Respiratory Gas Humidification System

Abstract

To provide a humidification apparatus to facilitate sensing a liquid level in a humidification chamber and flow characteristics in a fluid flow.SOLUTION: A humidification system comprises a first sensor and a second sensor. The first and second sensors are adapted to sense flow characteristics within the system. The first and second sensors are isolated from the flow by barriers formed by respective first and second sealing members. The sealing members extend through apertures formed in the system and have a portion that contacts the sensing elements of the respective first and second sensors. A cartridge holds the sensors and provide repeatable penetration depths into a flow passage of the system. A medical tube has a composite structure made of two or more distinct components that are spirally wound to form an elongate tube. One component can be a spirally wound elongate hollow body. The other component can be an elongate structural component spirally wound between turns of the spirally wound hollow body.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority benefit of U.S. Provisional Patent Application Nos. 61 / 610,109, filed March 13, 2012; 61 / 733,360, filed December 4, 2012; 61 / 733,359, filed December 4, 2012; 61 / 611,331, filed March 15, 2012; and 61 / 722,659, filed November 5, 2012, the entirety of each of which is hereby incorporated by reference herein.

[0002] The present invention relates generally to respiratory methods or devices and methods and devices for delivering heated and humidified gas to a user. More particularly, the present invention relates to methods for measuring flow characteristics within such devices and to tubing used in medical circuits suitable for delivering and / or removing gas from a patient, such as positive airway pressure (PAP), mechanical ventilation, anesthesia, ventilators, and insufflation systems. [Background technology]

[0003] Many gas humidification systems deliver heated and humidified gas for various medical procedures including respiratory therapy, laparoscopy, etc. These systems can be configured to control temperature, humidity, and flow rate.

[0004] To provide the desired level of control, sensors must be used to detect flow characteristics. These sensors are often inserted directly into the flow and, because the sensor is not isolated from fluid exchange with the patient, the sensors must be cleaned or discarded. In other words, the sensor cannot be reused immediately after removal from the original patient. Such systems are described, for example, in U.S. Pat. No. 6,584,972, hereby incorporated by reference in its entirety.

[0005] Gas humidification systems also include medical circuits, which include various components that deliver heated and / or humidified gas to and from a patient. For example, in some breathing circuits, such as PAP or respiratory assistance circuits, the gas a patient inhales is delivered from a heated and humidified device through an inspiratory tube. As another example, in an insufflation circuit, a tube may deliver humidified gas (typically CO2) into the abdominal cavity. This can help prevent the patient's internal organs from "drying out" and can shorten the time required for post-operative recovery. Unheated tubing allows significant heat loss to ambient cooling. This cooling can result in undesirable condensation or "rainout" along the length of the tubing that delivers the humidified warm air. There remains a need for tubing that insulates against heat loss and allows for improved temperature and / or humidity control, for example, in medical circuits. Accordingly, it is an object of certain features, aspects, and advantages of the present invention to overcome or ameliorate one or more of the shortcomings of the prior art, or at least to provide the public with a useful option. Summary of the Invention [Means for solving the problem]

[0006] Thus, described herein is a humidification device that can facilitate sensing of the liquid level and flow characteristics of the fluid flow in the humidification chamber, while reducing waste and promoting reasonable reuse of certain components. Medical tubing and methods of manufacturing medical tubing are also disclosed herein in various embodiments. Certain features, aspects, and advantages of the present invention go some way to overcoming the above-mentioned shortcomings and / or at least providing the public with a useful choice.

[0007] In some configurations, the humidification device includes a pressurized gas source. The pressurized gas source includes an outlet. The outlet of the pressurized gas source connects to an inlet leading to the humidification unit. The humidification unit includes an outlet. The outlet of the humidification unit connects to an air delivery component. A flow path is defined between the pressurized gas source and the air delivery component. A sensor is adapted to sense flow characteristics within the flow path. The flow path includes an opening. The sensor extends through the opening into the flow path. The sensor includes a sensing portion. A barrier is positioned between the flow path and the sensor. The barrier contacts the sensing portion of the sensor, and the barrier includes a substantially constant thickness in the area contacting the sensing portion.

[0008] In some configurations, the humidification unit includes a humidification chamber, the humidification chamber includes a port, and the opening extends through a wall that defines at least a portion of the port.

[0009] In some configurations, the sensor includes a first thermistor and a second thermistor. The barrier includes a first sleeve that receives the first thermistor and a second sleeve that receives the second thermistor. In some configurations, the two thermistors can be positioned within a single barrier.

[0010] In some configurations, the first thermistor is heated and the second thermistor is non-heated.

[0011] In some configurations, the barrier includes a mounting portion, a first thickness, and a second thickness less than the first thickness, the second thickness being located adjacent to the sensing portion of the sensor, and the region having the first thickness is positioned between the mounting portion and the portion having the second thickness.

[0012] In some configurations, the barrier includes a tip portion and a mounting portion, the mounting portion securing the barrier within the opening and the tip portion having a reduced thickness.

[0013] In some configurations, the barrier hermetically seals the opening and receives at least a portion of the sensor such that the sensing portion can be positioned within the flow path and the mounting portion is positioned outside the flow path.

[0014] In some configurations, the sensor is supported by the cartridge. The humidification unit includes a humidification chamber. The cartridge and the humidification chamber are removably attached and include an interlock connector.

[0015] In some configurations, the cartridge includes a connector adapted to make electrical connection with the humidification unit when the cartridge is attached to the humidification chamber and the humidification chamber is attached to the humidification unit.

[0016] In some configurations, the cartridge supports the sensor in a repeatable manner relative to a portion of the flow path through the humidification chamber so that the sensing portion of the sensor is consistently positioned even with repeated removal and replacement of the cartridge from the humidification chamber.

[0017] In some configurations, the barrier includes a generally cylindrical base and a generally bell-shaped head.

[0018] In some configurations, the generally bell-shaped head includes a plurality of flexible ribs.

[0019] In some configurations, the ribs are triangular and positioned around the periphery of the bell-shaped head.

[0020] In some configurations, one or more of the plurality of ribs has a ratio of rib width to spacing width of about 3.7.

[0021] In some configurations, the humidification chamber includes an outer body defining the chamber. The inlet port includes a wall defining a passageway into the chamber. The outlet port includes a wall defining a passageway out of the chamber. The inlet port wall includes a first opening. The first opening receives a first seal member. The first seal member hermetically seals the first opening extending through the inlet port wall. The outlet port wall includes a second opening. The second opening receives a second seal member. The second seal member hermetically seals the second opening extending through the outlet port wall. A cartridge is removably attachable to the chamber's outer body by an interlocking structure. The cartridge supports a first sensor receivable within the first seal and extending through the first opening. The cartridge supports a second sensor receivable within the second seal and extending through the second opening.

[0022] In some configurations, the first sensor includes a first sensing component and a second sensing component, and a first seal member separates the first sensing component from the second sensing component.

[0023] In some configurations, the first sensing component is a first thermistor and the second sensing component is a second thermistor.

[0024] In some configurations, the first seal member and the second seal member are removable.

[0025] In some configurations, the first seal member has a contact portion adapted to contact the sensing portion of the first sensor, the contact portion having a reduced thickness.

[0026] In some configurations, the first seal member has a contact portion adapted to contact the sensing portion of the first sensor, the contact portion having a thickness of about the contact.

[0027] In some configurations, the cartridge includes an electrical connector, which is electrically connected to the first sensor and the second sensor.

[0028] In some configurations, the interlocking structure includes a recess defined in the outer body of the chamber and a boss defined in the cartridge.

[0029] Some embodiments provide a chamber having a liquid level sensing system and adapted to hold a conductive liquid. The chamber comprises a body including a non-conductive wall having an inner surface and an outer surface, and a conductive base attached to the non-conductive wall to form a container adapted to hold a liquid. The chamber comprises a sensor electrode positioned on the outer surface of the non-conductive wall. The chamber comprises a base electrode electrically coupled to the conductive base and positioned on the outer surface of the conductive base. The chamber comprises a conductive bridge attached to the inner surface of the non-conductive wall. The chamber comprises a voltage source and a detection system electrically coupled to the sensor electrode. The conductive bridge and the sensor electrode are capacitively coupled to each other in the chamber, and when a conductive liquid contacts both the bridge and the base electrode, the conductive bridge and the base electrode can be conductively coupled to each other. To determine the liquid level in the chamber, the voltage source is configured to supply a variable voltage to the sensor electrode, and the detection system is configured to measure the capacitance of the sensor electrode.

[0030] Some embodiments provide a chamber having a liquid level sensing system and adapted to hold a non-conductive liquid. The chamber comprises a body including a non-conductive wall having an inner surface and an outer surface, and a conductive base attached to the non-conductive wall to form a container adapted to hold a liquid. The chamber comprises a sensor electrode positioned on the outer surface of the non-conductive wall. The chamber comprises a base electrode electrically coupled to the conductive base and positioned on the outer surface of the conductive base. The chamber comprises a conductive bridge attached to the inner surface of the non-conductive wall. The chamber comprises a voltage source and a detection system electrically coupled to the sensor electrode. The conductive bridge and the sensor electrode are capacitively coupled to each other in the chamber, and the conductive bridge and the base electrode are capacitively coupled to each other. To determine the liquid level in the chamber, the voltage source is configured to supply a variable voltage to the sensor electrode, and the detection system is configured to measure the capacitance of the sensor electrode.

[0031] Some embodiments provide a chamber having a liquid level sensing system and adapted to hold a conductive liquid. The chamber comprises a body including a non-conductive wall having an inner surface and an outer surface; a wicking material attached to the inner surface of the non-conductive wall, the wicking material configured to allow the conductive liquid to move up the non-conductive wall via the wicking material; and a conductive base attached to the non-conductive wall to form a container adapted to hold the liquid. The chamber comprises a sensor electrode positioned on the outer surface of the non-conductive wall. The chamber comprises a voltage source and a detection system electrically coupled to the sensor electrode. The sensor electrode and the conductive liquid are capacitively coupled to each other. To determine the liquid level in the chamber, the voltage source is configured to supply a variable voltage to the sensor electrode, and the detection system is configured to measure the capacitance of the sensor electrode.

[0032] In some configurations, composite tubing usable in various medical circuits includes a first elongate member including a helically wound elongate hollow body and a second elongate member including an elongate structural component helically wound between the turns of the helically wound hollow body. The first elongate member may define, in longitudinal cross section, a plurality of flat-faced bubbles in the lumen. Adjacent bubbles may be separated by gaps above the second elongate member or may not be directly connected to each other. The bubbles may have perforations. In some configurations, a "double-bubble" tubing includes multiple bubbles between the turns of the second elongate member, e.g., two adjacent turns of the first elongate member. The second elongate member may have a longitudinal cross section that is wider near the lumen and narrower radially away from the lumen. Specifically, the second elongate member may have a generally triangular, T-, or Y-shaped longitudinal cross section. One or more conductive filaments may be embedded or encapsulated in the second elongate member. The one or more conductive filaments may be heating filaments (or more specifically, resistive heating filaments) and / or sensing filaments. The tube may include a pair of conductive filaments, e.g., two or four conductive filaments. The pair of conductive filaments may be formed into a connecting loop at one end of the composite tube. The one or more conductive filaments may be spaced apart from the lumen wall. In at least one embodiment, the second elongate member may have a generally triangular, T-shaped, or Y-shaped longitudinal cross-section, and one or more conductive filaments may be embedded or encapsulated in the second elongate member on opposite sides of the triangle, T-shape, or Y-shape.

[0033] In some configurations, the humidification device includes a pressurized gas source including an outlet. The outlet of the pressurized gas source is connected to an inlet leading to the humidification unit. The humidification unit includes an outlet. The outlet of the humidification unit is connected to an air delivery component. A flow path is defined between the pressurized gas source and the air delivery component. A sensor is adapted to sense a flow characteristic within the flow path. The flow path includes an opening. The sensor extends through the opening into the flow path. The sensor includes a sensing portion. A barrier is positioned between the flow path and the sensor. The barrier contacts the sensing portion of the sensor, and the barrier includes a substantially constant thickness in the area contacting the sensing portion.

[0034] In some configurations, the humidification unit includes a humidification chamber that includes a port with an opening extending through a wall that defines at least a portion of the port.

[0035] In some configurations, the sensor includes a first thermistor and a second thermistor, and the barrier includes a first sleeve that receives the first thermistor and a second sleeve that receives the second thermistor.

[0036] In some configurations, the first thermistor is heated and the second thermistor is non-heated.

[0037] In some configurations, the barrier includes a mounting portion, a first thickness, and a second thickness less than the first thickness, the second thickness being located adjacent to the sensing portion of the sensor, and the region having the first thickness being positioned between the mounting portion and the portion having the second thickness.

[0038] In some configurations, the barrier includes a tip portion and a mounting portion, the mounting portion securing the barrier within the opening and the tip portion including a reduced thickness.

[0039] In some configurations, the barrier hermetically seals the opening and receives at least a portion of the sensor such that the sensing portion can be positioned within the flow path and the mounting portion can be positioned outside the flow path.

[0040] In some configurations, the sensor is supported by the cartridge. The humidification unit includes a humidification chamber. The cartridge and humidification chamber are removably attachable and may include an interlocking connector.

[0041] In some configurations, the cartridge includes a connector adapted to make electrical connection with the humidification unit when the cartridge is attached to the humidification chamber and the humidification chamber is attached to the humidification unit.

[0042] In some configurations, the cartridge supports the sensor in a repeatable manner relative to a portion of the flow path through the humidification chamber so that the sensing portion of the sensor is consistently positioned even with repeated removal and replacement of the cartridge from the humidification chamber.

[0043] In some configurations, the humidification chamber includes an outer body defining the chamber. The inlet port includes a wall defining a passageway into the chamber. The outlet port includes a wall defining a passageway out of the chamber. The inlet port wall includes a first opening. The first opening receives a first seal member. The first seal member hermetically seals the first opening extending through the inlet port wall. The outlet port wall includes a second opening. The second opening receives a second seal member. The second seal member hermetically seals the second opening extending through the outlet port wall. A cartridge is removably attachable to the chamber's outer body by an interlocking structure. The cartridge supports a first sensor receivable within the first seal and extending through the first opening. The cartridge supports a second sensor receivable within the second seal and extending through the second opening.

[0044] In some configurations, the first sensor includes a first sensing component and a second sensing component, and a first seal member separates the first sensing component from the second sensing component.

[0045] In some configurations, the first sensing component is a first thermistor and the second sensing component is a second thermistor.

[0046] In some configurations, the first seal member and the second seal member are removable.

[0047] In some configurations, the first seal member has a contact portion adapted to contact the sensing portion of the first sensor, the contact portion having a reduced thickness.

[0048] In some configurations, the first seal member has a contact portion adapted to contact the sensing portion of the first sensor, the contact portion having a thickness of about the contact.

[0049] In some configurations, the cartridge includes an electrical connector that is electrically connected to the first sensor and the second sensor.

[0050] In some configurations, the interlocking structure includes a recess defined in the outer body of the chamber and a boss defined in the cartridge.

[0051] In some configurations, the chamber has a liquid level sensing system and is adapted to hold a conductive liquid. The chamber includes a body having a non-conductive wall having an inner surface, an outer surface, and a conductive base attached to the non-conductive wall to form a container adapted to hold a liquid. A sensor electrode may be positioned on the outer surface of the non-conductive wall. A base electrode may be electrically coupled to the conductive base and may be positioned on the outer surface of the conductive base. A conductive bridge may be attached to the inner surface of the non-conductive wall. The conductive bridge may be capacitively coupled to the sensor electrode. When a conductive liquid contacts both the bridge and the base electrode, the conductive bridge and the base electrode may be conductively coupled. A voltage source may be electrically coupled to the sensor electrode and may be configured to supply a variable voltage to the sensor electrode. A detection system may be electrically coupled to the sensor electrode and may be configured to measure the capacitance of the sensor electrode.

[0052] In some configurations, the sensor electrode is positioned farther from the conductive base than the conductive bridge such that at least a portion of the sensor electrode extends beyond the conductive bridge in a direction away from the conductive base.

[0053] In some configurations, the detection system is configured to detect a change in capacitance of the sensor electrode when the level of the conductive liquid rises above the conductive bridge.

[0054] In some configurations, the detection system is configured to detect a change in capacitance of the sensor electrode when the level of the conductive liquid falls below the sensor electrode.

[0055] In some configurations, the sensor electrode is larger than the conductive base.

[0056] In some configurations, the base electrode is electrically coupled to electrical ground.

[0057] In some configurations, the conductive base provides a virtual electrical ground for the liquid level sensing system.

[0058] In some configurations, the voltage source comprises an AC voltage source.

[0059] In some configurations, the capacitance of the sensor electrode increases by a discrete amount when a conductive liquid contacts the conductive bridge.

[0060] In some configurations, the humidification unit incorporates a chamber as discussed above.

[0061] In some configurations, the chamber has a liquid level sensing system and is adapted to hold a non-conductive liquid. The chamber includes a body including a non-conductive wall having an inner surface and an outer surface, and a conductive base attached to the non-conductive wall to form a container adapted to hold a liquid. A sensor electrode may be positioned on the outer surface of the non-conductive wall. A base electrode may be electrically coupled to the conductive base and may be positioned on the outer surface of the conductive base. A conductive bridge may be attached to the inner surface of the non-conductive wall. A voltage source may be electrically coupled to the sensor electrode. A detection system may be electrically coupled to the sensor electrode. The conductive bridge and the sensor electrode may be capacitively coupled. The conductive bridge and the base electrode may be capacitively coupled. The voltage source may be configured to supply a variable voltage to the sensor electrode. The detection system may be configured to measure the capacitance of the sensor electrode.

[0062] In some configurations, the detection system is further configured to determine a liquid level corresponding to the capacitance of the sensor electrode.

[0063] In some configurations, the detection system is configured to determine at least one of an out of liquid condition or a full liquid condition.

[0064] In some configurations, the detection system is further configured to provide a notification corresponding to the liquid level.

[0065] In some configurations, the sensor electrodes are removably attached to the outer surface of the non-conductive wall.

[0066] In some configurations, the humidification unit incorporates a chamber as described above.

[0067] In some configurations, the chamber has a liquid level sensing system and is adapted to hold a conductive liquid. The chamber includes a body including a non-conductive wall having an inner surface and an outer surface. A wicking material may be attached to the inner surface of the non-conductive wall. The wicking material may be configured to allow the conductive liquid to move up the non-conductive wall through the wicking material. A conductive base is attached to the non-conductive wall to form a container adapted to hold a liquid. A sensor electrode may be positioned on the outer surface of the non-conductive wall. A voltage source may be electrically coupled to the sensor electrode. A detection system may be electrically coupled to the sensor electrode. The sensor electrode and the conductive liquid may be capacitively coupled. The voltage source may be configured to supply a variable voltage to the sensor electrode. The detection system may be configured to measure the capacitance of the sensor electrode.

[0068] In some configurations, the detection system is configured to determine an out-of-liquid condition when the chamber is free of conductive liquid.

[0069] In some configurations, the detection system is configured to provide notification when an out-of-liquid condition is determined.

[0070] In some configurations, the humidification unit may incorporate a chamber as described above.

[0071] In some configurations, the composite tube includes a first elongate member including a hollow body helically wound to at least partially define 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 is helically wound and joined between adjacent turns of the first elongate member, the second elongate member defining at least a portion of the lumen of the elongate tube.

[0072] In some configurations, the first elongate member is a tube.

[0073] In some configurations, the first elongate member defines, in longitudinal cross section, a plurality of flat-faced bubbles in the lumen.

[0074] In some configurations, adjacent bubbles are separated by a gap above the second elongate member.

[0075] In some configurations, adjacent bubbles are not directly connected to each other.

[0076] In some configurations, the bubble has perforations.

[0077] In some configurations, the second elongate member has a longitudinal cross-section that is wider adjacent the lumen and narrower radially away from the lumen.

[0078] In some configurations, the second elongate member has a generally triangular longitudinal cross-section.

[0079] In some configurations, the second elongate member has a generally T-shaped or Y-shaped longitudinal cross-section.

[0080] In some configurations, one or more conductive filaments may be embedded or encapsulated in the second elongate member.

[0081] In some configurations, the conductive filament is a heating filament.

[0082] In some configurations, the conductive filament is a sensing filament.

[0083] In some configurations, the two conductive filaments may be embedded or encapsulated in the second elongate member.

[0084] In some configurations, the four conductive filaments may be embedded or encapsulated in the second elongate member.

[0085] In some configurations, pairs of conductive filaments are formed into connecting loops at one end of the composite tube.

[0086] In some configurations, the second elongate member has a generally triangular, T-shaped, or Y-shaped longitudinal cross-section, and one or more conductive filaments are embedded or encapsulated in the second elongate member on opposite sides of the triangle, T-shape, or Y-shape.

[0087] In some configurations, one or more filaments are spaced from the lumen wall.

[0088] In some configurations, the medical circuit components include the composite tubing described above.

[0089] In some configurations, the intake pipe comprises the composite pipe described above.

[0090] In some configurations, the expiratory tube comprises the composite tube described above.

[0091] In some configurations, the PAP components include the composite tubing described above.

[0092] In some configurations, the insufflation circuitry includes the composite tubing described above.

[0093] In some configurations, the exploratory component includes the composite tube described above.

[0094] In some configurations, the surgical component includes the composite tube described above.

[0095] In some configurations, a method of manufacturing a composite pipe includes providing a first elongate member including a hollow body and a second elongate member configured to provide structural support for the first elongate member; helically winding the second elongate member around a mandrel while spacing opposing side edge portions of the second elongate member apart relative to adjacent wraps, thereby forming a second elongate member spiral; and helically winding the first elongate member around the second elongate member spiral such that a portion of the first elongate member overlaps adjacent wraps of the second elongate member spiral and a portion of the first elongate member is disposed adjacent the mandrel in a space between wraps of the second elongate member spiral, thereby forming the first elongate member spiral.

[0096] In some configurations, the method further includes supplying air at a pressure greater than atmospheric pressure to the end of the first elongate member.

[0097] In some configurations, the method further includes cooling the second elongate member spiral and the first elongate member spiral, thereby forming a composite tube having a lumen extending along the longitudinal axis and a hollow space surrounding the lumen.

[0098] In some configurations, the method further includes forming a second elongate member.

[0099] In some configurations, the method further includes forming the second elongate member includes extruding the second elongate member with a second extruder.

[0100] In some configurations, the method further includes a second extruder configured to encapsulate the one or more conductive filaments into a second elongate member.

[0101] In some configurations, the method further includes forming the second elongate member includes embedding a conductive filament in the second elongate member.

[0102] In some configurations, the method further includes the conductive filament being non-reactive with the second elongate member.

[0103] In some configurations, the method further includes the conductive filaments comprising aluminum or copper.

[0104] In some configurations, the method further includes forming the pair of conductive filaments into a connecting loop at one end of the composite tube.

[0105] In some configurations, the method further includes forming a first elongate member.

[0106] In some configurations, the method further includes forming the first elongate member includes extruding the first elongate member with a first extruder.

[0107] In some configurations, the method further includes the first extruder being different from the second extruder.

[0108] In some configurations, the medical tubing includes an elongate hollow body wound in a helical manner to form an elongate tube having a longitudinal axis. A lumen extends along the longitudinal axis. A hollow wall surrounds the lumen. The elongate hollow body has a wall that, in transverse cross section, defines at least a portion of the hollow body. A reinforcing portion extends along the length of the elongate hollow body and is helically positioned between adjacent turns of the elongate hollow body. The reinforcing portion forms a portion of the lumen of the elongate tube. The reinforcing portion is relatively thick or stiff compared to the wall of the elongate hollow body.

[0109] In some configurations, the reinforcement portion is formed from the same piece of material as the elongated hollow body.

[0110] In some configurations, the elongated hollow body includes, in transverse cross section, two reinforcing portions on opposite sides of the elongated hollow body, wherein the helical windings of the elongated hollow body join adjacent reinforcing portions to one another such that opposing edges of the reinforcing portions contact adjacent turns of the elongated hollow body.

[0111] In some configurations, opposing side edges of the reinforcing portion overlap adjacent turns of the elongated hollow body.

[0112] In some configurations, the reinforcement portion is made from a separate piece of material from the elongated hollow body.

[0113] In some configurations, the hollow body defines, in longitudinal cross section, a plurality of flat-faced bubbles in the lumen.

[0114] In some configurations, the bubble has perforations.

[0115] In some configurations, one or more conductive filaments are embedded or encapsulated within the reinforcement portion.

[0116] In some configurations, the conductive filament is a heating filament.

[0117] In some configurations, the conductive filament is a sensing filament.

[0118] Some configurations include two conductive filaments, where one conductive filament is embedded or encapsulated in each of the reinforcement portions.

[0119] In some configurations, two conductive filaments are positioned on only one side of the elongated hollow body.

[0120] In some configurations, pairs of conductive filaments are formed into connecting loops at one end of an elongated tube.

[0121] In some configurations, one or more filaments are spaced from the lumen wall.

[0122] In some configurations, the medical circuit components include the medical tubing described above.

[0123] In some configurations, the intake tubing includes the medical tubing described above.

[0124] In some configurations, the expiratory tube comprises the medical tube described above.

[0125] In some configurations, the PAP components include the medical tubing described above.

[0126] In some configurations, the insufflation circuitry includes the medical tubing described above.

[0127] In some configurations, the exploratory component includes the medical tubing described above.

[0128] In some configurations, the surgical component includes the medical tubing described above.

[0129] In some configurations, a method of manufacturing a medical tube includes helically winding an elongate hollow body around a mandrel, thereby forming an elongate tube having a longitudinal axis along which a lumen extends and a hollow wall surrounding the lumen, wherein the elongate hollow body, in transverse cross section, has a wall that defines at least a portion of the hollow body, and wherein two reinforcing portions on opposite sides of the elongate body form part of the wall of the lumen, the two reinforcing portions being relatively thick or stiff compared to the wall that defines at least a portion of the hollow body; and joining adjacent reinforcing portions to one another so that opposing edges of the reinforcing portions contact adjacent turns of the elongate hollow body.

[0130] In some configurations, the method further includes joining adjacent reinforcement portions to one another, thereby creating an overlap at the edges of the reinforcement portions.

[0131] In some configurations, the method further includes supplying air at a pressure greater than atmospheric pressure to the end of the elongated hollow body.

[0132] In some configurations, the method further includes cooling the elongated hollow body, thereby bonding adjacent reinforcement portions to one another.

[0133] In some configurations, the method further includes extruding the elongated hollow body.

[0134] In some configurations, the method further includes embedding a conductive filament in the reinforcement portion.

[0135] In some configurations, the method further includes forming the pair of conductive filaments into a connecting loop at one end of the elongate tube.

[0136] For purposes of summarizing the invention, certain aspects, advantages, and novel features of the invention have been described herein. It is to be understood that not necessarily all such advantages may be achieved in any particular embodiment of the invention. Thus, the invention may be embodied or practiced in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0137] These and other features, aspects and advantages of the present invention will be explained with reference to the following drawings, which are illustrative and should not be construed as limiting the invention. [Brief explanation of the drawings]

[0138] [Figure 1] 1 is a simplified diagram of a humidification system arranged and configured in accordance with certain features, aspects and advantages of the present invention; [Figure 1A] FIG. 1 is a simplified diagram of a humidification system. [Figure 1B] 1 illustrates an insufflation system according to at least one embodiment. [Figure 2] 1 is a side elevational view of a humidification chamber arranged and configured for use with certain features, aspects and advantages of the present invention; [Figure 2A]FIG. 1 shows a block diagram of a liquid level sensing system combined with a controller for a humidification system. [Figure 2B] An exemplary liquid level sensing system in a humidification chamber is shown with an associated voltage source and detection system. [Figure 2C] 1 illustrates an exemplary liquid level sensing system in a humidification chamber having wicking material along the interior walls. [Figure 2D] 1 shows a flow chart of an exemplary method for detecting the liquid level in a humidification chamber. [Figure 3] 3 is a perspective view of the humidification chamber of FIG. 2 with a seal inserted into an opening formed in a port of the humidification chamber. [Figure 4] FIG. 10 is a cross-sectional view taken along one of the seals and the inlet port of the humidification chamber. [Figure 5] 5 is a top view of the seal of FIG. 4, which is substantially the same as a bottom view of the seal. [Figure 6] 5 is a side view of the seal of FIG. 4, which is substantially the same as the opposite side view of the seal. [Figure 7] FIG. 5 is a front view of the seal of FIG. 4. [Figure 8] FIG. 5 is a rear view of the seal of FIG. 4. [Figure 9] FIG. 5 is a perspective view of the seal of FIG. 4. [Figure 10] FIG. 10 is a cross-sectional view taken along one of the seals and the outlet port of the humidification chamber. [Figure 11] 11 is a side view of the seal of FIG. 10, which is substantially the same as the opposite side view of the seal. [Figure 12] 11 is a top view of the seal of FIG. 10, which is substantially the same as a bottom view of the seal. [Figure 13] FIG. 11 is a front view of the seal of FIG. 10. [Figure 14] FIG. 11 is a rear view of the seal of FIG. 10. [Figure 15] FIG. 11 is a perspective view of the seal of FIG. 10. [Figure 16] FIG. 11 is an exploded perspective view of the seal of FIGS. 4 and 10 together with the corresponding sensor. [Figure 17]FIG. 10 is a partial cross-sectional view of a chamber having a port with a sleeve and a bias sensor. [Figure 18A] FIG. [Figure 18B] FIG. 18B is a side view of the seal of FIG. 18A. [Figure 18C] FIG. 18B is another perspective view of the seal of FIG. 18A. [Figure 18D] FIG. 18B is a cross-sectional view of the seal of FIG. 18A. [Figure 18E] FIG. 18B is a perspective view of the seal of FIG. 18A shown at the port of the humidification chamber. [Figure 18F] FIG. 18F is another perspective view of the seal and chamber of FIG. 18E. [Figure 18G] FIG. 18F is another perspective view of the seal and chamber of FIG. 18E. [Figure 19A] FIG. [Figure 19B] FIG. 19B is a cross-sectional view of the seal of FIG. 19A. [Figure 19C] FIG. 19B is a perspective view of the seal of FIG. 19A. [Figure 20A] FIG. [Figure 20B] FIG. [Figure 20C] FIG. [Figure 21] FIG. 1 is a perspective view of a cartridge with a sensor attached thereto. [Figure 22] FIG. 10 is another perspective view of the cartridge and the sensor. [Figure 23] FIG. 2 is a top view of the cartridge and the sensor. [Figure 24] FIG. 10 is a rear view of the cartridge and the sensor. [Figure 25] FIG. 2 is a left side view of the cartridge and the sensor. [Figure 26] FIG. [Figure 27] FIG. 10 is a right side view of the cartridge and the sensor. [Figure 28] FIG. 10 is a bottom view of the cartridge and the sensor. [Figure 29]FIG. 1 is a perspective view of a cartridge assembled into a humidification chamber. [Figure 30] FIG. 1 is a top view of the cartridge assembled into the humidification chamber. [Figure 31] FIG. 1 is a front view of the cartridge assembled in the humidification chamber. [Figure 32] FIG. 10 is a right side view of the cartridge assembled in the humidification chamber. [Figure 33] FIG. 10 is a rear view of the cartridge assembled in the humidification chamber. [Figure 34] FIG. 10 is a left side view of the cartridge assembled in the humidification chamber. [Figure 35] FIG. 10 is an exploded perspective view showing the cartridge assembled into the humidification chamber. [Figure 36] FIG. 10 is an exploded perspective view showing an alternative cartridge assembled into an alternative humidification chamber. [Figure 37A] 1 illustrates a side view of a portion of an exemplary composite pipe. [Figure 37B] 37B shows a longitudinal cross section of the upper portion of a tube similar to the exemplary composite tube of FIG. 37A. [Figure 37C] 10 shows another longitudinal cross section showing the first elongated member of the composite pipe. [Figure 37D] 4 shows another longitudinal cross section of the upper part of the tube. [Figure 37E] 4 shows another longitudinal cross section of the upper part of the tube. [Figure 37F] The tube is shown with a partial exposed longitudinal cross section. [Figure 37G] 37F shows a longitudinal cross section of a portion of a tube similar to the exemplary tube of FIG. [Fig. 37H-37L] 10A-10C illustrate variations of a tube adapted to provide increased lateral stretch of the tube, shown in a relaxed state. [Fig. 37V-37Z] 37A-37L respectively show the tubes shown in FIGS. 37H-37L in an expanded state. [Figure 38A] 1 shows a schematic cross-sectional front view of a flexibility test jig. [Figure 38B]38B shows a detailed schematic cross-sectional front view of the roller in the flexibility test jig of FIG. 38A. [Fig. 38C-38F] The flexible test jig is shown in use. Figures 38C and 38E show a front perspective view of a test sample in the jig. Figures 38D and 38F show a back perspective view of a test sample in the jig. [Figure 39A] 1 shows a crush resistance test jig. [Figure 39B] 1 shows a plot of load versus elongation used to measure crush stiffness. [Figure 40A] 1 shows a transverse cross section of a second elongated member of a composite pipe. [Figure 40B] 10 shows another transverse cross section of the second elongate member. [Figure 40C] 1 illustrates another exemplary second elongate member. [Figure 40D] 1 illustrates another exemplary second elongate member. [Figure 40E] 1 illustrates another exemplary second elongate member. [Figure 40F] 1 illustrates another exemplary second elongate member. [Figure 40G] 1 illustrates another exemplary second elongate member. [Figure 40H] 10 illustrates an alternative embodiment of the second elongate member. [Figure 41A] 1 illustrates one embodiment of a method for forming a composite pipe. [Figure 41B] 1 shows a spirally wound second elongate member. [Figure 41C] 1 illustrates another embodiment of a method for forming a composite pipe. [Figure 41D] 1 illustrates another embodiment of a method for forming a composite pipe. [Figure 41E] 1 illustrates another embodiment of a method for forming a composite pipe. [Figure 41F] 1 illustrates another embodiment of a method for forming a composite pipe. [Figure 41G-41I] 1 shows an exemplary configuration of a longitudinal cross section of a tube. [Fig. 41J-41Q] 10 illustrates an alternative method of forming a tube. [Figure 42A-42B]10 shows another example illustrating spiral winding of a single elongated hollow body to form a medical tube. [Fig. 42C-42F] Another example is shown in which a single elongated hollow body is spirally wound to form a medical tube. [Figures 43A-43L] 1 shows a schematic flow chart and more detailed schematic diagrams and photographs of a method for attaching a connector to the end of a tube that is adapted to connect to a humidifier in use; [Figures 44A-44I] 10 shows a schematic diagram of a connector suitable for attaching tubing to a patient interface. [Figures 45A-45E] A schematic diagram of a connector suitable for attaching the tubing to a humidifier port, a patient interface, or any other suitable component is shown. [Figures 46A-46F] 1 shows a connector that can be used in a medical circuit with electrical wires passing through it. [Figure 47] 1 is a schematic diagram of a coaxial tube according to at least one embodiment. [Figures 48A-48C] 10 shows an example of the shape of the first elongated member configured to improve thermal efficiency. [Fig. 48D-48F] 1 illustrates an example of a filament device configured for improved thermal efficiency. [Figures 49A-49C] 1 shows an example of lamination of first elongated members. [Figures 50A-50D] 1 illustrates the radius of curvature profile of a tube according to various embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0139] Specific embodiments and examples of humidification systems and / or liquid level sensing systems are described herein. Those skilled in the art will appreciate that the disclosure extends beyond the specifically disclosed embodiments and / or uses and obvious variations and equivalents thereof. Accordingly, it is intended that the scope of the disclosure disclosed herein not be limited by any particular embodiment described herein.

[0140] Humidification system 1 and 1A illustrate a respiratory humidification system 20 that may include a sensing device 22, a liquid level sensing system 222, composite tubing, and / or other features arranged and configured in accordance with certain features, aspects, and advantages of the present disclosure. The sensing device 22, sensing system 222, composite tubing, and other features are illustrated and described herein in connection with respiratory humidification system 20, but may find applicability in other applications involving the delivery of a heated, humidified gas stream to a user or patient, including, but not limited to, laparoscopy, ventilation, etc.

[0141] The illustrated respiratory humidification system 20 includes a pressurized gas source 30. In some applications, the pressurized gas source 30 includes a fan, blower, etc. In some applications, the pressurized gas source 30 includes a ventilator or other positive pressure generating device. The pressurized gas source 30 includes an inlet 32 ​​and an outlet 34.

[0142] The pressurized gas source 30 provides a flow of fluid (e.g., oxygen, anesthetic gas, air, etc.) to the humidification unit 40. The fluid flow passes from an outlet 34 of the pressurized gas source 30 to an inlet 42 of the humidification unit 40. In the illustrated configuration, the humidification unit 40 is shown separate from the pressurized gas source 30, with the inlet 42 of the humidification unit 40 connected to the outlet 34 of the pressurized gas source 30 by a conduit 44. In some applications, the pressurized gas source 30 and the humidification unit 40 may be combined into a single housing.

[0143] Although other types of humidification units may be used with certain features, aspects, and advantages of the present invention, the illustrated humidification unit 40 is a pass-over humidifier that includes a humidification chamber 46, with the inlet 42 to the humidification unit 40 including an inlet to the humidification chamber 46. In some configurations, the humidification chamber 46 includes a molded plastic body 50 enclosed by a thermally conductive base 52. A compartment may be defined within the humidification chamber 46. The compartment is adapted to hold a predetermined amount of water that can be heated by heat conducted from the base 52. In some applications, the base 52 is adapted to contact a heating plate 54. The heating plate 54 may be controlled by a controller 56 or other suitable component, thereby varying the heat transferred to the water.

[0144] 2 , in the illustrated configuration, the body 50 of the humidification chamber 46 includes a port 60 that defines the inlet 42, and the body 50 also includes a port 62 that defines the outlet 64 of the humidification chamber 46. In some configurations, one or more of the ports 60, 62 may be formed at the end of a conduit or as a connector. In some configurations, the ports 60, 62 may have a portion that is received within an opening in the chamber. When the water contained within the humidification chamber 46 is heated, gas and water vapor drawn into the humidification chamber 46 through the inlet port 60 mix. The gas and water vapor mixture exits the humidification chamber 46 through the outlet port 62.

[0145] Referring again to FIG. 1 , an intake conduit 70 or other suitable gas-carrying pathway may be connected to the outlet 64 defining the outlet port 62 of the humidification unit 40. The conduit 70 carries the gas and water vapor mixture exiting the humidification chamber 46 toward the user. A condensation reduction component may be positioned along at least a portion of the conduit 70. In the illustrated configuration, the condensation reduction component includes a heating element 72 positioned along at least a portion of the conduit 70. The heating element 72 may increase or maintain the temperature of the gas and water vapor mixture being carried by the conduit 70. In some configurations, the heating element 72 may be a wire defining a resistive heater. Other configurations are possible. Increasing or maintaining the temperature of the gas and water vapor mixture reduces the likelihood of condensation of the water vapor in the mixture.

[0146] An air delivery component, such as, without limitation, an interface 74, may be provided to connect the conduit 70 with a user. In the illustrated configuration, the interface 74 includes a mask. Further, in the illustrated configuration, the interface 74 includes a mask that extends over the user's mouth and nose. Any suitable interface 74 may be used. Depending on the application, certain features, aspects, and advantages of the present invention may be used in intubation components, laparoscopy components, insufflators, and the like. In some applications, such as those used with a ventilator, a suitable fitting (e.g., a Y-piece 75) may be positioned between the user and the conduit 70, thereby connecting the expiratory conduit 71 between the user and the inlet of the ventilator, for example, without limitation.

[0147] As discussed above, the sensing device 22, tubing, and other features illustrated and described herein can be used in connection with laparoscopic surgery, also known as minimally invasive or keyhole surgery. In laparoscopic procedures involving insufflation, it may be desirable to humidify the insufflation gas (typically CO2) before insufflation into the abdominal cavity. This can help reduce or eliminate the possibility of the patient's internal organs "drying out" and can shorten the time required for post-operative recovery. FIG. 1B shows an exemplary embodiment of an insufflation system 701, which includes an insufflator 703 that generates a flow of insufflation gas at a pressure above atmospheric pressure that is insufflated into the abdominal or peritoneal cavity of a patient 705. The gas enters a humidification unit 707, which includes a heater base 709 and a humidifier chamber 711 that is in contact with the heater base 709 during use so that the heater base 709 can provide heat to the chamber 711. In the humidifier 707, the insufflation gas passes through a chamber 711, thereby humidifying it to the appropriate moisture level. The system 701 includes an air delivery conduit 713 that delivers the humidified insufflation gas from the humidifier chamber 711 to the peritoneal cavity or surgical site of the patient 705. A smoke evacuation system 715 leading out of the body cavity of the patient 705 includes an exhaust or vent rim 717, an exhaust assembly 719, and a filter 721.

[0148] In some configurations, the air delivery conduit 713 may also retain smoke rather than (or in addition to) using a smoke evacuation system. For example, in some configurations, rather than evacuating the smoke from the patient's body cavity via an evacuation system, the smoke may be aspirated, drawn, or directed back through the conduit 713 pathway (i.e., into and through the outer wall of the tube). The pathway 203 may include a filter / absorbent medium to accept the smoke. The conduit may generally be disposable after surgery, so that it does not need to be cleaned afterwards. A valve or other type of exhaust assembly (e.g., exhaust assembly 719) may be incorporated between the body cavity and the pathway 203 to direct the smoke into the pathway after / during surgery.

[0149] Detection and Control Systems The controller 56 of the humidification unit 40 can control the operation of the various components of the respiratory humidification system 20. While the illustrated configuration is shown with a single controller 56, in other configurations, multiple controllers can be used. The multiple controllers may communicate, or separate functions may be provided so the controllers need not communicate. In some configurations, the controller 56 may include a microprocessor, processor, or logic circuitry with associated memory or storage containing software code for a computer program. In such configurations, the controller 56 can control the operation of the humidification system 20 according to instructions, such as those contained in a computer program, and in response to external inputs.

[0150] In some configurations, the controller 56 may receive input from a heater plate sensor 80. The heater plate sensor 80 may provide the controller 56 with information regarding the temperature and / or power usage of the heater plate 54. In some configurations, another input to the controller 56 may be a user input component 82. The user input component 82 may include a switch, a dial, a knob, or other suitable control input device, including, but not limited to, a touchscreen. The user input component 82 may be operated by a user, a medical professional, or another person to set a desired temperature of the gas delivered to the user, a desired humidity level of the delivered gas, or both. In some configurations, the user input component 82 may be operated to control other operating characteristics of the humidification system 20. For example, the user input component 82 may control the heating provided by the heating element 72 or any desired characteristic of the airflow (e.g., pressure, flow rate, etc.).

[0151] Liquid Level Detection System The controller 56 also receives input from a liquid level sensing system 222. The liquid level sensing system 222 may include one or more sensors positioned in or near the chamber 46 or the base 52. The liquid level sensing system 222 may include a voltage source and a detection system for determining the liquid level in the chamber 46 as described herein. The controller 56 may receive liquid level information from the liquid level sensing system 222 and adjust control characteristics in response to the liquid level information. In some embodiments, the controller 56 may notify a user regarding the liquid level status using the user interface component 82.

[0152] 2 illustrates an exemplary humidification chamber 46 having a liquid level sensing system 222 according to some embodiments. The liquid level sensing system 222 may include one or more sensors 200. The sensors 200 may be positioned such that they are capacitively and / or conductively coupled to each other and / or to ground. The capacitance of one or more of the sensors 200 may change in response to changes in the liquid level. The liquid level sensing system 222 can detect these changes and determine a fluid level or fluid level condition (e.g., empty, full chamber, etc.) based at least in part on the change in capacitance of the one or more sensors 200.

[0153] The humidification chamber 46 may include a body 50 having at least one non-conductive wall 53. The non-conductive wall 53 may be made of any suitable material that does not effectively conduct electricity, such as an insulating material. The humidification chamber 46 includes a base 52 that encloses the body 50. The base 52 may be made of any suitable conductive material, any suitable non-conductive material, or a combination of conductive and non-conductive materials. For example, the base 52 may include a conductive material covered by a non-conductive material. In some embodiments, when the base electrode 206 is present, the base 52 is made of a non-conductive material.

[0154] The liquid detection system 222 includes a sensor electrode 202 positioned on or near the outer surface of the non-conductive wall 53. The sensor electrode 202 may be made of a conductive material, such as a metal. The sensor electrode 202 may be attached to the non-conductive wall 53 using any conventional means. In some embodiments, the sensor electrode 202 is removably attached to the non-conductive wall 53 so that the position of the sensor electrode 202 can be changed or so that the sensor electrode 202 can be used with different humidification chambers 46.

[0155] The liquid sensing system 222 may include a bridge 204 attached to the inner surface of the non-conductive wall 53. The bridge 204 is made of a conductive material and is positioned on or near the inner surface of the non-conductive wall 53. In some embodiments, the bridge 204 is attached to the inner surface of the non-conductive wall 53 using any conventional means to prevent the bridge 204 from moving substantially in response to changes in the liquid level in the chamber 46. The bridge 204 may be positioned relatively close to the location of the sensor electrode 202 on the outer surface of the non-conductive wall 53. The relative positions of the sensor electrode 202 and the bridge 204 may be configured such that when liquid contacts the bridge 204, a discrete, measurable increase in capacitance occurs in the capacitance of the sensor electrode 202. The measurable change may be any capacitance change that is detected by the fluid level sensing system 222, as described in more detail herein. By placing the bridge 204 in the chamber 46, a discrete jump in capacitance may be observed when liquid contacts the bridge 204. It should be understood that bridge 204 is not electrically coupled to sensor electrode 202 by a physical connection or wired means, but is capacitively coupled to sensor electrode 202 based at least in part on their respective electrical properties and / or their physical proximity. Furthermore, bridge 204 is not electrically coupled to any other components of liquid level sensing system 222 by wired means. Instead, bridge 204 may be capacitively coupled to base electrode 206, in which case chamber 46 contains a non-conductive liquid, or bridge 204 may be conductively coupled to base electrode 206, in which case chamber 46 contains a conductive liquid that provides a conductive path between bridge 204 and base 52. Thus, there are no wires or cables running from outside chamber 46 to inside chamber 46, as in other systems having sensors located inside a chamber. This allows the liquid level sensing system 222 described herein to be used even if the structure of the humidification chamber 46 does not include a path for cables or wires passing from the outside to the inside of the chamber 46 (which may require sealing to prevent fluid loss through the path).

[0156] The liquid level sensing system 222 may include a base electrode 206 positioned on the base 52 of the humidification chamber 46. In some embodiments, the base 52 serves as a virtual electrical ground for the fluid level sensing system 222, i.e., it is not electrically coupled to electrical ground, but provides a virtual electrical ground for the system 222. In some embodiments, the base electrode 206 is coupled to electrical ground through the base 52 (e.g., the base 52 may provide a virtual ground or it may be electrically coupled to ground), through an electrical circuit, or through some other means.

[0157] In some embodiments, the sensor electrode 202 is not positioned on the opposite side of the bridge 204 as shown in FIG. 2 . The sensor electrode 202 may be positioned at other locations and / or moved relative to the bridge 204 and still experience a discrete and measurable change in capacitance as described herein. This is due, at least in part, to the change in capacitance of the sensor electrode 202 when liquid contacts the bridge 204. This allows for flexible positioning of the sensor electrode 202. The sensor electrode 202 may be positioned to accommodate various designs of the body 50. For example, some humidification chambers may have shapes where mechanical constraints prevent the sensor electrode 202 from being located on the outer surface opposite the bridge 204. It may be desirable to position the sensor electrode 202 farther from the base 52 compared to the location of the bridge 204. This may increase the distance between ground (e.g., the base 52) and the sensor electrode 202, increasing the change in capacitance relative to ground. Although the positions of the two electrodes relative to one another may change, the capacitance of the sensor electrode 202 changes when liquid contacts the bridge 204, so the sensor electrode 202 can be moved vertically from the bridge 204 (e.g., farther from the base 52 than the bridge 204). This allows the liquid level sensing system 222 to detect a liquid level below the location of the electrode sensor 202. Additionally, the sensor electrode 202 may be larger than the bridge 204. This allows for full-water detection, where there is a first discrete capacitance change when the liquid level reaches the bridge 204 and a second discrete capacitance change when the liquid level reaches the sensor electrode 202. Thus, the liquid level sensing system 222 can be configured to detect a full-water condition by sizing and positioning the sensor electrode 202 so that the second discrete capacitance change occurs when the liquid level approaches the top of the chamber. The sensor electrode 202 can be sized and positioned to cause the second discrete capacitance change when the liquid level reaches any desired height.

[0158] In some embodiments, the humidification chamber 46 includes a reservoir within the body 50 for holding the liquid without the liquid contacting the wall 53. Such a reservoir may include, for example, a tube or other such structure within the body 50 of the humidification chamber 46. The liquid level sensing system 222 may be configured to determine the liquid level in such a humidification chamber by positioning the bridge 204 within the reservoir. The sensor electrode 202 may be positioned external to the body 50 as before. Thus, when liquid reaches the bridge 204, there is a similar measurable change in the capacitance of the system that can be detected by the liquid level sensing system 222.

[0159] 2A shows a block diagram of a liquid level sensing system 222 in combination with the controller 56 of the humidification unit 40. The liquid level sensing system 222 includes a voltage source 302, a detection system 304, and a liquid level sensor 200, and may be configured to detect a change in capacitance of the liquid level sensing system 222 corresponding to a liquid level condition, such as an out-of-liquid condition or a chamber-full condition. The controller 56 may control the voltage source 302 and receive signals from the detection system 304 to determine the liquid level condition. The controller 56 may use user interface components to control the determination of the liquid level condition or to notify a user of the liquid level condition.

[0160] The controller 56 may include hardware, software, and / or firmware components used to control the humidification unit 40. The controller 56 may be configured to control the voltage source 302, receive information from the detection system 304, receive user input from the user interface component 82, determine the liquid level in the chamber 46, and determine the liquid level status. The controller 56 may include modules configured to control attached components and analyze received information. The controller 56 may include data storage for storing received information, control parameters, executable programs, and other such information.

[0161] The liquid level sensing system 222 includes a voltage source 302 coupled to the liquid level sensor 200, and in particular the electrode sensor 202 described in connection with Figures 2, 2B, and 2C. The voltage source 302 may be a source of alternating current ("AC") and variable voltage. The voltage source 302 may be electrically coupled to the sensor electrode 202.

[0162] The liquid level sensing system 222 includes a detection system 304 coupled to the liquid level sensing sensor 200. The detection system 304 may be configured to measure a change in capacitance of the liquid level sensor 200. For example, the detection system 304 may include electronic circuitry configured to generate a voltage across the sensor electrodes 202 (which may be different from the supply voltage from the voltage source 302). The difference between the supply voltage and the voltage across the sensor electrodes 202 can be related to the capacitance of the system 222. The detection system 304 may include data acquisition hardware configured to generate a signal corresponding to the measured voltage, capacitance, resistance, or some combination thereof. The detection system 304 may include a metrology tool configured to obtain and / or display values ​​corresponding to capacitance, voltage, resistance, etc.

[0163] The level sensing system 222 may be coupled to the controller 56 such that it can send information to and receive commands from the controller 56. For example, the level sensing system 222 may receive commands from the controller 56 to vary the voltage supplied by the voltage source 302 to the sensor electrode 202. In some embodiments, the voltage source 302 produces a defined, known, or programmed voltage without input from the controller 56. The level sensing system 222 may send information from the detection system 304 to the controller. The controller 56 may receive this information and analyze it to determine the liquid level condition. For example, the controller 56 may receive information indicating that the chamber is out of liquid or is about to run out of liquid. The controller 56 may then generate an out-of-liquid warning, notification, or signal. Similarly, the controller may receive information indicating that there is too much liquid in the chamber. The controller 56 may then issue a full-liquid warning, notification, or signal. In some embodiments, the detection system 304 analyzes information from the level sensor 200 to determine the liquid level status. In some embodiments, the controller 56 may receive information from the detection system 304 and analyze this information to determine the liquid level status. In some embodiments, the liquid level sensing system 222 and / or the controller 56 may be configured to determine the amount of liquid present in the humidification chamber 46 in addition to, or instead of, determining whether the chamber is out of liquid or whether there is too much liquid in the chamber. In some embodiments, the controller 56 may use the liquid level information as feedback in controlling other systems, such as the heating plate 54.

[0164] A user interface component 82 may be coupled to the controller 56 to display information and / or receive input from a user. The user interface component 82 may display information regarding, for example, the liquid level status, the voltage supplied by the voltage source 302, measurements taken by the detection system 304, the results of analysis by the controller 56, or any combination thereof. The user interface component 82 may be used to input control parameters such as the voltage supplied to the sensor electrodes 202, the characteristics (e.g., frequency, amplitude, waveform, etc.) of the supplied voltage, the frequency of measurements taken by the detection system 304, thresholds associated with measurements from the detection system 304 used to determine a full or low liquid condition, or any combination thereof.

[0165] The controller 56 is configured to interact with the modules of the humidification unit 40, data storage, and external systems. The controller 56 may include one or more physical processors and may be used by any of the other components, such as the detection system 304, for information processing. The controller 56 includes data storage. The data storage may include physical memory configured to store digital information and may be coupled to other components of the humidification unit 40, such as the liquid level sensing system and the user interface components 82.

[0166] FIG. 2B illustrates an exemplary liquid level sensing system 222 in a humidification chamber 46, along with an associated voltage source 302 and detection system 304. The humidification chamber 46 may include a non-conductive wall 53 with a sensor electrode 202 attached to the exterior side of the wall 53 and a conductive bridge 204 attached to the interior side of the wall 53. The humidification chamber includes a base 52 enclosing the non-conductive wall 53. A base electrode 206 may be attached to the base 52, which may act as a virtual ground for the base electrode 206, or the base electrode 206 may be coupled to ground by some other means. The voltage source 302 may provide a current, a voltage, or both to the sensor electrode 202. A detection system 304 may be coupled to the sensor electrode 202 and the base electrode to measure changes in capacitance. By determining the change in capacitance, the detection system can determine the liquid level status of the humidification chamber 46.

[0167] When the conductive liquid in the humidification chamber 46 reaches the bridge 204, the bridge 204 is conductively coupled to the base electrode 206. This creates a virtual short to ground from the bridge 204 through the liquid to ground. The bridge 204 is also capacitively coupled to the sensor electrode 202. The virtual short from the bridge 204 to the base electrode 206 can change the capacitance of the system, which can be measured as a discrete increase in the capacitance of the sensor electrode 202 to ground. As described in more detail herein, the liquid level sensing system 222 can detect this discrete increase in capacitance and determine a corresponding liquid level condition.

[0168] When non-conductive liquid in the humidification chamber 46 reaches the bridge 204, the non-conductive liquid can act as a dielectric in a capacitive system. In this scenario, the bridge 204 is capacitively coupled to both the sensor electrode 202 and the base electrode 206. The presence of non-conductive liquid in the bridge 204 causes a discrete change in the capacitance of the system, which can be detected by measuring the capacitance of the sensor electrode 202 to ground. As described in more detail herein, the liquid level sensing system 222 can detect this change in capacitance and determine a corresponding liquid level condition.

[0169] 2B, the sensor electrode 202 can be vertically offset relative to the bridge 204. As a result, the liquid level sensing system 222 can experience two discrete capacitance changes. A first change occurs when liquid reaches the bridge 204. A second change occurs when liquid reaches the sensor electrode 202. The sensing system can be configured to detect these two discrete changes and determine the corresponding liquid level condition. For example, the second discrete change can correspond to the chamber 46 having excess liquid, i.e., a full condition.

[0170] In some embodiments, the sensor electrode 202 may be larger than the bridge 204. Because capacitance generally correlates with the physical size of an object, increasing size may increase capacitance. This increase in capacitance may increase the system's sensitivity to changes in liquid level. In some embodiments, increasing the size of the sensor electrode 202 may be used to detect a full-liquid condition due, at least in part, to a change in capacitance when the liquid level rises above the bridge 204. For example, the sensor electrode 202 and the bridge 204 may be positioned opposite each other. Because the sensor electrode 202 is larger than the bridge 204, it may extend vertically beyond the bridge 204. As a result, there will be a first discrete capacitance change when the liquid level reaches the bridge 204, and a second discrete capacitance change when the liquid level is level with the top of the sensor electrode 202 as the liquid level rises above the top of the bridge 204. These capacitance changes may be used to detect various liquid level conditions, including an out-of-liquid condition or a full-liquid condition.

[0171] In some embodiments, the detection system 304 is configured to detect any changes in capacitance in the liquid level sensing system 222. The detection system 304 can be configured to correlate these changes with the amount of liquid in the chamber 46. For example, as the liquid level increases, the capacitance of the sensor electrode 202 can change in relation to the change in liquid level. The detection system 304 can determine an approximate liquid level value that corresponds to the capacitance value. In this manner, the liquid level sensing system 222 can estimate the water level in the humidification chamber 46.

[0172] 2C illustrates an exemplary liquid level sensing system 222 in a humidification chamber 46 having a wicking material 502 along the inner surface of the non-conductive wall 53. The wicking material 502 is configured to provide a means for liquid to move up the material by capillary action when liquid is present in the chamber 46, thereby enabling the liquid level sensing system 222 to detect the presence of liquid in the chamber 46.

[0173] When chamber 46 receives some conductive liquid, the conductive liquid may rise through the wicking material by capillary action. When the conductive liquid reaches the same level as sensor electrode 202, the capacitance of sensor electrode 202 changes because the conductive liquid is grounded, at least in part, due to its conductive connection with base 52. Detection system 304 can detect this change in capacitance and signal the presence of liquid in chamber 46, which can be used to determine whether chamber 46 has liquid or is out of liquid.

[0174] 2D shows a flowchart of an example method 600 for detecting a liquid level in the humidification chamber 46 based at least in part on determining a change in capacitance of the sensor electrode 202. The example method 600 as described herein provides several advantageous features. One such feature is that the example method 600 may be used in systems in which the humidification chamber 46 contains a conductive or non-conductive liquid without changing how the method works. For example, determining a liquid level based at least in part on a change in capacitance between the sensor electrode 202 and ground, as described herein, works whether the chamber 46 contains a conductive or non-conductive liquid. For ease of explanation, the method is described as being performed by the liquid level sensing system 222, although any individual step or combination of steps may be performed by any component of the liquid level sensing system 222 or the controller 56 of the humidification unit 40.

[0175] In block 605, the liquid level sensing system 222 generates a variable electrical output using a voltage source 302 coupled to a sensor electrode 202 attached to the outer surface of the non-conductive wall 53 of the body 50 of the humidification chamber 46. The voltage source 302 can generate electrical signals that vary in current, voltage, or both. For example, the voltage source 302 can be an AC voltage source. In some embodiments, the voltage source 302 is controlled by the controller 56. In some embodiments, the voltage source 302 is independently controlled or generates a selected, known, defined, or predetermined electrical output.

[0176] In block 610, the liquid level sensing system 222 determines the capacitance of the sensor electrode 202 to ground. The detection system 304 can measure a parameter of the liquid level sensing system 222, such as capacitance, resistance, voltage, or any combination thereof. The detection system 304 can use this information to detect changes in the capacitance of the system 222.

[0177] The detection system 304 may include circuitry configured to generate a measurable difference in a parameter in response to a change in capacitance of the sensor electrode 202. For example, the detection system 304 may include a circuit having a voltage divider with a resistor in series with the sensor electrode 202. The voltage source 302 may provide an AC voltage to the circuit. The detection system 304 may measure the voltage across the resistor and the sensor electrode 202. The capacitance of the sensor electrode 202 may be calculated based at least in part on the measured voltage value. As another example, the detection system 304 may include a circuit having a known capacitor in series with the sensor electrode 202. The voltage source may provide an AC voltage to the circuit. The detection system 304 may measure the voltage across the known capacitor and the sensor electrode 202 to calculate the capacitance of the sensor electrode 202. Other known methods of measuring capacitance may be used by the detection system 304.

[0178] In some embodiments, the chamber 46 may be configured to hold a conductive liquid. The sensor electrode 202 may be capacitively coupled to the bridge 204, which may be conductively coupled to the base electrode 206, which is grounded. The conductive liquid grounds the bridge 204, thereby creating capacitance between the sensor electrode 202 and ground through the bridge 204. In some embodiments, the chamber 46 may be configured to hold a non-conductive liquid. The sensor electrode 202 may be capacitively coupled to the bridge 204, which may be capacitively coupled to the base electrode 206, which is grounded. This system creates a capacitive system with a dielectric that affects the capacitance between the sensor electrode 202 and the bridge 204 and between the bridge 204 and the grounded base electrode 206. In some embodiments, the chamber 46 includes a wicking material on the inner surface of the non-conductive wall 53. The chamber 46 is configured to hold a conductive liquid, and when a conductive liquid is placed in the chamber 46, the conductive liquid moves up the wicking material. When the conductive material reaches the sensor electrode 202, the conductive liquid acts to change the capacitance of the sensor electrode 202, where it is capacitively coupled to the conductive liquid in the grounded wicking material.

[0179] At block 615, the liquid level sensing system 222 determines the liquid level based at least in part on the capacitance determined at block 610. According to some embodiments described herein, the liquid level sensing system 222 can determine the amount of liquid within the chamber and / or it can determine a liquid level condition, such as an out-of-liquid condition or a full-liquid condition.

[0180] In block 620, the liquid level sensing system 222 may generate a notification regarding the liquid level determined in block 615. For example, if an out-of-liquid condition is determined, the liquid level sensing system 222 may generate an audio or visual alert to a user or send a signal to the controller 56 of the humidification unit 40. The controller 56 may alter a control parameter based at least in part on the received liquid level notification, such as de-energizing the heating plate 54. The liquid level sensing system 222 may include its own notification system or may use the user interface component 82 to notify an operator or user of the liquid level condition.

[0181] Examples of liquid level sensing systems and related components and methods have been described with reference to the figures. These figures illustrate various systems and modules and the relationships between them. The various modules and systems can be combined in various configurations, and the relationships between the various modules and systems may represent physical or logical associations. The representations in the figures are provided to clearly illustrate the principles of liquid level sensing using capacitive and conductive techniques, and details regarding module or system divisions are provided for ease of description without attempting to describe separate physical embodiments. The examples and figures are intended to be illustrative and not to limit the scope of the inventions described herein. For example, the principles herein may be applied to respiratory humidifiers as well as other types of humidification systems, including surgical humidifiers. The principles herein may be applied to respiratory applications as well as other scenarios in which liquid level sensing is desirable.

[0182] As used herein, the term "processor" broadly refers to any suitable device, logic block, module, circuit, or combination of elements for executing instructions. For example, controller 56 may include any conventional general-purpose single-chip or multi-chip microprocessor, such as a Pentium® processor, a MIPS® processor, a Power PC® processor, an AMD® processor, or an ALPHA® processor. In addition, controller 56 may include any conventional special-purpose microprocessor, such as a digital signal processor. The various example logic blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed by a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic element, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The controller 56 may be implemented as a combination of computing devices, for example, a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0183] Data storage may refer to electronic circuitry that allows for the storage and retrieval of information, typically computer or digital data. Data storage may refer to external devices or systems, such as disk drives or solid-state drives. Data storage may also refer to high-speed semiconductor memory devices (chips), such as random access memory (RAM) or various forms of read-only memory (ROM), which are connected to a communication bus or directly to the controller 56. Other types of memory include bubble memory and core memory. Data storage may also be physical hardware configured to store information on a non-transitory medium.

[0184] Flow and Temperature Sensing System 1, the controller 56 also receives inputs from a flow sensor 84 and at least one temperature sensor 86. Any suitable flow sensor 84 may be used, and any suitable temperature sensor 86 may be used. In some configurations, the flow sensor 84 may include the temperature sensor 86.

[0185] Preferably, the flow sensor 84 is positioned between the ambient air and the humidification chamber 46. More preferably, the flow sensor 84 is positioned between the pressurized gas source 30 and the humidification chamber 46. In the illustrated configuration, the flow sensor 84 is positioned at the inlet port 60 of the humidification chamber 46. In some configurations, the sensor 84 may be positioned at the connector used to couple a conduit to the inlet port 60. The sensor 84 may also be positioned in any suitable location.

[0186] Preferably, the temperature sensor 86 is positioned between the humidification chamber 46 and the user. More preferably, the temperature sensor 86 is positioned between the humidification chamber 46 and the interface 74. In the illustrated configuration, the temperature sensor 86 is positioned at the outlet port 62 of the humidification chamber 46. In some configurations, the sensor 86 may be positioned at the connector used to couple the conduit to the outlet port 62. The sensor 86 may also be positioned in any suitable location.

[0187] At least a portion of one or more of the sensors 84, 86 may be mounted outside of the flow path defined through the humidification system 20. In some configurations, one or more of the sensors 84, 86 are configured to be removable from the flow path without direct access to the flow path through the humidification system 20. Preferably, the one or more sensors 84, 86 are configured to sense one or more characteristics of flow through a portion of the flow path through the humidification system while remaining hermetically sealed from the flow path.

[0188] With reference to FIG. 2 , in the illustrated configuration, the inlet port 60 includes an opening 90. The opening 90 extends through the wall of the inlet port 60, providing a communication path through the wall 60 of the inlet port. Similarly, in the illustrated configuration, the outlet port 62 includes an opening 92. The opening 92 extends through the wall of the outlet port 62, providing a communication path through the wall of the outlet port 62. In some configurations, the openings 90 and 92 are each defined around a cylinder having an axis, the axes extending generally parallel to one another. Other configurations are possible. Additionally, while the illustrated configuration positions the openings 90, 92 within a portion of the humidification chamber 46, one or more of the openings may be positioned elsewhere in the humidification system 20.

[0189] 3, the humidification chamber 46 is shown with a first seal 100 positioned within the opening 90 of the inlet port 60 and a second seal 102 positioned within the opening 92 of the outlet port 62. The first seal 100 preferably hermetically seals the opening 90, and the second seal 102 preferably hermetically seals the opening 92, such that the gas paths defined within the respective portions of the humidification system 20 are isolated from the environment by the seals 100, 102. In other words, the seals 100, 102 substantially close the openings 90, 92. Thus, in the illustrated configuration, the seals 100, 102 define a barrier that reduces the likelihood of fluid or gas passing through the openings 90, 92. Depending on the application, at least one of the seals 100, 102, and preferably both seals 100, 102, are also resistant to the passage of water vapor.

[0190] The first seal 100 and the second seal 102 may be formed of any suitable material. Depending on the application, the first seal 100 and the second seal 102 may be formed of a resilient or flexible material. Preferably, at least one of the seals 100, 102 is formed entirely of a resilient or flexible material. Depending on the application, at least a portion of at least one of the seals 100, 102 is formed entirely of a resilient or flexible material. Depending on the application, one or more of the seals 100, 102 may be formed of a material having a Shore A hardness of about 20 to about 60, more preferably about 30 to about 40. Depending on the application, one or more of the seals 100, 102 may be formed of silicone, polyethylene, or thermoplastic polyurethane.

[0191] Depending on the application, at least a portion of at least one of the seals 100, 102 may be formed from a hard material, as shown in FIG. 17 . For example, without limitation, at least a portion of at least one of the seals 100, 102 may be formed from a metal. When at least one of the seals 100, 102 is formed entirely from a hard material, the seal is preferably configured to provide repeatable contact and thermal conduction between the barrier formed by the seals 100, 102 and an associated sensor. In some embodiments, the seals 100, 102 may be formed from the same material as the chamber 46, a different material having a different (preferably higher) thermal conductivity, or a combination thereof. When a combination is used, preferably at least a portion of the tip 101 of the seal, or at least the portion exposed to flow in the port, and in some configurations, the very distal end of the tip 101, is formed from a material having a higher thermal conductivity (e.g., aluminum, copper). In some configurations, the tip 101 is positioned so that the seals 100, 102 extend to the axial center of the port. In some configurations, the tip 101 is positioned so that the seals 100, 102 traverse at least half of the lateral dimension of the ports 60, 62. The seals 100, 102 may be integrally formed with the chamber 46, or may be, for example, but not limited to, overmolded, press-fit and glued, co-molded, or welded with the chamber 46.

[0192] In some embodiments, at least one of the seals 100, 102 may be formed from a first, highly thermally conductive portion positioned to receive the end or sensing portion of the associated sensor 130, 132, and a second, less thermally conductive or non-thermally conductive portion. The second portion is preferably positioned to reduce or eliminate conduction or other transfer of heat from the sensing element or tip of the sensor 130, 132 to the surrounding area of ​​the device. For example, if the associated sensor 130, 132 includes a thermistor, the second portion preferably generally or substantially thermally isolates the thermistor. In other words, the tip of the thermistor may be positioned in the first, highly thermally conductive portion, which may be positioned within the gas flow the thermistor is measuring. In some configurations, the less thermally conductive or non-thermally conductive portion may comprise a different material than the more thermally conductive portion. In some configurations, porous or foam materials may be used to provide improved thermal insulation. In such an arrangement, less heat is transferred from the first portion through the second portion to the surrounding environment. This reduced conduction maximizes or increases heat transfer between the first portion and the tip of the thermistor, thereby increasing the accuracy of the gas reading provided by the thermistor.

[0193] In some embodiments, means may be provided to increase the reliability of contact between an associated sensor and a tip portion of the seal. For example, in the arrangement of FIG. 17, a spring or any other suitable biasing or damping member may be interposed between the sensors 130, 132 and the cartridge 160 carrying or otherwise supporting the sensors 130, 132. In such an arrangement, compression of the member 103 (e.g., spring, biasing member, or damping member) provides a relatively repeatable force between the end of the sensor 130, 132 and, for example, but not limited to, the tip 101. Depending on the application, a flexible or elastic membrane may connect the tip 101 to the chamber 46. In such a configuration, the tip 101 may be movable relative to at least a portion of the chamber 46 (including the ports 60, 62). In other words, the flexible or elastic membrane can stretch due to the sensors 130, 132 contacting the tip 101 when the sensors 130, 132 are inserted, providing a thermal mass that is in approximate contact with the tip 101 while providing an approximately reproducible force between the ends of the sensors 130, 132 and the tip 101.

[0194] In some arrangements, at least one, and preferably both, of the seals 100, 102 include features for retaining the seals 100, 102 in place within the openings 90, 92, respectively. With reference to FIG. 4, the illustrated first seal 100 includes an outer flange 104 and an inner flange 106. As shown in FIG. 5, a channel 108 is defined between the outer flange 104 and the inner flange 106. The channel 108 is preferably sized to fit within the wall 110 of the inlet port 60. More preferably, the channel 108 is sized to form a fluid-tight and / or gas-tight seal with the wall 110 surrounding the opening 90. In the configurations shown in FIGS. 3-9, the bottom surface of the channel 108 has an at least partially curved or sloped surface, thereby improving the seal between the seal 100 and the wall defining the opening 90. In some configurations, as shown in FIGS. 18A-18G, the bottom surface may be substantially flat rather than at least partially curved or sloped.

[0195] In some arrangements, at least one of the seals 100, 102 may be permanently or at least semi-permanently attached to the openings 90, 92. In some arrangements, at least one of the seals 100, 102 may be removable and replaceable. The seals 100, 102 may be configured to have a service life similar to that of one of the other components. For example, the seals 100, 102 preferably include a service life similar to that of the chamber 46, such that the chamber 46 and the seals 100, 102 may be discarded at the same time. In some arrangements, particularly when the seals 100, 102 are permanently attached to the chamber 46, the seals 100, 102 preferably have a longer service life than the chamber 46, such that the seals 100, 102 are not a limiting component with respect to the life of the chamber 46.

[0196] In the illustrated configuration, the inner flange 106 has a smaller outer circumference than the outer flange 104. The smaller outer circumference of the inner flange 106 facilitates insertion of the seal 100 into the opening 90. The inner flange 106 of the first seal 100 may include a sloped surface 112 to further assist in fitting the first seal 100 into the opening 90. While the surface of the outer flange 104 can be sloped or tapered to facilitate fitting, the sloped or tapered surface 112 is preferably positioned on the inner flange 106 because the illustrated first seal 100 is designed to be pressed into the opening 90 from outside the inlet port 60.

[0197] With reference to FIG. 10 , the illustrated second seal 102, similar to the first seal 100, includes an outer flange 114 and an inner flange 116. As best seen in FIG. 12 , a channel 118 is defined between the outer flange 114 and the inner flange 116. As shown in FIG. 10 , the channel 118 is preferably sized to fit within the wall 120 of the outlet port 62. More preferably, the channel 118 is sized to form a fluid-tight and / or gas-tight seal with a portion of the wall 120 that generally surrounds the opening. As with seal 100, the bottom surface of the channel 118 has at least a partially curved or sloped surface to enhance sealing between the seal 102 and the wall defining the opening 92. In some configurations, the bottom surface may be substantially flat (see, e.g., FIGS. 18A-18G ).

[0198] The inner flange 116 has a smaller outer circumference than the outer flange 104. The smaller outer circumference of the inner flange 116 facilitates insertion of the seal 102 into the opening 92. The inner flange 116 of the second seal 102 may include a curved surface 122 that assists in fitting the second seal 102 into the opening 92. As with the first seal 100, the surface of the outer flange 114 can be sloped or tapered to facilitate insertion, but because the illustrated second seal is designed to be pressed into the opening 92 from outside the outlet port 62, the sloped or tapered surface is preferably positioned on the inner flange 116.

[0199] With reference to FIG. 16 , a first sensor 130 can be inserted into the first seal 100, and a second sensor 132 can be inserted into the second seal 102. In some configurations, the sensors 130, 132 do not seal the opening unless the seals 100, 102 are positioned within the opening. The first seal 100 and the second seal 102 define a barrier positioned between the gas flow path and the first sensor 130 and the second sensor 132, respectively. Because the first seal 100 and the second seal 102 define a barrier, the sensors 130, 132 are always outside the flow path. Because the first sensor 130 and the second sensor 132 are always outside the flow path, the sensors 130, 132 can be reused and do not need to be cleaned before reuse. However, even if the sensors 130, 132 are always outside the flow path, the sensors 130, 132 can still provide measurements of flow characteristics. For example, a first sensor 130 may be used to sense flow rate, while a second sensor may be used to sense temperature.

[0200] Any suitable components may be used as sensors. For example, thermocouples, resistance temperature detectors, fixed resistors, etc. may be used as sensors 130, 132. In the illustrated arrangement, sensors 130, 132 include thermistors. A second sensor 132 uses a single thermistor 134 mounted to a body 136. The sensor 132 may be used to sense the temperature of the flow in the flow path. As shown in the illustrated arrangement, the temperature sensor 132 may be positioned such that the thermistor 134 extends into the flow path of the outlet port 62. In some configurations, temperature sensors may be positioned in other areas of the humidification system 20 (e.g., in the conduit 44, the conduit 70, etc.).

[0201] The illustrated first sensor 130 preferably includes a first thermistor 140 and a second thermistor 142 mounted on a single body 144. In some configurations, the first thermistor 140 and the second thermistor 142 may be mounted on separate bodies; however, mounting the first thermistor 140 and the second thermistor 142 on a single body 144 improves the accuracy of positioning the first thermistor 140 and the second thermistor 142 relative to one another. As shown in the illustrated arrangement, the first sensor 130 can be positioned so that the two thermistors 140, 142 extend into the flow path of the inlet port 60. Positioning the first sensor 130 at the inlet is desirable because this sensor detects flow rate, and it is desirable to position the first sensor 130 in a relatively dry region of the flow. Depending on the configuration, flow sensor 130 may be positioned in other areas of humidification system 20 (eg, in conduit 44, conduit 70, etc.).

[0202] The use of the first thermistor 140 and the second thermistor 142 allows for a constant temperature flow measurement technique. In this technique, the first thermistor 140 serves as a reference sensor measuring the flow temperature at the sensing location, and the second thermistor 142, which may be a heated thermistor, is heated to a temperature above the flow temperature by a predetermined temperature difference. In some applications, instead of using a heated thermistor, a resistor may be used to heat the second thermistor 142. In some configurations, the thermistors may all be both heated and unheated thermistors. The measured flow temperature, the known heat transfer characteristics of the heated second thermistor 142, and the power consumption to maintain the temperature difference between the two thermistors 140, 142 can be used to determine the flow rate. In other words, the flow rate is determined by processing the power required to maintain the second thermistor 142 at an elevated temperature. Thus, first sensor 130 and second sensor 132 preferably measure flow velocity within about 50% of the actual point velocity and temperature within about 0.3° C. Other techniques may also be used. For example, but not limited to, a constant power may be supplied to a thermistor and the heat conducted to a nearby thermistor may be used to determine the flow rate.

[0203] 16, a first sensor 130 can be inserted into the first seal 100, and a second sensor 132 can be inserted into the second seal 102. The seals 100, 102 isolate the sensors 130, 132 from the flow, protecting the sensors 130, 132 from contamination by the flow. Therefore, the sensors 130, 132 do not need to be cleaned and can be reused without a cleaning process.

[0204] With reference to FIGS. 4 and 10 , one or more of the seals 100, 102 may have a decreasing thickness toward their respective distal ends 124, 126. With particular reference to FIG. 4 , the seal 100 has a first thickness t1 that is greater than a thickness t2 present at the distal end 124 of the seal 100. Preferably, the portion of the seal 100 adapted to contact the sensing portion of the first sensor 130 has the decreased thickness t2 to improve sensitivity, while the thicker portion improves robustness. In some configurations, the portion of the seal 100 adapted to contact the sensing portion of the first sensor has a substantially constant thickness to improve performance. With reference to FIG. 10 , the seal 102 is similar in structure to the seal 100, but has a first thickness t3 that is greater than a second thickness t4. Other suitable configurations are possible. In some configurations, the sensors 103, 132 are inserted into the seals 100, 102 to a depth such that the tips of the seals 100, 102 are stretched by the insertion. In some configurations, the tips of the seals 100, 102 stretch further than other regions of the seals 100, 102. The stretched tips may reduce the thickness of the seals 100, 102 toward the distal end when compared to the seals 100, 102 without the sensors 130, 132 inserted. The stretched tips also reduce the likelihood of air bubbles forming between the tips of the sensors 130, 132 and the tips of the seals 100, 102, which may reduce thermal conduction between the seals 100, 102 and the sensors 130, 132.

[0205] 4 and 10, the distal ends 124, 126 of the illustrated seals 100, 102 have reduced diameters. In the illustrated configuration, the distal ends 124, 126 are narrower than the other ends. Depending on the configuration, a smooth taper or other suitable configuration may be used.

[0206] In the illustrated configuration, the first sensor 130 includes a first thermistor 140 and a second thermistor 142 in a single body 144. The first sensor 130 is received within the first seal 100. Desirably, thermal conduction between the first thermistor 140 (i.e., the reference temperature) and the second thermistor 142 (i.e., the heated thermistor for flow measurement) is minimized. Thermal conduction between the thermistors 140, 142 within a single barrier has been found. This thermal conduction can result in a cyclic reference: the flow temperature is measured using the unheated first thermistor 140, while a fixed temperature offset (e.g., approximately 60°C) is applied to the heated second thermistor 142, and the power required to achieve this temperature offset is measured; if the heated second thermistor 142 heats the unheated first thermistor 140, the target temperature will increase, and the cycle will repeat. Thus, the illustrated first seal 100 includes two separate sleeves 146, 148 for the two thermistors 140, 142. By positioning the first thermistor 140 in the first sleeve 146 and the second thermistor 142 in the second sleeve 148, the first thermistor 140 and the second thermistor 142 are substantially isolated, with the seal 100 providing an independent barrier layer for each thermistor 140, 142. In some configurations, the first thermistor 140 and the second thermistor 142 may be substantially isolated by, for example, but not limited to, using a baffle between the thermistors 140, 142, providing the thermistors 140, 142 with different orientations, and / or using a flow sensor.

[0207] An alternative seal configuration is shown in Figures 19A-19C. In the illustrated embodiment, the seal 102 includes a generally cylindrical base 115. The seal 102 also includes a generally bell-shaped head 117. The illustrated bell-shaped head 117 includes a plurality of triangular ribs 119 around its periphery. In some embodiments, a channel 118 is defined between the base 115 and the head 117, which may be sized to fit within the wall 120 of the exit port 62. The ribs 119 are flexible, allowing the seal 102 to be inserted into the opening 92 and then return to an expanded state to facilitate holding the seal 102 in place within the opening 92. As the ribs 119 are compressed, they expand into the spaces 121 between them. In some embodiments, the ratio of the width of the ribs 119 to the width of the spaces 121 between the ribs 119 is approximately 1:1. In some embodiments, this ratio is approximately 3:7. If the ratio is too large (i.e., if the spaces 121 between the ribs 119 are small compared to the ribs 119), the ribs 119 may not be compressed enough, making it significantly more difficult to seat the seal 102 within the opening 92. If the ratio is too small (i.e., if the spaces 121 are large compared to the ribs 119), reduced retention force may occur, and the seal 102 may not be held as securely in the opening 92. In the illustrated embodiment, the seal includes eight ribs 119, although more or fewer ribs 119 are also possible. However, if too many ribs 119 are included, the ribs 119 may become thin and weak. Alternatively, if too few ribs 119 are included, larger ribs 119 may be required, leaving less space for expansion.

[0208] When a sensor 132 is inserted into the seal 102 of FIGS. 19A-19C, the tip 123 of the seal 102 may stretch to conform to the shape of the sensor 132. The greater the amount of stretch to accommodate the sensor 132, the thinner the seal material becomes. This advantageously improves the responsiveness and accuracy of the sensor, increases the contact area between the sensor and the seal as the seal stretches to conform to the shape of the sensor, and may more securely hold the seal in the opening 92. However, if the seal tip 123 is too flat and requires excessive stretching to accommodate the sensor, inserting the sensor through the seal may become more difficult and the seal material may deteriorate or break. In the illustrated embodiment, the seal is approximately 7.50 mm long, has a base 115 diameter of approximately 7 mm, a diameter of the ribs 119 measured at their widest point of approximately 6.50 mm, and a tip 123 thickness of approximately 0.020 mm. An alternative configuration of a seal with ribs 119 is shown in FIGS. 20A-20C. The seals of Figures 20A and 20B may both be approximately 6 mm in length, have a base 115 diameter of approximately 8 mm, a diameter of the ribs 119 measured at their widest point of approximately 7.50 mm, and a tip thickness of approximately 0.20 mm. However, the seal of Figure 20A may have ribs 119 sized such that the spacing 121 between the ribs is approximately 1.4 mm, while the seal of Figure 20B may have ribs 119 sized such that the spacing 121 is approximately 1.1 mm. The seal of Figure 20C may be approximately 4.50 mm in length, have a base diameter of approximately 8 mm, a diameter of the ribs 119 measured at their widest point of approximately 7.50 mm, and a tip thickness of approximately 0.20 mm. The ribs 119 of the seal of Figure 20C may have slightly rounded or curved ends.

[0209] 16, because the sensors 130, 132 are removable and replaceable, they preferably have a repeatable tip thermal mass. Depending on the configuration, the accuracy of the sensors 130, 132 may be improved if the thermal mass exposed to the inside of the flow path is repeatable. Thus, the insertion depth of the sensors 130, 132 relative to each flow path is preferably generally repeatable.

[0210] To provide a repeatable insertion depth for the sensors 130, 132 and to simplify installation of the sensors 130, 132, the illustrated configuration includes a cartridge 160. With reference to FIGS. 3 and 21, the cartridge 160 and the top of the illustrated humidification chamber 46 include mating features. In the illustrated configuration, the top of the humidification chamber 46 includes a recessed structure 162, while the cartridge 160 includes a corresponding boss structure 164. In some configurations, the top of the humidification chamber may include at least a portion of the boss structure, while the bottom of the cartridge 160 includes at least a portion of the corresponding recessed structure. Another configuration is shown in FIG. 36, in which an upwardly protruding member 165 is positioned on the top of the chamber 46 and a corresponding recess 167 is formed in the cartridge 160. In the configuration shown in FIG. 36, cooperation between the protruding member 165 and the recess 167 may guide the connection between the cartridge 160 and the chamber 46. Any other suitable configuration may be used.

[0211] The sensors 130, 132 may include a shield configured to protect at least the tip or sensing components of the sensors 130, 132 from damage that may be caused by accidental or inadvertent contact, such as, but not limited to, a bump or a bang. In some configurations, the shield may include one or more fingers 131 disposed around the tip or sensing element of the sensor 130, 132. In some configurations, one or more of the fingers may be curved such that a portion of the finger is substantially above the tip or sensing element of the sensor 130, 132 and another portion of the finger is substantially aligned with the tip or sensing element of the sensor 130, 132.

[0212] In the illustrated configuration shown in FIG. 3 , a ridge 166 defines at least a portion of the recess structure 162. The ridge 166 extends upward from the upper surface 170. The ridge defines a stop 172 and a pair of snap recesses 174. As shown in FIG. 21 , a pair of protrusions 180 extend downward from a lower surface 182 of the illustrated cartridge 160. Each of the protrusions 180 includes a locking tab 184. Each locking tab 184 is at the end of a respective arm 186 in the illustrated configuration. The locking tabs 184 can be deflected inward while the cartridge 160 is slid into place in the chamber 46. The locking tabs 184 snap into place within the snap recesses 174 formed in the ridge 166. When the locking tabs 184 snap into place within the snap recesses 174, the cartridge 160 is secured in place in the sliding direction. Additionally, stops 190 on cartridge 160 come into close proximity or contact with stops 172 on ridges 162. As sensors 130, 132 are slid into place within ports 60, 62, cartridge 160 is also generally fixed against movement in the sliding direction.

[0213] 36, in some configurations, the cartridge 160 includes one or more arms 191. The arms 191 may be adapted to extend along the outside of the ports 60, 62 of the chamber 46. The arms may assist in properly positioning the cartridge 160 relative to the chamber 46. Additionally, if the installed cartridge 160 is bumped or banged, the force of the bump or bang may be transferred to the one or more arms 191 and directed away from the more vulnerable sensors 130, 132.

[0214] In the illustrated configuration, arm 191 includes interlocking portion 195, while chamber 46 includes interlocking portion 197. In some configurations, chamber interlocking portion 197 is positioned laterally outward of ports 60, 62. This lateral displacement provides a stable connection. Interlocking portion 197 may be positioned on a boss 199 or the like. In some configurations, gripping portion 193 may be defined in or along the outer surface of chamber 46. In one configuration, gripping portion 193 may be defined on one side of interlocking portion 197 or boss 199, while the majority of cartridge 160 may be positioned on the other side of interlocking portion 197.

[0215] Any suitable shape can be used for the interlocking portions 195, 197. In the illustrated configuration, the interlocking portion 197 of the chamber 46 includes an upwardly extending bump, while the interlocking portion 195 of the chamber includes a recess that corresponds to the bump of the interlocking portion 197. Preferably, when the chamber 46 and the cartridge 160 are fully mated, the two interlocking portions 195, 197 hold the chamber 46 and the cartridge 160 together to the extent that at least a small force must be overcome to separate the chamber 46 from the cartridge 160.

[0216] The cartridge 160 defines a chassis that carries the sensors 130, 132 and other desired electrical components. In the illustrated configuration, the cartridge includes wings 192 that define sockets, as shown in FIG. 21 , into which the sensors 130, 132 plug. In some configurations, the sensors 130, 132 are designed to be removed and replaced with the same cartridge 160. In some configurations, the cartridge 160 is designed for limited use and the sensors 130, 132 cannot be removed and replaced, but are discarded. In some configurations, the portion of the cartridge 160 that carries the sensors 130, 132 is separable from the central portion of the cartridge 160 (which generally houses the electronics, etc.). This configuration allows the sensors 130, 132 to be replaced without replacing the portion of the cartridge 160 that contains the majority of the housed electronics.

[0217] 22 , the cartridge includes a recessed electrical connector 161. The electrical connector 161 is electrically connected to the sensors 130, 132 in any suitable manner. Preferably, the electrical connector 161 is a female USB connector. Additionally, the electrical connector 161 is adapted to provide an electrical connection with the controller 56 or any other suitable component. Preferably, when the cartridge 160 is attached to the humidification chamber 46, a corresponding connector (preferably a male USB connector, etc.) on the humidification unit 40 makes electrical connection with the connector 161 when the humidification chamber 46 is installed in the humidification unit 40. In this manner, connection between the sensor and the controller 56 is greatly simplified and the possibility of making an improper electrical connection is greatly reduced.

[0218] The wings 192 of the illustrated chassis provide a mounting structure for the sensors 130, 132 and also position the sensors 130, 132 so that the sensing portions of the sensors 130, 132 have a repeatable insertion depth within the flow path. Advantageously, when the sensors 130, 132 are installed in the cartridge 160 and the cartridge 160 is snapped into place in the chamber 46, the sensing portions of the sensors 130, 132 are positioned at desired locations within the flow path.

[0219] composite pipe As described above, respiratory humidification system 20 may include conduit 44 connecting gas source 30 with humidification unit 40, inspiratory conduit 70, and / or expiratory conduit. In some embodiments, any or all of these conduits may be partially or entirely composite tubing, which may be tubing having two or more sections or components. Composite tubing as described herein may also be used in other applications, such as, but not limited to, laparoscopic surgery. For example, using composite tubing as conduit 713 in exemplary insufflation system 701 shown in FIG. 1B may facilitate delivery of humidified gas to a surgical site on patient 705 with minimal heat loss. This may advantageously reduce overall energy consumption in the insufflation system because less heat input is required to compensate for heat loss.

[0220] 37A , the exemplary composite tubing includes a first elongate member 203 and a second elongate member 205. In the illustrated embodiment, the first elongate member 203 and the second elongate member 205 are separate components; however, in other embodiments, the first and second elongate members may be regions of tubing formed from a single material. Thus, the first elongate member 203 may represent a hollow portion of the tubing, while the second elongate member 205 may represent a structural support or reinforcing portion of the tubing that adds structural support to the hollow portion. The hollow portion and the structural support portion may have a helical configuration as described herein. The composite tubing 201 may be used to form an inspiratory conduit 70 and / or an expiratory conduit, a coaxial tube, or any other medical tubing, as described above.

[0221] In this example, the first elongate member 203 includes a hollow body that is helically wound to at least partially form an elongate tube having a longitudinal axis LA-LA, and a lumen 207 extending along the longitudinal axis LA-LA. In at least one embodiment, the first elongate member 203 is a tube. Preferably, the first elongate member 203 is flexible. Furthermore, the first elongate member 203 is preferably transparent, or at least translucent or opaque in color. Having some optical transparency allows a caregiver or user to inspect the lumen 207 for blockages or contamination and to identify the presence of moisture. Various plastics, including medical-grade plastics, are suitable for the body of the first elongate member 203. Examples of suitable materials include polyolefin elastomers, polyether block amides, thermoplastic copolyester elastomers, EPDM-polypropylene blends, and thermoplastic polyurethanes.

[0222] In at least one embodiment, the extrudate used to form the first elongated member 203 further comprises an anti-blocking additive. The anti-blocking additive can reduce adhesion between two adjacent thin film layers. Anti-blocking additives can include calcined kaolin (CaK), hydrous kaolin (HyK), calcium carbonate (CaC), talc (TaC), natural silica (NSiI), natural silica (NSi2), diatomaceous earth (DiE), and synthetic silica (SSi). Depending on the configuration, the anti-blocking additive is food-safe. In some embodiments, the anti-blocking additive is talc. Adding talc to the plastic extrudate advantageously reduces the stickiness of the resulting first elongated member 203. Adding talc to the extrudate also reduces noise generated when the first elongated member 203 is dragged over the edge of an object, such as a desk or bedside table. Additionally, the addition of talc reduces the degree to which adjacent bubbles adhere to (and separate from) each other as they bunch up (and unbundle) around bends, thereby reducing noise generated when the tubing is moved, bent, etc. In certain embodiments, the talc is in the range of 1.5 to 10 (or about 1.5 to about 10) weight percent of the total extrudate. In certain embodiments, the talc is in the range of 1.5 to 5 (or about 1.5 to about 5) weight percent of the total extrudate. In certain embodiments, the talc is in the range of 10 (or about 10) weight percent or less of the total extrudate. In certain embodiments, the talc is in the range of 5 (or about 5) weight percent or less of the total extrudate. In certain embodiments, the talc is in the range of 1.5 (or about 1.5) weight percent or more of the total extrudate. Desirably, the amount of talc is small enough so that the tubing is reasonably clear, allowing for inspection of the inside of the tubing.

[0223] The hollow body structure of the first elongated member 203 contributes insulating properties to the composite tube 201. An insulated tube 201 is desirable because it prevents heat loss as explained above. This may allow the tube 201 to deliver gas from the heater and humidifier to the patient while maintaining a conditioned state of the gas with minimal energy consumption.

[0224] In at least one embodiment, the hollow portion of the first elongate member 203 is filled with a gas. The gas may be air, which is advantageous due to its low thermal conductivity (2.62×10 at 300 K). -2 Gases with higher viscosities than air can also be used advantageously, as high viscosity reduces convective heat transfer. Thus, argon (17.72 x 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 HCl (Hg, HCl ...

[0225] The first elongated member 203 may contain a predetermined amount of fluid (e.g., air) and may be substantially sealed to prevent leakage of the predetermined amount of fluid. During use, the fluid may be configured to be used to measure one or more properties of the tube 201, the first elongated member 203, the second elongated member 205, and / or a gas moving along the tube 201. In at least one embodiment, the pressure of the gas flowing along the tube may be measured. A baseline measurement of the fluid pressure is taken before the gas begins circulating. As the gas begins to flow through the tube 201, the pressure of the gas tends to increase proportionally to the pressure of the fluid in the first elongated member 203. By comparing measurements taken during use with the baseline measurement, the pressure of the gas in the tube 201 can be determined. In another embodiment, a fluid is selected that changes one or more properties based on the operating thermal range of the gas in the tube 201. In this manner, measuring the properties of the fluid can determine the temperature of the gas. For example, a fluid that expands with temperature may be used. During use, the temperature of the fluid tends to approach the temperature of the gas flow. By measuring the pressure of the fluid, the temperature of the fluid can then be determined, which can be particularly beneficial when it is difficult or undesirable to measure the temperature of the gas stream directly.

[0226] In some embodiments, at least a portion of the first elongated member 203 is formed from a vapor-permeable material, e.g., an activated perfluorinated polymer material with extremely high hydrophilic properties, such as NAFION, or a hydrophilic polyester block copolymer, such as SYMPATEX. Preferably, the portion of the first elongated member 203 that forms the lumen of the tube 201 is formed from this material. During use, a predetermined amount of humidifying fluid (e.g., water) passes through the space formed by the first elongated member. As the humidifying fluid is heated (e.g., by a heating filament 215 disposed in the second elongated member 205), some of the humidifying fluid tends to evaporate. This then passes through the breathable portion into the gas stream, thereby humidifying the gas stream. In such embodiments, the tube 201 may provide sufficient humidification to the gas stream, eliminating the need for a standalone humidifier in the system.

[0227] In some embodiments, a gas flow may be directed along the interior space of the first elongate member 203. For example, exhaled respiratory gas may be carried. In some embodiments, the first elongate member or at least a portion of the first elongate member (preferably the outward-facing side) may be made of a material that allows water vapor to pass through, for example, an activated perfluorinated polymer material with very high hydrophilic properties, such as NAFION, or a hydrophilic polyester block copolymer, such as SYMPATEX. In this way, exhaled gas tends to dry out as it travels along the length of the first elongate member, from approximately 100% relative humidity at the patient end to a reduced humidity level at the opposite end.

[0228] The second elongate member 205 is also helically wound between adjacent turns of the first elongate member 203 and joined to the first elongate member 203. The second elongate member 205 forms at least a portion of the lumen 207 of the elongate tube. The second elongate member 205 serves as structural support for the first elongate member 203.

[0229] In at least one embodiment, the second elongate member 205 is wider at its base (closer to the lumen 207) and narrower at its top. For example, the second elongate member may be generally triangular, T-shaped, or Y-shaped. However, any shape that matches the contour of the corresponding first elongate member 203 is suitable.

[0230] Preferably, the second elongated member 205 is flexible to facilitate bending of the tube. Desirably, the second elongated member 205 is less flexible than the first elongated member 203. This improves the second elongated member's ability to provide structural support to the first elongated member 203. For example, the second elongated member 205 preferably has an elastic modulus of 30-50 MPa (or approximately 30-50 MPa). The first elongated member 203 has an elastic modulus lower than that of the second elongated member 205. The second elongated member 205 may be solid or substantially solid. Additionally, the second elongated member 205 may encapsulate or enclose a conductive material, such as a filament, particularly a heating filament or sensor (not shown). The heating filament may minimize cold surfaces where condensation can occur from moisture-laden air. The heating filament may also be used to modify the temperature profile of the gas in the lumen 207 of the composite tube 201. Various polymers and plastics, including medical-grade plastics, are suitable for the body of the second elongate member 205. Examples of suitable materials include polyolefin elastomers, polyether block amides, thermoplastic copolyester elastomers, EPDM-polypropylene blends, and thermoplastic polyurethanes. In certain embodiments, the first elongate member 203 and the second elongate member 205 may be made from the same material. The second elongate member 205 may also be made from a material of a different color than the first elongate member 203, and may be transparent, translucent, or opaque. For example, in one embodiment, the first elongate member 203 may be made from a clear plastic, and the second elongate member 205 may be made from an opaque blue (or other color) plastic.

[0231] In some embodiments, the second elongate member 205 may be made of a material that absorbs water. For example, an absorbent sponge-like material may be used. Preferably, the second elongate member 205 is connected to a water source, such as a water bag. During use, water is conveyed along at least a portion (preferably substantially the entire length) of the second elongate member 205. As gas flows along the second elongate member 205, the gas tends to pick up water vapor, thereby humidifying the gas stream. In some embodiments, one or more heater filaments embedded in the second elongate member 205 may be controlled to vary the evaporation rate, thereby varying the level of humidification imparted to the gas stream.

[0232] This spirally wound structure, including a flexible hollow body and integral support, provides crush resistance while leaving the tube wall flexible enough to allow for tight bending radii without kinking, obstruction, or indentation. Preferably, the tube is capable of bending a 25 mm diameter metal cylinder without kinking, obstruction, or indentation, as defined in the test for increased flow resistance with bending according to ISO 5367:2000(E). This structure also provides a smooth lumen 207 surface (tube bore), which helps keep the tube free of deposits and improves gas flow. It has been found that this hollow body allows the tube to remain lightweight while improving its thermal insulation properties.

[0233] As explained above, the composite tube 201 can be used as an expiratory and / or inspiratory tube in a breathing circuit or in a portion of a breathing circuit. Preferably, the composite tube 201 is used at least as an inspiratory tube.

[0234] Figure 37B shows a longitudinal cross-section of the upper portion of the exemplary composite tube 201 of Figure 37A. Figure 37B is in the same orientation as Figure 37A. This example further illustrates the hollow body shape of the first elongate member 203. As can be seen in this example, the first elongate member 203 forms a plurality of hollow bubbles in the longitudinal cross-section. Portion 209 of the first elongate member 203 overlaps with adjacent wraps of the second elongate member 205. Portion 211 of the first elongate member 203 forms the wall of the lumen (lumen).

[0235] It has been unexpectedly found that the presence of gaps 213 between adjacent turns of the first elongated member 203, i.e., between adjacent bubbles, unexpectedly improves the overall insulating properties of the composite pipe 201. Accordingly, in certain embodiments, adjacent bubbles are separated by gaps 213. Additionally, certain embodiments include the recognition that providing gaps 213 between adjacent bubbles increases the thermal resistance (R-value) and therefore decreases the thermal conductivity of the composite pipe 201. This gap configuration has also been found to improve the flexibility of the composite pipe 201 by allowing for smaller bend radii. A T-shaped second elongated member 205, as shown in FIG. 37B , can help maintain the gaps 213 between adjacent bubbles. Nevertheless, in certain embodiments, adjacent bubbles are in contact. For example, adjacent bubbles may be bonded to one another.

[0236] The second elongated member 205 may be provided with one or more conductive materials for heating or sensing the gas flow. In this example, two heating filaments 215 are encapsulated in the second elongated member 205, one on each side of the longitudinal portion of the "T." The heating filaments 215 comprise a conductive material, such as an alloy of aluminum (Al) and / or copper (Cu), or a conductive polymer. Preferably, the material forming the second elongated member 205 is selected so as not to be reactive with the metal in the heating filament 215 when the heating filament 215 reaches its operating temperature. The filaments 215 may be spaced from the lumen 207 so that they are not exposed to the lumen 207. The pair of filaments may be formed into a connecting loop at one end of the composite tube.

[0237] In at least one embodiment, the second elongate member 205 includes multiple filaments disposed thereon. These filaments are electrically connected together and share a common rail. For example, a first filament, e.g., a heating filament, may be disposed on a first side of the second elongate member 205. A second filament, e.g., a sensing filament, may be disposed on a second side of the second elongate member 205. A third filament, e.g., a ground filament, may be disposed between the first and second filaments. The first, second, and / or third filaments may be connected together at one end of the second elongate member 205.

[0238] FIG. 37C shows a longitudinal cross-section of the bubble of FIG. 37B. As shown, the portion 209 of the first elongate member 203 that overlaps the adjacent winding of the second elongate member 205 is characterized by a degree of bonded area 217. A larger bonded area improves the peel resistance of the tube at the interface between the first and second elongate members. Additionally or alternatively, the shape of the bead and / or bubble can be adapted to increase the bonded area 217. For example, FIG. 37D shows a relatively small bonded area on the left side. FIG. 48B, discussed in more detail herein, also shows a smaller bonded area. In contrast, FIG. 37E has a significantly larger bonded area compared to that shown in FIG. 37D due to the size and shape of the bead. FIGS. 48A and 48C, discussed in more detail herein, also show larger bonded areas. It should be understood that while the configurations of Figures 37E, 48A, and 48C may be preferred in certain embodiments, other configurations, including the configurations of Figures 37D, 48B, and other variations may be utilized in other embodiments as desired.

[0239] Figure 37D shows a longitudinal cross section of the top portion of another composite tube. Figure 37D is in the same orientation as Figure 37B. This example further illustrates the hollow body shape of the first elongate member 203 and shows how the first elongate member 203 forms multiple hollow bubbles in the longitudinal cross section. In this example, the bubbles are completely spaced apart from one another by gaps 213. A generally triangular second elongate member 205 supports the first elongate member 203.

[0240] FIG. 37E shows a longitudinal cross section of the top portion of another composite tube. FIG. 37E is in the same orientation as FIG. 37B. In the example of FIG. 37E, the heating filaments 215 are spaced further apart than the filaments 215 in FIG. 37B. It has been recognized that increasing the space between heating filaments can improve heating efficiency, and certain embodiments incorporate this recognition. Heating efficiency refers to the ratio of heat input to the tube to the amount of energy output or recoverable from the tube. Generally speaking, the more energy (or heat) dissipated from the tube, the lower the heating efficiency. To improve heating performance, the heating filaments 215 can be evenly (or nearly evenly) spaced along the bore of the tube. Alternatively, the filaments 215 can be positioned at the end of the second elongate member 205, which can simplify manufacturing.

[0241] In Figure 37F, the first elongate member 203 forms multiple hollow bubbles in longitudinal cross section. In this example, there are multiple bubbles, more specifically, two adjacent wraps, of the first elongate member 203 between wraps of the second elongate member 205. This configuration is shown in more detail in Figure 37G. As described and illustrated elsewhere in this disclosure, certain configurations may implement more than two, for example, three, wraps of the first elongate member 203 between wraps of the second elongate member 205.

[0242] Embodiments that include multiple adjacent wraps of the first elongate member 203 between wraps of the second elongate member 205 may be advantageous because they improve the overall flexibility of the tube. A substantially solid second elongate member 205 is generally less flexible than a hollow first elongate member 203. Accordingly, certain embodiments recognize that increasing the number of bubbles of the first elongate member 203 between wraps of the second elongate member 205 may improve the overall flexibility of the tube.

[0243] A first 300 mm long sample of tubing containing two bubbles between the wraps of the second elongate member 205, and a second 300 mm long sample of tubing containing one bubble between the wraps of the second elongate member 205, were each tested in a flexibility test jig. A front cross-sectional schematic of the flexibility test jig is shown in FIG. 38A. The jig 1201 applied a force to each tube 201 using a rod 1203 with a fixed mass of 120 g, with the tube 201 positioned between two rollers 1205 and 1207. The force exerted by the rod 1203 was approximately 1.2 N (0.12 kg x 9.81 m / s 2 ) A detailed front cross-sectional schematic of rollers 1205 and 1207 is shown in FIG. 38B. Both rollers 1205 and 1207 had the same dimensions. Vertical deflection was measured using the position of the fixed weight relative to the vertical support 1209 of the flexibility test jig, as shown in the photographs of FIGS. 38C-38F.

[0244] FIG. 38C shows a front perspective view of the second test sample in jig 1201. FIG. 38D shows a rear perspective view of the second test sample in jig 1201. FIG. 38E shows a front perspective view of the first test sample in jig 1201. FIG. 38F shows a rear perspective view of the first test sample in jig 1201. As shown in FIGS. 38C-38F, the second sample shown in FIGS. 38E and 38F had substantially more vertical deflection than the first sample shown in FIGS. 38C and 38D. Specifically, the second sample had a vertical deflection of 3 mm, while the first sample was significantly more flexible, with a vertical deflection of 42 mm.

[0245] Another advantage of embodiments including multiple adjacent wraps of the first elongate member 203 between wraps of the second elongate member 205 is improved recovery from crushing. After crushing, samples with multiple bubbles between the wraps of the first elongate member 203 were observed to recover their shape faster than samples with only one bubble between the wraps of the first elongate member 203.

[0246] Yet another advantage of embodiments including multiple adjacent wraps of the first elongate member 203 between wraps of the second elongate member 205 is improved resistance to crushing. Crush resistance is a mechanical property that plays an important role in the elastic recovery of a tube during service. A hospital environment can be harsh, as tubes can be subjected to crushing by patients' arms or legs, bed frames, and other equipment.

[0247] Crush resistance tests were performed on four tube samples using an Instron testing machine set up as shown in the photograph in Figure 39A. Cylinder 1301 was pressed 16 mm down from the top of the tube at a rate of 60 mm / min. The Instron testing machine has a load cell that accurately measures the force applied to a component relative to the elongation. Load versus elongation was plotted as shown in Figure 39B.

[0248] The crush stiffness of each sample was determined by fitting a best-fit line to the data in Figure 39B and calculating the slope. The calculated crush stiffness for each sample is shown in Table 1A. In Table 1A (and elsewhere in this disclosure), the designation "double bubble" refers to a tubing sample that contains two bubbles between the wraps of the second elongate member 205 when the sample is viewed in longitudinal cross-section. The designation "single bubble" refers to a tubing sample that contains a single bubble between the wraps of the second elongate member 205 when the sample is viewed in longitudinal cross-section. The average crush stiffness (measured in N / mm) represents the average of the greatest force per unit width that does not cause crushing.

[0249] [Table 1]

[0250] As shown in the table above, the average crush stiffness of the single-bubble tube was 3.86 N / mm, while the average crush stiffness of the double-bubble tube was 3.21 N / mm. In other words, the double-bubble tube was approximately 16.8% less resistant to crushing than the single-bubble tube. Nevertheless, the crush stiffness per unit thickness of the double-bubble tube was observed to be approximately 165% of the value for the single-bubble tube, as shown in Table 1B below.

[0251] [Table 2]

[0252] In other words, when considering the outer bubble thickness, double-bubble tubing is approximately 65% ​​more resistant to crushing than single-bubble tubing. As shown in Figures 37F and 37G, the bubbles in the double-bubble configuration are taller than when the bubbles are wider, resulting in more material on the vertical surfaces. Therefore, it is believed that this unexpected improvement in crush resistance per unit bubble thickness can be attributed to the additional vertical webs between the beads acting in the direction of the crush.

[0253] Tensile tests were also performed on the single and double bubble tubing samples. Both samples were 230 mm long and were stretched 15 mm at a rate of 10 mm / min. The force required to stretch the samples was measured. The results are shown in Table 1C.

[0254] [Table 3]

[0255] As shown in Table 1C, the double-bubble tube had significantly greater elongation in the axial (longitudinal) plane. This increased longitudinal elongation is believed to be due to the single-bubble tube having more material between the beads acting in the axial plane.

[0256] Yet another advantage of the multiple bubble configuration described above is that it provides the ability to hold or deliver additional fluids. As explained above, the hollow portion of the first elongate member 203 can be filled with a gas. Multiple individual bubbles or hollow portions can be filled with multiple individual gases. For example, one hollow portion may hold or deliver a first gas, and a second hollow portion may be used as a secondary air connection, such as a pressure sample line that carries pressure feedback from the patient end of the tubing to a controller. As another example, multiple individual bubbles or hollow portions may be filled with a combination of liquids, or a combination of liquid and gas. For example, a first bubble may hold or deliver a gas, and a second bubble may hold or deliver a liquid. Suitable liquids and gases are described above.

[0257] It should be understood that while the configurations of Figures 37F and 37G may be preferred in certain embodiments, other configurations may be utilized in other embodiments as desired.

[0258] 37H-37L and 37V-37Z, several variations of tube 201 are shown that are adapted to provide increased lateral stretch in the tube. Figures 37V-37Z show the tubes shown in Figures 37H-37L, respectively, in stretched states.

[0259] Certain embodiments include the recognition that the tubes shown in Figures 37H, 37I, and 37L include a second elongate member 205 having a shape that enhances its elongation capability. For example, in Figure 37H, the second elongate member 205 is a generally oblate spheroid with an outer profile that is substantially the same height as the first elongate member 203. As shown in Figure 37V, this allows the second elongate member 205 to deform outwardly to at least twice its width as compared to the second elongate member 205 at rest.

[0260] 37I and 37L, the second elongate member 205 is shaped to have a concertina-like shape, such that upon stretching, the second elongate member 205 can accommodate incremental stretching by flattening (as shown in FIGS. 37W and 37Z, respectively).

[0261] In Figures 37J and 37K, the first elongate member 203 is given a shape that allows it to deform outward, thereby allowing for increased lateral stretch (as shown in Figures 37X and 37Y, respectively).

[0262] Reference is now made to Figures 40-40H, which illustrate exemplary configurations of the second elongate member 205. Figure 40A shows a cross section of the second elongate member 205 having a shape similar to the T-shape shown in Figure 37B. In this exemplary embodiment, the second elongate member 205 does not have a heating filament. Other shapes for the second elongate member 205 may also be utilized, including variations of the T-shape and a triangular shape, as described below.

[0263] 40B shows another exemplary second elongate member 205 having a T-shaped cross-section. In this example, heating filaments 215 are embedded in cuts 301 on either side of the longitudinal portion of the "T" in the second elongate member 205. In some embodiments, the cuts 301 can be formed in the second elongate member 205 during extrusion. Alternatively, the cuts 301 can be formed in the second elongate member 205 after extrusion. For example, a cutting tool can form the cuts in the second elongate member 205. Preferably, the cuts are formed by the heating filament 215 by pushing or pulling (mechanically securing) the heating filament 215 into the second elongate member 205 immediately after extrusion while the second elongate member 205 is relatively soft. Alternatively, one or more heating filaments can be attached (e.g., glued, bonded, or partially embedded) to the base of the elongate member with the filaments exposed to the tube lumen. In such embodiments, it may be desirable to encase the filament in a shield to reduce the risk of fire if a flammable gas, such as oxygen, passes through the tube lumen.

[0264] 40C shows in cross section yet another exemplary second elongate member 205. The second elongate member 205 has a generally triangular shape. In this example, heating filaments 215 are embedded on opposite sides of the triangle.

[0265] FIG. 40D illustrates yet another exemplary second elongate member 205 in cross section. The second elongate member 205 includes four grooves 303. The grooves 303 are indentations or constrictions in the cross-sectional profile. In some embodiments, the grooves 303 can facilitate the formation of a cut (not shown) for embedding a filament (not shown). In some embodiments, the grooves 303 facilitate the positioning of a filament (not shown) that is embedded in the second elongate member 205 by pushing or pulling the filament into the second elongate member 205. In this example, the four starting grooves 303 facilitate the placement of up to four filaments, such as 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 filament can be located on the exterior of the second elongate member 205. The sensing filament can be located on the interior.

[0266] 40E illustrates in cross section yet another exemplary second elongate member 205. The second elongate member 205 has a T-shaped profile and multiple grooves 303 for placement of heating filaments.

[0267] FIG. 40F illustrates yet another exemplary second elongate member 205 in cross section. Four filaments 215 are encapsulated within the second elongate member 205, two on each side of the vertical portion of the “T.” As described in more detail below, the second elongate member 205 is extruded around the filaments, so the filaments are encapsulated within the second elongate member 205. No cuts were made to embed the heating filaments 215. In this example, the second elongate member 205 also includes multiple grooves 303. Because the heating filaments 215 are encapsulated within the second elongate member 205, the grooves 303 are not used to facilitate the creation of cuts for embedding the heating filaments. In this example, the grooves 303 can facilitate separation of the embedded heating filaments, which can facilitate stripping of individual wires, for example, during heating filament termination.

[0268] 40G illustrates, in cross section, yet another exemplary second elongate member 205. The second elongate member 205 has a generally triangular shape. In this example, the shape of the second elongate member 205 is similar to that of FIG. 40C; however, four filaments 215 are encapsulated within the second elongate member 205, all of which are centered in the lower third of the second elongate member 205 and aligned along a generally horizontal axis.

[0269] 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 filaments 215 are incorporated into the composite pipe 201, the filaments 215 may be positioned relatively centrally in the second elongate member 205. A centralized location promotes robustness of the composite pipe for reuse, in part because the filaments are less likely to break when the composite pipe 201 is repeatedly flexed. Centralizing the filaments 215 may also reduce the risk of fire hazards, since the filaments 215 are covered with a barrier layer and removed from the gas path.

[0270] As discussed above, some of these examples illustrate preferred arrangements of the filaments 215 in the second elongate member 205. In the aforementioned examples including two or more filaments 215, the filaments 215 are generally aligned along a horizontal axis. Alternative configurations are also suitable. For example, two filaments may be aligned along a vertical axis or along a diagonal axis. Four filaments may be aligned along a vertical or diagonal axis. Four filaments may be aligned in a cross configuration, with one filament disposed at the top of the second elongate member, one filament disposed at the bottom of the second elongate member (near the vessel lumen), and two filaments disposed on either side of a "T," "Y," or triangular base.

[0271] 40H, an alternative embodiment of second elongate member 205 is shown. Second elongate member 205 includes one or more coaxial cables 1901 having conductors 1902 surrounded by an insulating layer 1903, a shielding layer 1904, and a sheath layer 1905. In certain embodiments, one or more of cables 1901 may be multiaxial, i.e., have multiple conductors 1902 disposed within insulating layer 1903. In this manner, second elongate member 205 may use a single assembly including multiple wires (including heating and / or sensing wires), thereby simplifying assembly and providing some shielding (via shielding layer 1904) from RF interference and the like.

[0272] In some embodiments, the second elongate member 205 can include one or more data transmission cables. The data transmission cables can include fiber optic cables. In at least one embodiment, the second elongate member 205 includes a single fiber optic cable and is used in a passive mode. In the passive mode, a light source and a light sensor are provided at a first end of the cable. A reflector is provided at a second end. In use, the light source provides a predetermined amount of light with specific characteristics toward the reflector. The reflector then reflects the light toward the light sensor, which can analyze the reflected light to determine the characteristics of the light. The reflector can be adapted to change the characteristics of the reflected light depending on the characteristics of the system. For example, the reflector can be used to monitor condensation within the interface. The reflector can include, for example, a material that changes color depending on the presence of condensation at the second end. Alternatively or additionally, the reflector can include a material that changes color, etc., depending on the humidity level (relative humidity or absolute humidity) and / or temperature of the gas at the second end.

[0273] Tables 2A and 2B show some exemplary dimensions of the medical tubing described herein, as well as some ranges of those dimensions. Dimensions refer to the transverse cross-section of the tubing. In these tables, lumen diameter refers to the inner diameter of the tubing. Pitch refers to the distance between two repeating points measured axially along the tubing, i.e., the distance between the tips of adjacent "T" segments of the second elongate member. Bubble width refers to the width (maximum outer diameter) of the bubble. Bubble height refers to the height of the bubble from the tubing lumen. Bead height refers to the maximum height of the second elongate member from the tubing lumen (e.g., the height of the "T" segment). Bead width refers to the maximum width of the second elongate member (e.g., the width of the "T" segment). Bubble thickness refers to the thickness of the bubble wall.

[0274] [Table 4]

[0275] [Table 5]

[0276] In another exemplary embodiment, the medical tubing has the approximate dimensions shown in Table 2C.

[0277] [Table 6]

[0278] The dimensions shown in Table 2C may be particularly advantageous for obstructive sleep apnea (OSA) applications. Compared to conduits used for respiratory management, conduits used in OSA applications are desirably more flexible, have a smaller outer diameter, are lighter, and are quieter and less sticky to the touch.

[0279] To improve flexibility, the conduit can be formed with a reduced pitch. In some configurations, the first elongate member can be formed into a conduit with a pitch of about 2 mm to about 8 mm. In some configurations, the conduit can have a pitch of about 4.5 mm to about 5.6 mm. In some configurations, the conduit can have a pitch of about 5.1 mm. In some configurations, the conduit may incorporate a heater, have an inner diameter of about 17 mm, and have a length of about 72 inches (183 cm), while including a pitch of about 5 to 5.1 mm. In such configurations, the resistance of the heater, as a function of the length of the first elongate member (and a second elongate member including a heater and positioned alongside the first elongate member), can have an acceptable resistance level for use within CPAP or other OSA applications. In some configurations, the first elongate member may be configured to be a conduit, such that the first elongate member has a portion having a first thickness that defines a lumen within the conduit and a second portion having a second thickness that defines at least a portion of the outer surface of the conduit. In some such configurations, the first thickness is less than the second thickness. Surprisingly, when the first thickness is less than the second thickness, the conduit exhibits greater flexibility compared to simply reducing the thickness throughout the first elongate member. In some such configurations, the first thickness is about 0.16 mm and the second thickness is about 0.22 mm. In some configurations, the conduit incorporates a heater, has an inner diameter of about 17 mm, and is about 72 inches (183 cm) long, while weighing about 85 grams to about 90 grams.

[0280] The first elongate member may be formed with a reduced wall thickness, and the wall may be flexible and deformable, to provide a quieter conduit when moved or dragged along a surface. In some configurations, the first elongate member may be formed with a wall thickness of about 0.05 mm to about 44 mm. In some configurations, the first elongate member may be formed with a wall thickness of about 0.13 mm to about 0.44 mm. In some configurations, the first elongate member may be formed with a wall thickness of about 0.13 mm to about 0.26 mm. In some configurations, the first elongate member may be formed with a wall thickness of about 0.16 mm to about 0.24 mm. In some configurations, the first elongate member may be formed with a wall thickness of about 0.17 mm to about 0.225 mm. Forming the elongate member with a reduced thickness also reduces the overall weight of the conduit.

[0281] The diameter may be reduced to reduce the size of the conduit while maintaining a sufficient diameter to reduce the likelihood of unacceptable pressure drop. In some configurations, the inner diameter may be about 13 mm to about 22 mm. In some configurations, the inner diameter may be about 16 mm to about 19 mm. In some configurations, the conduit may have an outer diameter of about 22.5 mm. In some configurations, the conduit may have an outer diameter of about 22.5 mm, an inner diameter of about 17.2 mm, and a length of about 72 inches (183 cm). Such a configuration provides a suitable pressure drop for conduit of this length while still providing the desired size reduction for the conduit while having the bubbled conduit extending around the circumference of the conduit, which would otherwise result in an undesirable size increase compared to standard corrugated tubing.

[0282] To provide a desired tactile feel, the conduit desirably has an improved surface texture. Surprisingly, the improved surface texture also results in a quieter conduit during use. In some configurations, the first elongated member may be formed from an extrudate including an anti-blocking additive. As discussed above, the anti-blocking additive can reduce adhesion between layers of the conduit, which has been found to aid in reducing noise levels associated with the conduit (e.g., when the conduit is dragged over furniture corners). In some configurations, the first elongated member may be formed from an extrudate including talc. In some configurations, the first elongated member may be formed from an extrudate including about 1.5 weight percent to about 10 weight percent talc. In some configurations, the first elongated member may be formed from an extrudate including about 1.5 weight percent to about 3 weight percent talc. In some configurations, the first elongated member may be formed from an extrudate including about 1.5 weight percent talc.

[0283] Tables 3A and 3B provide exemplary ratios between tube feature dimensions for the tubes described in Tables 2A and 2B, respectively.

[0284] [Table 7]

[0285] [Table 8]

[0286] The following table shows some exemplary properties of a composite tubing (designation "A") having a heating filament incorporated inside the second elongate member as described herein. For comparison, properties of a Fisher & Paykel model RT100 disposable corrugated tubing (designation "B") having a heating filament helically wound inside the lumen of the tubing are also provided.

[0287] Resistance to Flow (RTF) measurements were carried out in accordance with Annex A of ISO 5367:2000(E). The results are summarized in Table 4. As can be seen below, the RTF of the composite pipe is lower than that of the model RT100 pipe.

[0288] [Table 9]

[0289] Condensate or "rainout" in the tube refers to the weight of condensate collected per day at a gas flow rate of 20 L / min and a room temperature of 18°C. Humidified air is continuously flowed through the tube from the chamber. The tube weight is recorded before and after each day's test. Three consecutive tests are performed, with the tube allowed to dry between tests. The results are shown in Table 5 below. The results show significantly less rainout with the composite tube compared to the Model RT100 tube.

[0290] [Table 10]

[0291] The power requirements refer to the power consumed during the condensation test. In this test, the ambient air was maintained at 18°C. The humidification chamber, e.g., humidification chamber 46 in Figure 1, was powered by an MR850 heater base. The heating filament in the tube was independently powered by a DC power supply. Various flow rates were set and the chamber was placed in a state where the chamber output reached 37°C. Next, a temperature of 40°C was produced at the circuit output by varying the DC voltage to the circuit. The voltage required to maintain this output temperature was recorded, and the resulting power was calculated. The results are shown in Table 6. The results show that Composite Tube A uses significantly more power than Tube B. This is because Tube B uses a helical heating filament in the tube bore to heat the gas from 37°C to 40°C. The composite tube tends not to heat the gas as quickly because the heating filament is in the tube wall (embedded in the second elongated member). Instead, the composite tube is designed to maintain the gas temperature and prevent rainout by maintaining the tube bore above the dew point of the humidified gas.

[0292] [Table 11]

[0293] The flexibility of the tubes was tested using a three-point bending test. The tubes were placed in a three-point bending test jig and the load and elongation were measured using an Instron 5560 testing system. Each tube sample was tested three times; the elongation of the tube was measured against the applied load, and the average stiffness constant for each was calculated. The average stiffness constants for Tube A and Tube B are listed in Table 7.

[0294] [Table 12]

[0295] Manufacturing method Reference is now made to Figures 41A-41F, which illustrate an exemplary method for manufacturing a composite pipe.

[0296] 41A , in at least one embodiment, a method of manufacturing a composite tube includes providing a second elongate member 205 and helically winding the second elongate member 205 around a mandrel 401, with opposing side edge portions 403 of the second elongate member 205 spaced apart relative to adjacent wraps, thereby forming a second elongate member helix 405. The second elongate member 205 may be wound directly around the mandrel in certain embodiments. In other embodiments, a sacrificial layer may be provided over the mandrel.

[0297] In at least one embodiment, the method further includes forming the second elongate member 205. Extrusion is a preferred method for forming the second elongate member 205. The second extruder may be configured to extrude the second elongate member 205 with a particular bead height. Thus, in at least one embodiment, the method includes extruding the second elongate member 205.

[0298] 41B, extrusion can be advantageous because it can allow for the heating filament 215 to be encapsulated in the second elongate member 205 during formation, for example, using an extruder having a crosshead extrusion die. Thus, in certain embodiments, the method includes providing one or more heating filaments 215 and encapsulating the heating filaments 215 to form the second elongate member 205. The method also includes providing the second elongate member 205 with one or more heating filaments 215 embedded or encapsulated in the second elongate member 205.

[0299] In at least one embodiment, the method includes embedding one or more filaments 215 into the second elongate member 205. For example, as shown in FIG. 41C, the filaments 215 can be pushed (pulled or mechanically positioned) into the second elongate member 205 to a specific depth. Alternatively, cuts can be made in the second elongate member 205 to specific depths, and the filaments 215 can be placed in those cuts. Preferably, the pushing or cutting occurs immediately after the second elongate member 205 is extruded, while the second elongate member 205 is still soft.

[0300] 41D and 41E, in at least one embodiment, the method includes providing a first elongate member 203 and helically winding the first elongate member 203 around a second elongate member spiral 405 such that portions of the first elongate member 203 overlap adjacent windings of the second elongate member spiral 405 and the first elongate member 203 is disposed adjacent the mandrel 401 in spaces between windings of the second elongate member spiral 405, thereby forming a first elongate member spiral 407. FIG. 41D illustrates such an exemplary method, in which a heating filament 215 is encapsulated in the second elongate member 205 prior to forming the second elongate member spiral. 41E shows such an exemplary method, in which a heating filament 215 is embedded in the second elongate member 205 as the second elongate member spiral is formed. An alternative method of incorporating the filament 215 into the composite tube includes encapsulating one or more filaments 215 between the first elongate member 203 and the second elongate member 205 in the region where the first elongate member 203 overlaps the second elongate member 205.

[0301] As discussed above, at least one embodiment includes a tube having multiple wraps of the first elongate member 203 between wraps of the second elongate member 205. Accordingly, in certain embodiments, the method includes providing the first elongate member 203 and helically winding the first elongate member 203 around the second elongate member spiral 405 such that a first side portion of the first elongate member 203 overlaps the wrap of the second elongate member spiral 405 and a second side portion of the first elongate member 203 contacts an adjacent side portion of the first elongate member 203. A portion of the first elongate member 203 is disposed adjacent to the mandrel 401 in the space between the windings of the second elongate member spiral 405, thereby forming a first elongate member spiral 407 including multiple windings of the first elongate member 203 between the windings of the second elongate member 205.

[0302] In at least one embodiment, the first elongate member 203 is wrapped multiple times between the turns of the second elongate member 205. An exemplary schematic of the resulting longitudinal cross section is shown in FIG. 41G. Adjacent turns of the first elongate member 203 can be fused together using any suitable technique, such as heat sealing, gluing, or other attachment mechanisms. In at least one embodiment, adjacent molten or softened bubbles can be brought into contact with each other while hot, thereby bonding, and subsequently cooled with an air jet. Adjacent turns of the first elongate member 203 can also be joined by winding them in a softened state onto a mandrel and allowing them to cool.

[0303] In at least one embodiment, the first elongate member 203 is wrapped one or more times between the turns of the second elongate member 205, and one or more bubbles between the turns of the second elongate member 205 are further indented into additional individual bubbles using a suitable technique, such as heat treatment. An exemplary schematic representation of the resulting longitudinal cross-section is shown in FIG. 41H. As shown in FIG. 41H, a single bubble of the first elongate member 203 can be indented into two, three, or more individual bubbles using any suitable technique, such as applying mechanical force with an object or applying force with a directed air jet. Another exemplary schematic representation of the resulting longitudinal cross-section is shown in FIG. 41I. In this example, the central portion of the bubble is indented such that the top surface of the bubble joins with the bottom surface of the bubble to form two individual bubbles separated by a flat bottom portion. Adjacent side portions of the two individual bubbles are then joined to form a structure including three individual bubbles.

[0304] The above-described alternative for incorporating one or more heating filaments 215 into the composite tubing has advantages over the alternative of having the heating filament in the gas path. Having the heating filament 215 outside the gas path improves performance because the filament heats the tubing wall, where condensation is most likely to form. This configuration reduces the risk of fire in high-oxygen environments by moving the heating filament out of the gas path. This feature also reduces performance because it reduces the effectiveness of the heating wire in heating the gas passing through the tubing. Nevertheless, in certain embodiments, the composite tubing 201 includes one or more heating filaments 215 located within the gas path. For example, the heating filament may be installed on the lumen wall (tube bore), e.g., in a helical configuration. An exemplary method for disposing one or more heating filaments 215 on the lumen wall includes bonding, embedding, or otherwise forming the heating filament on a surface of the second elongate member 205 that will become the lumen wall when assembled. Thus, in certain embodiments, the method includes disposing one or more heating filaments 215 on the lumen wall.

[0305] Regardless of whether the heating filaments 215 are embedded or encapsulated in the second elongate member 205, disposed on the second elongate member 205, or otherwise placed in or on the tube, in at least one embodiment, a pair of filaments can be formed into a connecting loop at one end of the composite tube to form a circuit.

[0306] Figure 41F shows a longitudinal cross section of the assembly shown in Figure 41E, focusing on the upper portion of the mandrel 401 and the upper portions of the first elongate member spiral 407 and second elongate member spiral 405. This example shows a second elongate member spiral 405 having a T-shaped second elongate member 205. As the second elongate member is formed, a heating filament 215 is embedded in the second elongate member 205. The right side of Figure 41F shows the bubble-shaped profile of the first elongate member spiral, as described above.

[0307] The method also includes forming the first elongate member 203. Extrusion is a preferred method for forming the first elongate member 203. Thus, in at least one embodiment, the method includes extruding the first elongate member 203. The first elongate member 203 may also be manufactured by extruding two or more sections and joining them to form a single piece. As another alternative, the first elongate member 203 may also be manufactured by extruding sections that, when formed adjacently or joined in a helical tube forming process, create a hollow shape.

[0308] The method also includes supplying a gas at a pressure greater than atmospheric pressure to the end of the first elongate member 203. The gas may be, for example, air. As explained above, other gases may also be used. Supplying the gas to the end of the first elongate member 203 may help maintain an open, hollow body shape of the first elongate member 203 as it is wrapped around the mandrel 401. The gas may be supplied before the first elongate member 203 is wrapped around the mandrel 401, while the first elongate member 203 is wrapped around the mandrel 401, or after the first elongate member 203 is wrapped around the mandrel 401. For example, an extruder including an extrusion die head / tip combination may supply or deliver air to the hollow cavity of the first elongate member 203 as it is extruded. Thus, in at least one embodiment, the method includes extruding a first elongate member 203 and, after extrusion, supplying a gas at a pressure greater than atmospheric pressure to an end of the first elongate member 203. A pressure of 15-30 cmH2O (or about 15-30 cmH2O) has been found to be suitable.

[0309] In at least one embodiment, the first elongate member 203 and the second elongate member 205 are spirally wound around the mandrel 401. For example, the first elongate member 203 and the second elongate member 205 may exit the extrusion die at a temperature of 200°C (or about 200°C) or higher and then applied to the mandrel after a short distance. Preferably, the mandrel is cooled to a temperature of 20°C (or about 20°C) or lower, for example, near 0°C (or about 0°C), using a water jacket, chiller, and / or other suitable cooling method. After five (or about five) spiral wraps, the first elongate member 203 and the second elongate member 205 are further cooled with a cooling fluid (liquid or gas). In one embodiment, the cooling fluid is air emitted from a ring, jet of which surrounds the mandrel. Once the components are cooled and removed from the mandrel, a composite tube is formed having a lumen extending along the longitudinal axis and a hollow space surrounding the lumen. In such embodiments, no adhesive or other attachment mechanism is required to connect the first elongate member and the second elongate member. Other embodiments may utilize adhesive or other attachment mechanisms to bond or otherwise connect these two members. In another embodiment, the second elongate member 205 may be cooled after extrusion and heating filament placement to prevent movement of the heating filament. The second elongate member 205 may then be reheated to improve bonding when applied to the mandrel. Exemplary methods of reheating include the use of spot heating devices, hot rollers, etc.

[0310] The method also includes forming a pair of heating or sensing filaments into a connecting loop at one end of the composite tube. For example, the distal portions of two heating or sensing filaments may be extracted from the second elongate member 205 and then formed into a connecting loop by, for example, tying, bonding, gluing, fusing, etc. the two filaments together. As another example, the distal portions of the heating filaments may be left free from the second elongate member 205 during manufacturing and then formed into a connecting loop during assembly of the composite tube.

[0311] 41J-41Q, an alternative method of forming tube 201 includes an extrusion tool 2001 having a series of flow channels extending therealong. The extrusion tool 2001 can be used to form tubes such as the exemplary tubes shown in FIGS. 41P and 41Q. As shown, tubes made using the extrusion tool 2001 can include a plurality of first elongate members 203 extending generally along the longitudinal axis of the tube. In some embodiments, the extrusion tool 2001 comprises a body 2010 and a central extension 2020. In some embodiments, the body 2010 and extension 2020 are generally cylindrical. The body 2010 can include one or more flow channels 2012 that allow molten plastic or another material to flow from an input end 2014, through the body 2010, to an output or extrusion end 2016. In some embodiments, the flow channel has a substantially conical longitudinal cross-section (i.e., it is wider where the molten plastic first enters the input 2014 and narrows closer to the extrusion end 2016). The flow channel can have various configurations to produce tube 201 with various profiles. For example, the flow channel configurations shown at the output end or extrusion end 2016 in FIGS. 41L and 41M can produce tube 201 with an end view profile as shown in FIG. 41J. FIG. 41K shows an end view of the tube of FIG. 41J including a second elongated member 205 (which may include a heating filament 215) positioned between adjacent bubbles or first elongated members 203. In use, the tool 2001 is adapted to rotate to induce the tube 201 to form into a spiral. As shown in FIG. 41O, a central extension 2020 can connect the extrusion tool 2001 to an extruder 2030. A bearing 2022 disposed between the central extension 2020 and the extruder 2030 allows the central extension 2020 and the body 2010 to rotate relative to the extruder 2030. By adjusting the rotational speed of the tool 2001, the pitch angle or twist angle of the first elongated member 203 can be varied. For example, increasing the rotational speed can provide a smaller twist angle, as shown in FIG. 41P. Decreasing the rotational speed can provide a larger twist angle, as shown in FIG. 41Q.

[0312] Medical tubing having a single spirally wound tube 42A-42F show transverse cross-sections of an exemplary embodiment of a tube comprising a single tubular-shaped element having a first elongate member or portion 203 and a second elongate member or portion 205. As shown, the second elongate portion 205 is integral with the first elongate portion 203 and extends along the entire length of the single tubular-shaped element. In the illustrated embodiment, the single tubular-shaped element is an elongate hollow body that, in transverse cross-section, has a relatively thin wall that partially defines a hollow portion 501, with two relatively thick or relatively stiff reinforcing portions 205 on opposite sides of the elongate hollow body adjacent the relatively thin wall. These reinforcing portions form part of the inner wall of the lumen 207 after the elongate hollow body is helically wound, and thus these reinforcing portions are also helically positioned between adjacent turns of the elongate hollow body.

[0313] In at least one embodiment, the method includes forming an elongate hollow body including a first elongate portion 203 and a reinforcing portion 205. Extrusion is a preferred method for forming the elongate hollow body. Preferred cross-sectional shapes for the tubular shaped element are shown in Figures 42A-42F.

[0314] The elongate hollow body can be formed into medical tubing as described above, and the foregoing discussion is incorporated herein by reference. For example, in at least one embodiment, a method for manufacturing medical tubing includes helically winding or winding the elongate hollow body around a mandrel. This may be performed at an elevated temperature, so that the elongate hollow body is helically wound and then cooled, bonding adjacent turns together. As shown in FIG. 42B, opposing side edge portions of the reinforcing section 205 may contact adjacent turns. In other embodiments, opposing side edge portions of the second elongate member 205 may overlap adjacent turns, as shown in FIGS. 42D and 42E. A heating filament 215 may be incorporated into the second elongate member, as described above and shown in FIGS. 42A-42F. For example, heating filaments may be provided on opposing sides of the elongate hollow body, as shown in FIGS. 42A-42D. Alternatively, the heating filament may be provided on only one side of the elongate hollow body, as shown in Figures 42E-42F. Any of these embodiments can incorporate the presence of a sensing filament.

[0315] Arrangement of chamber end connectors with electrical connectivity Reference is now made to Figure 43A, which illustrates an exemplary flowchart for attaching a connector to the end of a tube that is configured to connect to a humidifier during use. For example, as described above in connection with Figure 1, the inlet conduit 70 connects to the humidification unit 40 via the inlet 42. The exemplary flowchart in Figure 43A may enable the inlet conduit 70 to be physically and electrically connectable with the humidification unit 40.

[0316] In the example of FIG. 43A, a seal 1503 is inserted into a seal housing 1501. The seal insertion operation is also shown in more detail in FIG. 43B. The seal housing 1501 is made of molded plastic. One open end is sized and configured for connection to a humidifier. The seal 1503 may be an O-ring, as shown in FIG. 43B. A suitable configuration for the O-ring may be a dual ring configuration including a thick concentric torus connected by a thin web. In this example, the O-ring is molded from a single elastomeric material, such as rubber. The seal 1503 seats on a compliant ridge on the seal housing 1501. The seal 1503 is designed to seal against the outer surface of the port in the humidifier chamber. The seal 1503 can flex to extend along the outer surface of the port. In other words, the dual O-ring configuration includes an inner O-ring and an outer O-ring connected by a flange. The outer O-ring is sealed within the connector, while the inner O-ring can flex along the flange portion and clamp against the outer surface of the port. In such a position, the horizontal plane extending through the central axis of the inner O-ring can be in a different plane than the horizontal plane extending through the central axis of the outer O-ring.

[0317] Returning to the example of FIG. 43A , a printed circuit board (PCB) is inserted into a compliant dock of the seal housing 1501. The PCB insertion operation is shown in more detail in FIG. 43C . In FIG. 43C , an assembly 1505 including a PCB and PCB connector is inserted into the compliant dock of the seal housing 1501. In this example, the PCB connector is an off-the-shelf connector sold by Tyco Electronics Corp. (Berwyn, PA). The PCB includes four terminals suitable for receiving four conductive filaments encased in the second elongated member of the tube. However, if the second elongated member includes more or fewer conductive filaments than four, the PCB can be configured to receive any suitable number of conductive filaments.

[0318] 43A , a seal retainer 1507 is clipped onto one open end of a seal housing 1501, which has a seal 1503 seated on a compliant ridge. Clipping the seal retainer 1507 into place compresses the seal 1503, thereby forming a liquid- and gas-tight connection between the seal housing 1501 and the seal retainer 1507. In this example, the seal retainer is made from molded plastic and includes a protruding portion sized and shaped to fit around the PCB. This protruding portion serves to support and protect the more flexible and fragile PCB. The resulting assembly, including the seal housing 1501, seal 1503, PCB and PCB connector assembly 1505, and seal retainer 1507, is referred to herein as a connector tube assembly 1515.

[0319] Returning to the example of FIG. 43A, a tube is prepared for connection with a connector tube assembly 1515. As shown in FIG. 43A and in more detail in FIG. 43E, in step 1511, a portion of the second elongated member at one end of the tube is separated from the first elongated member. Next, in step 1513, a length of the separated second elongated member is stripped away, exposing four (or the number of conductive filaments contained in the second elongated member). Step 1513 is shown in more detail in FIG. 43F.

[0320] As illustrated in Figure 43A and shown in more detail in Figure 43G, a portion of the tube comprising the stripped length of the second elongated member is inserted into a connector tube assembly 1515. As shown in Figures 43A and 43H, step 1517, four conductive filaments are inserted into four terminals on the PCB. The filaments are then secured to the terminals by providing a bead of solder 1519 on each filament-terminal connection, ensuring a good electrical connection between each filament and its corresponding terminal, as shown in Figures 43A and 43I.

[0321] To ensure that all parts of the connector tube assembly 1515 are securely fastened together, a glue layer 1521 is then applied. Glue is a broad term that refers to a material for joining, fastening, or attaching other materials. Glue can be tacky or sticky to the touch when it is in a liquid or semi-solid state. When the glue dries or otherwise hardens to a solid state, the glue can be tacky or non-tacky or non-sticky to the touch. The glue can be a resin, such as an epoxy resin, or a thermoplastic elastomer (TPE). The use of a TPE material can be advantageous because it is generally flexible and can handle twisting, bending, or pressure without fracturing.

[0322] An exemplary method for applying glue 1521 is shown in FIG. 43J. In this method, a two-block mold is provided. In this example, the mold is stainless steel, although any suitable material can be used. For example, the mold may be made of Teflon® PTFE blocks. One block is configured to receive the protruding PCB and PCB connector assembly 1505 and adjacent tubing of the connector tube assembly 1515, while the other block is configured to receive the opposite portion of the tubing and connector tube assembly 1515. The tubing is placed into a compliant mold section with the blocks stacked one on top of the other. Liquid glue is dispensed into the mold's entry hole, and the glue is allowed to harden. The mold is then removed, revealing the bonded tubing and connector assembly 1523, which includes a layer of cured glue 1507 covering the joints between the PCB and tubing and the connector tube assembly 1515. This glue layer may cover the PCB and all of the soldered connections on the PCB. In this way, the glue layer can protect the PCB and connections from corrosion. In other words, the glue performs three functions: seals the connectors and conduits, holds the PCB in place, and pots the PCB; the glue layer forms a hermetic seal, a mechanical bond, and a PCB potting compound.

[0323] Returning again to FIG. 43A, the tubing and connector assembly 1523 is now ready for final assembly. As shown in more detail in FIG. 43K, a front clamshell 1525 and a rear clamshell 1527 are snapped together around the tubing and connector assembly 1523, leaving a portion of the PCB connector exposed. The clamshell 1525, 1527 portions can be made of molded plastic or any other suitable material. The clamshell 1525, 1527 portions serve to further protect the tubing and connector assembly 1523 and to hold the tubing and connector assembly in a flexed position that facilitates the return of condensate to the humidifier unit during use. As shown in FIG. 43L, this final assembly can be easily snapped into a humidifier that has a compliant electrical connector near the connection port.

[0324] Although the foregoing manufacturing methods have been described with reference to a flowchart, the flowchart merely provides an exemplary method for attaching a connector to the end of a tube configured to connect to a humidifier during use. The methods described herein do not imply a specific order of steps, nor do they imply that any one step is essential to practicing the method. Embodiments may be practiced in any order or combination that is feasible.

[0325] Positioning of patient-end connector with electrical connectivity Reference is now made to Figures 44A-44H, which illustrate an exemplary connector 1600 that connects one end of tubing 201 to a patient interface (not shown). The portion of connector 1600 that connects with the patient interface is designated by reference numeral 1601. Figure 44A illustrates a side perspective view of connector 1600. As shown in Figures 44B-44E, connector 1600 includes tubing 201, PCB 1603, insert 1605 (which, when assembled together, are collectively referred to as a computational fluid dynamics (CFD) assembly 1607), and cover 1609. Each of Figures 44B-44E illustrates a side perspective view that generally corresponds to the view of Figure 44A.

[0326] The insert 1605 and cover 1609 are preferably molded plastic parts. The insert 1605 may serve one or more of several purposes, including providing a spigot for the tube, providing a suitable conduit for the gas flow path, providing a housing for the PCB, and providing a housing for the thermistor (discussed below). The cover 1609 protects and covers the relatively fragile PCB and protects the connection between the tube and the insert. As shown in FIG. 44A, the end of the insert 1605 that is inserted into the tube 201 is preferably angled to aid in insertion into the tube 201. Additionally, as shown in FIG. 44D, the insert desirably includes a stop portion 1606, which promotes proper placement of the tube 201 relative to the insert 1605 and also serves to protect the PCB 1603.

[0327] To electrically connect the conductive filaments of the second elongated member of the tube 201 to the terminals of the PCB 1603, a procedure similar to that shown and described above in connection with Figures 43E-43I may be used.

[0328] Figure 44F shows a cross section of connector 1600 and generally corresponds to the same side perspective view as Figure 44A. Figure 44H shows a cross section of CFD assembly 1607 and generally corresponds to the side perspective view of Figure 44D. These figures provide further detail regarding the relative placement of tube 201, CFD assembly 1607, and cover 1609.

[0329] Figure 44H shows a cross section of the connector 1600 along the width of the connector, looking from the patient interface end 1601 of the connector towards the tube (not shown). Figure 441 shows a slide-plan cross section of the CFD assembly 1607 showing further details of the PCB and thermistor 1611. As shown in Figures 44H and 441, the thermistor 1611 is placed in the flow path. The thermistor 1611 provides temperature and gas flow information that may enable assessment of thermal conditions near the patient interface.

[0330] Spiral connector placement 45A-45E, which show a connector that does not have electrical connectivity to a PCB. However, depending on the configuration, the connector could equally well be adapted to have electrical connectivity to a PCB. This connector is suitable for connection to a patient interface or humidifier. It is particularly suited for use as a patient-end connector and / or device-end connector in obstructive sleep apnea environments.

[0331] A molded insert 1701 is provided with a spiral end, the end of the insert 1701 opposite the spiral end being molded for insertion into or attachment to a humidifier port, and / or a patient interface port, and / or any other desired component.

[0332] 45C, the helical end of the insert 1701 is threaded onto the compliant turns of the tube 201. In this example, the helical turns of the insert 1701 are sized and configured to fit over and around the turns of the first elongate member 203 of the tube 201.

[0333] It should be noted that if the tube has one or more energized wires therein, an electrical connection may be provided on at least a portion of the insert 1701. When the insert 1701 is installed, the electrical connector preferably aligns with the wires, thereby facilitating the electrical connection. The connection may then be secured using solder or the like.

[0334] A soft rubber or TPE member 1703 may be inserted or molded over insert 1701, and possibly at least a portion of tube 201, to facilitate attachment between insert 1701 and tube 201. In some cases, high-pressure molding may be used because insert 1701 (or at least the spiral end of insert 1701) provides sufficient lateral crush resistance (the pressures in high-pressure molding may exceed the lateral crush resistance of tube 201 without insert 1701). Member 1703 may also advantageously provide a soft surface to grip when inserting and removing the tube from the component.

[0335] The foregoing method of attaching a connector to spirally wound tubing is provided as an example. The methods described herein do not imply a specific order of steps, nor do they imply that any one step is essential to practicing the method. Embodiments may be practiced in any order or combination that is feasible.

[0336] Alternative Device-End Connector Arrangements 46A-46F, which illustrate a connector that can be used in a medical circuit with electrical wires passing through it. Connector 1801 includes a cutout 1802, which in certain embodiments is 30 mm (or approximately 30 mm) wide. In certain embodiments, one end of cutout 1802 has an L-shaped arm 1803 that extends partially outward from connector 1801 and partially parallel to the longitudinal axis of connector 1801.

[0337] Arm 1803 may have one or more electrical conductors 1804 embedded therein. Conductors 1804 may be made of copper or brass or another suitably conductive material and may be formed as a flat, L-shaped piece that extends substantially along the length of arm 1803.

[0338] The connector 1801 may further include an inner portion 1805 adapted to seat substantially inside a portion of the tube 201 and an outer portion 1806 adapted to substantially surround a portion of the tube 201.

[0339] A portion of second elongate member 205 is stripped away to expose one or more filaments 215 embedded therein. Preferably, approximately 5 mm of filament 215 is exposed. Connector 1801 is then attached to tube 215 such that inner portion 1805 seats within tube 201 and outer portion 1806 seats around tube 201. Preferably, connector 1801 is oriented so that the exposed end of filament 215 is located at or near cutout 1802.

[0340] The exposed end of filament 215 is then electrically and / or physically connected to conductor 1804. This can be done by soldering the end to conductor 1804 or by any other method known in the art.

[0341] A soft rubber or TPE member 1807 may be inserted or molded onto the connector 1801 and possibly at least a portion of the tube 201 to facilitate attachment between the connector 1801 and the tube 201 .

[0342] In some embodiments, a generally L-shaped elbow 1808 may be placed over the assembly. The elbow 1808 may provide some additional strength to the connection and may provide for a predetermined bend in the tube 201 (which may cause the connector 1701 to tend to seat at approximately a 90° angle with the body of the tube 201).

[0343] coaxial tube A coaxial breathing tube may also be included in the composite tube described above. In the coaxial breathing tube, the first gas space is the inhalation rim or the exhalation rim, and the second gas space is the other of the inhalation rim or the exhalation rim. One gas passage is provided between the inhalation rim inlet and the inhalation rim outlet, and one gas passage is provided between the exhalation rim inlet and the exhalation rim outlet. In one embodiment, the first gas space is the inhalation rim and the second gas space is the exhalation rim. Alternatively, the first gas space may be the exhalation rim and the second gas space may be the inhalation rim.

[0344] Reference is now made to FIG. 47, which illustrates a coaxial tube 801 according to at least one embodiment. In this example, the coaxial tube 801 is provided between a patient and a ventilator 805. Exhaled and inhaled air flows through one of the spaces 809 between the inner tube 807 or the inner tube 807 and the outer tube 811, respectively. It will be appreciated that the outer tube 811 need not be strictly aligned with the inner tube 807. Rather, "coaxial" refers to one tube being located inside another.

[0345] For heat transfer reasons, the inner tube 807 may carry inhaled air in the space 813 therein, while exhaled air is carried in the space 809 between the inner tube 807 and the outer tube 811. This air flow configuration is shown by the arrows. However, the reverse configuration is also possible, where the outer tube 811 carries inhaled air and the inner tube 807 carries exhaled air.

[0346] In at least one embodiment, inner tube 807 is formed of corrugated tubing, such as Fisher & Paykel model RT100 disposable tubing. Outer tube 811 is formed of composite tubing as described above.

[0347] The coaxial tube 801 may prevent the ventilator 805 from sensing a leak in the inner tube 807. Such a leak could short out the patient, meaning the patient would not receive enough oxygen. Such a short can be detected by placing a sensor at the patient end of the coaxial tube 801. This sensor may be located at the patient end connector 815. If the short is closer to the ventilator 805, the patient may continually rebreathe a volume of air closer to the patient. This results in an increase in carbon dioxide concentration in the inspiratory flow space 813 closer to the patient, which can be detected directly by a CO sensor. Such a sensor may include any one of a number of such sensors currently available on the market. Alternatively, this rebreathing may be detected by monitoring the gas temperature at the patient end connector 815, where an increase in temperature above a predetermined level is an indication that rebreathing is occurring.

[0348] In addition to the above, to reduce or eliminate the formation of condensation inside the inner tube 807 or outer tube 811 and to maintain a substantially uniform temperature in the gas flow through the coaxial tube 801, a heater such as a resistive heating filament may be provided inside the inner tube 807 or outer tube 811, or disposed within the gas space 809 or 813, or within the wall of the inner tube 807 or outer tube 811 itself.

[0349] Thermal Properties In embodiments of the composite tube 201 incorporating a heating filament 215, heat may be lost through the wall of the first elongated member 203, resulting in uneven heating. As explained above, one way to compensate for this heat loss is to apply an external heat source to the wall of the first elongated member 203, which helps regulate the temperature and offset the heat loss. However, other methods of optimizing thermal properties may also be used.

[0350] Reference is now made to Figures 48A-48C, which illustrate exemplary configurations of bubble height (i.e., the cross-sectional height of the first elongate member 203 measured from the surface facing the inner lumen to the surface forming the maximum outer diameter) that improve thermal properties.

[0351] The dimensions of the bubbles can be selected to reduce heat loss from the composite tube 201. Generally, increasing the bubble height increases the effective thermal resistance of the tube 201 because the increased bubble height allows the first elongated member 203 to retain more insulating air. However, it has been found that at certain bubble heights, changes in air density cause convection currents inside the tube 201, thereby increasing heat loss. Also, at certain bubble heights, the surface area becomes so large that heat loss through the surface negates the benefits of increasing the bubble height. Certain embodiments incorporate these recognitions.

[0352] The radius of curvature and 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 larger the radius of curvature of an object, the less curved the object is. For example, a flat surface has a radius of curvature of ∞, and therefore a curvature of 0.

[0353] Figure 48A shows a longitudinal cross section of the upper portion of the composite pipe. Figure 48A shows an embodiment of the composite pipe 201 with a tall bubble. In this example, the bubble has a relatively small radius of curvature, and therefore a large curvature. The bubble also has a height that is approximately 3 to 4 times greater than the height of the second elongated member 205.

[0354] Figure 48B shows a longitudinal cross section of the top portion of another composite tube. Figure 48B shows an embodiment of composite tube 201 with a flat bubble top. In this example, the bubble has a very large radius of curvature, but a small curvature. Also, the bubble is approximately the same height as second elongate member 205.

[0355] Figure 48C shows a longitudinal cross section of the upper portion of another composite tube. Figure 48C shows an embodiment of a composite tube 201 in which the bubble width is greater than the bubble height. In this example, the bubble radius is between that of Figures 48A and 48B, and the center of the radius of the upper portion of the bubble is on the outside of the bubble (compared to Figure 48A). The inflection points on the left and right sides of the bubble are approximately in the center (height) of the bubble (as opposed to at the bottom of the bubble, as in Figure 48A). Additionally, the bubble height is approximately twice that of the second elongate member 205, resulting in a bubble height between that of Figures 48A and 48B.

[0356] The configuration of Figure 48A achieved the least heat loss from the tubes. The configuration of Figure 48B achieved the most heat loss from the tubes. The configuration of Figure 48C achieved heat loss intermediate between the configurations of Figures 48A and 48B. However, the configuration of Figure 48A experienced insufficient heating due to its large external surface area and convective heat transfer. Therefore, of the three bubble configurations of Figures 48A-48C, Figure 48C was determined to have the best overall thermal performance. With the same thermal energy input to the three tubes, the configuration of Figure 48C achieved the greatest temperature rise along the tube length. The bubbles in Figure 48C are large enough to increase the amount of insulating air, but not large enough to cause significant convective heat loss. The configuration of Figure 48C was determined to have the poorest thermal performance; i.e., the configuration of Figure 48B achieved the smallest temperature rise along the tube length. The configuration of Figure 48A had intermediate thermal performance and achieved a smaller temperature rise than the configuration of Figure 48C.

[0357] It should be understood that while the configuration of FIG. 48C may be preferred in certain embodiments, other configurations, including the configurations of FIGS. 48A and 48B, and other variations, may be utilized in other embodiments as desired.

[0358] Table 8 shows the bubble height, tube outer diameter, and radius of curvature for each of the configurations shown in Figures 48A, 48B, and 48C.

[0359] [Table 13]

[0360] Table 8A shows the bubble height, outer diameter, and radius of curvature for additional configurations as shown in Figures 50A-50C.

[0361] [Table 14]

[0362] It should be noted that, in general, the smaller the radius of curvature, the more difficult it may be to bend the tube without indenting or "kinking" the bubble. For example, Figure 50D shows a tube that has been bent beyond its radius of curvature, thereby creating a kink in the bubble wall (specifically, this shows the tube of Figure 50A bent around a 5.7 mm radius of curvature). Kinks are generally undesirable because they can detract from the appearance of the tube and can harm the thermal properties of the tube.

[0363] Thus, in some applications, a configuration with increased bending properties (such as the configuration shown in FIG. 48A or 48B) may be desirable even if it results in less efficient thermal properties. It has been found that, in some applications, a tube having an outer diameter of 25 mm to 26 mm (or about 25 mm to about 25 mm) provides a good balance between thermal efficiency, flexibility, and bending performance. While the configurations of FIGS. 48A and 48B may be preferred in certain embodiments, it should be understood that other configurations, including the configurations of FIGS. 50A-50D, and other variations may be utilized in other embodiments, as desired.

[0364] 48C-48F, which illustrate exemplary positioning of heating elements 215 in a similar bubble shape to enhance thermal properties. The position of the heating elements 215 can change the thermal properties within the composite tube 201.

[0365] Figure 48C shows a longitudinal cross section of the top portion of another composite tube. Figure 48C shows an embodiment of composite tube 201 in which the heating elements 215 are located in the center of the second elongate member 205. This example shows the heating elements 215 closer to each other and not closer to the bubble walls.

[0366] Figure 48D shows a longitudinal cross section of the top portion of another composite tube. Figure 48D shows an embodiment of composite tube 201 in which the heating elements 215 are spaced further apart in the second elongate member 205 compared to Figure 48C. These heating elements are closer to the bubble wall, resulting in better thermal regulation of the interior of composite tube 201.

[0367] Figure 48E shows a longitudinal cross section of the upper portion of another composite tube. Figure 48E shows an embodiment of a composite tube 201 in which the heating elements 215 are spaced above and below on the vertical axis of the second elongate member 205. In this example, the heating elements 215 are equally close to each bubble wall.

[0368] Figure 48F shows a longitudinal cross section of the top portion of another composite tube. Figure 48F illustrates an embodiment of a composite tube 201 in which heating elements 215 are spaced apart on opposite ends of the second elongate member 205. The heating elements 215 are closer to the bubble wall, especially compared to Figures 48C-48E.

[0369] Of the four filament configurations shown in Figures 48C-48F, Figure 48F was determined to have the best thermal performance. Because their bubble shapes were similar, all configurations experienced similar heat loss from the tube. However, for the same heat energy input to the tube, the filament configuration of Figure 48F achieved the greatest temperature rise along the length of the tube. The configuration of Figure 48D was determined to have the next best thermal performance, achieving the next largest temperature rise along the length of the tube. The configuration of Figure 48C performed next best. The configuration of Figure 48E performed the worst, achieving the smallest temperature rise along the length of the tube for the same amount of heat input.

[0370] It should be understood that while the configuration of FIG. 48F may be preferred in certain embodiments, other configurations, including the configurations of FIGS. 48C, 48D, and 48E, as well as other variations, may be utilized in other embodiments as desired.

[0371] Reference is now made to Figures 49A-49C, which illustrate exemplary configurations for stacking the first elongate member 203. It has been found that stacking multiple bubbles can improve heat distribution in certain embodiments. These embodiments may be more beneficial when using an internal heating filament 215. Figure 49A shows a longitudinal cross section of the top portion of another composite tube. Figure 49B shows a cross section of the composite tube 201 without any stacking.

[0372] FIG. 49B shows a longitudinal cross section of the top portion of another composite pipe. FIG. 49B shows another exemplary composite pipe 201 with stacked bubbles. In this example, two bubbles are stacked on top of each other to form the first elongated member 203. Compared to FIG. 49A, the overall bubble height is maintained, but the bubble pitch is half that of FIG. 49A. The embodiment of FIG. 49B also has only a slight reduction in air volume. Stacking the bubbles reduces natural convection and heat transfer in the gaps between the bubbles 213, lowering the overall thermal resistance. Stacked bubbles increase the heat flow path, allowing heat to be more easily distributed throughout the composite pipe 201.

[0373] Figure 49C shows a longitudinal cross section of the top portion of another composite pipe. Figure 49C shows another example of a composite pipe 201 with stacked bubbles. In this example, three bubbles are stacked on top of each other to form the first elongated member 203. Compared to Figure 49A, the overall bubble height is maintained, but the bubble pitch is one-third that of Figure 49A. The embodiment of Figure 49A also has only a slight reduction in air volume. The stacking of bubbles reduces natural convection and heat transfer in the gaps between the bubbles 213.

[0374] cleaning In at least one embodiment, the composite tubing material may be selected to handle various cleaning methods. In some embodiments, the composite tubing 201 may be cleaned using a high-level disinfection (approximately a 20-minute cleaning cycle). In high-level disinfection, the composite tubing 201 is subjected to pasteurization at approximately 75°C for approximately 30 minutes. Next, the composite tubing 201 is treated in a 2% glutaraldehyde bath for approximately 20 minutes. The composite tubing 201 is removed from the glutaraldehyde and immersed in 6% hydrogen peroxide for approximately 30 minutes. Finally, the composite tubing 201 is removed from the hydrogen peroxide and treated in a 0.55% orthophthalaldehyde (OPA) bath for approximately 10 minutes.

[0375] In another embodiment, sterilization (approximately 20 cycles) may be used to clean the composite tubing 201. First, the composite tubing 201 is placed in autoclave steam at approximately 121°C for approximately 30 minutes. Next, the temperature of the autoclave steam is increased to approximately 134°C for approximately 3 minutes. After autoclaving, the composite tubing 201 is surrounded by 100% ethylene oxide (ETO) gas. Finally, the composite tubing 201 is removed from the ETO gas and immersed in approximately 2.5% glutaraldehyde for approximately 10 hours.

[0376] The composite pipe 201 may be made of a material that can withstand repeated cleaning processes. In some embodiments, some or all of the composite pipe 201 may be made of a styrene-ethylene-butene-styrene block thermoplastic elastomer, such as, but not limited to, Kraiburg TF6STE. In other embodiments, the composite pipe 201 may be made of, but not limited to, hytrel, urethane, or silicone.

[0377] Although certain preferred embodiments and examples are disclosed herein, the inventive subject matter extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses, as well as modifications and equivalents thereof. Accordingly, the claims or embodiments appended hereto are not limited by any of the specific embodiments described herein. For example, in any method or process disclosed herein, the acts or operations of the method or process can be performed in any suitable order and are not necessarily limited to any particular disclosed order. Various operations may be described sequentially as multiple separate operations, in a manner that may aid in understanding particular embodiments; however, the order of description should not be construed to imply that the operations are order-dependent. Additionally, structures described herein may be embodied as integrated or separate components. For purposes of comparing various embodiments, certain aspects and advantages of these embodiments are described. Not all such aspects or advantages are achieved by any particular embodiment. Thus, for example, various embodiments can be implemented in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other aspects or advantages as may also be taught or suggested herein.

[0378] The methods and processes described herein may be implemented in software code modules executed by one or more general-purpose and / or special-purpose computers, and thereby partially or fully automated. The term "module" refers to logic implemented in hardware and / or firmware, or a set of software instructions written in a programming language, e.g., C or C++, which may optionally have entry and exit points. Software modules may be compiled and linked into executable programs, installed in dynamically linked libraries, or written in interpreted programming languages, e.g., BASIC, Perl, or Python. It will be understood that software modules may be callable from other modules or from themselves, and / or may be invoked in response to detected events or interrupts. Software instructions may be embedded in firmware, such as erasable programmable read-only memory (EPROM). It will further be understood that hardware modules may include coupled logic units, such as gates and flip-flops, and / or may include programmable units, such as programmable gate arrays, application-specific integrated circuits, and / or processors. The modules described herein may be implemented as software modules, but may also be represented in hardware and / or firmware. Further, in some embodiments, the modules may be separately compiled, while in other embodiments, the modules may represent a subset of instructions of a separately compiled program and may not have an interface available to other logical program units.

[0379] In particular embodiments, the code modules may be embodied in and / or stored on any type of computer-readable medium or other computer storage device. Depending on the system, data (and / or metadata) input to the system, data generated by the system, and / or data utilized by the system may be stored in any type of computer data repository, such as a relational database and / or a flat file system. Any of the systems, methods, and processes described herein may include interfaces configured to enable interaction with users, operators, other systems, components, programs, etc.

[0380] It must be emphasized that many variations and modifications may be made to the embodiments described herein, and that elements thereof should be understood as included in other acceptable examples. Such modifications and modifications are intended to be included herein within the scope of this disclosure and protected by the following claims. Moreover, nothing in the foregoing disclosure is intended to imply that any particular component, feature, or method step is essential or critical.

Claims

1. A combination of articles for use with a humidification device, said combination of articles including at least a humidification chamber and a composite tube; The humidification chamber comprises: a first port extending upward from a top surface of the humidification chamber and defining a first gas flow path, the first port including a first opening configured to receive a sensor; a second port extending upward from a top surface of the humidification chamber and defining a second gas flow path, the second port including a second opening configured to receive a sensor; Equipped with The composite pipe is a first elongate member including a hollow body helically wound to at least partially form an elongate tube having a longitudinal axis; a lumen extending along the longitudinal axis; a second elongate member that is 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 composite tube; Equipped with A combination of articles wherein said composite tube is removably connectable to a first or second port of said humidification chamber.

2. A combination of articles as described in claim 1, wherein the first elongated member has a first portion having a first thickness that defines the lumen and a second portion having a second thickness that defines an outer surface, the first thickness being less than the second thickness.

3. 3. The combination of articles of claim 1 or 2, wherein the humidification chamber is adapted to be connected to a cartridge, the cartridge including a sensor.

4. A combination of articles described in any one of claims 1 to 3, wherein a first barrier and a second barrier are configured to be received or inserted into the first opening and the second opening, respectively, and the first opening is configured to receive a single sensor and the second opening is configured to receive two sensors.

5. 5. The combination of articles of any one of claims 1 to 4, wherein the humidification chamber includes a barrier secured to a wall of one or more of the first and second ports, the barrier hermetically sealing the first or second opening, and at least a portion of the sensor probe removably positioned within the barrier such that the barrier isolates the probe from a gas flow path.

6. 6. The combination of articles of claim 5, wherein said barrier is disposed in each of said first and second ports, whereby said humidification chamber has at least two barriers.

7. 7. The combination of articles of claim 5 or 6, wherein the barrier has a mounting portion located outside the gas flow path.

8. 8. The combination of articles of claim 7, wherein the barrier comprises a region having a first thickness and a region having a second thickness less than the first thickness, the region having the second thickness being located adjacent to a sensing portion of the sensor, and the region having the first thickness being located between the mounting portion and the region having the second thickness.

9. 9. The combination of articles of any one of claims 5 to 8, wherein the barrier has a tip portion adapted to contact a sensitive portion of the sensor, the tip portion having a substantially constant thickness.

10. 10. The combination of articles of any one of claims 5 to 9, wherein the barrier is adapted to stretch as the sensor is inserted into the gas flow path through the opening.

11. 11. The combination of articles of any one of claims 1 to 10, wherein the lumen defines a hollow gas passageway.

12. 12. The combination of articles of any one of claims 1 to 11, wherein the spirally wound and joined first and second elongate members provide crush resistance while being sufficiently flexible to allow bending at a small radius without kinking, obstruction, or indentation.

13. 13. The combination of articles of any one of claims 1 to 12, wherein a portion of the first elongate member overlaps an adjacent turn of the second elongate member.

14. 14. The combination of articles of any one of claims 1 to 13, wherein the second elongate member is solid or solid.

15. 15. The combination of articles of any one of claims 1 to 14, wherein the first elongate member defines, in longitudinal cross section, a plurality of bubbles having flattened surfaces at the lumen.

16. 16. The combination of articles of claim 15, wherein adjacent bubbles are separated by a gap above the second elongate member.

17. 17. The combination of articles of claim 16, wherein the gaps allow for tighter radius bending.

18. 18. The combination of articles of any one of claims 15 to 17, wherein the bubbles have perforations.

19. 19. The combination of articles of any one of claims 1 to 18, wherein the second elongate member has a longitudinal cross-section that is wider proximal to the lumen and narrower radially away from the lumen.

20. 20. The combination of articles of any one of claims 1 to 19, wherein the second elongate member acts as structural support or reinforcement for the first elongate member.

21. 21. The combination of articles of any one of claims 1 to 20, further comprising one or more conductive filaments embedded or encapsulated or encased in said second elongate member.

22. 22. The combination of articles of any one of claims 1 to 21, further comprising a plurality of conductive filaments embedded or encapsulated in the second elongate member, the second elongate member having a generally triangular, T-shaped, or Y-shaped longitudinal cross-section, and at least two of the plurality of conductive filaments embedded or encapsulated on opposite sides of the triangular, T-shaped, or Y-shaped cross-section.

23. 23. The combination of articles of any one of claims 1 to 22, wherein the composite tube is one or more of a medical circuit component, an inspiratory tube, an expiratory tube, a PAP component, an insufflation circuit component, an exploratory component, and a surgical component.

24. A humidifying unit, 24. A combination of articles according to any one of claims 1 to 23, wherein the humidification chamber is removably connectable to the humidification unit; and A humidifying device comprising:

25. 25. The humidification device of claim 24, wherein the humidification unit has one sensor at one end and two sensors at the other end, the sensors configured to extend through openings in the ports.

26. 25. The humidification device of claim 24, further comprising a cartridge removably attached to the humidification unit and having one sensor at one end and two sensors at the other end, the sensors configured to extend through the opening of the port.

27. A humidifier comprising the combination of articles of claim 1.

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