Patent Description:
In medical circuits, various components transport warm and/or humidified gases to and from patients. For example, in some breathing circuits such as PAP or assisted breathing circuits, gases inhaled by a patient are delivered from a heater-humidifier through an inspiratory tube. As another example, tubes can deliver humidified gas (commonly CO<NUM>) into the abdominal cavity in insufflation circuits. This can help prevent "drying out" of the patient's internal organs, and can decrease the amount of time needed for recovery from surgery. Unheated tubing allows significant heat loss to ambient cooling. This cooling may result in unwanted condensation or "rainout" along the length of the tubing transporting warm, humidified air. <CIT> (D1) discloses a tube with heating filaments which are equally spaced along the bore of the tube see D1.

The present disclosure discloses tubing that allows for improved temperature and/or humidity control in medical circuits. Medical tubes and methods of manufacturing medical tubes are disclosed herein. The tube can include a plurality of heating wires and at least one sensor wire. Arrangements are disclosed for reducing the effects of noise on the sensor wire caused by the heating wires. The noise can include undesired capacitance effects between the heating wires and the sensor wire that result in inaccurate sensor measurements. The arrangements can include placing each of at least two heating wires an equal distance from the sensor wire to effectively cancel the capacitance effect. The arrangements can include providing an additional offsetting physical capacitance in the tube arrangement. Other possible arrangements are further disclosed herein to correct for potential inaccuracies.

Although the present disclosure is described mainly with respect to a spirally wound tube structure, it is to be understood that the presently disclosed filament arrangement between heating wires and sensor wires is not limited to the particular tubes disclosed herein, but extends to any tube structures which include heating wires and sensor wires.

A tube for conveying humidified gases to a patient can comprise first and second heating wires traversing at least a portion of the length of the tube; and a sensor wire in electrical communication with a temperature sensor, wherein the first and second heating wires and the sensor wire can be arranged in close proximity within the tube and the first and second heating wires are spaced equal distance from the sensor wire. The first and second heating wires and the sensor wire can be all located along a line on a longitudinal cross-sectional plane of the tube. The first and second heating wires and the sensor wire can be located along a line substantially parallel to a longitudinal axis of the tube in the longitudinal cross-sectional plane of the tube. The first heating wire can be located on a first side of the sensor wire and the second heating wire can be located on a second side of the sensor wire. The tube can further comprise a ground wire. The first and second heating wires can be spaced equal distance from both the sensor wire and the ground wire. The sensor wire can be between the first and second heating wires, and the ground wire can be on an opposite side of the first or second heating wire as the sensor wire. The sensor wire and the ground wire can be between the first and second sensor wires. The sensor wire and the ground wire can be arranged substantially vertically in the longitudinal cross-sectional plane of the tube.

A tube for conveying humidified gases to a patient can comprise first and second heating wires traversing at least a portion of the length of the tube; a sensor wire in electrical communication with a temperature sensor; and a capacitor coupled between one of the first and second heater wires, and the sensor wire, wherein at least one of the first and second heating wires and the sensor wire can be arranged in close proximity within the tube and the capacitor is configured to correct for capacitive coupling between the at least one of the first and second heating wires and the sensor wire. The first and second heating wires and the sensor wire can be all located along a line on a longitudinal cross-sectional plane of the tube. The first heating wire can be located on a first side of the sensor wire and the second heating wire can be located on a second side of the sensor wire. A distance between the first heating wire and the sensor wire can be smaller than a distance between the second heating wire and the sensor wire. The capacitor can be coupled between the second heater wire and the sensor wire. The tube can further comprise a ground wire. The sensor wire can be between the first and second heating wires, and the ground wire can be on an opposite side of the first or second heating wire as the sensor wire. The sensor wire and the ground wire can be between the first and second sensor wires. The sensor wire and the ground wire can be arranged substantially vertically in the longitudinal cross-sectional plane of the tube.

The foregoing tubes can have one, some, or all of the following properties, as well as properties described elsewhere in this disclosure. The tube can have a length of greater than <NUM> meters. The tube can have a length of greater than <NUM> meters. The tube can have a length of greater than <NUM> meters. The tube can have a length of greater than <NUM> meters. The tube can have a length of greater than <NUM> meters.

The foregoing tubes can have one, some, or all of the following properties, as well as properties described elsewhere in this disclosure. The foregoing tubes may be a composite structure made of two or more distinct components that are spirally wound to form an elongate tube. One of the components may be a spirally wound elongate hollow body, and the other component may be an elongate structural component also spirally wound between turns of the spirally wound hollow body. The foregoing tubes need not be made from distinct components. An elongate hollow body formed (for example, extruded) from a single material may be spirally wound to form an elongate tube. The elongate hollow body itself may, in transverse cross-section, have a thin wall portion and a relatively thicker or more rigid reinforcement portion. The tubes can be incorporated into a variety of medical circuits or may be employed for other medical uses.

The foregoing tubes can have one, some, or all of the following properties, as well as properties described elsewhere in this disclosure. The foregoing tubes can be a composite tube comprising a first elongate member comprising a hollow body spirally wound to form at least in part 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 may be spirally wound and joined between adjacent turns of the first elongate member, the second elongate member forming at least a portion of the lumen of the elongate tube. The name "first elongate member" and "second elongate member" do not necessarily connote an order, such as the order in which the components are assembled. As described herein, the first elongate member and the second elongate member can also be portions of a single tube-shaped element.

The foregoing tubes can have one, some, or all of the following properties, as well as properties described elsewhere in this disclosure.

The first elongate member can be a tube. The first elongate member can form, in longitudinal cross-section, a plurality of bubbles. A portion of surfaces of the plurality of bubbles can form the lumen. The bubbles can have a flattened surface at the lumen. Adjacent bubbles can be separated by a gap above the second elongate member, or may not be directly connected to each other. The plurality of bubbles can be adjacent one another without stacking. The plurality of bubbles can be adjacent one another and stacked. The bubbles can have perforations. The second elongate member can have a longitudinal cross-section that is wider proximal the lumen and narrower at a radial distance from the lumen. The second elongate member can have a longitudinal cross-section that is generally triangular, generally T-shaped, or generally Y-shaped. One or more conductive filaments can be embedded or encapsulated in the second elongate member. The one or more conductive filaments can be heating filaments (such as resistance heating filaments) and/or sensing filaments. The one or more conductive filaments embedded or encapsulated in the second elongate member can be one or more of the first heater wire, the second heater wire, the sensor wire, and/or the ground wire. The tube can comprise pairs of conductive filaments, such as two or four conductive filaments. Pairs of conductive filaments can be formed into a connecting loop at one end of the composite tube. The one or more conductive filaments can be spaced from the lumen wall. The second elongate member can have a longitudinal cross-section that is generally triangular, generally T-shaped, or generally Y-shaped, and one or more conductive filaments, such as the one or more of the first heater wire, the second heater wire, the sensor wire, and/or the ground wire can be embedded or encapsulated in the second elongate member on opposite sides of the triangle, T-shape, or Y-shape. The filaments can have specific arrangements to reduce capacitive noise between the filaments as described above. Alternatively, physical capacitors can be included in the tube arrangement to offset capacitive effects as described above. Further, software can be included in a medical device connected to the tube for adjusting measurements due to known capacitive effects.

The foregoing tubes can be incorporated into a medical circuit component, an inspiratory tube, an expiratory tube, a PAP component, an insufflation circuit, an exploratory component, or a surgical component, among other applications.

The foregoing tubes can be manufactured by the following method of manufacturing a composite tube. The resulting tube can have one, some, or all of the properties described above or anywhere in this disclosure. The method can comprise providing a first elongate member comprising a hollow body and a second elongate member configured to provide structural support for the first elongate member. The second elongate member can be spirally wrapped around a mandrel with opposite side edge portions of the second elongate member being spaced apart on adjacent wraps, thereby forming a second-elongate-member spiral. The first elongate member can be spirally wrapped around the second-elongate-member spiral, such that portions of the first elongate member overlap adjacent wraps of the second-elongate-member spiral and a portion of the first elongate member can be disposed adjacent the mandrel in the space between the wraps of the second-elongate-member spiral, thereby forming a first-elongate-member spiral.

The foregoing method can comprise one, some, or all of the following. The method can comprise supplying air at a pressure greater than atmospheric pressure to an end of the first elongate member. The method can comprise cooling the second-elongate-member spiral and the first-elongate-member spiral, thereby forming a composite tube having a lumen extending along a longitudinal axis and a hollow space surrounding the lumen. The method can comprise forming the first elongate member. The method can comprise extruding the first elongate member with a first extruder. The method can comprise forming the second elongate member. The method can comprise extruding the second elongate member with a second extruder. The second extruder can be configured to encapsulate one or more conductive filaments in the second elongate member. Forming the second elongate member can comprise embedding conductive filaments in the second elongate member. The conductive filaments can be non-reactive with the second elongate member. The conductive filaments can comprise alloys of aluminum or copper or other conductive materials. The method can comprise forming pairs of conductive filaments into a connecting loop at one end of the composite tube. The first extruder can be distinct from the second extruder.

The foregoing tubes can have one, some, or all of the following properties, as well as properties described elsewhere in this disclosure. The tube can comprise an elongate hollow body spirally wound to form an elongate tube having a longitudinal axis, a lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen, wherein the elongate hollow body can have, in transverse cross-section, a wall defining at least a portion of the hollow body. The tube can further comprise a reinforcement portion extending along a length of the elongate hollow body being spirally positioned between adjacent turns of the elongate hollow body, wherein the reinforcement portion can form a portion of the lumen of the elongate tube. The reinforcement portion can be relatively thicker or more rigid than the wall of the elongate hollow body.

The foregoing tube can have one, some, or all of the following properties, as well as properties described elsewhere in this disclosure. The reinforcement portion can be formed from the same piece of material as the elongate hollow body. The elongate hollow body in transverse cross-section can comprise two reinforcement portions on opposite sides of the elongate hollow body, wherein spiral winding of the elongate hollow body can join adjacent reinforcement portions to each other such that opposite edges of the reinforcement portions can touch on adjacent turns of the elongate hollow body. Opposite side edges of the reinforcement portions can overlap on adjacent turns of the elongate hollow body. The reinforcement portion can be made of a separate piece of material than the elongate hollow body. The hollow body can form in longitudinal cross-section a plurality of bubbles. A portion of surfaces of the plurality of bubbles can form the lumen. The bubbles can have a flattened surface at the lumen. The bubbles can have perforations. The medical tube can also comprise one or more conductive filaments embedded or encapsulated within the reinforcement portion. The conductive filament can be a heating filament and/or or sensing filament, such as one or more of the first heater wire, the second heater wire, the sensor wire, and/or the ground wire. The medical tube can comprise two conductive filaments, wherein one conductive filament is embedded or encapsulated in each of the reinforcement portions. The medical tube can comprise two or more conductive filaments positioned on only one side of the elongate hollow body. Pairs of conductive filaments can be formed into a connecting loop at one end of the elongate tube. The one or more filaments can be spaced from the lumen wall.

The foregoing tube can be incorporated into a medical circuit component, an inspiratory tube, an expiratory tube, a PAP component, an insufflation circuit, an exploratory component, or a surgical component, among other applications.

The foregoing tubes can be manufactured by the following method of manufacturing a medical tube. The method can comprise spirally winding an elongate hollow body around a mandrel to form an elongate tube having a longitudinal axis, a lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen, wherein the elongate hollow body can have, in transverse cross-section, a wall defining at least a portion of the hollow body and two reinforcement portions on opposite sides of the elongate body forming a portion of the wall of the lumen, the two reinforcement portions being relatively thicker or more rigid than the wall defining at least a portion of the hollow body. The method can further comprise joining adjacent reinforcement portions to each other such that opposite edges of the reinforcement portions can touch on adjacent turns of the elongate hollow body.

The foregoing method can comprise one, some, or all of the following or any other properties described elsewhere in this disclosure. Joining adjacent reinforcement portions to each other can cause edges of the reinforcement portions to overlap. The method can further comprise supplying air at a pressure greater than atmospheric pressure to an end of the elongate hollow body. The method can further comprise cooling the elongate hollow body to join the adjacent reinforcement portions to each other. The method can further comprise extruding the elongate hollow body. The method can further comprise embedding conductive filaments in the reinforcement portions. The method can further comprise forming pairs of conductive filaments into a connecting loop at one end of the elongate tube.

A patient gases supply controller configured to determine a temperature of gases supplied to a patient and adjust a one or more heating elements of a gases supply system can comprise a processor configured to receive information about an arrangement of any of the foregoing tubes. The received information can comprise heater and/or sensor wires arrangements of the tube, and/or capacitive effects between the heater and sensor wires. The processor can be further configured to calibrate sensor measurements, and/or change modes and/or operational parameters based at least in part on the received information. The sensor measurements can comprise temperature measurements.

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 accordance with any particular embodiment of the invention. Thus, the invention may be embodied or carried out 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.

Example embodiments that implement the various features of the disclosed systems and methods will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments and not to limit the scope of the disclosure.

Throughout the drawings, reference numbers are re-used to indicate correspondence between referenced (or similar) elements. In addition, the first digit of each reference number indicates the figure in which the element first appears.

Details regarding several illustrative embodiments for implementing the apparatuses and methods described herein are described below with reference to the figures. The invention is not limited to these described embodiments.

For a more detailed understanding of the disclosure, reference is first made to <FIG>, which shows an example respiratory system including one or more medical tubes. Tube is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art (that is, it is not to be limited to a special or customized meaning) and includes, without limitation, non-cylindrical passageways. A composite tube may generally be defined as a tube comprising two or more portions or components, as described in greater detail below. Such a respiratory system can be a continuous, variable, or bi-level positive airway pressure (PAP) system or other form of respiratory therapy.

Gases can be transported in a gases flow path of <FIG> as follows. Dry gases can pass from a flow generator <NUM>, such as a ventilator or blower, to a humidifier <NUM> via an inlet port. The humidifier <NUM> can humidify the dry gases. The humidifier <NUM> can connect to an inlet <NUM> (the end for receiving humidified gases) of an inspiratory tube <NUM> via a humidifier outlet port <NUM>, thereby supplying humidified gases to the inspiratory tube <NUM>. An inspiratory tube is a tube that is configured to deliver breathing gases to a patient, and may be made from a composite tube or other tubes as described in further detail below. The gases can flow through the inspiratory tube <NUM> to an outlet <NUM> (the end for expelling humidified gases), and then to the patient <NUM> through a patient interface <NUM> connected to the outlet <NUM>.

An expiratory tube <NUM> can also optionally connect to the patient interface <NUM>. An expiratory tube is a tube that is configured to move exhaled humidified gases away from a patient. Here, the expiratory tube <NUM> can return exhaled humidified gases from the patient interface <NUM> to the flow generator <NUM>.

The dry gases enter the flow generator <NUM> through a vent <NUM>. A fan <NUM> can improve the gases flow into the flow generator by drawing air or other gases through vent <NUM>. The fan <NUM> can be, for example, a variable speed fan, where an electronic controller <NUM> can control the fan speed. The function of the electronic controller <NUM> can be controlled by an electronic master controller <NUM> in response to inputs from the master controller <NUM> and/or a user-set predetermined required value (preset value) of pressure and/or fan speed via a dial <NUM>.

The humidifier <NUM> comprises a humidification chamber <NUM> containing a volume of water <NUM> or other suitable humidifying liquid. The humidification chamber <NUM> can be removable from the humidifier <NUM> after use. Removability allows the humidification chamber <NUM> to be more readily sterilized or disposed. However, the humidification chamber <NUM> portion of the humidifier <NUM> can be a unitary construction. The body of the humidification chamber <NUM> can be formed from a non-conductive glass or plastics material. The humidification chamber <NUM> can also include conductive components. The humidification chamber <NUM> can include a heat-conductive base (for example, an aluminum base) contacting or associated with a heater plate <NUM> on the humidifier <NUM>.

The humidifier <NUM> can also include electronic controls. The humidifier <NUM> includes an electronic, analog or digital master controller <NUM>. The master controller <NUM> can be a microprocessor-based controller executing computer software commands stored in associated memory. In response to the user-set humidity and/or temperature value input via a user interface <NUM>, and/or other inputs, the master controller <NUM> can determine when (or to what level) to energize heater plate <NUM> to heat the water <NUM> within humidification chamber <NUM>.

Any suitable patient interface <NUM> can be incorporated. Patient interface is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art (that is, it is not to be limited to a special or customized meaning) and includes, without limitation, masks (such as tracheal mask, face masks and nasal masks), cannulas, and nasal pillows. A temperature sensor <NUM> can connect to the inspiratory tube <NUM> near the patient interface <NUM>, or to the patient interface <NUM>. The temperature sensor <NUM> can monitor the temperature near or at the patient interface <NUM>. A heating filament (not shown) associated with the temperature sensor <NUM> can be used to adjust the temperature of the patient interface <NUM> and/or inspiratory tube <NUM> to raise the temperature of the inspiratory tube <NUM> and/or patient interface <NUM>. The temperature of the patient interface <NUM> and/or inspiratory tube <NUM> can be raised above the saturation temperature, thereby reducing the opportunity for condensation, which can be unwanted and/or undesirable.

In <FIG>, exhaled humidified gases can be returned from the patient interface <NUM> to the flow generator <NUM> via an expiratory tube <NUM>. The expiratory tube <NUM> can also be a composite tube, or other tubes, as described in greater detail below. However, the expiratory tube <NUM> can also be a medical tube. The expiratory tube <NUM> can have a temperature sensor and/or heating element, such as a heater wire, as described above with respect to the inspiratory tube <NUM>. The temperature sensor and/or the heating element can be integrated with the expiratory tube <NUM> to reduce the opportunity for condensation. The expiratory tube <NUM> need not return exhaled gases to the flow generator <NUM>. Exhaled humidified gases can be passed directly to ambient surroundings or to other ancillary equipment, such as an air scrubber/filter. The expiratory tube can be omitted in some breathing circuits.

The medical tube may be a composite structure made of two or more distinct components. The two or more distinct components can be spirally wound to form an elongate tube. One of the components may be a spirally wound elongate hollow body, and the other component may be an elongate structural component also spirally wound between turns of the spirally wound hollow body. The tube also need not be made from distinct components. An elongate hollow body formed (for example, extruded) from a single material may be spirally wound to form an elongate tube. The elongate hollow body itself may, in transverse cross-section, have a thin wall portion and a relatively thicker or more rigid reinforcement portion. The tubes can be incorporated into a variety of medical circuits or may be employed for other medical uses.

A composite tube can comprise a first elongate member comprising a hollow body spirally wound to form at least in part 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 may be spirally wound and joined between adjacent turns of the first elongate member, the second elongate member forming at least a portion of the lumen of the elongate tube. The name "first elongate member" and "second elongate member" do not necessarily connote an order, such as the order in which the components are assembled. As described herein, the first elongate member and the second elongate member can also be portions of a single tube-shaped element.

The composite tube can have one, some, or all of the following properties, as well as properties described elsewhere in this disclosure.

The first elongate member can be a tube. The first elongate member can form, in longitudinal cross-section, a plurality of bubbles with a flattened surface at the lumen. Adjacent bubbles can be separated by a gap above the second elongate member, or may not be directly connected to each other. The bubbles can have perforations. The second elongate member can have a longitudinal cross-section that is wider proximal the lumen and narrower at a radial distance from the lumen. Specifically, the second elongate member can have a longitudinal cross-section that is generally triangular, generally T-shaped, or generally Y-shaped. One or more conductive filaments can be embedded or encapsulated in the second elongate member. The one or more conductive filaments can be heating filaments (or more specifically, resistance heating filaments) and/or sensing filaments. The tube can comprise pairs of conductive filaments, such as two or four conductive filaments. Pairs of conductive filaments can be formed into a connecting loop at one end of the composite tube. The one or more conductive filaments can be spaced from the lumen wall. The second elongate member can have a longitudinal cross-section that is generally triangular, generally T-shaped, or generally Y-shaped, and one or more conductive filaments can be embedded or encapsulated in the second elongate member on opposite sides of the triangle, T-shape, or Y-shape. The filaments can have specific arrangements to reduce capacitive noise between the filaments. Physical capacitors can also be included in the tube arrangement to offset capacitive effects. Further, software can be included in a medical device connected to the tube for adjusting measurements due to known capacitive effects.

The composite tube described herein can be incorporated into a medical circuit component, an inspiratory tube, an expiratory tube, a PAP component, an insufflation circuit, an exploratory component, or a surgical component, among other applications.

<FIG> shows a side-plan view of a section of example composite tube <NUM>. The composite tube <NUM> can comprise a first elongate member <NUM> and a second elongate member <NUM>. Member is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art, which is not to be limited to a special or customized meaning, and includes, without limitation, integral portions, integral components, and distinct components. Thus, although <FIG> illustrates an example tube made of two distinct components, the first elongate member <NUM> and second elongate member <NUM> can also represent regions in a tube formed from a single material (such as described in <FIG> below). The first elongate member <NUM> can represent a hollow portion of a tube, while the second elongate member <NUM> can represent a structural supporting or reinforcement portion of the tube which adds structural support to the hollow portion. The hollow portion and the structural supporting portion can have a spiral configuration, as described herein. The composite tube <NUM> may be used to form the inspiratory tube <NUM> and/or the expiratory tube <NUM> as described above, a coaxial tube as described below, or any other tubes as described elsewhere in this disclosure.

As shown in <FIG>, the first elongate member <NUM> comprises a hollow body spirally wound to form, at least in part, an elongate tube <NUM> having a longitudinal axis LA-LA. The tube <NUM> can have a lumen <NUM> extending along the longitudinal axis LA-LA. The first elongate member <NUM> can be a hollow tube. The first elongate member <NUM> can be flexible. The first elongate member <NUM> can be transparent or, at least, semi-transparent or semi-opaque. A degree of optical transparency allows a caregiver or user to inspect the lumen <NUM> for blockage and/or contaminants, and/or to confirm the presence of moisture. A variety of plastics, including medical grade plastics, are suitable for the body of the first elongate member <NUM>. Examples of suitable materials include Polyolefin elastomers, Polyether block amides, Thermoplastic co-polyester elastomers, EPDM-Polypropylene mixtures, Thermoplastic polyurethanes, and the like.

The hollow body structure of the first elongate member <NUM> can contribute to the insulating properties to the composite tube <NUM>. An insulating tube, such as the tube <NUM>, is desirable because, as explained above, it prevents heat loss. This can allow the tube <NUM> to deliver gas from a humidifier to a patient while maintaining the gas's conditioned state, such as temperature and/or humidity, with minimal energy consumption.

The hollow portion of the first elongate member <NUM> can be filled with a gas. The gas can be air, which is desirable because of its low thermal conductivity (<NUM>×<NUM>-<NUM> W/m·K at <NUM>) and very low cost. A gas that is more viscous than air may also advantageously be used, as higher viscosity reduces convective heat transfer. Thus, gases such as argon (<NUM>×<NUM>-<NUM> W/m·K at <NUM>), krypton (<NUM>×<NUM>-<NUM> W/m·K at <NUM>), and xenon (<NUM>×<NUM>-<NUM> W/ m·K at <NUM>) can increase insulating performance. Each of these gases is non-toxic, chemically inert, fire-inhibiting, and/or commercially available. The hollow portion of the first elongated member <NUM> can be sealed at both ends of the tube, causing the gas within to be substantially stagnant. The hollow portion can also function as a secondary pneumatic connection, such as a pressure sample line for conveying pressure feedback from the patient-end of the tube <NUM> to a controller. The first elongate member <NUM> can be optionally perforated. The surface of the first elongate member <NUM> can be perforated on an outward-facing surface, opposite the lumen <NUM>. The hollow portion of the first elongate member <NUM> can also be filled with a liquid. Examples of liquids can include water or other biocompatible liquids with a high thermal capacity. Nanofluids can also be used. An example nanofluid with suitable thermal capacity comprises water and nanoparticles of substances such as aluminum.

The second elongate member <NUM> can also be spirally wound. The second elongate member <NUM> can be joined to the first elongate member <NUM> between adjacent turns of the first elongate member <NUM>. The second elongate member <NUM> can form at least a portion of the lumen <NUM> of the elongate tube <NUM>. The second elongate member <NUM> can act as structural support for the first elongate member <NUM>.

The second elongate member <NUM> can be wider at the base (proximate the lumen <NUM>) and narrower at the top (radially further away from the lumen <NUM>). For example, the second elongate member can be generally triangular in shape, generally T-shaped, or generally Y-shaped. However, any shape that meets the contours of the corresponding first elongate member <NUM> is suitable.

The second elongate member <NUM> can be flexible, to facilitate bending of the tube <NUM>. The second elongate member <NUM> can be less flexible than the first elongate member <NUM>. This improves the ability of the second elongate member <NUM> to structurally support the first elongate member <NUM>. The modulus of the second elongate member <NUM> can be <NUM> - 50MPa (or about <NUM> - <NUM> MPa). The modulus of the first elongate member <NUM> can be less than the modulus of the second elongate member <NUM>. The second elongate member <NUM> can be solid or mostly solid. In addition, the second elongate member <NUM> can encapsulate or house conductive material, such as filaments including but not limited to heating filaments or sensor signal wires. Heating filaments can minimize the cold surfaces onto which condensate from moisture-laden air can form. Heating filaments can also be used to alter the temperature profile of gases in the lumen <NUM> of composite tube <NUM>.

A variety of polymers and plastics, including medical grade plastics, are suitable for the body of the second elongate member <NUM>. Examples of suitable materials include Polyolefin elastomers, Polyether block amides, Thermoplastic co-polyester elastomers, EPDM-Polypropylene mixtures, Thermoplastic polyurethanes, and the like. The first elongate member <NUM> and the second elongate member <NUM> may be made from the same material. The second elongate member <NUM> may also be made of a different color material from the first elongate member <NUM>, and may be transparent, translucent or opaque. The first elongate member <NUM> may be made from a clear plastic, and the second elongate member <NUM> may be made from an opaque blue (or other colored) plastic.

This spirally-wound structure comprising a flexible, hollow body and an integral support can provide crush resistance, while leaving the tube wall flexible enough to permit short-radius bends without kinking, occluding and/or collapsing. The tube can be bent around a <NUM> diameter metal cylinder without kinking, occluding, and/or collapsing, as defined in the test for increase in flow resistance with bending according to ISO <NUM>:<NUM>(E). This structure also can provide a smooth lumen <NUM> surface (tube bore), which helps keep the tube free from deposits and improves gases flow. The hollow body has been found to improve the insulating properties of a tube, while allowing the tube to remain light weight.

As explained above, the composite tube <NUM> can be used as an expiratory tube and/or an inspiratory tube in a breathing circuit, or a portion of a breathing circuit. The composite tube <NUM> is used at least as an inspiratory tube in some breathing circuits.

<FIG> shows a longitudinal cross-section of a top portion of the example composite tube <NUM> of <FIG>. <FIG> has the same orientation as <FIG>. This example further illustrates the hollow-body shape of the first elongate member <NUM>. As seen in this example, the first elongate member <NUM> forms in longitudinal cross-section a plurality of hollow bubbles. Portions <NUM> of the first elongate member <NUM> overlap adjacent wraps of the second elongate member <NUM>. A portion <NUM> of the first elongate member <NUM> forms the wall of the lumen (tube bore). A portion of the second elongate member <NUM> forms the wall of the lumen with the portion <NUM> of the first elongate member <NUM>.

It was discovered that having a gap <NUM> between adjacent turns of the first elongate member <NUM>, that is, between adjacent bubbles, unexpectedly improved the overall insulating properties of the composite tube <NUM>. Thus, adjacent bubbles can be separated by a gap <NUM>. Providing a gap <NUM> between adjacent bubbles can increase the heat transfer resistivity (the R value) and, accordingly, can decrease the heat transfer conductivity of the composite tube <NUM>. This gap configuration can also improve the flexibility of the composite tube <NUM> by permitting shorter-radius bends. A T-shaped second elongate member <NUM>, as shown in <FIG>, can help maintain a gap <NUM> between adjacent bubbles. Adjacent bubbles can also be touching. For example, adjacent bubbles can be bonded together.

One or more conductive materials can be disposed in the second elongate member <NUM> for heating or sensing the gases flow. As shown in <FIG>, two heating filaments <NUM> are encapsulated in the second elongate member <NUM>. The two heating filaments <NUM> can each be on either side of the vertical portion of the "T. " The heating filaments <NUM> comprise conductive material, such as alloys of Aluminum (Al) and/or Copper (Cu), or conductive polymer. The material forming the second elongate member <NUM> can be selected to be non-reactive with the metal in the heating filaments <NUM> when the heating filaments <NUM> reach their operating temperature. The filaments <NUM> may be spaced away from the lumen <NUM> so that the filaments <NUM> are not exposed to the lumen <NUM>. At one end of the composite tube <NUM>, pairs of filaments can be formed into a connecting loop.

A plurality of filaments can be disposed in the second elongate member <NUM>. The filaments can be electrically connected together to share a common rail. For example, a first filament, such as a heating filament, can be disposed on a first side of the second elongate member <NUM>. A second filament, such as a sensing filament, can be disposed on a second side of the second elongate member <NUM>. A third filament, such as a ground filament, can be disposed between the first and second filaments. The first, second, and/or third filaments can be connected together at one end of the second elongate member <NUM>.

<FIG> shows a longitudinal cross-section of the bubbles in <FIG>. As shown, the portions <NUM> of the first elongate member <NUM> overlapping adjacent wraps of the second elongate member <NUM> are characterized by a bond region <NUM>. A larger bond region improves the tubes resistance to delamination at the interface of the first and second elongate members. Additionally or alternatively, the shape of the cross section of the second elongate member <NUM> (hereinafter referred to as a "bead") and/or the bubble can be adapted to increase the bond region <NUM>. For example, <FIG> shows a relatively small bonding area on the left-hand side. <FIG> also demonstrates a smaller bonding region. In contrast, <FIG> shows a larger bonding region than that shown in <FIG>, because of the size and shape of the bead. <FIG> and <FIG> also illustrate a larger bonding region. Each of these figures is discussed in more detail below. It should be appreciated that although the configurations in <FIG>, <FIG>, and <FIG> may be utilized, other configurations, including those of <FIG>, <FIG>, and other variations, may also be utilized as may be desired.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> has the same orientation as <FIG>. This example further illustrates the hollow-body shape of the first elongate member <NUM> and demonstrates how the first elongate member <NUM> forms in longitudinal cross-section a plurality of hollow bubbles. In this example, the bubbles are completely separated from each other by a gap <NUM>. A generally triangular second elongate member <NUM> supports the first elongate member <NUM>.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> has the same orientation as <FIG>. In the example of <FIG>, the heating filaments <NUM> are spaced farther apart from each other than the filaments <NUM> in <FIG>. It was discovered that increasing the space between heating filaments can improve heating efficiency. Heating efficiency refers to the ratio of the amount of heat input to the tube to the amount of energy output or recoverable from the tube. Generally speaking, the greater the energy (or heat) that is dissipated from the tube, the lower the heating efficiency. For improved heating performance, the heating filaments <NUM> can be equally (or about equally) spaced along the bore of the tube. Alternatively, the filaments <NUM> can be positioned at extremities of the second elongate member <NUM>, which may provide simpler manufacturing.

Reference is next made to <FIG> which demonstrate example configurations for the second elongate member <NUM>. <FIG> shows a cross-section of a second elongate member <NUM> having a shape similar to the T-shape shown in <FIG>. As shown in <FIG>, the second elongate member <NUM> does not have heating filaments. Other shapes for the second elongate member <NUM> may also be utilized, including variations of the T-shape as described below and triangular shapes.

<FIG> shows another example second elongate member <NUM> having a T-shape cross-section. In this example, heating filaments <NUM> are embedded in grooves <NUM> in the second elongate member <NUM> on either side of the vertical portion of the "T. " The grooves <NUM> can be formed in the second elongate member <NUM> during extrusion. The grooves <NUM> can alternatively be formed in the second elongate member <NUM> after extrusion. A cutting tool can form the cuts in the second elongate member <NUM>. The grooves <NUM> can also be formed by the heating filaments <NUM> as the heating filaments <NUM> are pressed or pulled (mechanically fixed) into the second elongate member <NUM> shortly after extrusion, while the second elongate member <NUM> is relatively soft. Alternatively, one or more heating filaments <NUM> can be mounted (for example, adhered, bonded, or partially embedded) on the base of the second elongate member <NUM>, such that the filament(s) are exposed to the tube lumen. It can be desirable to contain the exposed filament(s) in insulation to reduce the risk of fire when a flammable gas such as oxygen is passed through the tube lumen.

<FIG> shows yet another example second elongate member <NUM> in cross-section. The second elongate member <NUM> has a generally triangular shape. In this example, heating filaments <NUM> are embedded on opposite sides of the triangle.

<FIG> shows yet another example second elongate member <NUM> in cross-section. The second elongate member <NUM> comprises four grooves <NUM>. The grooves <NUM> are indentations or furrows in the cross-sectional profile. The grooves <NUM> can facilitate the formation of cuts (not shown) for embedding filaments. The grooves <NUM> can facilitate the positioning of filaments, which are pressed or pulled into, and thereby embedded in, the second elongate member <NUM>. In this example, the four initiation grooves <NUM> can facilitate placement of up to four filaments. The four filaments can be 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. The heating filaments can also be located on the outside of the second elongate member <NUM>. The sensing filaments can be located on the inside of the second elongate member <NUM>.

<FIG> shows still another example second elongate member <NUM> in cross-section. The second elongate member <NUM> has a T-shape profile and a plurality of grooves <NUM> for placing heating filaments.

<FIG> shows yet another example second elongate member <NUM> in cross-section. Four filaments <NUM> are encapsulated in the second elongate member <NUM>, two on either side of the vertical portion of the "T. " As explained in more detail below, the filaments <NUM> can be encapsulated in the second elongate member <NUM> because the second elongate member <NUM> was extruded around the filaments. No cuts may be formed to embed the heating filaments <NUM>. As shown in <FIG>, the second elongate member <NUM> also comprises a plurality of grooves <NUM>. Because the heating filaments <NUM> are encapsulated in the second elongate member <NUM>, the grooves <NUM> are not used to facilitate formation of cuts for embedding heating filaments. The grooves <NUM> can facilitate separation of the embedded heating filaments <NUM>, which makes stripping of individual cores easier when, for example, terminating the heating filaments.

<FIG> shows yet another example second elongate member <NUM> in cross-section. The second elongate member <NUM> has a generally triangular shape. In this example, the shape of the second elongate member <NUM> is similar to that of <FIG>, but four filaments <NUM> are encapsulated in the second elongate member <NUM>. All of the filaments <NUM> can be centrally located in about the bottom third of the second elongate member <NUM>. The filaments <NUM> can be disposed along a generally horizontal axis.

As explained above, it can be desirable to increase the distance between filaments to improve heating efficiency. However, when heating filaments <NUM> are incorporated into the composite tube <NUM>, the filaments <NUM> can also be positioned relatively central in the second elongate member <NUM>. A centralized position promotes robustness of the composite tubing for reuse, due in part to the position reducing the likelihood of the filament breaking upon repeating flexing of the composite tube <NUM>. Centralizing the filaments <NUM> can also reduce the risk of an ignition hazard because the filaments <NUM> are coated in layers of insulation and removed from the gases flow path.

As explained above, some of the examples illustrate suitable placements of filaments <NUM> in the second elongate member <NUM>. In the foregoing examples comprising more than one filament <NUM>, the filaments <NUM> are generally aligned along a horizontal axis. Alternative configurations are also suitable. For example, two filaments can be aligned along a vertical axis or along a diagonal axis. Four filaments can be aligned along a vertical axis or a diagonal axis. Four filaments can be aligned in a cross-shaped 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 tube lumen), and two filaments disposed on opposite arms of a "T," "Y," or triangle base.

TABLES 1A and 1B show some example dimensions of medical tubes described herein, as well as some example ranges for these dimensions. The dimensions refer to a transverse cross-section of a tube. In these tables, lumen diameter represents the inner diameter of a tube. Pitch represents the distance between two repeating points measured axially along the tube, namely, the distance between the tip of the vertical portions of adjacent "T"s of the second elongate member. Bubble width represents the width (maximum outer diameter) of a bubble. Bubble height represents the height of a bubble from the tube lumen. Bead height represents the maximum height of the second elongate member from the tube lumen (for example, the height of the vertical portion of the "T"). Bead width represents the maximum width of the second elongate member (for example, the width of the horizontal portion of the "T"). Bubble thickness represents the thickness of the bubble wall.

TABLES 2A and 2B provide example ratios between the dimensions of tube features for the tubes described in TABLES 1A and 1B respectively.

The following tables show some example properties of a composite tube (labeled "A"), described herein, having a heating filament integrated inside the second elongate member. For comparison, properties of a Fisher & Paykel model RT100 disposable corrugated tube (labeled "B") having a heating filament helically wound inside the bore of the tube are also presented.

Measurement of resistance to flow (RTF) was carried out according to Annex A of ISO <NUM>:<NUM>(E). The results are summarized in TABLE <NUM>. As seen below, the RTF for the composite tube is lower than the RTF for the model RT100 tube.

Condensate or "rainout" within the tube refers to the weight of condensate collected per day at <NUM>/min gases flow rate and room temperature of <NUM>. Humidified air is flowed through the tube continuously from a chamber. The tube weights are recorded before and after each day of testing. Three consecutive tests are carried out with the tube being dried in between each test. The results are shown below in TABLE <NUM>. The results showed that rainout is significantly lower in the composite tube than in the model RT100 tube.

The power requirement refers to the power consumed during the condensate test. In this test, the ambient air was held at <NUM>. Humidification chambers (see, for example, the humidification chamber <NUM> in <FIG>) were powered by MR850 heater bases. The heating filaments in the tubes were powered independently from a DC power supply. Different flow rates were set and the chamber was left to settle to <NUM> at the chamber output. Then, the DC voltage to the circuits was altered to produce a temperature of <NUM> at the circuit output. The voltage required to maintain the output temperature was recorded and the resulting power calculated. The results are shown in TABLE <NUM>. 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 <NUM> to <NUM>. The composite tube does not tend to heat gas quickly because the heating filament is in the wall of the tube (embedded in the second elongate member). Instead, the composite tube is designed to maintain the gas temperature and prevent rainout by maintaining the tube bore at a temperature above the dew point of the humidified gas.

Tube flexibility was tested by using a three-point bend test. Tubes were placed in a three point bend test jig and used along with an Instron <NUM> Test System instrument, to measure load and extension. Each tube sample was tested three times; measuring the extension of the tube against the applied load, to obtain average respective stiffness constants. The average stiffness constants for Tube A and Tube B are reproduced in TABLE <NUM>.

A method of manufacturing a composite tube is also disclosed. The resulting tube can have one, some, or all of the properties described above or anywhere in this disclosure. The method can comprise providing a first elongate member including a hollow body and a second elongate member configured to provide structural support for the first elongate member. The second elongate member can be spirally wrapped around a mandrel with opposite side edge portions of the second elongate member being spaced apart on adjacent wraps, thereby forming a second-elongate-member spiral. The first elongate member can be spirally wrapped around the second-elongate-member spiral, such that portions of the first elongate member can overlap adjacent wraps of the second-elongate-member spiral and a portion of the first elongate member can be disposed adjacent the mandrel in the space between the wraps of the second-elongate-member spiral, thereby forming a first-elongate-member spiral.

The foregoing method can also comprise one, some, or all of the following. The method can comprise supplying air at a pressure greater than atmospheric pressure to an end of the first elongate member. The method can comprise cooling the second-elongate-member spiral and the first-elongate-member spiral, thereby forming a composite tube having a lumen extending along a longitudinal axis and a hollow space surrounding the lumen. The method can comprise forming the first elongate member. The method can comprise extruding the first elongate member with a first extruder. The method can comprise forming the second elongate member. The method can comprise extruding the second elongate member with a second extruder. The second extruder can be configured to encapsulate one or more conductive filaments in the second elongate member. Forming the second elongate member can comprise embedding conductive filaments in the second elongate member. The conductive filaments can be non-reactive with the second elongate member. The conductive filaments can comprise alloys of aluminum or copper or other conductive materials. The method can comprise forming pairs of conductive filaments into a connecting loop at one end of the composite tube. The first extruder can be distinct from the second extruder.

Reference is next made to <FIG> which demonstrate example methods for manufacturing composite tubes.

Turning first to <FIG>, a method of manufacturing a composite tube can comprise providing the second elongate member <NUM> and spirally wrapping the second elongate member <NUM> around a mandrel <NUM> with opposite side edge portions <NUM> of the second elongate member <NUM> being spaced apart on adjacent wraps, thereby forming a second-elongate-member spiral <NUM>. The second elongate member <NUM> may be directly wrapped around the mandrel or around a sacrificial layer provided over the mandrel.

The method can further comprise forming the second elongate member <NUM>. Extrusion can be used for forming the second elongate member <NUM>. The extruder can be configured to extrude the second elongate member <NUM> with a specified bead height. Thus, the method can comprise extruding the second elongate member <NUM>.

As shown in <FIG>, extrusion can be advantageous because it can allow heating filaments <NUM> to be encapsulated in the second elongate member <NUM> as the second elongate member is formed <NUM>, for example, using an extruder having a cross-head extrusion die. The method can comprise providing one or more heating filaments <NUM> and encapsulating the heating filaments <NUM> to form the second elongate member <NUM>. The method can also comprise providing a second elongate member <NUM> having one or more heating filaments <NUM> embedded or encapsulated in the second elongate member <NUM>.

The method can comprise embedding one or more filaments <NUM> in the second elongate member <NUM>. For example, as shown in <FIG>, filaments <NUM> can be pressed (pulled or mechanically positioned) into the second elongate member <NUM> to a specified depth. Alternatively, cuts can be made in the second elongate member <NUM> to a specified depth, and the filaments <NUM> can be placed into the cuts. Pressing or cutting can be done shortly after the second elongate member <NUM> is extruded and when the second elongate member <NUM> is soft.

As shown in <FIG> and <FIG>, the method comprises providing the first elongate member <NUM> and spirally wrapping the first elongate member <NUM> around the second-elongate-member spiral <NUM>. Portions of the first elongate member <NUM> can overlap adjacent wraps of the second-elongate-member spiral <NUM> and a portion of the first elongate member <NUM> can be disposed adjacent the mandrel <NUM> in the space between the wraps of the second-elongate-member spiral <NUM>, thereby forming a first-elongate-member spiral <NUM>. <FIG> shows such an example method, in which heating filaments <NUM> are encapsulated in the second elongate member <NUM>, prior to forming the second-elongate-member spiral. <FIG> shows such an example method, in which heating filaments <NUM> are embedded in the second elongate member <NUM>, as the second-elongate-member spiral is formed. An alternative method of incorporating filaments <NUM> into the composite tube comprises encapsulating one or more filaments <NUM> between the first elongate member <NUM> and the second elongate member <NUM> at a region where the first elongate member <NUM> overlaps the second elongate member <NUM>.

The above-described alternatives for incorporating one or more heating filaments <NUM> into a composite tube have advantages over the alternative of having heating filaments in the gases flow path. Having the heating filament(s) <NUM> out of the gases flow path can improve performance because the filaments heat the tube wall where the condensation is most likely to form. This configuration can also reduce fire risk in high oxygen environments by moving the heating filament out of the gases flow path. Although this feature may reduce the heating wires effectiveness at heating the gases that are passing through the tube, a composite tube <NUM> can also comprises one or more heating filaments <NUM> placed within the gases flow path. For example, heating filaments can be emplaced on the lumen wall (tube bore), for example, in a spiral configuration. An example method for disposing one or more heating filaments <NUM> on the lumen wall can comprise bonding, embedding, or otherwise forming a heating filament on a surface of the second elongate member <NUM> that, when assembled, forms the lumen wall. Thus, the method can also comprise disposing one or more heating filaments <NUM> on the lumen wall.

Regardless of whether the heating filaments <NUM> are embedded or encapsulated on the second elongate member <NUM> or disposed on the second elongate member <NUM>, or otherwise placed in or on the tube, pairs of filaments can be formed into a connecting loop at one end of the composite tube to form a circuit.

<FIG> shows a longitudinal cross-section of the assembly shown in <FIG>, focusing on a top portion of the mandrel <NUM> and a top portion of the first-elongate-member spiral <NUM> and second-elongate-member spiral <NUM>. This example shows the second-elongate-member spiral <NUM> having a T-shaped second elongate member <NUM>. As the second-elongate member <NUM> is formed, heating filaments <NUM> are embedded in the second elongate member <NUM>. The right side of <FIG> shows the bubble-shaped profile of the first-elongate-member spiral <NUM>, as described above.

The method can also comprise forming the first elongate member <NUM>. Extrusion can be used for forming the first elongate member <NUM>. Thus, the method can comprise extruding the first elongate member <NUM>. The first elongate member <NUM> can also be manufactured by extruding two or more portions and joining them to form a single piece. As another alternative, the first elongate member <NUM> can also be manufactured by extruding sections that produce a hollow shape when formed or bonded adjacently on a spiral-tube forming process.

The method can also comprise supplying a gas at a pressure greater than atmospheric pressure to an end of the first elongate member <NUM>. The gas can be air, for example. Other gases can also be used, as explained above. Supplying a gas to an end of the first elongate member <NUM> can help maintain an open, hollow body shape as the first elongate member <NUM> is wrapped around the mandrel <NUM>. The gas can be supplied before the first elongate member <NUM> is wrapped around the mandrel <NUM>, while the first elongate member <NUM> is wrapped around the mandrel <NUM>, or after the first elongate member <NUM> is wrapped around the mandrel <NUM>. For instance, an extruder with an extrusion die head/tip combination can supply or feed air into the hollow cavity of the first elongate member <NUM> as the first elongate member <NUM> is extruded. Thus, the method can comprise extruding the first elongate member <NUM> and supplying a gas at a pressure greater than atmospheric pressure to an end of the first elongate member <NUM> after extrusion. A pressure of <NUM> to <NUM> H<NUM>O (or about <NUM> to <NUM> H<NUM>O) can be used to supply the gas.

The first elongate member <NUM> and the second elongate member <NUM> can be spirally wound about the mandrel <NUM>. For example, the first elongate member <NUM> and second elongate member <NUM> may come out of an extrusion die at an elevated temperature of <NUM> (or about <NUM>) or more and then be applied to the mandrel after a short distance. The mandrel can be cooled using a water jacket, chiller, and/or other suitable cooling method to a temperature of <NUM> (or about <NUM>) or less, for example, approaching <NUM> (or about <NUM>). After <NUM> (or about <NUM>) spiral wraps, the first elongate member <NUM> and second elongate member <NUM> can be further cooled by a cooling fluid (liquid or gas). The cooling fluid can be air emitted from a ring with jets encircling the mandrel. After cooling and removing the components from the mandrel, a composite tube is formed having a lumen extending along a longitudinal axis and a hollow space surrounding the lumen. No adhesive or other attachment mechanism is needed to connect the first and second elongate members. An adhesive or other attachment mechanism can also be utilized to bond or otherwise connect the two members. The second elongate member <NUM> after extrusion and placement of the heating filaments may be cooled to freeze the location of the heating filaments. The second elongate member <NUM> may then be re-heated when applied to the mandrel to improve bonding. Example methods for re-heating include using spot-heating devices, heated rollers, or others.

The method can also comprise formed pairs of heating or sensing filaments into a connecting loop at one end of the composite tube. For example, end sections of two heating or sensing filaments can be extricated from the second elongate member <NUM> and then formed into a connecting loop, for example, by tying, bonding, adhering, fusing, or otherwise, the two filaments together. As another example, end sections of the heating filaments can be left free from the second elongate member <NUM> during the manufacturing process and then formed into a connecting loop when the composite tube is assembled.

A medical tube can comprise an elongate hollow body spirally wound to form an elongate tube having a longitudinal axis, a lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen, wherein the elongate hollow body can have in transverse cross-section a wall defining at least a portion of the hollow body. The tube can further comprise a reinforcement portion extending along a length of the elongate hollow body being spirally positioned between adjacent turns of the elongate hollow body, wherein the reinforcement portion can form a portion of the lumen of the elongate tube. The reinforcement portion can be relatively thicker or more rigid than the wall of the elongate hollow body.

The medical tube can also have one, some, or all of the following properties, as well as properties described elsewhere in this disclosure. The reinforcement portion can be formed from the same piece of material as the elongate hollow body. The elongate hollow body in transverse cross-section can comprise two reinforcement portions on opposite sides of the elongate hollow body, wherein spiral winding of the elongate hollow body can join adjacent reinforcement portions to each other such that opposite edges of the reinforcement portions touch on adjacent turns of the elongate hollow body. Opposite side edges of the reinforcement portions can overlap on adjacent turns of the elongate hollow body. The reinforcement portion can be made of a separate piece of material than the elongate hollow body. The hollow body can form in longitudinal cross-section a plurality of bubbles with a flattened surface at the lumen. The bubbles can have perforations. The medical tube can also comprise one or more conductive filaments embedded or encapsulated within the reinforcement portion. The conductive filament can be a heating filament and/or or sensing filament. The medical tube can comprise two conductive filaments, wherein one conductive filament is embedded or encapsulated in each of the reinforcement portions. The medical tube can comprise two or more conductive filaments positioned on only one side of the elongate hollow body. Pairs of conductive filaments can be formed into a connecting loop at one end of the elongate tube. The one or more filaments can be spaced from the lumen wall.

The medical tube described herein can be incorporated into a medical circuit component, an inspiratory tube, an expiratory tube, a PAP component, an insufflation circuit, an exploratory component, or a surgical component, among other applications.

Reference is next made to <FIG> which show transverse cross-sections of tubes comprising a single tube-shaped element having a first elongate member or portion <NUM> and a reinforcement portion 205A. As illustrated, the reinforcement portions 205A are integral with the first elongate portions <NUM>, and can extend along the entire length of the single tube-shaped element. The single tube-shaped element can be an elongate hollow body having in transverse cross-section a relatively thin wall defining in part the hollow portion <NUM>, with two reinforcement portions 205A with a relatively greater thickness or relatively greater rigidity on opposite sides of the elongate hollow body adjacent the relatively thin wall. These reinforcement portions form a portion of the inner wall of the lumen <NUM> after the elongate hollow body is spirally wound, such that these reinforcement portions are also spirally positioned between adjacent turns of the elongate hollow body.

The method can comprise forming an elongate hollow body comprising the first elongate portion <NUM> and the reinforcement portion 205A. Extrusion can be used for forming the elongate hollow body. Example cross-sectional shapes for the tube-shaped element are shown in <FIG>.

The elongate hollow body can be formed into a medical tube, as explained above, and the foregoing discussion is incorporated by this reference.

A method of manufacturing a medical tube can comprise spirally winding an elongate hollow body around a mandrel to form an elongate tube having a longitudinal axis, a lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen, wherein the elongate hollow body can have in transverse cross-section a wall defining at least a portion of the hollow body and two reinforcement portions on opposite sides of the elongate body forming a portion of the wall of the lumen, the two reinforcement portions being relatively thicker or more rigid than the wall defining at least a portion of the hollow body. The method can further comprise joining adjacent reinforcement portions to each other such that opposite edges of the reinforcement portions touch on adjacent turns of the elongate hollow body.

The foregoing method can also comprise one, some, or all of the following or any other properties described elsewhere in this disclosure. Joining adjacent reinforcement portions to each other can cause edges of the reinforcement portions to overlap. The method can further comprise supplying air at a pressure greater than atmospheric pressure to an end of the elongate hollow body. The method can further comprise cooling the elongate hollow body to join the adjacent reinforcement portions to each other. The method can further comprise extruding the elongate hollow body. The method can further comprise embedding conductive filaments in the reinforcement portions. The method can further comprise forming pairs of conductive filaments into a connecting loop at one end of the elongate tube.

For example, a method of manufacturing a medical tube can comprise spirally wrapping or winding the elongate hollow body around a mandrel. This may be done at an elevated temperature, such that the elongate hollow body is cooled after being spirally wound to join adjacent turns together. As shown in <FIG>, opposite side edge portions of the reinforcement portions 205A can touch on adjacent turns. Opposite side edge portions of the reinforcement portions <NUM> A can also overlap on adjacent turns, as shown in <FIG>. Heating filaments <NUM> can be incorporated into the reinforcement portions 205A as explained above and as shown in <FIG>. For example, heating filaments may be provided on opposite sides of the elongate hollow portion such as shown in <FIG>. Alternatively, heating filaments may be provided on only one side of the elongate hollow portion, such as shown in <FIG>. Any of these features can also incorporate the presence of sensing filaments.

Reference is next made to <FIG>, which shows an example medical circuit. The circuit comprises one or more composite tubes as described above, namely for the inspiratory tube <NUM> and/or the expiratory tube <NUM>. The properties of the inspiratory tube <NUM> and the expiratory tube <NUM> are similar to the tubes described above with respect to <FIG>. The inspiratory tube <NUM> has an inlet <NUM>, communicating with a humidifier <NUM>, and an outlet <NUM>, through which humidified gases are provided to the patient <NUM>. The expiratory tube <NUM> also has an inlet <NUM>, which receives exhaled humidified gases from the patient, and an outlet <NUM>. As described above with respect to <FIG>, the outlet <NUM> of the expiratory tube <NUM> can vent exhaled gases to the atmosphere, to the ventilator/blower unit <NUM>, to an air scrubber/filter, or to any other location.

As described above, heating filaments <NUM> can be placed within the inspiratory tube <NUM> and/or the expiratory tube <NUM> to reduce the risk of rain out in the tubes by maintaining the tube wall temperature above the dew point temperature.

Laparoscopic surgery, also called minimally invasive surgery (MIS), or keyhole surgery, is a modern surgical technique. In laparoscopic surgeries, operations in the abdomen are performed through small incisions (usually <NUM> to <NUM>) as compared to larger incisions needed in traditional surgical procedures. Laparoscopic surgery includes operations within the abdominal or pelvic cavities. During laparoscopic surgery with insufflation, it may be desirable for the insufflation gas (commonly CO<NUM>) to be humidified before being passed into the abdominal cavity. This can help prevent "drying out" of the patient's internal organs, and can decrease the amount of time needed for recovery from surgery. Insufflation systems generally comprise humidifier chambers that hold a quantity of water within them. The humidifier generally includes a heater plate that heats the water to create a water vapour that is transmitted into the incoming gases to humidify the gases. The gases are transported out of the humidifier with the water vapor.

Reference is next made to <FIG>, which shows an insufflation system <NUM>. The insufflation system <NUM> includes an insufflator <NUM> that produces a stream of insufflation gases at a pressure above atmospheric for delivery into the patient's <NUM> abdominal or peritoneal cavity. The gases pass into a humidifier <NUM>, which includes a heater base <NUM> and humidifier chamber <NUM>. In use, the chamber <NUM> is in contact with the heater base <NUM> so that the heater base <NUM> provides heat to the chamber <NUM>. In the humidifier <NUM>, the insufflation gases are passed through the chamber <NUM> so that the gases become humidified to an appropriate level of moisture for delivery to the patient.

The system <NUM> includes a delivery conduit <NUM> that connects between the humidifier chamber <NUM> and the patient's <NUM> peritoneal cavity or surgical site. The conduit <NUM> has a first end and a second end. The first end can be connected to the outlet of the humidifier chamber <NUM> and receive humidified gases from the chamber <NUM>. The second end of the conduit <NUM> can be placed in the patient's <NUM> surgical site or peritoneal cavity. Humidified insufflation gases travel from the chamber <NUM>, through the conduit <NUM> and into the surgical site to insufflate and expand the surgical site or peritoneal cavity. The system <NUM> also includes a controller that regulates the amount of humidity supplied to the gases by controlling the power supplied to the heater base <NUM>. The controller can also be used to monitor water level in the humidifier chamber <NUM>. A smoke evacuation system <NUM> is shown leading out of the body cavity of the patient <NUM>.

The smoke evacuation system <NUM> can be used in conjunction with the insufflation system <NUM> described above or may be used with other suitable insufflation systems. The smoke evacuation system <NUM> comprises a discharge or exhaust limb <NUM>, a discharge assembly <NUM>, and a filter <NUM>. The discharge limb <NUM> connects between the filter <NUM> and the discharge assembly <NUM>. The discharge assembly <NUM>, when in use, is located in or adjacent to the patient's <NUM> surgical site or peritoneal cavity. The discharge limb <NUM> is a self-supporting tube (that is, the tube is capable of supporting its own weight without collapsing) with two open ends: an operative site end and an outlet end.

The composite tube described herein can be used as the conduit <NUM> to deliver humidified gases to the patient's <NUM> surgical site. The composite tube can deliver humidified gases with minimized heat loss. This can advantageously reduce overall energy consumption in the insufflation system, because less heat input is needed to compensate for heat loss.

A coaxial breathing tube can also comprise a composite tube as described above. In a coaxial breathing tube, a first gas space is an inspiratory limb or an expiratory limb, and the second gas space is the other of the inspiratory limb or expiratory limb. One gas passageway is provided between the inlet of said inspiratory limb and the outlet of said inspiratory limb, and one gas passageway is provided between the inlet of said expiratory limb and the outlet of said expiratory limb. The first gas space can be the inspiratory limb, and the second gas space can be the expiratory limb. Alternatively, the first gas space can be the expiratory limb, and the second gas space can be the inspiratory limb.

Reference is next made to <FIG>, which shows a coaxial tube <NUM>. In this example, the coaxial tube <NUM> is provided between a patient <NUM> and a ventilator <NUM>. Expiratory gases and inspiratory gases each flow in one of the inner tube <NUM> or the space <NUM> between the inner tube <NUM> and the outer tube <NUM>. It will be appreciated that the outer tube <NUM> may not be exactly aligned with the inner tube <NUM>. Rather, "coaxial" refers to a tube situated inside another tube.

For heat transfer reasons, the inner tube <NUM> can carry the inspiratory gases in the space <NUM> therewithin, while the expiratory gases are carried in the space <NUM> between the inner tube <NUM> and the outer tube <NUM>. This airflow configuration is indicated by arrows. However, a reverse configuration is also possible, in which the outer tube <NUM> carries inspiratory gases and the inner tube <NUM> carries expiratory gases.

The inner tube <NUM> can be formed from a corrugated tube, such as a Fisher & Paykel model RT100 disposable tube. The outer tube <NUM> can be formed from a composite tube, as described above.

With a coaxial tube <NUM>, it may be difficult to detect a leak in the inner tube <NUM>. Such a leak may short circuit the patient <NUM>, meaning that the patient <NUM> will not be supplied with sufficient oxygen. Such a short circuit may be detected by placement of a sensor at the patient end of the coaxial tube <NUM>. This sensor may be located in the patient end connector <NUM>. A short circuit closer to the ventilator <NUM> will lead to continued patient <NUM> re-breathing of the air volume close to the patient <NUM>. This will lead to a rise in the concentration of carbon dioxide in the inspiratory flow space <NUM> close to the patient <NUM>, which can be detected directly by a CO<NUM> sensor. Such a sensor may comprise any one of a number of such sensors as is currently commercially available. Alternatively, this re-breathing may be detected by monitoring the temperature of the gases at the patient end connector <NUM>, wherein a rise in temperature above a predetermined level indicates that re-breathing is occurring.

In addition, to reduce or eliminate the formation of condensation within either the inner tube <NUM> or outer tube <NUM>, and to maintain a substantially uniform temperature in the gases flow through the coaxial tube <NUM>, a heater, such as a resistance heater filament, may be provided within either the inner tube <NUM> or outer tube <NUM>, disposed within the gases spaces <NUM> or <NUM>, or within the inner tube <NUM> or outer tube <NUM> walls themselves.

In a composite tube, such as the tube <NUM> incorporating a heating filament <NUM>, heat can be lost through the walls of the first elongate member <NUM>, resulting in uneven heating. As explained above, one way to compensate for these heat losses is to apply an external heating source at the first elongate member <NUM> walls, which helps to regulate the temperature and counter the heat loss. Other methods for optimizing thermal properties can also be used.

Reference is next made to <FIG>, which demonstrate example configurations for bubble height (that is, the cross-sectional height of the first elongate member <NUM> measured from the surface facing the inner lumen to the surface forming the maximum outer diameter) to improve thermal properties.

The dimensions of the bubble can be selected to reduce heat loss from the composite tube <NUM>. Generally, increasing the height of the bubble increases the effective thermal resistance of the tube <NUM>, because a larger bubble height permits the first elongate member <NUM> to hold more insulating air. However, it was discovered that, at a certain bubble height, changes in air density can cause convection inside the tube <NUM>, thereby increasing heat loss. Also, at a certain bubble height, the surface area becomes so large that the heat lost through surface outweighs the benefits of the increased height of the bubble.

The radius of curvature and the curvature of the bubble can also be useful for determining a desirable bubble height. The curvature of an object is defined as the inverse of the radius of curvature of that object. Therefore, the larger a radius of curvature an object has, the less curved the object is. For example, a flat surface would have a radius of curvature of ∞, and therefore a curvature of <NUM>.

<FIG> shows a longitudinal cross-section of a top portion of a composite tube. <FIG> shows an example composite tube <NUM> where the bubble has a large height. In this example, the bubble has a relatively small radius of curvature and therefore a large curvature. Also, the bubble is approximately three to four times greater in height than the height of the second elongate member <NUM>.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows an example composite tube <NUM> where the bubble is flattened on 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 the second elongate member <NUM>.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows an example composite tube <NUM> where the width of the bubble is greater than the height of the bubble. In this example, the bubble has radius of curvature and the curvature between that of <FIG> and <FIG>. The center of the radius for the upper portion of the bubble is outside of the bubble (as compared to <FIG>). The inflection points on the left and right sides of the bubble are about at the middle (heightwise) of the bubble (as opposed to in the lower portion of the bubble, as in <FIG>). Also, the height of the bubble is approximately double that of the second elongate member <NUM>, resulting in a bubble height between that of <FIG> and <FIG>.

The configuration of <FIG> resulted in the lowest heat loss from the tube. The configuration of <FIG> resulted in the highest heat loss from the tube. The configuration of <FIG> had intermediate heat loss between the configurations of <FIG> and <FIG>. However, the large external surface area and convective heat transfer in the configuration of <FIG> can lead to inefficient heating. Thus, of the three bubble arrangements of <FIG>, <FIG> was determined to have the best overall thermal properties. When the same thermal energy was input to the three tubes, the configuration of <FIG> allowed for the largest temperature rise along the length of the tube. The bubble of <FIG> is sufficiently large to increase the insulating air volume, but not large enough to cause a significant convective heat loss. The configuration of <FIG> was determined to have the poorest thermal properties, namely that the configuration of <FIG> allowed for the smallest temperature rise along the length of the tube. The configuration of <FIG> had intermediate thermal properties and allowed for a lower temperature rise than the configuration of <FIG>.

It should be appreciated that although the <FIG> configuration may be preferred, other configurations, including those of <FIG>, <FIG> and other variations, may also be utilized as may be desired.

TABLE <NUM> shows the height of the bubble, the outer diameter of the tube, and the radius of curvature of the configurations shown in each of <FIG>, <FIG>.

TABLE 7A shows the height of the bubble, the outer diameter and the radius of curvature of further configurations as shown in <FIG>, and <FIG>.

It should be noted that, in general, the smaller the radius of curvature, the tighter the tube can be bent around itself without the bubble collapsing or "kinking. " For example, <FIG> shows a tube that has been bent beyond its radius of curvature (specifically, it shows the tube of <FIG> bent around a radius of curvature of <NUM>), thereby causing kinking in the walls of the bubble. Kinking is generally undesirable, as it can detract from the appearance of the tube, and can impair the thermal properties of the tube.

Accordingly, configurations with increased bending properties (such as those shown in <FIG> or <FIG>) can be desirable despite having less efficient thermal properties. In some applications, it has been found that a tube with an outer diameter of <NUM> to <NUM> (or about <NUM> to about <NUM>) provides a good balance between thermal efficiency, flexibility, and bending performance. It should be appreciated that although the configurations of <FIG> and <FIG> may be preferred, other configurations, including those of <FIG> and other variations, may also be utilized as may be desired.

Reference is next made to <FIG> which demonstrate example positioning of heating element <NUM> with similar bubble shapes to improve thermal properties. The location of the heating element <NUM> can change the thermal properties within the composite tube <NUM>.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows an example composite tube <NUM> where the heating elements <NUM> are centrally located in the second elongate member <NUM>. This example shows the heating elements <NUM> close to one another and not close to the bubble wall.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows an example composite tube <NUM> in which the heating elements <NUM> are spaced farther apart, as compared to <FIG>, in the second elongate member <NUM>. These heating elements are closer to the bubble wall and provide for better regulation of heat within the composite tube <NUM>.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows an example composite tube <NUM> wherein the heating elements <NUM> are spaced on top of each other in the vertical axis of the second elongate member <NUM>. In this example, the heating elements <NUM> are equally close to each bubble wall.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows example composite tube <NUM> where the heating elements <NUM> are spaced at opposite ends of the second elongate member <NUM>. The heating elements <NUM> are close to the bubble wall, as compared to <FIG>.

Of the four filament arrangements of <FIG>, <FIG> was determined to have the best thermal properties. Because of their similar bubble shapes, all of the configurations of <FIG> experienced similar heat loss from the tube. However, when the same thermal energy was input to the tubes, the filament configuration of <FIG> allowed for the largest temperature rise along the length of the tube. The configuration of <FIG> was determined to have the next best thermal properties and allowed for the next largest temperature rise along the length of tube. The configuration of <FIG> performed next best. The configuration of <FIG> had the poorest performance and allowed for the smallest temperature rise along the length of the tube, when the same amount of heat was input.

It should be appreciated that although the <FIG> configuration may be preferred, other configurations, including those of <FIG>, <FIG>, and other variations, may also be utilized as may be desired.

<FIG> illustrate various filament (also referred to herein as "wire") arrangements in a tube. In these arrangements, both heating wires, sensor and ground wires are included in the arrangement. The heating wires in combination with a temperature sensor and associated wiring enable fine control of air temperature. <FIG> illustrates an example wire arrangement in which two heater wires A and B are spaced apart as far as possible with a sensor wire and a ground wire located between the heater wires. As discussed with respect to <FIG> and <FIG>, it is advantageous to space the heating wires as far apart as possible for better heating performance. Additionally, this configuration provides a lower risk of heating wires sparking as a result of larger distances between the heating wires.

It has been discovered, however, that with increased lengths of tubing and closer proximity of heating and sensor wires, increased electrical interference between the temperature sensing signal wire and the heating wires develops. This increased electrical interference leads to incorrect sensor measurements. For example, in tubing with lengths of about <NUM> meters or greater, or about <NUM> meters or greater, or about <NUM> meters or greater, or about <NUM> meters or greater, or about <NUM> meters or greater, alternating current at mains power frequency in the heating wires creates a capacitive effect on the sensor wire leading to errors in the temperature measurements from the inbuilt temperature sensor in the circuit. The heater wires in the tubes described herein can have lengths of, for example, about <NUM> meters to about <NUM> meters, or about <NUM> meters to about <NUM> meters, or about 25meters to about <NUM> meters, or about <NUM> meters. The sensor wire can run along next to the heater wires. The heater wire length and/or sensor wire length can be affected by the pitch of the windings during manufacturing. The tighter the pitch and/or the larger the diameter of the mandrel, the longer are the heater wires and/or the sensor wire. The relatively large length of wire coiled in the tubing and a relatively small separation gap between the wires effectively creates a small capacitor significant enough to affect the temperature measurement system. The longer the heater wires and/or sensor wires, the greater is the capacitive coupling effect. Referring to <FIG>, the signal wire in the illustrated arrangement experienced coupling with both the A and B heating wires (the effect of which is illustrated by capacitances C1 and C2, which it is to be understood are not physical capacitors, but rather only conceptual illustrations of the capacitive effects). The effects from these couplings are anti-phased, as currents A and B flow in opposite directions and follow the principle of superposition. The net signal voltage read by the device can be expressed as <MAT> where Vcoupled A and Vcoupled B are opposite in sign due to A and B being antiphase.

As the A wire is closer to the signal wire than the B wire, the A-signal capacitance is larger, (C1 > C2). This is observed as a stronger coupling of the A wire to the signal wire. As a result: <MAT>
<MAT>.

As Vcoupled A and Vcoupled B are supplied by mains frequency, the unequal voltage occurs on the signal as <NUM> noise. With increased length, there is a significant increase in capacitances C1 and C2; and therefore the coupled noise.

Solutions are identified as spacing the wires, offsetting the measurement system for the known noise, adding a compensation capacitor to reduce the difference in capacitance and altering the wire arrangement, or any combination of the foregoing. The solutions can benefit tubes of any length as the capacitive coupling occurs in tubes of any length.

Wire spacing distance may be limited by the tube arrangement. One solution to compensate for the noise is to incorporate a heating wires voltage feedback into the temperature measurement system. However, this can be complex and costly to implement and may be undesirable.

Another solution is to add a physical capacitor between the B heating wire and signal wire, for example, as shown in <FIG>. Adding a physical capacitor, C3, parallel to the B heating wire to signal wire capacitance C2 may equalize the difference in capacitance between C1 and C2, (C1 = C2 + C3). This may make the capacitive coupling to each wire equally strong. After addition of the capacitor C3, heating wires A and B will still interfere with the signal wire, but the net effect can be destructive, and/or the net effect can be nominally zero. This removes most of the noise in the system and improves signal measurement accuracy. This solution involves a small increase in cost and an additional manufacturing step and may involve individual calibration.

Another solution is to swap the locations of the B heating wire and the GND wire, for example, as shown in <FIG>. In the resulting arrangement, the A and B heating wires are equidistant from the signal wire. The effective capacitance between the signal wire and the B heating wire increases as compared with the configurations in <FIG>. As a result, the capacitances are equal, C1 = C2*, and there is equally strong coupling between the signal wire and each heater wire. This results in cancelation of noise, similar to the previously mentioned solution. While there is still unequal coupling occurring on the GND wire, this has been found to not affect the sensor system design, as the GND signal has lower impedance than the sensor wire. The lower impedance results in capacitive coupling on the GND wire having minimal effect on its voltage, as opposed to the effect of capacitive coupling on the voltage of the sensor wire.

Multiple configurations for the wires are possible and fall within the scope of the present disclosure. For example, other configurations that allow for equal capacitive coupling between the heating wires and the sensor wires are possible. An alternative design is shown in <FIG>, which also reduces noise on the GND wire and still has maximum displacement between the two heating tubes. In <FIG>, the GND wire and the sensor wire can be equidistant between the heater wires A and B and stacked in a vertical or substantially vertical arrangement. The GND wire can be on top of the sensor wire, or the sensor wire can be on top of the GND wire. Other wire configurations can also be used to allow the sensor wire to be equidistant from the two heater wires. For example, the wires can be arranged generally horizontally in the order of the GND wire, the heater wire A or B, the sensor wire, and the heater wire B or A. This arrangement can be a mirror image of the arrangement in <FIG>.

Although the present disclosure is described mainly with respect to the bubble tube arrangement provided herein, it is to be understood that solutions provided to the capacitive coupling effect described are applicable to any tubes of any lengths having closely spaced heating wire and sensor wire configurations. Accordingly, the present disclosure is not to be limited to the particular tube configuration, but rather extends to any tube configurations that include closely spaced wire configurations.

Reference is next made to <FIG>, which demonstrate example configurations for stacking of the first elongate member <NUM>. It was discovered that heat distribution can be improved by stacking multiple bubbles. These stacking can be more beneficial when using an internal heating filament <NUM>. <FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows a cross section of a composite tube <NUM> without any stacking.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows another example composite tube <NUM> with stacked bubbles. In this example, two bubbles are stacked on top of each other to form the first elongate member <NUM>. As compared to <FIG>, the total bubble height is maintained, but the bubble pitch is half of <FIG>. Also, the tube <NUM> in <FIG> has only a slight reduction in air volume. The stacking of the bubbles reduces natural convection and heat transfer in the gap between bubbles <NUM> and lowers the overall thermal resistance. The heat flow path increases in the stacked bubbles allowing heat to more easily distribute through the composite tube <NUM>.

<FIG> shows a longitudinal cross-section of a top portion of another composite tube. <FIG> shows another example of a composite tube <NUM> with stacked bubbles. In this example, three bubbles are stacked on top of each other to form the first elongate member <NUM>. As compared to <FIG>, the total bubble height is maintained, but the bubble pitch is a third of <FIG>. Also, the tube <NUM> in <FIG> has only a slight reduction in air volume. The stacking of the bubbles reduces natural convection and heat transfer in the gap between bubbles <NUM>.

The tubes and/or other associated components described herein can include an information element. The information element can identify characteristics of the tube(s) and/or peripheral components coupled to the information element, such as arrangements and/or wire configurations of the tubes described herein. The information element can be a resistor or a thermistor measuring a resistance of a wire on or in the tube or associated components. The tube information identified by the information element can be provided to a controller or processor via wired and/or wireless communications. The controller or processor can calibrate sensor measurements, and/or change modes and/or operational parameters based at least in part on the received tube information. Other examples of an information element can include, but are not limited to, an EPROM, an RF information element, a bar code, and the like.

Materials for a composite tube can be selected to handle various methods of cleaning. High level disinfection (around <NUM> cleaning cycles) can be used to clean the composite tube, such as the tube <NUM>. During high level disinfection, the composite tube <NUM> is subject to pasteurization at about <NUM> for about <NUM> minutes. Next, the composite tube <NUM> is bathed in <NUM>% glutaraldehyde for about <NUM> minutes. The composite tube <NUM> is removed from the glutaraldehyde and submerged in <NUM>% hydrogen peroxide for about <NUM> minutes. Finally, the composite tube <NUM> is removed from the hydrogen peroxide and bathed in <NUM>% orthophthalaldehyde (OPA) for about <NUM> minutes.

Sterilization (around <NUM> cycles) can also be used to clean the composite tube <NUM>. First, the composite tube <NUM> is placed within autoclave steam at about <NUM> for about <NUM> minutes. Next, the temperature of the autoclave steam is increased to about <NUM> for about <NUM> minutes. After autoclaving, the composite tube <NUM> is surrounded by <NUM>% ethylene oxide (ETO) gas. Finally, the composite tube <NUM> is removed from the ETO gas and submerged in about <NUM>% glutaraldehyde for about <NUM> hours.

The composite tube <NUM> may be made of materials to withstand the repeated cleaning process. Part or all of the composite tube <NUM> can be made of, but is not limited to, styrene-ethylene-butene-styrene block thermo plastic elastomers, for example Kraiburg TF6STE. The composite tube <NUM> can also be made of, but is not limited to, hytrel, urethanes, or silicones.

Claim 1:
A tube (<NUM>) for conveying humidified gases to a patient, the tube (<NUM>) comprising:
first and second heating wires traversing at least a portion of the length of the tube (<NUM>); and
a sensor wire in electrical communication with a temperature sensor (<NUM>), characterised by that the first and second heating wires and the sensor wire are arranged in close proximity within the tube (<NUM>) and the first and second heating wires are spaced equal distance from the sensor wire.