to be located at either end of the patient-end PCB 4370. In an exemplary embodiment, the patient-end PCB 4370 may have two connection pads 4372 on the front side of the slot 4373. Although not shown in FIG. 43, the patient-end PCB 4370 may also have two connection pads 4372 on the back side of the slot 4373. By having the connection pads 4372 on either end of the PCB 4370, water ingress may be advantageously prevented or reduced. The patient-end PCB 4370 may also have a thermistor 4374. Unlike the patient-end PCB 270 of FIG. 15A, the thermistor 4374 on the patient-end PCB 4370 may be located near the center of the patient-end PCB 4370. In some embodiments, the patient-end PCB 4370 can have tracks that run substantially linearly from the connection pads 4372 to the thermistor 4374. Those skilled in the art will appreciate that any suitable configuration of tracks can be arranged on the patient-end PCB 4370. Additionally, the location of the thermistor 4374 can allow for easier fabrication of the PCB 4370.

[0299] In some embodiments, the lower locating slot 4375 may not be present. In other embodiments, the patient-end PCB 4370 may not include a portion below the upper locating slot 4373. In one embodiment, the patient-end PCB 4370 may be unmolded and may terminate below the upper locating slot 4373.

[0300] Chamber Edge PCB Design Embodiment 44A and 44B show an exemplary chamber end PCB 4490 for connecting to a complementary connector on the cartridge (shown in FIG. 8A), which may include electrical connection pads. A detailed description of the shape and function of the chamber end PCB is set forth in U.S. Patent Application No. 15 / 105,531, filed June 16, 2016, entitled "HUMIDIFICATION SYSTEM CONNECTIONS"; and U.S. Patent Application No. 15 / 021,673, filed March 11, 2016, entitled "CONNECTIONS FOR HUMIDICATION SYSTEM," each of which is incorporated herein by reference in its entirety. As shown in FIG. 44B, which shows a detailed view of the top portion of the chamber end PCB 4490, the chamber end PCB 4490 can have connection pads 4492 on the same side. 44A and 44B, the chamber end PCB 4490 can have four connection pads 4492 located on the right side of the PCB 4490. In other embodiments, the connection pads can all be located on the left side or any other suitable side of the PCB 4490. The PCB 4490 is plasma treated to reduce water ingress.

[0301] 44B, the connection pads 4492 can be angled. The chamber end PCB 4490 can also have a deep slot 4494 that is deeper than those described in the above referenced U.S. Patent Application Nos. 15 / 021,673 and 15 / 105,531. The deep slot 4494 and angled connection pads 4492 can advantageously allow for proper and even wire tension to reduce the risk of the wires moving around. The chamber end PCB 4490 can also accommodate a flat tag that is raised at an angle and positioned straight up on the chamber end PCB 4490.

[0302] Exemplary embodiments Below is a numbered list of exemplary embodiments within the scope of this disclosure. The exemplary embodiments listed should not be construed as limiting the scope of the embodiments. Various features of the exemplary embodiments listed may be removed, added, or combined to form further embodiments, which are also part of this disclosure. 1. A medical tubing comprising a first section of medical tubing, the first section comprising: a first structure forming a conduit configured to transport a humidified gas; a first heater wire circuit; The medical tubing further comprises a second section of the medical tubing, the second section comprising: a second structure forming a conduit configured to transport the humidified gas; and a second heater wire circuit; the medical tubing further comprises an intermediate connector comprising a connection circuit electrically coupling the first heater wire circuit to the second heater wire circuit, the intermediate connector being coupled to a patient end of the first section of the medical tubing and a chamber end of the second section of the medical tubing to form a single conduit for the humidified gas; at least a portion of the intermediate connector is covered by a portion of the first section of the medical tubing and / or a portion of the second section of the medical tubing such that the intermediate connector is interior to the medical tubing; In a first mode, power passes through the connection circuit to provide power to the first heater wire circuit and not to the second heater wire circuit, and in a second mode, power passes through the connection circuit to provide power to both the first heater wire circuit and the second heater wire circuit. Medical tube. 2. The medical tube of embodiment 1, wherein the connection circuit comprises a diode. 3. The medical tube of embodiment 1 or 2, further comprising a first sensor positioned at the patient end of the first section. 4. The medical tube of embodiment 3, wherein the first sensor is one of a temperature sensor or a humidity sensor. 5. The medical tubing of any one of embodiments 1-4, further comprising a second sensor positioned at a patient end of the second section of the medical tubing. 6. The medical tube of embodiment 5, wherein the second sensor is one of a temperature sensor or a humidity sensor. 7. The first structure comprises an elongated tube, the elongated tube comprising: a first elongate member comprising a hollow body helically wound to at least partially define a conduit having a longitudinal axis, a lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen; a second elongate member helically wound and joined between adjacent turns of the first elongate member, the second elongate member forming at least a portion of the lumen of the elongate tube; The medical tube according to any one of embodiments 1 to 6, comprising: 8. The medical tubing of embodiment 7, wherein the first elongate member, in longitudinal cross-section, defines a plurality of bubbles having flattened surfaces in the lumen. 9. The medical tube of embodiment 8, wherein adjacent foam bodies are separated by gaps above the second elongate member. 10. The medical tubing of embodiment 8, wherein adjacent foam bodies are not directly connected to each other. 11. The medical tubing of embodiment 8, wherein the plurality of foam bodies have perforations. 12. An inspiratory limb comprising a first segment of the inspiratory limb having a first heater wire circuit, a second segment of the inspiratory limb having a second heater wire circuit, an intermediate connector having a connector circuit configured to electrically couple the first heater wire circuit to the second heater wire circuit, a first sensor positioned at a patient end of the first segment, and a second sensor positioned at a patient end of the second segment; Control device and A respiratory humidification system comprising: A controller is adapted to selectively switch between a first mode and a second mode, in which the controller provides power through the connector circuit to the first heater wire circuit, and in which the controller provides power to the first and second heater wire circuits. Respiratory humidification system. 13. The system of embodiment 12, wherein switching is based on input from one or both sensors. 14. The system of embodiment 13, wherein the input from one or both sensors includes one or more of temperature, flow rate, humidity, and power. 15. The system of any one of embodiments 12-14, wherein the first and second modes are defined by a direction of current provided by the power source. 16. A system in any one of embodiments 12 to 15, wherein the control device is adapted to selectively switch between a first sensor reading mode and a second sensor reading mode, and in the first sensor reading mode, the control device reads a signal from the second sensor, and in the second sensor reading mode, the control device reads signals from both the first sensor and the second sensor. 17. The system of any one of embodiments 12-16, wherein the first sensor and the second sensor are temperature sensors. 18. An inspiratory limb comprising a first segment of the inspiratory limb having a first heater wire circuit, a second segment of the inspiratory limb having a second heater wire circuit, an intermediate connector having a connector circuit configured to electrically couple the first heater wire circuit to the second heater wire circuit, a first sensor positioned at a patient end of the first segment, and a second sensor positioned at a patient end of the second segment; The expiratory limb, an interface connected to the inspiratory limb and the expiratory limb; Control device and A dual limb circuit comprising: A controller is adapted to selectively switch between a first mode and a second mode, in which the controller provides power through the connector circuit to the first heater wire circuit, and in which the controller provides power to the first and second heater wire circuits. Double limb circuit. 19. The dual limb circuit of embodiment 18, in which the expiratory limb comprises an expiratory heater wire circuit. 20. The dual limb circuit of embodiment 19, in which the expiratory limb is heated using an expiratory heater wire circuit. 21. The dual limb circuit of embodiment 19, wherein the expiratory heater wire circuit is powered in parallel with a first heater wire circuit in a first section of the inspiratory limb. 22. The dual limb circuit of embodiment 21, wherein the breath heater wire circuit can be configured to be powered in only the first mode, only the second mode, or in both the first and second modes. 23. The dual-limb circuit of any one of embodiments 18-22, wherein the interfaces are connected via a Y-piece. 24. A segmented inspiratory limb configured to be heated along at least two segments, each segment of the inspiratory limb comprising: a first elongate member comprising a hollow body helically wound to at least partially form an elongate tube having a longitudinal axis, a lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen; a second elongate member helically wound and joined between adjacent turns of the first elongate member, the second elongate member forming at least a portion of the lumen of the elongate tube; A segmented inspiratory limb comprising: 25. Medical tubing having two sections, each section having: an elongated hollow body spirally wound to form an elongated tube having a longitudinal axis, a lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen, the elongated hollow body having a wall that, in transverse cross section, defines at least a portion of the hollow body; a reinforcing portion extending along the length of the elongated hollow body helically positioned between adjacent turns of the elongated hollow body, the reinforcing portion forming a portion of the lumen of the elongated tube; one or more conductive filaments embedded or encapsulated within the reinforcement portion; Equipped with The reinforcement is relatively thicker or stiffer than the wall of the hollow body; The medical tubing further comprises a segment connector attached to the first segment, the segment connector comprising: a connection pad configured to electrically couple a conductive filament from the first section to a conductive filament from the second section when the first section is physically coupled to the second section; a power diode electrically coupled to the conductive filament of the first section; Equipped with a power diode, when provided with an electrical signal of a first polarity, for transmitting power to the conductive filaments of the first section and for preventing transmission of power to the conductive filaments of the second section; A power diode provides power to the conductive filaments of the first section and the conductive filaments of the second section when provided with an electrical signal of the second polarity. Medical tube. 26. A first heater wire input connection configured to be electrically coupled to a first input heater wire; a second heater wire input connection configured to be electrically coupled to the second input heater wire; a first heater wire output connection electrically coupled to the first output heater wire and configured to be electrically coupled to the first heater wire input connection; a second heater wire output connection electrically coupled to the second output heater wire and configured to be electrically coupled to the second heater wire input connection; a first signal wire input connection configured to be electrically coupled to the first input signal wire; a second signal wire input connection configured to be electrically coupled to the second input signal wire; a first signal wire output connection electrically coupled to the first output signal wire and configured to be electrically coupled to the first signal wire input connection; a second signal wire output connection electrically coupled to the second input signal wire and configured to be electrically coupled to the second signal wire input connection; a power diode electrically coupled to the first heater wire input connection and the second heater wire input connection, the power diode configured to allow current to flow from the second input heater wire to the first input heater wire and to prevent current from flowing from the first input heater wire to the second input heater wire; a sensor electrically coupled to the first signal wire input connection; a signal diode electrically coupled to the sensor and the second signal wire input connection, the signal diode allowing current to flow from the second input signal wire through the sensor to the first input signal wire and preventing current from flowing from the first input signal wire through the sensor to the second input signal wire; A connector comprising: 27. An inspiratory limb including a first section having a first heater wire, a second section having a second heater wire, and a sensor positioned at a patient end of the second section for measuring a patient end parameter, wherein the first and second heater wires are electrically coupled, the first heater wire forming a first heater circuit and the first and second wires forming a second heater circuit; a hardware controller configured to receive an output of the sensor, the hardware controller further configured to provide power to the first heater circuit when a difference between the output of the sensor and a patient-end parameter set point is less than a predetermined threshold, and to provide power to the second heater circuit when a difference between the output of the sensor and the patient-end parameter set point is equal to or greater than the predetermined threshold; A respiratory humidification system comprising: The hardware controller is configured to provide maximum power to the first heater circuit when the hardware controller provides power to the first heater circuit. Respiratory humidification system. 28. An inspiratory limb comprising a first section comprising a first heater wire, a second section comprising a second heater wire, and a sensor positioned at a patient-end of the second section for measuring a patient-end parameter, wherein the first and second heater wires are electrically coupled, the first heater wire forming a first heater circuit and the first and second wires forming a second heater circuit, and the first and second heater wires are configured to heat respiratory gas passing through the inspiratory limb. A respiratory humidification system comprising: the first and second heater wires are configured to communicate with a hardware processor configured to execute software instructions that cause the processor to control the first and second heater circuits; The processor is configured to heat the respiratory gas using the first heater circuit until a maximum temperature is reached at the first heater wire when a difference between an output of the sensor and a patient-end parameter set point is less than a predetermined threshold, and the processor is configured to heat the respiratory gas using the second heater circuit when a difference between the output of the sensor and the patient-end parameter set point is equal to or greater than the predetermined threshold. Respiratory humidification system. 29. A hardware processor configured to communicate with a first heater wire circuit in a first segment of an inspiratory limb and a second heater wire circuit in a second segment of the inspiratory limb, the hardware processor also configured to communicate with a connector circuit in an intermediate connector configured to electrically connect the first heater wire circuit to the second heater wire circuit, the hardware processor further configured to communicate with a first sensor positioned at a patient end of the first segment and a second sensor positioned at a patient end of the second segment. A respiratory humidification system comprising: the hardware processor is configured to execute software instructions that cause the processor to selectively switch between a first mode and a second mode; In the first mode, the processor provides power through the connector circuit to the first heater wire circuit, and in the second mode, the processor provides power to the first and second heater wire circuits. Respiratory humidification system. 30. An inspiratory limb comprising a first segment of the inspiratory limb having a first heater wire circuit, a second segment of the inspiratory limb having a second heater wire circuit, an intermediate connector having a connector circuit configured to electrically couple the first heater wire circuit to the second heater wire circuit, a first sensor positioned at a patient end of the first segment, and a second sensor positioned at a patient end of the second segment. A respiratory humidification system comprising: the first and second heater wire circuits, the connector circuit, and the first and second sensors are each configured to communicate with a hardware controller, the hardware controller adapted to selectively switch between a first mode and a second mode; In the first mode, the hardware controller provides power through the connector circuit to the first heater wire circuit, and in the second mode, the hardware controller provides power to the first and second heater wire circuits. Respiratory humidification system. 31. An inspiratory limb comprising a first segment of the inspiratory limb having a first heater wire circuit, a second segment of the inspiratory limb having a second heater wire circuit, an intermediate connector having a connector circuit configured to electrically couple the first heater wire circuit to the second heater wire circuit, a first sensor positioned at a patient end of the first segment, and a second sensor positioned at a patient end of the second segment; Expiratory limb and an interface connected to the inspiratory limb and the expiratory limb; A dual limb circuit comprising: the first and second heater wire circuits, the connector circuit, and the first and second sensors are each configured to communicate with a hardware controller, the hardware controller adapted to selectively switch between a first mode and a second mode; In the first mode, the hardware controller provides power through the connector circuit to the first heater wire circuit, and in the second mode, the hardware controller provides power to the first and second heater wire circuits. Double limb circuit. 32. A heater circuit comprising a first heater, a second heater, a first switch pair, a second switch pair, and a power supply. A respiratory humidification system comprising: the heater circuit is configured to communicate with a hardware control module, the hardware control module adapted to control a flow of current from the power source to the first heater by selectively opening and closing the first pair of switches and to control a flow of current from the power source to the second heater by selectively opening and closing the second pair of switches; The first pair of switches and the second pair of switches can be selectively opened and closed independently of one another, thereby providing independent control of the first and second heaters. Respiratory humidification system. 33. A hardware processor configured to communicate with a heater circuit comprising a first heater, a second heater, a first pair of switches, a second pair of switches, and a power source. A respiratory humidification system comprising: the hardware processor is configured to execute software instructions that cause the processor to control a flow of current from the power source to the first heater by selectively opening and closing the first pair of switches and to control a flow of current from the power source to the second heater by selectively opening and closing the second pair of switches; The first pair of switches and the second pair of switches can be selectively opened and closed independently of one another, thereby providing independent control of the first and second heaters. Respiratory humidification system. 34. A heater circuit comprising a first switch pair, a second switch pair, a power supply, a main relay, and a mode relay. A respiratory humidification system comprising: the heater circuit is configured to communicate with a logic module and a control module; the control module is adapted to provide control signals to the logic module to control a flow of current from the power source to the mode relay by selectively opening and closing the first and second switch pairs; the control module is adapted to provide mode signals to the logic module, the mode signals including a first mode signal and a second mode signal; The first pair of switches and the second pair of switches can be selectively opened and closed independently of each other. Respiratory humidification system. 35. A heater circuit comprising a first switch pair, a second switch pair, a power supply, a main relay, and a heater module. A respiratory humidification system comprising: the heater circuit is configured to communicate with a logic module and a control module; the control module is adapted to provide control signals to the logic module to control a flow of current from the power source to the heater module by selectively opening and closing the first and second switch pairs; the control module is adapted to provide mode signals to the logic module, the mode signals including a first mode signal and a second mode signal; The first pair of switches and the second pair of switches can be selectively opened and closed independently of each other. Respiratory humidification system. 36. Further comprising a flow sensor in the flow path of the system and configured to measure the flow rate of the gas; the maximum power provided to the first heater circuit has first and second maximum values, the first maximum value being greater than the second maximum value; and The maximum power is the first maximum when the measured flow rate is greater than a flow rate threshold and is a second maximum when the measured flow rate is less than the flow rate threshold. A respiratory humidification system according to any one of embodiments 32 to 36. 37. Further comprising a flow sensor in a flow path of the system and configured to measure a flow rate of the gas; the maximum power provided to the first heater circuit has first and second maximum values, the first maximum value being greater than the second maximu...

Claims

1. an inspiratory limb including a first section including a first heater wire, a second section including a second heater wire, and a temperature sensor positioned at or near a patient end of the second section, the first and second heater wires configured to heat respiratory gas passing through the inspiratory limb, the first and second heater wires being electrically coupled, the first heater wire forming a first heater circuit and the first and second heater wires together forming a second heater circuit; a control module including a hardware processor configured to be in electrical communication with the temperature sensor and the first and second heater wires; The hardware processor includes: determining a first power demand to the first heater circuit necessary to maintain a temperature profile within the inspiratory limb; determining a second power demand to the second heater circuit necessary to reduce or eliminate a difference between a set point temperature and a patient end temperature measured by the temperature sensor; selectively controlling power supplied to the first and second heater circuits to meet the first and second power demands; configured to execute software instructions; A respiratory humidification system, wherein the control module is configured to operate in an open loop control mode when supplying power to the first heater circuit.

2. 2. The respiratory humidification system of claim 1, wherein the first power demand to the first heater circuit is set to a particular duty cycle used for control of the first heater circuit.

3. 3. The respiratory humidification system of claim 2, further comprising a flow sensor within a flow path of the system and configured to measure the flow rate of the respiratory gas, and the particular duty cycle is a fixed duty cycle value determined at least in part by the flow rate of the respiratory gas measured by the flow sensor.

4. 4. A respiratory humidification system as described in claim 2 or 3, wherein the specific duty cycle is determined using a model configured to be applicable independently of at least the temperature and / or humidity of the surrounding environment.

5. 5. A respiratory humidification system according to any one of claims 1 to 4, wherein the first power demand to the first heater circuit is configured to reach a target temperature profile within the first section.

6. 6. The respiratory humidification system of claim 5, wherein the target temperature profile utilizes a greater amount of heating in the first heater circuit compared to the second heater circuit.

7. 7. A respiratory humidification system as claimed in claim 5 or 6, wherein the target temperature profile within the first section heats the respiratory gas within the first section to a temperature higher than the set point temperature.

8. 8. A respiratory humidification system according to any one of claims 1 to 7, wherein the processor is configured to operate in a closed loop control mode when supplying power to the second heater circuit.

9. The first power demand for the first heater circuit is i) being satisfied by heating of the first heater circuit; ii) partially filled by heating of the first heater circuit and partially filled by heating of the second heater circuit; or iii) being satisfied by heating of the second heater circuit; A respiratory humidification system according to any one of claims 1 to 8.

10. The processor, using the second heater circuit as the primary means of controlling heating of the inspiratory limb; and using the first heater circuit to provide supplemental heating; 10. A respiratory humidification system as claimed in any one of claims 1 to 9, configured as follows:

11. 11. A respiratory humidification system according to any preceding claim, comprising a temperature sensor positioned on a portion of the inspiratory limb for measuring a surface temperature of the inspiratory limb.

12. An inspiratory limb comprising a first section having a first heater wire, a second section having a second heater wire, and a temperature sensor positioned at or near a patient end of the second section, wherein the first and second heater wires are configured to heat respiratory gas passing through the inspiratory limb, the first and second heater wires being electrically coupled, the first heater wire forming a first heater circuit and the first and second heater wires together forming a second heater circuit; a control module including a hardware processor configured to be in electrical communication with the temperature sensor and the first and second heater wires; The hardware processor includes: determining a first power demand to the first heater circuit necessary to maintain a temperature profile within the inspiratory limb; determining a second power demand to the second heater circuit necessary to reduce or eliminate a difference between a set point temperature and a patient end temperature measured by the temperature sensor; applying power to the first heater circuit based on a duty cycle determined to satisfy the first power demand to the first segment; applying power to the second heater circuit based on a duty cycle determined to satisfy the second power demand to the first and second segments. configured to execute software instructions; A respiratory humidification system, wherein the control module is configured to operate in an open loop control mode when applying power to the first heater circuit.

Images