Components for medical circuits

Abstract

This invention discloses breathable medical circuit components, as well as materials and methods for forming such components. [Solution] These components incorporate a breathable foam material that is permeable to water vapor and substantially impermeable to liquid water and gas bulk flows. The disclosed materials and methods can be incorporated into a variety of components, including tubes, Y-connectors, catheter mounts and patient interfaces, and are suitable for use in a variety of medical circuits, including inhalation circuits, anesthesia circuits and respiratory circuits.

Description

Background Art

[0001] Cross-reference of related applications This utility patent application claims priority based on U.S. Provisional Patent Application No. 61 / 289,089, filed on December 22, 2009, entitled "Components for Medical Circuits", the contents of which are incorporated herein by reference in their entirety.

[0002] Technical field The present disclosure generally relates to components for medical circuits, and more particularly to components for medical circuits that supply humidified gas to a patient and / or remove humidified gas from a patient, for example, in positive airway pressure (PAP), respirators, anesthesia, ventilators (breathing machines), and inhalation systems.

[0003] Description of related technologies In medical applications, gases with high relative humidity levels are transported to or from a patient by various components. When a high humidity gas contacts the walls of a component at a low temperature, condensate, i.e., "rain out", can be a problem. However, condensation depends on many factors, including not only the temperature characteristics of the component, but also the gas flow rate, component shape, and the inherent "breathability" of the materials used to form the component. "Breathability" is the ability of a material to allow water vapor to permeate while substantially resisting bulk flow of liquid water and bulk flow of gas.

[0004] For example, PAP systems (ventilation systems that deliver respiratory gases to a patient at positive pressure) use a breathing tube for the delivery and removal of inhaled and exhaled gases. In these applications, and other respiratory applications such as assisted breathing, the gas inhaled by the patient is typically delivered through the inspiratory tube at near-saturation humidity. The respiratory gas exhaled by the patient flows through the expiratory tube and is typically fully saturated. Condensants can form on the inner walls of respiratory circuit components during the patient's inhalation, and significant levels of condensation can form during the patient's exhalation. Such condensations are particularly harmful if they are close to the patient. For example, fluid condensations that form in the breathing tube (either the inspiratory or expiratory tube) can be breathed or inhaled by the patient, potentially causing coughing fits or other discomfort.

[0005] As another example, inhalation systems also deliver and remove humidified gases. During laparoscopic surgery under inhalation, it may be desirable to humidify the inhaled gas (generally CO2) before delivering it into the abdominal cavity. This can help prevent the "drying" of the patient's internal organs and reduce the time required for recovery from surgery. Even when using dry inhaled gases, the gas can become saturated as it draws moisture from the patient's body cavities. The moisture in the gas tends to condense on the exhaust rim or the walls of the tubes of the inhalation system. Water vapor can also condense on other parts of the inhalation system, such as filters. It is highly undesirable for vapor to condense on the filter and for moisture to flow out along the rim (inlet rim or exhaust rim). For example, water condensed on the walls can saturate the filter and cause it to become clogged. This can increase back pressure and hinder the system's ability to remove smoke. Furthermore, liquid water in the rim can flow into other connecting devices, which is also undesirable.

[0006] Attempts have been made to mitigate the harmful effects of condensation by incorporating highly "permeable" materials—that is, materials that are highly permeable to water vapor but substantially impermeable to liquid water and bulk gas flows—into tube walls. However, this required ultra-thin walls to achieve sufficiently high permeability to prevent or reduce condensation. As a result, tubes with acceptable permeability had thin walls, requiring considerable reinforcement. These reinforcements add time, cost, and complexity to the manufacturing process. Therefore, there is a need for permeable yet strong medical circuit components for humidifying gas delivery. [Overview of the Initiative]

[0007] Materials and methods for forming breathable medical circuit components, such as components for breathable inhalation circuits, anesthesia circuits, or respiratory circuits, are disclosed herein in various embodiments. These breathable components incorporate breathable foam materials that are permeable to water vapor and substantially impermeable to liquid water and gas bulk flows. The disclosed materials and methods can be incorporated into a variety of components, including tubes, Y-connectors, catheter mounts, and patient interfaces.

[0008] Disclosed are medical circuit components for use with humidifying gases. In at least one embodiment, the component is a wall defining an internal space, the wall comprising at least a portion of which is made of a breathable foam material configured to allow water vapor to pass through but substantially impermeable to liquid water.

[0009] In various embodiments, the aforementioned component has one, some, or all of the following characteristics: The diffusion coefficient of the breathable foam material is at least 3 × 10⁻⁶. -7 cm 2It can be / second. The wall thickness can be between 0.1mm and 3.0mm. The breathable foam material may contain a blend of polymers. The breathable foam material may contain a thermoplastic elastomer containing polyether soft segments. The breathable foam material may contain a copolyester thermoplastic elastomer containing polyether soft segments. The breathable foam material may be sufficiently rigid so that it can be bent around a 25mm diameter metal cylinder without kinking or crushing, as specified by a test for the increase in flow resistance with bending in accordance with ISO 5367:2000(E). g-mm / m of the part 2 The permeability P on a daily basis was at least 60 g-mm / m² when measured according to ASTM E96 Procedure A (using the desiccant method at a temperature of 23°C and a relative humidity of 90%). 2 It can be / day. The elastic modulus of the component can be between 30 and 1000 MPa. The permeability P is given by the following formula:

number

[0010] In addition, in various embodiments, parts of some or all of the above embodiments have one, some or all of the following characteristics: The foam material may contain voids. The foam material may have a void fraction greater than 25%. The foam material may have an average lateral void size of less than 30% of the wall thickness. The foam material may contain voids that are flattened along the longitudinal axis of the wall. At least 80% of these voids may have an aspect ratio of longitudinal to lateral length greater than 2:1. At least 10% of these voids may be interconnected.

[0011] In certain embodiments, some or all of the components of the above embodiments may form the wall of a tube or the wall of a mask. When the wall of a tube is made of foam material, the tube may be, for example, an extruded tube, a corrugated tube, or an extruded corrugated tube. Any of these aforementioned tubes may be used in a suction system.

[0012] In at least one embodiment, the component is a wall defining a space, and at least a portion of the wall may be made of a foamed material that is permeable to water vapor and substantially impermeable to liquid water, wherein the g-mm / m² density is measured according to procedure A of ASTM E96 (using the drying method at a temperature of 23°C and a relative humidity of 90%). 2 The permeability P of the foam material on a daily basis is at least 60 g-mm / m². 2 / day and the following formula:

number

[0013] In various embodiments, the aforementioned component has one, some, or all of the following characteristics: P is at least 70 g-mm / m 2It can be per day. M can be between 30 and 800 MPa. The wall thickness can be between 0.1 mm and 3.0 mm. The foamed material can have a porosity greater than 25%. The foamed material can comprise voids. The foamed material can have a lateral average void size less than 30% of the wall thickness. At least some of those voids can be flattened along the longitudinal axis of the wall. At least 80% of those voids can have an aspect ratio of the longitudinal length to the lateral length greater than 2:1. At least 10% of those voids can be interconnected. The breathable foamed material can comprise a thermoplastic elastomer containing a polyether soft segment. The breathable foamed material can comprise a copolyester thermoplastic elastomer containing a polyether soft segment.

[0014] In certain embodiments, components according to some or all of the above embodiments can form the wall of a tube or the wall of a patient mask. When the wall of the tube is constituted by the foamed material, the tube can be, for example, an extruded tube, a coiled tube or an extruded coiled tube. Any of the aforementioned tubes can be a tube used in an inhalation system.

[0015] A method of manufacturing a medical circuit component is also disclosed. In at least one embodiment, the method comprises mixing a foaming agent masterbatch (a mixture of a carrier polymer and an active foaming agent) with a polymer substrate to form a liquefied mixture, releasing gas bubbles into the substrate portion of the liquefied mixture by the foaming agent portion, and stopping the release of the gas bubbles and processing the mixture to form a water vapor permeable component.

[0016] In various embodiments, the aforementioned method has one, some or all of the following characteristics. The foaming agent and / or the polymer substrate are selected to form a water vapor permeable component comprising a solid polymer and voids distributed throughout the solid polymer, and the mixture can be processed. The permeability P of the component in g-mm / m 2 / day unit is at least 60 g-mm / m measured according to Procedure A of ASTM E96 (using the drying method at a temperature of 23 °C and a relative humidity of 90%). 2 / day or at least 70g-mm / m 2 It can be / day. The elastic modulus of the part can be between 30 and 1000 MPa. P is given by the following formula:

number

[0017] In addition, in various embodiments, methods according to some or all of the above embodiments have one, some or all of the following characteristics: The foam material may contain voids. The foam material may have a porosity greater than 25%. The average lateral void size may be less than 30% of the wall thickness. The foam material may contain voids that are flattened along the longitudinal axis of the wall. At least 80% of these voids may have a longitudinal-to-lateral aspect ratio greater than 2:1. At least 10% of these voids may be interconnected. The breathable foam material may comprise a thermoplastic elastomer containing polyether soft segments. The breathable foam material may comprise a copolyester thermoplastic elastomer containing polyether soft segments.

[0018] In certain embodiments, methods according to some or all of the embodiments described above may include forming a water vapor permeable component into a tube or forming a water vapor permeable component into a mask. If the method includes forming a component into a tube, the processing of the mixture may include extruding the mixture into a tubular object. Processing the mixture may also include co-extruding a plurality of reinforcing ribs onto the surface of the tubular object. The ribs may be arranged on the inner surface of the tubular object, on the outer surface of the tubular object, or on both the inner and outer surfaces of the tubular object. In particular, the ribs may be arranged circumferentially to the tubular object, for example, circumferentially on the inner surface of the tubular object. The ribs may generally be aligned longitudinally along the length of the tubular object. Processing the mixture may also include corrugating the extruded tubular object. If corrugating the extruded tubular object, the tubular object may have ribs or may omit those ribs.

[0019] A tube for delivering humidifying gas to or from a patient is also disclosed. In at least one embodiment, the tube comprises an inlet and an outlet, and an extruded and corrugated foamed polymer conduit that is permeable to water vapor and substantially impermeable to liquid water and gas bulk flows, configured to allow humidifying gas to flow from the inlet to the outlet within the space enclosed by the conduit. The tube may further comprise a plurality of reinforcing ribs. The ribs may be arranged on the inner surface of the tubular object, or on the outer surface of the tubular object, or on both the inner and outer surfaces of the tubular object. In particular, the ribs may be arranged circumferentially of the tubular object, for example, circumferentially on the inner surface of the tubular object. The ribs may generally be aligned longitudinally along the length of the tubular object between the inlet and the outlet.

[0020] In various embodiments, the aforementioned tubes, with or without the ribs, have one, some or all of the following characteristics: The foamed polymer conduit may comprise a solid thermoplastic elastomer material and voids distributed throughout the solid material. The foamed polymer conduit may have an inner surface facing its enclosed space; and an internal volume facing its inner surface, where at least some of the voids in the internal volume are connected to other voids, thereby forming open cell pathways that facilitate the movement of water vapor through the conduit. At least 10% or at least 20% of those voids may be connected to other voids. The internal volume may have a porosity greater than 25%. The average void size in the lateral direction may be less than 30% of the wall thickness or less than 10% of the wall thickness. At least some of those voids may be flattened along the longitudinal axis of the conduit. Flattening can be expressed as having an aspect ratio of longitudinal length to transverse length greater than 2:1 or greater than 3:1. At least 80% of those voids can be flattened.

[0021] In addition, in various embodiments, the tubes according to some or all of the above embodiments have one, some or all of the following characteristics: The foamed polymer conduit may have a wall thickness between 0.1 mm and 3.0 mm. The g-mm / m of the component. 2 The permeability P on a daily basis was measured according to ASTM E96 Procedure A (using the drying method at a temperature of 23°C and relative humidity of 90%) and was at least 60 g-mm / m³. 2 It can be / day. The elastic modulus of the part can be between 30 and 1000 MPa. P is given by the following formula:

number

[0022] In at least one embodiment, the conduit comprises an inlet and an outlet, and a foamed polymer conduit that is permeable to water vapor and substantially impermeable to liquid water and gas bulk flows, allowing a humidifying gas to flow from the inlet to the outlet within a space enclosed by the conduit, wherein the foamed polymer conduit comprises a solid thermoplastic elastomer material and voids distributed throughout the solid material. The foamed polymer conduit may have an inner surface facing the enclosed space and an internal volume facing the inner surface. At least some of the voids in the internal volume may be connected to other voids, thereby forming a continuous void passage that facilitates the movement of water vapor through the conduit.

[0023] In various embodiments, the aforementioned tube has one, some, or all of the following characteristics: The foamed polymer conduit is 3 × 10 -7 cm 2 It may have a diffusion coefficient greater than / sec. The conduit may be extruded. The conduit may be corrugated. The tube may further comprise a number of reinforcing ribs. The ribs may be arranged on the inner surface of the tubular object, on the outer surface of the tubular object, or on both the inner and outer surfaces of the tubular object. In particular, the ribs may be arranged circumferentially to the tubular object, for example, circumferentially on the inner surface of the tubular object. The ribs may generally be aligned longitudinally along the length of the tubular object between the inlet and outlet. The tube may further comprise a heating line. The heating line may generally be aligned longitudinally along the length of the foamed polymer conduit between the inlet and outlet.

[0024] In addition, in various embodiments, tubes according to some or all of the above embodiments have one, some or all of the following characteristics: At least 10% or at least 20% of the bubble voids in the internal volume may be connected to other bubble voids. The internal volume may have a porosity greater than 25%. At least some of those voids may be flattened along the longitudinal axis of the conduit. Flattening can be expressed as having an aspect ratio of longitudinal length to transverse length greater than 2:1 or 3:1. At least 80% of those voids may be flattened. The internal volume may have an average transverse void size of less than 30% or less than 10% of the foamed polymer conduit wall thickness. The foamed polymer conduit may have a wall thickness between 0.1 mm and 3.0 mm. g-mm / m of the tube 2 The permeability P on a daily basis was measured according to ASTM E96 Procedure A (using the drying method at a temperature of 23°C and relative humidity of 90%) and was at least 60 g-mm / m³. 2 It can be / day. The elastic modulus of the pipe can be between 30 and 1000 MPa. P is given by the following formula:

number

[0025] Methods for manufacturing tubes suitable for the delivery of humidifying gas to or from a patient are also disclosed. In at least one embodiment, the method includes mixing a foaming agent with a substrate comprising one or more thermoplastic elastomers to form an extruder; applying pressure to the extruder using an extruder to form a hollow tube; delivering the hollow tube to a corrugator mold; cooling the hollow tube in the corrugator mold; and removing the cooled hollow tube from the corrugator to form a corrugated water vapor permeable tube.

[0026] In various embodiments, the method described above has one, some, or all of the following characteristics: The tube may have a wall thickness between 0.1 mm and 3.0 mm. The coiled tube may contain voids formed by gas bubbles released by a solid thermoplastic elastomer and a blowing agent. The maximum lateral void size diameter may be less than one-third of the minimum wall thickness. The porosity of the coiled tube may be greater than 25%. The substrate is 0.75 × 10 -7 cm 2 The diffusion coefficient may be greater than / sec. The substrate may have a tensile modulus greater than 15 MPa.

[0027] Methods for delivering humidifying gas to or from a patient are also disclosed. In at least one embodiment, the method includes preparing a medical circuit component having a wall formed from a breathable foam material, connecting the medical circuit component to a patient, and permeating the medical circuit component with a humidifying gas, wherein the medical circuit component allows water vapor to pass through its wall but substantially prevents liquid water and bulk gas flows from passing through its wall.

[0028] In various embodiments, the method described above has one, some, or all of the following characteristics: The diffusion coefficient of the breathable foam material is at least 3 × 10⁻⁶ -7 cm 2 It can be / second. The wall thickness can be between 0.1 mm and 3.0 mm. The breathable foam material may comprise a thermoplastic elastomer containing polyether soft segments. In particular, the breathable foam material may comprise a copolyester thermoplastic elastomer containing polyether soft segments. The breathable foam material may be sufficiently rigid so that its foam can be bent around a 25 mm diameter metal cylinder without kinking or crushing, as specified by a test for the increase in flow resistance with bending in accordance with ISO 5367:2000(E). g-mm / m of the part 2 The permeability P on a daily basis was measured according to ASTM E96 Procedure A (using the drying method at a temperature of 23°C and relative humidity of 90%) and was at least 60 g-mm / m³. 2It can be / day. The elastic modulus of the part can be between 30 and 1000 MPa. P is given by the following formula:

number

[0029] In addition, in various embodiments, methods according to some or all of the above embodiments have one, some or all of the following characteristics: The foamed material may contain voids. At least 10% of these voids may be interconnected. The foamed material may have a porosity greater than 25%. The foamed material may have an average lateral void size of less than 30% of the wall thickness. At least some of these voids may be flattened along the longitudinal axis of the part. Flattening can be expressed as having an aspect ratio of longitudinal length to transverse length greater than 2:1 or greater than 3:1. At least 80% of these voids may be flattened.

[0030] In certain embodiments, the permeation of humidifying gas by medical circuit components may include permeating the humidifying gas through a tube comprising a breathable foam material, or permeating the humidifying gas through a mask comprising a breathable foam material, or permeating the humidifying gas through an inhalation tube comprising a breathable foam material.

[0031] The present invention comprises all of the embodiments described above, and also intends to include the configurations of the following embodiments. [Brief explanation of the drawing]

[0032] Hereinafter, examples of embodiments demonstrating various features of the disclosed systems and methods are described with reference to the drawings. The drawings and related descriptions are provided to illustrate embodiments, not to limit the scope of this disclosure. [Figure 1] This is a schematic diagram of a medical circuit incorporating breathable components. [Figure 2A]This is a log / log plot of permeability and Young's modulus for several known permeable materials used in medical circuit components. [Figure 2B] This is a log / log plot of permeability and Young's modulus for known materials and for permeable foamed polymer materials according to the embodiments discussed herein. [Figure 3] This is a plot of relative diffusivity and porosity in the breathable foamed polymer material according to the embodiments discussed herein. [Figure 4A] This is a microscopic image of an example foamed tubing. [Figure 4B] This is a microscopic image of an example foamed tubing. [Figure 4C] This is a microscopic image of an example foamed tubing. [Figure 4D] This is a microscopic image of an example foamed tubing. [Figure 4E] This is a microscopic image of another example of a foamed tubing. [Figure 4F] This is a microscopic image of another example of a foamed tubing. [Figure 4G] This is a micrograph of an example foamed extruded strip. [Figure 4H] This is a micrograph of an example foamed extruded strip. [Figure 4I] This is a micrograph of another example foam extruded strip. [Figure 4J] This is a micrograph of another example foam extruded strip. [Figure 4K] This is a micrograph of a non-foamed extruded strip formed from a polymer blend. [Figure 4L] This is a micrograph of a foamed extruded strip formed from a polymer blend. [Figure 4M] This is a micrograph of a foamed extruded strip formed from a polymer blend. [Figure 4N] This is a micrograph of a non-foamed extruded polymer strip. [Figure 4O] This is a micrograph of a non-foamed extruded polymer strip. [Figure 5]This is a schematic diagram of a medical circuit component incorporating a breathable foamed polymer material. [Figure 6A] This is a side view of a tubular component incorporating a breathable foamed polymer material. [Figure 6B] Figure 6A is a cross-sectional view of the pipe component. [Figure 7A] This is a front perspective view of a tubular component incorporating a single reinforcing rib, and the component has a partially corrugated surface. [Figure 7B] This is a front perspective view of a tubular component with a corrugated surface. [Figure 8A] This is a front perspective photograph of an alternative structure for a tubular component that incorporates ribs and has a corrugated surface. [Figure 8B] Figure 8A is a front perspective view of the tubular component. [Figure 8C] This corrugator block is suitable for forming the tubular parts shown in Figures 8A and 8B. [Figure 9] This is a schematic diagram of a breathing circuit according to at least one embodiment. [Figure 10] This is a schematic diagram of a component including a coaxial tube according to at least one embodiment. [Figure 11A] This is a side view of a mask-type patient interface according to at least one embodiment. [Figure 11B] Figure 11A is a front perspective view of the patient interface. [Figure 12] This is a front view of a patient wearing a nasal cannula-type patient interface according to at least one embodiment. [Figure 13] This is a schematic diagram of a catheter mount according to at least one embodiment. [Figure 14] This is a schematic diagram of a humidifying inhalation system according to at least one embodiment, comprising an inlet rim and an exhaust rim. [Figure 15] This is a schematic diagram of a method for manufacturing a component according to at least one embodiment. [Figure 16A] This is a micrograph showing an extruded foam polymer with an outer skin layer. [Figure 16B] This is a micrograph showing an extruded foam polymer with an outer skin layer. [Figure 17] This flowchart shows a method for manufacturing a part according to at least one embodiment. [Figure 18] This is a plot of the ideal sorption / desorption curve at a constant diffusion rate. [Figure 19] This is a plot of a typical experimental desorption curve. [Figure 20] This is a plot of experimental desorption curves and calculated desorption curves.

[0033] Through the drawings, reference numbers are also used to indicate correspondences between reference (or similar) elements. In addition, the first digit of each reference number indicates the drawing in which that element first appears. Specific Description of the Invention

[0034] The following detailed description discloses novel materials and methods for forming breathable medical circuit components, such as components for breathable inhalation circuits, anesthesia circuits, or respiratory circuits. As described above, these breathable components are permeable to water vapor and substantially impermeable to liquid water and gas bulk flows. The disclosed materials and methods can be incorporated into a variety of components, such as tubing (e.g., inspiratory and expiratory tubes, as well as other tubing systems between various elements of a respiratory circuit, such as ventilators, humidifiers, filters, water traps, sample lines, connectors, gas analyzers, etc.), Y-connectors, catheter mounts, and patient interfaces (e.g., masks, nasal masks, cannulas, nasal pillows, etc., for covering the nose and face). The term "medical circuit" is a broad term and is intended to give the meaning commonly used by those skilled in the art (i.e., not limited to a specific meaning). Thus, "medical circuit" is intended to include both open circuits (such as certain CPAP systems, which may have a single inspiratory tube between the ventilator / blower and the patient interface) and closed circuits.

[0035] Breathing circuit including breathable components To better understand this disclosure, first refer to Figure 1. Figure 1 shows a breathing circuit according to at least one embodiment, comprising one or more breathable components. Such a breathing system may be a continuous positive airway pressure system, a variable positive airway pressure system, or a biphase positive airway pressure (PAP) system or other form of respiratory therapy. In the exemplary breathing circuit, patient 101 receives humidified gas through a breathable inspiratory tube 103. The term "tube" is used in a broad sense and gives the meaning commonly used by those skilled in the art (i.e., not limited to a specific sense), and includes, but is not limited to, a non-cylindrical passage. The inspiratory tube is a tube configured to deliver humidified breathing gas to the patient. The breathable tube will be discussed in more detail below.

[0036] The humidified gas can be transported in the circuit shown in Figure 1 as follows. The dry gas is transferred from the ventilator / blower 105 to the humidifier 107, where it is humidified. The humidifier 107 is connected by port 111 to the inlet 109 (humidified gas receiving end) of the inspiratory tube 103, thereby supplying the humidified gas to the inspiratory tube 103. The humidified gas flows through the inspiratory tube 103 to the outlet 113 (humidified gas discharge end), and then flows to the patient 101 through the patient interface 115 connected to the outlet 113. The exhalation tube 117 is also connected to the patient interface 115. The exhalation tube is a tube configured to allow the exhaled humidified gas to move away from the patient. In this case, the exhaled humidified gas returns to the ventilator / blower 105 from the patient interface 115 via the exhalation tube 117.

[0037] In this embodiment, dry gas enters the ventilator / blower 105 through the vent 119. The fan 121 can improve the gas flow to the ventilator / blower by drawing in air or other gas from the vent 119. The fan 121 may be, for example, a variable-speed fan, in which case the fan speed is controlled by the electronic control unit 123. In particular, the function of the electronic control unit 123 can be controlled by the master electronic control unit 125 in response to input from the master control unit 125 and by the user via the dial 127 to a predetermined required value (setpoint) of pressure or fan speed.

[0038] The humidifier 107 includes a humidifying chamber 129 that can hold a certain volume of water 130 or other suitable humidifying liquid. Preferably, the humidifying chamber 129 is removable from the humidifier 107 after use. Removability allows for easier sterilization or disposal of the humidifying chamber 129. However, the humidifying chamber 129 portion of the humidifier 107 may have a single structure. The body of the humidifying chamber 129 can be formed from a non-conductive glass or plastic material. However, the humidifying chamber 129 may also include conductive components. For example, the humidifying chamber 129 may include a highly thermally conductive substrate (e.g., an aluminum substrate) that is in contact with or bonded to the heater plate 131 on the humidifier 107.

[0039] The humidifier 107 may also include an electronic control unit. In this embodiment, the humidifier 107 includes an analog or digital master electronic control unit 125. The master control unit 125 is preferably a microprocessor-based control unit that executes computer software commands stored in associated memory. For example, in response to a humidity or temperature input set by the user via a dial 133, and other inputs, the master control unit 125 determines when (or to what level) to apply voltage to the heater plate 131 to heat the water 130 in the humidification chamber 129.

[0040] Any suitable patient interface 115 can be incorporated. The term "patient interface" is a broad term, and its meaning is as commonly used by those skilled in the art (i.e., not limited to a specific meaning), and includes, but is not limited to, masks (such as face masks and nasal masks), cannulas, and nasal pillows. Patient interfaces typically define a gas space during use, and because this gas space receives warm, moist respiratory gases, there is a risk of rainout. This is undesirable given the proximity of the patient interface 115 to the patient 101. To address the risk of rainout, a temperature probe 135 can be connected to the inspiratory tube 103 near the patient interface 115, or to the patient interface 115. The temperature probe 135 monitors the temperature near or in the patient interface 115. Using a heating line (not shown) in communication with a temperature probe, the temperature in the inspiratory tube 103 and / or the patient interface 115 can be adjusted to raise the temperature above the saturation temperature. In addition to the temperature probe and heating line (or as an alternative to the temperature probe and heating line), the patient interface 115 may also include a ventilator interface, as described in more detail below with respect to Figures 11A, 11B and 12.

[0041] In Figure 1, the exhaled humidified gas is returned to the ventilator / blower 105 from the patient interface 115 via the exhalation tube 117. The exhalation tube 117 preferably comprises a breathable foam material as described below. However, the exhalation tube 117 may also be a medical tube, as is known in the art. In either case, the exhalation tube 117 may be equipped with a temperature probe and / or heating line integrated to reduce the risk of rainout, as described above with respect to the inspiratory tube 103. Furthermore, the exhalation tube 117 does not need to return the exhaled gas to the ventilator / blower 105. Alternatively, the exhaled humidified gas can be sent directly to the ambient environment or to other auxiliary equipment, such as an air scrubber / filter (not shown). In certain embodiments, the exhalation tube is omitted entirely.

[0042] Foamed polymer for forming breathable components As explained above with respect to Figure 1, medical circuits such as breathing circuits can utilize breathable components, such as tubes or patient interfaces. It is desirable that these components be breathable to prevent rainout. One measure of material breathability is permeability (g-mm / m²). 2 It is expressed as per day. Another measure of breathability is the diffusivity of water in the material (diffusivity coefficient, cm²). 2 (Measured in seconds). Under similar test conditions, for example, at similar temperatures, the permeability and diffusivity of a given material are directly proportional to each other. Permeable thermoplastic elastomer materials (TPE in accordance with ISO 18064:2003(E), which is incorporated herein by reference as part of the disclosure) are known to be particularly suitable for forming these permeable components. However, these known materials are brittle and require sufficient reinforcement to be usable.

[0043] The relationship between permeability and strength has been found to be unexpectedly improved by the foamed polymer material (including known permeable polymers) used to form the parts. By incorporating highly permeable foamed materials, it is possible to manufacture parts that have both relatively high bending stiffness and high permeability. Similarly, parts formed from the foamed materials described herein may also have relatively high resistance to crushing and resistance to buckling. As a result, it is possible to manufacture tubes that meet the requirements of the ISO 5367:2000(E) standard (i.e., testing for increased flow resistance) without special reinforcement, and furthermore, have sufficient permeability and appropriate “internal” properties (e.g., thickness, material, material composition, modulus of elasticity, permeability, and / or internal stiffness), as will be defined in more detail later. ISO 5367:2000(E) is incorporated herein by reference. For example, permeable thermoplastic elastomer (TPE) materials, such as ARNITEL® VT 3108, have been found to be particularly suitable for foaming and molding parts in various embodiments. Since this material is molded into products or parts, the relationship between breathability and strength can be significantly improved by foaming the material.

[0044] Accordingly, certain embodiments involve realizing the formation of permeable components using specific foamed polymers to combine significantly improved properties, Young's modulus (rigidity) and permeability (air permeability) compared to known permeable materials. These novel foamed polymers, as well as techniques for forming foamed polymers and medical circuit components incorporating such foamed polymers, are described herein as illustrative examples. Because these foamed polymers are highly permeable, water vapor can rapidly diffuse through them. This reduces the accumulation of condensation within the component by allowing water vapor to permeate from the humidifying gas within the component to the surrounding atmosphere or to other dryer gases on the opposite side of the component. Furthermore, components formed from these foamed polymers are also rigid, self-supporting, compressively resistant, or semi-rigid, and may even not require further reinforcement. Because foamed polymers permeate water vapor from gases but not liquid water, they are useful for forming medical circuit components. Foamed polymers are also substantially impermeable to bulk gas flows, and therefore they can also be used to form components for delivering humidifying gases.

[0045] Generally, the foamed polymer according to at least one embodiment is a breathable foamed thermoplastic polymer. Preferably, the breathable thermoplastic polymer is a foamed thermoplastic elastomer (or TPE as defined by ISO 18064:2003(E)), for example, (1) a copolyester thermoplastic elastomer (e.g., ARNITEL®, which is a copolyester thermoplastic elastomer containing polyether soft segments, or other TPC or TPC-ET materials as defined by ISO 18064:2003(E)), or (2) a polyether block amide (e.g., PEBAX®, which is a polyamide thermoplastic elastomer containing polyether soft segments, or other TPA-ET materials as defined by ISO 18064:2003(E)), or (3) a thermoplastic polyurethane (TPU material as defined by ISO 18064:2003(E)), or (4) a foamed polymer blend, for example, a TPE / polybutylene terephthalate (PBT, e.g., DURANEX® 500FP) blend. If the breathable thermoplastic polymer is a foamed TPE / PBT blend, the blend preferably comprises between 80% and 99% by weight (or about 80% to 99% by weight) of TPE and between 20% and 1% by weight (or about 20% to 1% by weight) of PBT.

[0046] In any of the above embodiments, the porosity of the foamed material may be greater than 25% (or about 25%), for example, between 25% and 60% (or about 25% and 60%), or between 30% and 50% (or about 30% and 50%). In at least one embodiment, 5% (or about 5%) or less of the voids in the foamed material have a diameter greater than 500 μm. Figure 2A shows log / log plots of literature values ​​for permeability and Young's modulus for permeable materials known in the art. The values ​​vary by six orders of magnitude for both elastic modulus and permeability. Figure 2B adds data points to Figure 2A for examples of exemplary foamed polymers according to various embodiments disclosed herein, labeled 1 to 4 and 6. The combinations of permeability and modulus for all known materials are given by the following formula:

number

[0047] In the foamed polymer materials represented by points 1-4, 6, and 8 in Figure 2B, the permeability P is given by the following formula:

number

[0048] The permeability and modulus of the foamed polymer can be selected to provide improved stiffness and / or permeability in the component incorporating the foamed polymer. Preferably, the material must be sufficiently stiff so that it does not easily collapse or kink or change volume under pressure. For example, a permeable foamed polymer needs to be sufficiently stiff so that it can be bent around a 25 mm diameter metal cylinder without kinking or collapsing, as defined by a test for increased flow resistance with bending in accordance with ISO 5367:2000(E). Therefore, in at least one embodiment, the modulus M is greater than 30 MPa (or about 30 MPa). The line for M=30 MPa is shown as line 203 in Figure 2B. However, it may also be desirable to limit the stiffness of a component to make it easier to handle or to increase patient comfort. Therefore, in certain embodiments, the modulus M can be limited to less than 1000 MPa (or about 1000 MPa). The line for M=1000 MPa is shown as line 205. Furthermore, it may be desirable to limit the modulus of elasticity M to less than 800 MPa (or approximately 800 MPa) or less than 500 MPa (or approximately 500 MPa).

[0049] In addition, it is sometimes desirable to select a sufficiently high permeability to prevent or reduce condensation in various general-purpose and medical components. The diffusivity of foamed polymers was found to be a function of the void volume fraction. This is shown in Table 1, which summarizes the ratio of the diffusivity at a specific void fraction (D) at each relative humidity (RH) to the diffusivity of solid ARNITEL™ VT 3108 (D0) at the same RH. The data from Table 1 are plotted in Figure 3.

[0050] [Table 1]

[0051] Therefore, it is possible to determine appropriate permeability by selecting an appropriate level of permeability and / or porosity of the foamed polymer. In a particular embodiment, the permeability P is 60 g-mm / m² as measured according to procedure A of ASTM E96. 2 / day (or approximately 60g-mm / m 2 Larger than / day. Permeability 60g-mm / m 2 / day represents a 66% increase compared to solid ARNITEL™ VT 3108. P = 60 g-mm / m 2 The line for / day is shown as straight line 207. Also, in some embodiments, 70 MPa g-mm / m 2 / day (or approximately 70g-mm / m 2 It may sometimes be desirable to select a permeability P greater than / day.

[0052] It is possible to correlate permeability with the corresponding porosity. Permeability: 60 g-mm / m 2 The value per day is 1.66 times that of solid ARNITEL™ VT 3108. Since we know that permeability is directly proportional to diffusivity, we can determine the corresponding porosity when the diffusivity ratio is greater than 1.66 from Figure 3. According to Figure 3, the corresponding porosity is greater than 25%. Therefore, in certain embodiments, the porosity is greater than 25% (or about 25%). Also, in some embodiments, it may be desirable to select a porosity greater than 30% (or about 30%). A porosity of 30% corresponds to a permeability of 70 g-mm / m³, as described above. 2 / day (or approximately 70g-mm / m 2 Corresponds to / day)

[0053] Furthermore, it may be desirable to limit the porosity of the foamed polymer to prevent liquid water from leaking through the voids. If the foamed polymer does not have an outer skin layer structure (discussed in more detail below), it may be desirable for the porosity to be less than 45% (or about 45%). If the foamed polymer has an outer skin layer structure, it may be preferable for the porosity to be less than 60% (or about 60%). For the formation of medical circuit components described herein, it has been found that the porosity of foamed ARNITEL® VT 3108 is preferably between 25 and 60% (or about 25 and 60%). For example, at a porosity of 30% (or around that), the permeability of Arnitel VT3108 can be improved by up to twofold. Relatively minor decreases in elastic modulus can be compensated for by increasing the thickness of the component, as described below, while maintaining similar permeability. For the formation of these components, it has been found that foamed ARNITEL® VT 3108 is particularly well-suited when its porosity is between 30 and 50% (or approximately 30 and 50%). It should be understood that the foregoing is merely an example of a suitable porosity and corresponding material properties.

[0054] As discussed above, another measure of material permeability is the diffusivity of water in the material (diffusivity coefficient, cm²). 2 (Measured in / seconds). Under similar test conditions, the permeability and diffusivity of a particular substrate are directly proportional to each other. In various embodiments, the foamed polymer is 3 × 10⁻¹⁶. -7 cm 2 Greater than / second (or around that), more preferably 6 × 10 -7 cm 2 It has a diffusion coefficient greater than / sec (or around that). For example, a 0.1625 cm diameter rod of foamed ARNITEL™ VT 3108 with a porosity of 47% has a diffusion coefficient of 7.6 × 10⁻¹⁶. -7 cm 2 It is calculated to be equal to (or approximately equal to) / second. As another example, a 0.0505cm thick film of foamed ARNITEL™ VT 3108 with a 13% porosity has a diffusion coefficient of 3.3 × 10⁻⁶. -7 cm 2It is calculated to be equal to (or approximately equal to) / second.

[0055] Samples 1-4 in Figure 2B consist of foamed ARNITEL® VT 3108. These materials, particularly sample 4 with a 53% porosity, are found to perform better than any other known material in terms of the combination of permeability and modulus. In sample 4, the foaming process resulted in an average increase of approximately 6.5 times in permeability at 97% RH, and the modulus was 30% of that of pure ARNITEL® VT 3108.

[0056] In Figure 2B, point 1 represents the data for sample name "AB 14.2a". AB 14.2a is an ARNITEL™ VT 3108 adult tube with an outer diameter of 24.5 cm. The experimental data collected for this sample includes micrographs (shown in Figures 4A to 4D and summarized in Table 2), porosity and average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and changes in diffusivity with respect to RH (summarized in Table 1).

[0057] Point 2 represents the data for sample name "MB27 4%". MB27 4% is a foamed corrugated ARNITEL® VT 3108 infant tube with an outer diameter of 15.46 cm. The tube was extruded from a mixture of base polymer (ARNITEL® VT 3108) and 4 wt% (or approximately 4 wt%) of foaming agent masterbatch (containing polyethylene and 20 wt% Clariant HYDROCEROL® BIH-10E). Experimental data collected for this sample include micrographs (shown in Figures 4E and 4F, summarized in Table 2), porosity and average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and change in diffusivity with RH (summarized in Table 1).

[0058] Point 3 represents the data for sample "FIIA-2". FIIA-2 is a foamed extruded strip of ARNITEL® VT 3108. The experimental data collected for this sample includes micrographs (shown in Figures 4G and 4H, summarized in Table 2), porosity and average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and changes in diffusivity with respect to RH (summarized in Table 1). Changes in dimensions with respect to water content were also measured. The change in length with respect to water content is given by the following formula:

number

[0059] Point 4 represents the data for sample "FIIA-5". FIIA-5 is a foamed extruded strip of ARNITEL® VT 3108. The experimental data collected for this sample includes micrographs (shown in Figures 4I and 4J, summarized in Table 2), porosity and average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and changes in diffusivity with respect to RH (summarized in Table 1). Changes in dimensions with respect to water content were also measured. The change in length with respect to water content (ΔX / X0) is given by the following formula:

number

[0060] Point 5 represents the data for sample name "80 / 20 ARNITEL / PBT". 80 / 20 ARNITEL / PBT is an extruded polymer strip made from an 80 / 20 weight percent blend of ARNITEL® VT 3108 and polybutylene terephthalate (PBT). Experimental data collected for this sample include micrographs (shown in Figure 4K and summarized in Table 2), average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and diffusivity at RH=100 (summarized in Table 1).

[0061] Point 6 represents the data for the sample named "Foam 80 / 20 ARNITEL / PBT". Foam 80 / 20 ARNITEL / PBT is a trademark of ARNITEL (VT). This is a foamed extruded strip of polymer made from an 80 / 20 weight percent blend of 3108 and PBT. Experimental data collected for this sample include micrographs (shown in Figures 4L and 4M, summarized in Table 2), porosity and average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and diffusivity at RH=100 (summarized in Table 1).

[0062] Point 7 represents the data for sample "FIIA-1". FIIA-1 is an extruded strip of solid Arnitel 3108. The experimental data collected for this sample includes micrographs (shown in Figures 4N and 4O, summarized in Table 2), average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and change in diffusivity with respect to RH (summarized in Table 1). Changes in dimensions with respect to water content were also measured. The changes in all three dimensions (length, width, and thickness) with respect to water content were observed to be approximately the same (i.e., isotropic expansion), and the following formula applies:

number

[0063] Finally, point 8 represents the data for the sample named "Foamed TPU / Acetal 10%". Foamed TPU-Acetal 10% is an extruded strip of a foamed blend of ESTANE® 58245 (TPU) and acetal. The experimental data collected for this sample included porosity and average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and diffusivity (shown in Table 4).

[0064] Figure 2B also shows a point labeled "FmdAd1". FmdAd1 is an ARNITEL™ VT 3108 adult-use foamed corrugated tube with an outer diameter of 24.5 cm. The experimental data collected for this sample included porosity and average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and changes in diffusivity with respect to RH (summarized in Table 1).

[0065] Additional non-foaming and foaming polymer materials not shown in Figure 2A or Figure 2B are listed below.

[0066] "Batch 15 wts", "Batch 15 f", "MB27 0%", "MB27 6%", "MB22.1", "MB32.1", and "MB41.4" are foamed corrugated ARNITEL® VT 3108 infant tubes with an outer diameter of 15.46 cm. Experimental data collected for these samples included porosity and average sample thickness (shown in Table 3), as well as changes in diffusivity with respect to RH (summarized in Table 1). For MB32.1, the change in length with respect to water content was also measured. This change is expressed by the following formula:

number

[0067] "TPU, ESTANE 58245" is a non-foamed corrugated TPU (ESTANE® 58245) tube with a wall thickness of 0.048 cm. Experimental data collected for this sample (this same) included porosity and average sample thickness (shown in Table 3), elastic modulus (shown in Table 4), and diffusivity (shown in Table 4).

[0068] [Table 2]

[0069] Microscopic images reveal that the foamed polymer samples (samples 1-4 and 6) contain air bubbles or voids within the solid polymer. The lateral size of these voids should ideally be less than 30% (or approximately 30%) of the foamed polymer thickness, for example, less than 10% (or approximately 10%) of the total thickness.

[0070] From the microscope image, also, above lines 201 and 207 in Figure 2B (P>60g-mm / m 2 It can also be seen that in certain foamed polymer samples (i.e., samples 1-4) in [location], the voids are substantially flattened rather than spherical. The flattened shape of the voids causes the polymer within the voids to also be flattened. The flattened shape of the polymer has been found to improve the mechanical properties of parts comprising foamed polymers. It is believed that increasing the length of the continuous polymer in the longitudinal direction increases the modulus of elasticity in this direction. Therefore, at least one embodiment involves realizing that it may be advantageous for the foamed polymer to have at least some voids, e.g., at least 80% or so, and that these voids are flattened along the longitudinal axis. The aspect ratio (length to height) of this flattening is preferably at least 2:1 (or about 2:1) or at least 3:1 (or about 3:1), e.g., between 2:1 and 7:1 (or about 2:1 and 7:1) or between 3:1 and 7:1 (or about 3:1 and 7:1).

[0071] In addition, it was also observed in these samples that the voids were not isolated from each other. Many of these voids are connected or joined. That is, the foamed polymer has "closed cells". The closed cell structure of these foamed polymers allows the movement of water vapor over a greater distance both axially (or laterally) and longitudinally, without having to pass through the solid polymer, thus improving breathability. It is desirable that at least 10% (or about 10%) of the voids in the foamed polymer are interconnected. In some embodiments, at least 20% (or about 20%) of the voids are connected to other voids.

[0072]

Table 3

[0073]

Table 4

[0074] In Table 4, the permeability data for the samples based on ARNITEL (trademark) was calculated using the following relationship:

Equation

Equation

[0075] Another suitable foamed polymer material is polyether-based thermoplastic polyurethane (TPU), which has good breathability and tear resistance. However, TPU has insufficient stiffness (low Young's modulus). Many studies have attempted to improve its stiffness by mixing it with other polymers. However, while blending TPU with other polymers may be effective in increasing stiffness, it has been found that a serious decrease in the breathability of the blended polymer can occur.

[0076] After testing, a blend was identified that significantly improved mechanical stiffness without reducing permeability to an unacceptable level. An example blend is the copolyester TPE / PBT blend discussed above. Another example blend comprises TPU and polycarbonate-acrylonitrile butadiene styrene (PC-ABS, for example, marketed as WONDERLOY®). A preferred weight ratio of TPU:WONDERLOY® is 70:30 (or approximately 70:30). Tests conducted using a 19mm diameter uniscrew extruder showed that the tensile strength of the blend showed a significant improvement in stiffness (14 times or more) compared to TPU alone, while the water vapor permeability showed only a slight decrease in permeability (30% or more). As described above, further improvements in permeability and stiffness can be achieved by foaming the TPU-WONDERLOY® polymer blend.

[0077] As discussed above, yet another exemplary blend according to at least one embodiment comprises TPU (ESTANE® 58245) and acetal, which are compounds with very low permeability and water absorption. Foamed strips (porosity between 15–20% or about 15–20%) were prepared from ESTANE® 58245 and acetal in a weight ratio of 70:30 (or about 70:30). The average sample thickness was 0.139 cm. The water absorption of the blend at 100% RH was 0.38 g of water per 1 g of dry polymer (38%). The diffusivity of the sample was measured from the desorption curve and was 6.59 × 10⁻⁶ at 23°C. -6 cm 2 It was found to be / second. The elastic modulus of the sample was 34 MPa, and the permeability was 151 g-mm / m 2 It was calculated to be per day.

[0078] These results are compared to a control example containing non-foaming TPU (ESTANE® 58245). A bellows tube was extruded with a wall thickness of 0.048 cm, and water absorption at 100% RH was 0.53 g of water per gram of dry polymer (53%). The diffusion rate of the non-foaming sample was measured from the desorption curve and was 2.41 × 10⁻⁶ at 23°C. -7 cm 2 It was found to be / second. The elastic modulus was 18 MPa. The permeability of this polymer was 80 g-mm / m 2 / day

[0079] Parts containing foamed polymer The breathable foam materials described above are well-suited for many medical components where high breathability, self-supporting properties, and a semi-rigid nature are advantageous. Therefore, all the details of the breathable foam materials discussed above are applicable to these components. The following are just a few examples of components where these breathable foam materials offer new advantages that were previously impossible. By manipulating porosity, thickness, and void size, various customizations of the internal properties of the formed components become possible.

[0080] Generally, the component is a wall that defines an internal space, and at least a portion of the wall is made of the permeable foam material described above, which allows water vapor to pass through from the gas in the space but not liquid water. Preferably, the wall is also impermeable to bulk gas flows in the space, including breathing gases, anesthetic gases, inhaled gases and / or smoke.

[0081] The wall forms a water vapor passage from the gas space to the region opposite the wall for permeability. In some embodiments, a water vapor passage exists from the gas space to the atmosphere through the permeable foam material. This passage can be a direct path, and the wall is directly exposed to the atmosphere. Alternatively, the passage can be indirect, passing through one or more other walls between the gas space and the atmosphere. In other structures, a second gas space (called a sweep gas space) may exist on the opposite side of the wall instead of the atmosphere. From this sweep gas space, the water vapor can then be indirectly discharged to the atmosphere. In this case, the water vapor passage extends from the gas space to the sweep gas space.

[0082] In any of the above embodiments, the entire enclosure wall can be formed from a foamed material. In at least one embodiment, at least one region of the wall has a thickness between 0.1 and 3.0 mm (or about 0.1 and 3.0 mm), for example, between 0.1 and 1.5 mm (or about 0.1 and 1.5 mm). For example, at least one region of the wall may have a thickness between 0.7 and 1.0 mm (or about 0.7 and 1.0 mm) or between 0.7 and 3.0 mm (or about 0.7 and 3.0 mm).

[0083] In any of the above embodiments, the wall may include at least two zones. The first zone is an outer skin layer comprising a layer of substantially closed-cell foam material, and the second zone is an inner layer adjacent to the outer layer and located between the outer layer and the gas space. The thickness of the skin layer may be between 5-10% (or about 5-10%) of the wall thickness, for example, between 10-50 μm (or about 10-50 μm). Each of the first and second zones has voids. In certain embodiments, 5% (or about 5%) of the voids in the first zone have a diameter greater than 100 μm. The voids in the second zone are larger than the voids in the first zone. For example, in some embodiments, 5% (or about 5%) of the voids in the second zone of the foam material have a diameter greater than 700 μm.

[0084] In any of the above embodiments, the wall may also include at least one reinforcing rib that stiffens the wall or at least one region, in which part the wall is locally thickened to stiffen the wall.

[0085] The components may include a patient interface; or a tube, such as a breathing tube used in a breathing circuit; or a tube and at least a portion of a patient interface; or a conduit used in a breathing circuit (i.e., a portion of a tube that does not need to be sealed around its periphery); or a mask (including a mask frame and a seal extending around the mask frame, wherein the mask frame includes a wall, the substantial majority of which is formed from a breathable foam material); or a component of an inhalation system, such as a tube or conduit used in at least a portion of the exhaust arm of an inhalation system.

[0086] Next, refer to Figure 5. Figure 5 shows a component 501 according to at least one embodiment. Component 501 is configured with a wall 503 that defines a gas space 505 on one side. The wall 503 comprises a breathable foamed polymer as described above. As shown by the dotted line 507, the wall may or may not define a completely sealed gas space 505. In use, the gas space can be substantially sealed such that the wall 503 defines a gas space 505 on one side of the wall 503 and the space 505 contains a moist gas.

[0087] A second gas space 509 exists on the opposite side of the wall 503. In at least one embodiment, the second gas space 509 is the atmosphere. The wall 503 of component 501 is made of a permeable foam material that allows water vapor to pass through but substantially impermeable liquid water and breathing gas bulk flows. The outer surface of the wall 503 is exposed to the atmosphere or a dry sweep gas in the second gas space 509 so that the gas in the space 505 can be dried by allowing water vapor to pass through the wall 503 to the second gas space 509, which may be, for example, the atmosphere. Drying the gas in the gas space 505 is useful to cause and / or prevent rainout that occurs in the gas space 505 when it is filled with relatively warm or humid gas / air / breathing gas.

[0088] In one embodiment, component 501 may be a patient interface, such as a breathing mask, and the gas space 505 may be at least partially defined by a wall 503 and by the patient's face (not shown) substantially enclosing the space 505. In this embodiment, the patient's face is represented by a dotted line 507. In another embodiment, component 501 may be a breathing tube (inspiratory or expiratory tube). The patient interface and breathing tube will be discussed in more detail below.

[0089] Ventilated tube In assisted breathing, particularly in medical applications, gases with high relative humidity levels are supplied and returned through flexible breathing tubes of relatively limited size, generally in diameters ranging from 10 to 25 mm (or approximately 10 to 25 mm) (applicable to both neonatal and adult tubes). Such breathing tubes are ideally very light, resistant to kinking or pinching, and flexible to ensure maximum performance and patient comfort. Lightweight breathing tubes are crucial to reduce the force on the patient interface due to the tube's weight. Similarly, to achieve a high level of patient comfort, the breathing tube must be flexible and easily bendable, which in turn improves patient compliance. However, extremely light and flexible components are usually fragile and prone to excessive kinking. Tubes containing the aforementioned foamed polymer have been found to be resistant to kinking and pinching, and furthermore, light and flexible enough to enhance patient comfort.

[0090] Since a tube is a type of component, the details of the components discussed above apply to the tubes discussed herein. Generally, a medical circuit tube comprises an inlet (for receiving humidified gas), an outlet (for releasing humidified gas), and a surrounding wall defining at least one gas passage between the inlet and the outlet, wherein at least a portion of the surrounding wall is made of a breathable foam material that is permeable to water vapor but substantially impermeable to liquid water and respiratory gas bulk flow. In at least one embodiment, the tube is an extruded bellows. A medical circuit tube can be used as a tube or conduit for a breathing tube or conduit or for the rim of an inhalation system. For example, the tube may be an exhalation tube or an exhaust conduit, individually. The tube may also be part of the patient interface.

[0091] The tube may be flexible; that is, it can be bent around a 25 mm diameter rod without kinking or crushing. More specifically, the tube is flexible as defined by passing a test for the increase in flow resistance due to bending in accordance with ISO 5367:2000(E).

[0092] In any of the above embodiments, the pipe may be between 1 and 2 m (or about 1 and 2 m) in length, for example, 1.5 m (or about 1.5 m). The pipe may have an average diameter between 10 and 25 mm (or about 10 and 25 mm). In at least one embodiment, the pipe has a wall thickness between 0.1 and 1.2 mm (or about 0.1 and 1.2 mm), for example, between 0.6 mm and 1.0 mm (or about 0.6 and 1.0 mm). It is preferable that the pipe has a permeable enclosure wall over a substantial portion of its total length. For example, in at least one embodiment, at least 80% of the length of the pipe has a permeable enclosure wall. It is preferable that the permeable wall is located near the inlet end of the humidifying gas receiving pipe. For example, in a pipe 1.5 m (or about 1.5 m) long, at least 1.2 m (or about 1.2 m) of the pipe from near the inlet end has a permeable wall.

[0093] The wall forms a water vapor passage from the gas space to the region opposite the wall for permeability. In some embodiments, there is a water vapor passage from the gas space to the atmosphere through the permeable foam material. The passage can be a direct path, and the wall is directly exposed to the atmosphere. For example, in at least one embodiment, the tube is a breathing tube, with a first connector at the inlet and a second connector at the outlet. There is only one gas passage for the length from the inlet connector to the outlet connector.

[0094] Alternatively, the passage may be indirect, and the path may pass through one or more other walls between the gas space and the atmosphere. In other structures, on the opposite side of the wall, instead of the atmosphere, there may be a second gas space (called a sweep gas space). From this sweep gas space, the water vapor can then be indirectly discharged into the atmosphere. In this case, the water vapor passage extends from the gas space to the sweep gas space. For example, the tube may be a coaxial breathing tube. In a coaxial breathing tube, the gas space is the inspiratory limb or the expiratory limb, and the second gas space is the inspiratory limb or the remainder of the expiratory limb. There is one gas passage between the inlet and outlet of the inspiratory limb, and another gas passage between the inlet and outlet of the expiratory limb. In one embodiment, the gas space is the inspiratory limb and the second gas space is the expiratory limb. Alternatively, the gas space may be the expiratory limb and the second gas space may be the inspiratory limb.

[0095] As described above in relation to the description of the aforementioned components, in any of the above embodiments, the wall may include at least two zones. The first zone is an outer skin layer comprising a layer of substantially closed-cell foam material, and the second zone is an inner layer adjacent to the outer layer and located between the outer layer and the gas space. The thickness of the skin layer may be between 5-10% (or about 5-10%) of the wall thickness, for example, between 10-50 μm (or about 10-50 μm). Each of the first and second zones has voids. In certain embodiments, 5% (or about 5%) of the voids in the first zone have a diameter greater than 100 μm. The voids in the second zone are larger than the voids in the first zone. For example, in some embodiments, 5% (or about 5%) of the voids in the second zone of the foam material have a diameter greater than 700 μm.

[0096] Furthermore, in any of the above embodiments, the pipe may be provided with a plurality of reinforcing ribs arranged in the enclosure wall. These ribs can generally be co-extruded together with the pipe so as to be aligned with the longitudinal axis of the pipe. Preferably, there are 3 to 8 reinforcing ribs, and more particularly, 3 to 5 reinforcing ribs.

[0097] In addition to the above, heaters, such as resistance heating wires, may be installed in the pipe passage or pipe wall to reduce or eliminate the formation of condensates inside the pipe and to maintain a substantially uniform temperature in the gas flow through the pipe during use.

[0098] In certain embodiments, the tube has a length of 1.525 m (or approximately), a weight of 54 g (or approximately), a porosity of 35% (or approximately), an air pressure compliance of 0.23 mL / cm H2O / m (or approximately), and a permeability of 85 g-mm / m 2 The duration is / day (or around that). The tube is formed from 95% (or about 95%) ARNITEL® VT 3108 and 5% (or about 5%) foaming agent masterbatch (containing polyethylene and 20% (or about 20% by weight) Clariant HYDROCEROL® BIH-10E).

[0099] Next, refer to Figures 6A and 6B. Figures 6A and 6B show a breathable tube 601 according to at least one embodiment. Figure 6A shows a side view of the tube 601, while Figure 6B shows a cross-section of the tube 601 along the same side view as in Figure 2A. In both Figures 6A and 6B, the horizontal axis is represented as line 603-603. The tube wall, shown as wall 605 in Figure 6B, is a breathable foam material as described above. Typical dimensions—for breathing tubes with a diameter between 12 and 20 mm (or approximately 12 and 20 mm) and a length between 1 and 2 m (or approximately 1 and 2 m) for neonatal and adult use, respectively, the wall 605 may be between 100 and 1500 μm (or approximately 100 and 1500 μm) in thickness. However, the wall 605 may be up to 3 mm (or approximately 3 mm) thick and may also provide better breathability.

[0100] The tube 601 is corrugated (i.e., the tube has a raised or grooved surface). Methods for forming the serrated tube are discussed in more detail below with respect to Figure 15. However, in some embodiments, the tube has a smooth surface. Next, refer to Figures 7A and 7B. Figures 7A and 7B show a permeable tube 701 according to at least one embodiment. In this case as well, the tube 701 is manufactured from a permeable foam material, as described in one of the embodiments herein. The tube further comprises a number of reinforcing ribs 703, which can be co-extruded together with the tube. The shape of the ribs 703 is determined by the extruder die head, and their size and degree of foaming are controlled by the temperature and pressure when extruding from the die head.

[0101] The ribs 703 can be formed from the same foamed polymer as the tube 701. Alternatively, the ribs 703 may be made from a different material than the tube. This can be achieved by co-extrusion. As shown in Figure 7A, the tube 701 can be extruded with the ribs 703 positioned in place, and then the tube can be corrugated to form the “dotted” structure shown in Figure 7B. In certain embodiments, the tube may have between 3 and 8 reinforcing ribs, for example, between 3 and 5 reinforcing ribs. Such additionally reinforced tubes can find independent applications in one or more of the tube components described herein with respect to medical circuits.

[0102] Next, refer to Figures 8A and 8B. Figures 8A and 8B show alternative structures for the ribbed permeable tube 801 according to at least one embodiment. In Figure 8B, the protruding ribs 803 are visible inside the tube 801 within the space between the ridges. Figure 8C shows a corrugator suitable for forming the tubes shown in Figures 8A and 8B. The block comprises protruding portions 805 between the raised portions 807, and these protruding portions form the protruding ribs when the tube is removed from the corrugator. It will be understood that the tube may be further reinforced with other reinforcing processes to further improve performance characteristics (e.g., compliance, tensile strength, flow resistance and compressive resistance with bending, etc.). These processes may or may not be integrated with the tube forming process.

[0103] Next, refer to Figure 9. Figure 9 shows another exemplary medical circuit according to at least one embodiment. These circuits comprise two breathable tubes, namely an inspiratory tube 103 and an exhalatory tube 117, comprising the breathable foam polymer described above. The characteristics of the inspiratory tube 103 and the exhalatory tube 117 are the same as those of the tubes described above with respect to Figure 1. The inspiratory tube 103 comprises an inlet 109 communicating with a humidifier 115 and an outlet 113 through which humidified gas is supplied to the patient 101. The exhalatory tube 117 also comprises an inlet 109 receiving humidified gas exhaled from the patient and an outlet 113. As described above with respect to Figure 1, the exhaled gas can be discharged from the outlet 113 of the exhalatory tube 117 into the atmosphere, to a ventilator / blower unit 115, to an air scrubber / filter (not shown), or to any other suitable location.

[0104] As described above with respect to Figure 1, the heating element 901 can be placed inside the inhalation tube 103 and / or the exhalation tube 117 to reduce the risk of rainout in the tube by raising the temperature to a temperature above the saturation temperature.

[0105] In this embodiment, the exhalation tube 117 includes a connector (in this case, a Y-connector 903) for connecting to other components. For example, the Y-connector 903 is configured to connect to the inspiratory tube 103 and a patient interface (not shown). Of course, the embodiment in Figure 9 is merely illustrative. A component according to at least one embodiment includes a breathable foamed polymer tube. That component may further include a suitable connector. It is preferable that the connector also includes a breathable foamed polymer.

[0106] Next, refer to Figure 10. Figure 10 shows a coaxial tube 1001 according to at least one embodiment. In this embodiment, the coaxial tube 1001 is positioned between the patient 101 and the ventilator 1005. Exhaled and inhaled gases flow through either the inner tube 1007 or the space 1009 between the inner tube 1007 and the outer tube 1011, respectively. It will be understood that the outer tube 1011 does not need to be precisely aligned with the inner tube 1007. Rather, "coaxial" means a tube located inside another tube. During use, as will be explained below, water vapor permeates the permeable foam tube wall, but liquid water does not.

[0107] For heat transfer, the inner tube 1007 carries the inhaled gas within its internal space 1013, while the exhaled gas is carried in the space 1009 between the inner tube 1007 and the outer tube 1011. This airflow structure is indicated by the arrows.

[0108] The inner tube 1007 is formed using the permeable foam material described herein. Therefore, moisture in the exhalation space 1009 can pass through the permeable foam material and humidify the intake airflow in the intake space 1013. By using a gas flow in a counterflow configuration as shown in the embodiment, the permeable material provides substantially passive humidification of the intake airflow.

[0109] When using coaxial tube 1001, the ventilator 1005 may not detect leaks in the inner tube 1007. Such leaks may cause the patient 101 to bypass the airflow, resulting in insufficient oxygen supply to the patient. Such bypasses can be detected by placing a sensor at the patient-side end of the coaxial tube 1001. This sensor may be installed within the patient-side end connector 1015. If a bypass occurs near the ventilator 1005, the patient 101 will continuously rebreathe the airflow volume near the patient 101. This will cause an increase in carbon dioxide concentration in the inspiratory airflow space 1013 near the patient 101, an increase that can be directly detected by a CO2 sensor. Such a sensor may include any of several similar sensors currently on the market. Alternatively, this rebreathing may be detected by monitoring the gas temperature at the patient-side end connector 1015, in which case a temperature rise exceeding a predetermined level indicates that rebreathing is occurring.

[0110] In addition to the above, in order to reduce or eliminate the formation of condensates inside either the inner tube 1007 or the outer tube 1011, and to maintain a substantially uniform temperature in the gas flow through the coaxial tube 1001, heaters, such as resistance heating wires, may be placed inside either the inner tube 1007 or the outer tube 1011, within the gas space 1009 or 1013, or within the walls of the inner tube 1007 or the outer tube 1011 themselves.

[0111] In alternative embodiments of the coaxial tube 1001 where passive humidification is undesirable, the outer wall of the outer tube 1011 may be a breathable foam wall. In this configuration, the outer tube 1011 is in contact with the atmosphere, and its breathable wall allows for water vapor exchange between the relatively moist exhaled gas and the atmosphere. As a result, rainout can be addressed and / or prevented.

[0112] Breathing mask In the field of respiratory equipment, there are well-known types of respiratory masks that cover a patient's nose and / or mouth to provide a continuous seal around the nasal and / or oral regions of the patient's face, allowing for positive pressure delivery of gas within the mask for patient ingestion. The use of such masks ranges from breathing at high altitudes (e.g., aviation applications) to mining and firefighting applications, as well as various medical diagnostic and therapeutic applications.

[0113] One application of such masks is in humidification procedures for respiration. This system typically consists of a ventilator, humidifier, breathing circuit, and patient interface, such as a mask or nasal cannula. In this form of procedure, moist air is supplied to the patient, and as a result of the temperature difference between the moist air and the surrounding environment, the moist air can condense and form water droplets. If the procedure is prolonged (up to several days), these water droplets can accumulate inside the mask, potentially obstructing the procedure, increasing the risk of the patient inhaling water, and causing discomfort and / or difficulty breathing.

[0114] One requirement for such a respiratory mask was that it provide an effective seal to the patient's face to prevent leakage of the supplied gas. Generally, previous mask designs achieved a good mask-face seal, but often caused considerable discomfort to the patient. This problem is most significant in the aforementioned applications, particularly in medical applications where patients are required to wear such masks continuously for hours or even days. In such situations, patients may not be able to tolerate the mask for extended periods, and therefore the optimal treatment or diagnostic goals may not be achieved, or they may be achieved with great difficulty and considerable discomfort.

[0115] Various improvements in the delivery of respiratory therapy are described below. In particular, a patient interface that can be worn without discomfort by the patient is described herein, and which includes at least a partially water vapor permeable (breathable) area in the body of the patient interface made of the breathable foam material described herein. The majority (or the entirety) of the mask body can be made of the breathable foam material, taking advantage of its unique strength properties and high breathability.

[0116] Next, refer to Figures 11A and 11B. Figures 11A and 11B show a respiratory mask 1101 according to at least one embodiment. While it will be understood that this patient interface can be used in general respiratory management or with a ventilator, its use in a humidified positive airway pressure (PAP) system will be described below. It will also be understood that the following description may be applied to nasal masks, mouth masks, mouth-nasal masks, nasal prongs and full-face masks, rather than being limited to the ultrathin film structures of the prior art, due to the material's ability to form a self-supporting semi-rigid structure with high breathability.

[0117] The mask 1101 includes a hollow body 1103 with an inlet 1105 for connection to an inspiratory tube. The mask 1101 is fitted to the face of the patient 101, and the headgear 1109 is secured around the back of the patient's head. The securing force of the headgear 1109 to the hollow body 1103 ensures sufficient compressive force on the mask cushion 1111 to provide an effective seal against the face of the patient 101. Multiple connecting clips are attached to the hollow body for mounting sliding members for connecting the mask 1101 to the headgear 1109. Exhaled gases may be released from a valve (not shown) in the mask 1101, a further exhalation conduit (not shown), or any other similar means known in the art.

[0118] The hollow body 1103 is composed of the foamed polymer material described herein. Such material not only provides the mask 1101 with the necessary rigidity but also with high breathability. Previous attempts to provide breathable areas to the mask 1101 have required the use of thin films to achieve sufficiently high breathability. These films needed to be supported by additional reinforcement, such as a rigid mask frame, and also needed to be protected from damage. The areas of the breathable films are usually supported within the cutouts of the mask frame. However, with the self-supporting breathable foamed polymer described herein, its unique strength properties and high breathability allow a large portion (or the entire mask 1101) to be made of that foamed polymer. The result is a self-supporting semi-rigid mask 1101 that can be fully (and highly) breathable.

[0119] Alternatively, the hollow body 1103 may be largely composed of a front cutout, such that the hollow body 1103 is substantially composed of a framework having an outer perimeter. To prevent or reduce the formation of water droplets inside the mask 1101 during prolonged humidification treatment, inserts made from the self-supporting breathable foam material described herein can be placed and bonded within the cutout, thereby allowing moisture to be discharged into the surrounding environment. Several techniques exist for attaching the breathable structure to the hollow body 1103, and these techniques may include bonding, ultrasonic welding, overmolding, co-extrusion, or snap-fit ​​connections between the breathable foam insert and the hollow body 1103.

[0120] For example, it may be understood that additional structural reinforcement can be applied to a mask made of breathable foam material to further customize the bending properties of its components. For instance, ribs may be added to the inner and / or outer surfaces of the mask. Local variations in wall thickness may also be employed to stiffen / weather certain parts to improve the fit to the patient's facial features and / or to provide areas of higher breathability. In particular, this type of reinforcement can be very useful in matching the bending properties of the components to specific directions in which various load patterns are expected. These advantages were either impossible or not easily achievable with the ultrathin breathable membranes used until now.

[0121] Nasal cannula Next, refer to Figure 12. Figure 12 shows a patient interface for a nasal cannula 1201 according to at least one embodiment. The nasal cannula 1201 comprises a cannula body 1203 and a short delivery tube 1205. The breathable foam polymer described herein can be used in the cannula body 1203 and / or the short delivery tube 1205 to address and / or prevent rainout occurring in the gas space of these components. As previously described, applications can also be found in the inspiratory tube 601.

[0122] Catheter mount Another medical circuit component to which breathable foam polymers can be applied is the catheter mount. The catheter mount connects a patient interface component, such as a mouthpiece, nasal mask, or endotracheal intubation tube, to the dual rim or breathing tube of the breathing circuit. The connection to the dual rim of the breathing circuit is generally via a Y-connector. In the patient's inhalation-exhalation cycle, each of the dual rims of the breathing circuit has a different role: one acts as the inhalation conduit and the other as the exhalation conduit. The catheter mount plays a dual role, transporting both inhaled and exhaled gases. Therefore, the catheter mount can have significant drawbacks. Between exhalation and inhalation, a certain amount of exhaled air remains in the catheter mount. Consequently, some of the air is rebreathed by the patient. While not necessarily unacceptable, rebreathing is generally undesirable, and if significant rebreathing is anticipated, the oxygen supply level needs to be increased.

[0123] The gas inhaled by the patient is delivered by a well-controlled ventilation system at a temperature close to body temperature, typically between 33 and 37°C (or approximately 33-37°C), with near-saturation humidity. This temperature can be maintained by a heater in the inspiratory tube until the gas enters the catheter mount. The gas exhaled by the patient is returned fully saturated and undergoes further cooling as it flows through the catheter mount. Therefore, condensation rarely forms on the inner wall during patient inhalation, but significant levels of condensation can occur during patient exhalation. Condensation that forms inside the catheter mount, i.e., rainout, is particularly harmful due to its proximity to the patient. Fluid condensation rehaled or inhaled by the patient can cause coughing fits or other discomfort.

[0124] Next, refer to Figure 13. Figure 13 shows a catheter mount 1301 according to at least one embodiment. The catheter mount 1301 incorporates a Y-connector 1303 at the ventilator-side end. The inner tube 1305 extends coaxially with the outer tube 1307. The inner tube 1305 is supported at its patient-side end by an inner tube connector 1309, which is supported via a support strut 1311 of the patient-side end connector 1313. The inner tube 1305 is supported at its other end by a second inner tube connector 1315, which forms part of the ventilator-side end Y-connector 1303.

[0125] The second internal tube connector 1315 communicates with the intake tube connector 1317. The outer tube 1307 has at least a portion of its wall made of the breathable foam material described herein. In certain embodiments, the outer tube 1307 is formed entirely of the breathable foam material.

[0126] Therefore, during use, the catheter mount 1301 has an inspiratory flow entering it, as indicated by arrow 1319. This inspiratory flow passes through the inner tube 1305 and exits to the patient through the patient-side end connector 1313, as indicated by arrow 1319. After patient discharge, whether or not an auxiliary device is used, the exhaled gases pass through the patient-side end connector 1313 and enter the space around the inner tube 1305, as indicated by arrow 1321. These gases travel along the inside of the wall of the outer tube 1307, as indicated by arrow 1321, and are discharged through the exhalation tube connector 1323 of the Y connector 1303, as indicated by arrow 1325. Water vapor can pass through the water vapor permeable foam outer tube 1307 as it passes through the space between the inner tube 1305 and the outer tube 1307 in the catheter mount 1301. In certain embodiments, the entire outer tube 1307 is permeable. In this way, the temperature of the exhaled gas may decrease slightly as it travels through the catheter mount 1301 to the exhalation tube connector 1323, but this temperature decrease coincides with the decrease in humidity due to water vapor passing through the permeable foam material of the outer tube 1307. Consequently, the relative saturation of the exhaled airflow decreases, thereby reducing rainout. The tube wall made of permeable foam material may have a wall thickness between 0.1 and 3 mm (or approximately 0.1 and 3.0 mm) and may be self-supporting or rigid enough to be semi-rigid while maintaining high permeability.

[0127] The catheter mount 1301 incorporating the breathable foam polymer described herein has a clear separation between the inspiratory and expiratory airflows passing through the catheter mount 1301, thereby significantly reducing rebreathing. Rainout is also reduced by lowering the humidity of the expiratory gas, even if the temperature of the expiratory gas decreases.

[0128] Intake component or smoke exhaust system Laparoscopic surgery, also known as minimally invasive surgery (MIS) or keyhole surgery, is a modern surgical technique that allows abdominal surgery to be performed through small incisions (usually 0.5-1.5 cm) compared to traditional surgical procedures which require larger incisions. Laparoscopic surgery includes procedures performed within the abdominal cavity or pelvic cavity.

[0129] During laparoscopic surgery under inhalation, it may be desirable to humidify the inhaled gas (generally CO2) before delivering it into the abdominal cavity. This can help prevent the "drying" of the patient's internal organs and reduce the time required for recovery from surgery. Even when using dry inhaled gas, the gas can become saturated as it draws moisture from the patient's body cavities. The moisture in the gas tends to condense on the exhaust rim or conduit walls of the inhalation system. Water vapor can also condense on other parts of the inhalation system, such as filters. It is highly undesirable for vapor to condense on the filter and for moisture to flow out along the rim (inlet rim or exhaust rim). For example, water condensed on the wall can saturate the filter and cause it to become clogged. This can increase back pressure and impair the system's ability to remove smoke. Furthermore, liquid water in the rim can flow into other connecting devices, which is also undesirable.

[0130] In abdominal surgery, for example, carbon dioxide gas is usually injected into the abdomen (pneumoperitoneum) to create a surgical field. The gas used is generally CO2, which is commonly found in the human body, absorbed by tissues, and removed by the respiratory system. CO2 is also non-flammable, which is important because electrosurgical devices are commonly used in laparoscopic procedures. The use of dry gases has been common in laparoscopic surgery. However, it is also desirable to humidify CO2 or other inhaled gases before introducing them into the abdominal cavity. This can help prevent the "drying" of the patient's internal organs and reduce the time required for recovery from surgery. Inhalation systems generally include a humidifier chamber that can hold a certain amount of water. Humidifiers generally include a heater plate that heats water to produce steam, which is then permeated into the incoming gas to humidify it. Such incoming gas, containing the steam, is then transported out of the humidifier.

[0131] Surgical procedures often involve electrosurgery, electrocautery, or, progressively, the use of lasers. The use of these devices generates surgical smoke in the space as tissue burns. Smoke removal systems using exhaust arms or rims are commonly used to remove smoke from the surgical site, thereby allowing the surgeon to see what they are doing and preventing this potentially harmful material from remaining in the body cavity postoperatively. One end of the exhaust arm or rim is connected to or inserted into a second incision (or sometimes the same incision). A typical smoke removal system commonly features a trocar and cannula at its end to assist in insertion into the surgical site. The smoke exits through the exhaust rim from the pneumoperitoneum abdominal area. The exhaust rim may be attached to the end of a laparoscopic surgical instrument so that the exhaust occurs near the site where electrocautery is performed. Typically, gases and smoke from the body cavity are filtered to remove particulate matter before being discharged into the atmosphere. Filters can also be further configured to remove chemicals and any harmful microorganisms from the surgical smoke.

[0132] Next, refer to Figure 14. Figure 14 shows an inhalation system 1401 according to at least one embodiment. The inhalation system 1401 comprises an inhaler 1403 that creates a flow of inhaled gas at a pressure above atmospheric pressure for delivery into the abdominal or peritoneal cavity of a patient 1405. The inhaled gas enters a humidifier 1407, which comprises a heater base 1409 and a humidifier chamber 1411, and in use, the chamber 1411 is in contact with the heater base 1409 so that the heater base 1409 supplies heat to the chamber 1411. Inside the humidifier 1407, the inhaled gas passes through the chamber 1411 so that the inhaled gas is humidified to an appropriate moisture level.

[0133] The inhalation system 1401 has a delivery conduit 1413 connecting a humidifier chamber 1411 to the patient's 1405 peritoneal cavity or surgical site. The conduit 1413 has a first end and a second end, the first end being connected to the outlet of the humidifier chamber 1411 and receiving humidified gas from the chamber 1411. The second end of the conduit 1413 is inserted into the patient's 1405 surgical site or peritoneal cavity, and the humidified inhaled gas moves from the chamber 1411 through the conduit 1413 into the surgical site to be inflated, inflating the surgical site or peritoneal cavity. The system also includes a control device (not shown) that adjusts the amount of humidity supplied to the gas by controlling the power supplied to a heater base 1409. The control device can also be used to monitor the water in the humidifier chamber 1411. A smoke exhaust system 1415 is shown, leading from the patient's 1405 body cavity.

[0134] The smoke exhaust system 1415 may be used in conjunction with the inhalation system 1401 described above or with other suitable inhalation systems. The smoke exhaust system 1415 comprises an exhaust rim or exhaust rim 1417, an exhaust assembly 1419 and a filter 1421. The exhaust rim 1417 connects the filter 1421 and the exhaust assembly 1419, and when in use, positions the exhaust assembly 1419 within or adjacent to the surgical site or peritoneal cavity of the patient 1405. The exhaust rim 1417 is a self-supporting tube (i.e., the tube is capable of supporting its own weight without collapsing) and has two open ends: a surgical site end and an exit side end.

[0135] The gas supplied by the inhalation system 1401 is already humidified at the point of entry into the patient's 1405 body cavity. Since the body cavity is already moist, the gas will not lose moisture within the body, however, if the gas has not reached its saturation point, it may become fully saturated. If the gas is dry at the point of entry into the body cavity, it will be humidified as it passes through the body cavity and absorbs moisture from the moist air within the body cavity over the internal organs.

[0136] As these saturated gases are discharged from the patient's 1405 body cavity, the gases travel along the cooler wall of the discharge rim 1417 (which is typically 1 m (or so) in length). Moisture in the gases tends to condense from the gases onto the discharge rim 1417, the wall of the discharge assembly 1419, and / or the filter 1421. The vapors condense on the filter 1421, and the condensed moisture on the wall flows out along the discharge rim 1417, which can saturate the filter 1421 and cause it to become clogged. This can increase back pressure and impair the system's ability to remove smoke.

[0137] Condensed moisture within filter 1421 can partially or completely clog filter 1421, leading to increased back pressure and reduced filtration efficiency due to the blockage. This is undesirable because the increased back pressure hinders the system's ability to effectively remove surgical smoke. Surgical smoke remaining at the surgical site within the surgical cavity or in the conduits of the drainage system can be harmful to the patient because it contains several potential toxins that may be taken into the patient's surgical cavity or tissues. The retention and failure of surgical smoke at the surgical site can obstruct or impede the surgeon's view, potentially leading to a dangerous working environment for the surgeon. Condensation can partially clog filter 1421, causing a decrease in its ability to filter toxins from surgical smoke. As a result, potentially harmful substances such as odors, surgical smoke, and dead cell components may leak into the operating room. These types of materials can be harmful to health and can cause numerous health problems for both physicians and patients.

[0138] At least one embodiment includes realizing the mitigation of this problem by using an exhaust rim 1417 with a breathable wall or a rim wall containing a breathable material. In particular, the breathable foam materials described herein are, from the properties discussed with respect to the foam materials, components and breathing tubes described previously, particularly suitable for forming the conduit of this type of inhalation system exhaust rim 1417. A certain amount of moisture in the released gas passes through the wall of the exhaust rim 1417 until it reaches the filter 1421, so that there is less moisture in the gas that condenses from the gas and clogs the filter 1421. Therefore, it is preferable that the exhaust rim 1417 be made of the breathable foam material described herein. The process for manufacturing a breathing tube, detailed below, can be directly applied to the tube of an inhalation system having an inlet rim or an exhaust (smoke exhaust) rim.

[0139] Manufacturing method Next, refer to Figure 15. Figure 15 shows an exemplary method for manufacturing a permeable component suitable for the delivery of humidifying gases (e.g., the tubes in the cases of Figures 2A and 2B or any other tubes discussed herein) according to at least one embodiment.

[0140] Generally, the method for manufacturing a part involves mixing a foaming agent with a polymer substrate to form a liquefied mixture. The foaming agent causes gas bubbles to be released into the substrate portion of the liquefied mixture. Then, the release of gas bubbles is stopped, and the mixture solidifies to form the desired part. The desirable properties of the finished part are discussed above.

[0141] In at least one embodiment, the process used to manufacture a component such as a breathing tube includes extruding a molten extruded material 1501 into a corrugator 1503 to form a desired component, such as a tube 1505. In a particular embodiment, the polymer substrate for the extruder has a diffusion coefficient of 0.75 × 10 -7 cm 2Greater than / sec (or around that). The substrate may have the following stiffness properties: (a) Tensile modulus greater than 15 MPa (or about 15 MPa) (this may be desirable for substrates based on urethane thermoplastic elastomer (or TPU-based substrates as defined by ISO 18064:2003(E)); or (b) Tensile modulus greater than 100 MPa (or about 100 MPa) (this may be desirable for substrates based on copolyester thermoplastic elastomer (or TPC-based substrates as defined by 18064:2003(E)), such as substrates based on ARNITEL®). These aforementioned properties are illustrative only. The substrate does not need to have these properties to produce a foam material with the desired breathability and stiffness, and the illustrative modulus values ​​are not expressly limited to TPU and TPC-based substrates.

[0142] Extruders such as those manufactured by Welex, equipped with a 30mm diameter screw and a 12mm annular die head with a 0.5mm gap, were found to be suitable for low-cost, short-time production of pipes. After being extruded from the extruder die head 1507, the molten pipe 1501 can be fed between a series of rotating molds or blocks of a corrugator 1503. Corrugators such as those manufactured and supplied by UNICOR® were also found to be suitable. This forms a serrated tube 1505.

[0143] The above methods are illustrative only. Alternative methods for forming parts comprising the foam materials described herein are also preferred. For example, another method for manufacturing a breathable part includes extruding strips of foam material, winding the foam strips onto a mandrel, and sealing the seams of the wound strips with beads (e.g., foam material beads).

[0144] Foaming during the extrusion process can be carried out in several ways, including physical foaming and chemical foaming.

[0145] In physical foaming, the foaming agent is an inert gas (e.g., CO2 or N2), which is injected into the extruder barrel at a flow rate and pressure high enough to dissolve the inert gas in the molten polymer. For example, a pressure greater than 100 bar (or about 100 bar) and a flow rate as low as 1% (or about 1%) of the polymer flow rate may be preferable. It is also preferable to introduce a nucleating agent into the polymer to form regions where foam bubbles expand. An example of this method involves using a commercially available unit from Sulzer to inject the inert gas at the end of the extruder barrel and mixing the inert gas with a static mixer before the die outlet.

[0146] Chemical foaming requires the addition of chemicals that induce chemical decomposition reactions (either endothermic or exothermic) during heating, thereby releasing gas. The gas dissolves into the polymer molten material during the extrusion process because the molten material pressure is higher than the gas's critical solubilization pressure. When a pressure drop is encountered, such as at the die head exit (or immediately afterward), gas is released from the solution. The foaming agent acts as a plasticizer, thereby reducing the viscosity of the molten material. This decrease in viscosity, at certain temperatures, leads to a decrease in molten material pressure, shear rate, and die head shape. Therefore, care should be taken to ensure that the gas does not foam prematurely by maintaining the pressure inside the extruder above the critical solubilization pressure. This pressure can be maintained by controlling the shear rate and / or molten material temperature at the die head.

[0147] A suitable exemplary process for foaming the material in the extruder before corrugating the tube requires adding a chemical blowing agent to the base polymer (e.g., ARNITEL® VT 3108) in an amount of 0.3–1.5% by weight (or about 0.3–1.5% by weight). This can be achieved by directly mixing a foaming agent powder (e.g., HYDROCEROL® CT 671 or equivalent) with the base polymer, or by first mixing a foaming agent "masterbatch" (i.e., a carrier polymer (e.g., polyethylene) and an active foaming agent (e.g., HYDROCEROL® BIH-10E or equivalent)) in an 80 / 20 wt% or about 80 / 20 wt% mixture of carrier polymer / active foaming agent, and then feeding the mixture into the feed section of the extruder barrel. In the first case, the foaming agent powder is the foaming agent. In the second case, the foaming agent masterbatch is the foaming agent. HYDROCEROL® CT 671 has a decomposition temperature of 160°C and a solubilization pressure of 60 bar. ARNITEL® VT 3108 has a melting point of 185°C. Therefore, in this extrusion example, since viscosity increases as the melting point decreases, the processing temperature can be lowered by 10-20°C (or approximately 10-20°C) to prevent the pressure from dropping below the critical value.

[0148] The shear rate (depending on the extruder speed) is set high enough to ensure that the pressure is above the critical pressure and that the blowing agent is thoroughly mixed with the molten polymer. Once the polymer is extruded from the die head, foaming begins, bubbles are observed to nucleate, and the bubbles expand until the polymer cools to a temperature where the bubble expansion force is lower than the force required to deform the molten polymer (e.g., a temperature lower than the polymer's melting temperature or the blowing agent's activation temperature, at which temperature the foaming reaction begins / stops). Cooling begins once the polymer enters the corrugator and is formed in the corrugator block. The corrugator block is then cooled by the corrugator water supply and forming vacuum equipment.

[0149] Once foamed, the component consists of a tubular structure with thousands of foamed air voids distributed across the entire thickness of the component's wall. In typical respiratory tube components, it has been found that desirable products can be produced when the lateral void size diameter does not exceed approximately 700 μm (95% confidence level). However, it is advantageous for the lateral void size diameter to be less than 700 μm to prevent the voids from extending across the entire thickness of the tube wall and creating leak pathways. For example, in some embodiments, the lateral void size diameter does not need to exceed approximately 500 μm (95% confidence level). It has also been found that high-quality products for medical circuits can be produced when the lateral void size diameter is between 75 and 300 μm (or approximately 75 and 300 μm). The maximum lateral void size diameter will vary depending on the minimum wall thickness of the component. For example, the maximum lateral void size may be limited to less than 50% (or approximately 50%) of the minimum wall thickness. However, the maximum lateral void size diameter may be less than one-third (or approximately one-third), less than 30% (or approximately 30%), or less than one-quarter (or approximately one-quarter) of the minimum wall thickness.

[0150] As discussed above, foaming bubbles cease to grow as the material cools. It has been found that rapid cooling creates two zones within the wall thickness. Figures 16A and 16B show an extruded foam material having two zones according to at least one embodiment. The first zone 1601, 100 μm thick (or approximately 100 μm thick), arises as an outer "skin layer" of the closed-cell foam material on the surface in contact with the corrugator mold / block. In this zone, the average and maximum void sizes are smaller, and it is less likely that a leak path penetrating the wall will form in the skin layer. In the remaining second zone 1603, the material cools over a longer period of time, and larger voids can result in open-cell foam. Thus, at least one embodiment involves realizing that it is desirable to rapidly cool the material once foaming has begun after it has been extruded from the die head.

[0151] Once the tube comes into contact with the corrugator block (a metal block from which the contour shape is machined), the tube is cooled as part of the corrugation process. Rapid cooling is achieved by maintaining the corrugator block temperature at a low value, e.g., 15°C (or about 15°C), using a coolant such as water. Rapid cooling may also be achieved by changing the melting temperature at the extruder exit point (and before contact with the block) to a temperature close to the polymer's melting point so that the molten plastic solidifies rapidly. This can be achieved in the air gap between the extruder and the corrugator and can be enhanced using a cooling gas and / or air jet or a liquid bath, e.g., a water bath. Rapid cooling can also be achieved by increasing the vacuum pressure within the block so that the polymer is "drawn" into the metal shape in a very short time and thus cools before the bubbles have fully expanded. One or more of these techniques can be used individually or in combination to achieve rapid cooling in various embodiments.

[0152] Skin layer formation is not solely dependent on rapid cooling. It also depends on the material composition (e.g., degree of foaming), extruder speed, melting temperature and pressure, the gap before cooling, the water temperature and length of the bath, and finally the take-up speed (the mechanism for pulling the formed tube from the extruder). Rapid cooling primarily depends on the take-up speed, gap, and water temperature.

[0153] The thickness of the resulting skin layer may be between 5-10% (or approximately 5-10%) of the wall thickness, for example, between 10-50 μm (or approximately 10-50 μm). Each of the first and second zones has voids. In certain embodiments, less than 5% (or approximately 5%) of the voids in the first zone have a diameter greater than 100 μm. The voids in the second zone are larger than those in the first zone. For example, in some embodiments, less than 5% (or approximately 5%) of the voids in the second zone of the foamed material have a diameter greater than 700 μm.

[0154] Next, refer to Figure 17. Figure 17 illustrates an exemplary method for manufacturing a tube according to at least one embodiment. In the exemplary method, as shown in block 1701, a foaming agent is first mixed into a substrate to form an extruded material. The substrate has a diffusion coefficient of 0.75 × 10 -7 cm 2 / second (or approximately 0.75 × 10) -7 cm 2 It comprises one or more permeable thermoplastic elastomers with a tensile modulus greater than 15 MPa (m² / sec) and a tensile modulus greater than approximately 15 MPa. Then, as shown in block 1703, pressure is applied to the extruder to form a hollow tube. As shown in block 1705, the hollow tube is delivered to a corrugator mold. As shown in block 1707, the hollow tube is cooled in the corrugator mold, thereby releasing gas bubbles from the foaming agent portion of the extruder. Finally, as shown in block 1709, the cooled hollow tube is removed from the corrugator, thereby forming a tube containing voids formed by the solid thermoplastic elastomer and gas bubbles. In this embodiment, the resulting tube has a wall thickness between 0.1 and 3.0 mm (or approximately 0.1 and 3.0 mm). The maximum void size is less than one-third (or approximately one-third) of the minimum wall thickness, and the porosity of the bellows is greater than 25% (or approximately 25%).

[0155] measurement The properties, including elastic modulus, porosity, mass, diameter, thickness, and diffusivity, are described above. Preferred methods for measuring these properties are shown below. All measurements are performed at room temperature (23°C or around 23°C).

[0156] A. Elastic modulus Tensile tests were conducted to determine the force / strain relationship of foamed tubing under a constant elongation rate. This relationship was found to be typically linear up to a 10% elongation rate. The experiment was performed using an Instron testing machine equipped with a 500N load cell, and 200mm long tubing samples were used as test specimens.

[0157] The Young's modulus of the material was determined experimentally using a 2D axisymmetric finite element (numerical) model. The shape of this model was constructed from measurements of a bellows tube. The model included linear elastic (Hooke's Law) material behavior for the analysis of the modulus of elasticity (E). The use of linear elastic materials in this model is considered correct under low elongation conditions. The model was constrained at one end and pulled with a constant load from the other end, simulating behavior similar to that observed in an Instron testing machine. Elongation values ​​at different moduli of elasticity (E) were obtained from this model, and the model data was expressed using the following formula:

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[0158] The modulus of elasticity was selected as a value that satisfies this equation between the model and experimental values. Verification experiments were conducted using tubular tubes with known moduli of elasticity, and the results agreed well with the numerical model.

[0159] B. Porosity measurement Porosity of foamed polymer sample (φ v ) is given by the following formula 1:

number

[0160] The buoyancy method involves measuring the mass (M1) of a sample suspended in air, and further measuring the mass (M2) of a sample suspended in a known low-density fluid (e.g., heptane). The density of a foamed polymer sample is given by the following equation 2:

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[0161] The displacement method involves calculating the volume of a sample by measuring the amount of liquid displaced by the sample. A digital height measuring instrument is used to measure the height of the markings on an empty graduated cylinder. This calibrates the correlation between height and volume. Liquid is poured into the cylinder, and the height of the liquid in the cylinder is determined by measuring to the bottom of the concave meniscus or the top of the convex meniscus. This yields the initial volume (V1). Next, a sample of foamed polymer with a known dry mass (M1) is poured into the liquid, and the height of the liquid in the cylinder is determined again. This yields the final volume (V2). The density of the foamed polymer sample is given by the following formula 3:

number

[0162] C.Mass All mass is from Vibra AJ-420 manufactured by Shinko Denshi Co. The results were obtained using a CE tuning fork type microbalance (product number 504068).

[0163] D. Thickness and diameter The sample thickness and / or diameter can be obtained by the following method: For tubular samples, the diameter can be measured using a Mitutoyo digital caliper (CD-8 CSX model). The sample diameter can be measured at multiple locations, and the simple average of these measurements can be considered the sample diameter.

[0164] For film samples, the thickness can be measured at multiple points using a Mitutoyo D (0-25mm) RH NEO MODELSHOP caliper. In this case, the simple average can also be considered as the sample thickness.

[0165] When measuring the thickness of a corrugated tubular sample, the tube can be cut, and many measurements can be taken at various locations along the contour using a digital caliper. The area-weighted average thickness can then be calculated. Alternatively, the thickness of a corrugated tubular sample may be measured using a graduated microscope, such as a microscope from Meiju Techno. This method involves taking many (typically more than 90) measurements of both peak and valley thicknesses along the length of the tube at different locations around its circumference. This is achieved by cutting the tube in half along a helical path that spans 45 corrugations per helical turn.

[0166] E. Diffusion rate Time-dependent water sorption and desorption by polymer systems are functions of the diffusivity of water in the polymer. Crank J. *The mathematics of diffusion*, 2nd ed. Oxford: Clarendon Press; 1975, provides a detailed explanation of a method for obtaining the diffusion coefficient of water in polymers by analyzing experimental data. Pages 46–49, 60, 61, and 72–75 of Crank are incorporated herein by reference.

[0167] According to Crank, given a constant diffusion coefficient D, the desorption / absorption of water in a 2L thick sample is defined by Equation 4.

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[0168] Also,

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[0169] Figure 18 shows the ideal sorption / desorption curve at a constant diffusion coefficient D = 3.0×10 -7 cm 2 / s and l = 0.075 cm. The actual experimental curve looks different from the ideal curve, as shown in Figure 19. Compared with the ideal curve, the mass change rate in the experimental curve seems to be delayed in time, and the overall experimental curve is S-shaped. The S-shape is obtained when the desorption of water from the film is limited by the evaporation rate at the surface of the film. This is mathematically described by the boundary condition of Equation 8 at the surface of the material. [Number] In the formula, C0 represents the concentration in the film that is considered to be in equilibrium with the external environment, g / cm 3 and C s represents the concentration of water immediately inside the surface, g / cm 3 and α represents a constant related to the evaporation rate at the surface, cm / second. Regarding evaporation, the similar formula of Equation 1 can be expressed by Equation 9. [Number] In the formula, [Number] And β n is the solution of the equation L = β n tan(β n ) (11). Also, at the time point after a long time [Number] In the case of, Equation 9 is dominated by an induced (n = 1) exponential function regarding A1 and β1. When α, and as a result L, becomes larger, A n and β n change according to the definitions of Equation 5 and Equation 6.

[0170] Since there is a strong relationship among β, L, and D in Equation 9, it may be desirable to derive D from the data at the time point after a short time. In the case of ideal diffusion, the diffusion coefficient D was obtained by examining the experimental data at the time point after a short time using Equation 7. The equation corresponding to Equation 7 when using the boundary condition shown by Equation 8 was not shown by Crank. Therefore, the solution by Laplace transform was derived by terms up to n = 2. [Number] In the case of the value, equation 12 yields an approximate value that is very close to the actual result.

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[0171] Using the above derivation, we provide the following example method for calculating the diffusion rate.

[0172] 1. Time (t) (seconds)

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[0173] The foregoing description of the present invention includes preferred forms thereof. Modifications thereto can be made without departing from the scope of the invention. A person familiar with the art in which the invention relates will be able to envision many modifications to the construction and a variety of embodiments and uses of the invention without departing from the scope of the invention as defined in the appended claims. The disclosures and descriptions herein are illustrative and not limiting in any way.

Claims

1. A medical circuit component for use with humidifying gas, A component comprising a wall that defines an internal space, wherein at least a portion of the wall is made of a breathable foam material that allows water vapor to pass through but substantially prevents liquid water from passing through.

2. The diffusion coefficient of the aforementioned breathable foam material is at least 3 × 10 －７ cm ２ The component according to claim 1, wherein the value is per second.

3. The component according to claim 1 or 2, wherein the thickness of the wall is between 0.1 mm and 3.0 mm.

4. The component according to any one of claims 1 to 3, wherein the breathable foam material comprises a blend of polymers.

5. The component according to any one of claims 1 to 4, wherein the breathable foam material comprises a thermoplastic elastomer containing polyether soft segments.

6. The component according to any one of claims 1 to 5, wherein the breathable foam material comprises a copolyester thermoplastic elastomer containing a polyether soft segment.

7. The component according to any one of claims 1 to 6, wherein the breathable foam material is sufficiently rigid so that it can be bent around a 25 mm diameter metal cylinder without twisting or crushing, as specified by a test for the increase in flow resistance with bending in accordance with ISO 5367:2000(E).

8. g-mm / m of the parts ２ The permeability P on a daily basis, when measured according to ASTM E96 Procedure A (using the drying method at a temperature of 23°C and a relative humidity of 90%), is at least 60 g-mm / m³. ２ The component according to any one of claims 1 to 7, which is / day and satisfies the following formula: [Math 1] (In the formula, M represents the elastic modulus of the foamed polymer in MPa, and M is between 30 and 1000 MPa.)

9. The component according to any one of claims 1 to 8, wherein the foamed material has a void ratio greater than 25%.

10. The component according to any one of claims 1 to 9, wherein the foamed material has an average lateral void size of less than 30% of the wall thickness.

11. The component according to any one of claims 1 to 10, wherein the foamed material has voids that are flattened along the longitudinal axis of the wall, and at least 80% of the voids have an aspect ratio of longitudinal length to transverse length greater than 2:

1.

12. The component according to any one of claims 1 to 11, wherein the foamed material has voids, and at least 10% of the voids are interconnected.

13. The component according to any one of claims 1 to 12, wherein the foamed material constitutes the wall of the pipe.

14. The component according to claim 13, wherein the tube is an extruded tube.

15. The component according to claim 13 or 14, wherein the pipe is a bellows pipe.

16. The component according to any one of claims 1 to 12, wherein the foam material constitutes the wall of the mask.

17. The component according to any one of claims 1 to 15, wherein the foamed material constitutes the wall of a pipe used in an intake system.

18. A method for manufacturing medical circuit components, A process of mixing a foaming agent with a polymer substrate to form a liquefied mixture. A step of releasing gas bubbles into the base material portion of the liquefied mixture using the foaming agent portion, and The process includes stopping the release of gas bubbles and processing the mixture to form a water vapor permeable component. Here, the foaming agent and the polymer substrate are selected to form a water vapor permeable component comprising a solid polymer and voids distributed throughout the solid polymer, and the mixture is processed, where the g-mm / m of the component. ２ The permeability P on a daily basis was measured according to ASTM E96 Procedure A (using the drying method at a temperature of 23°C and a relative humidity of 90%) and was at least 60 g-mm / m³. ２ The method is such that the value is per day and satisfies the following equation: [Math 2] (In the formula, M represents the elastic modulus of the foamed polymer in MPa, and M is between 30 and 1000 MPa.)

19. P is at least 70 g-mm / m ２ The method according to claim 18, wherein the value is per day.

20. The method according to claim 18 or 19, wherein M is between 30 and 800 MPa.

21. The method according to any one of claims 18 to 20, wherein the wall thickness is between 0.1 mm and 3.0 mm.

22. The method according to any one of claims 18 to 21, wherein the foamed material has a porosity greater than 25%.

23. The method according to any one of claims 18 to 22, wherein the foamed material has an average lateral void size of less than 30% of the wall thickness.

24. The method according to any one of claims 18 to 23, wherein the foamed material has voids that are flattened along the longitudinal axis of the wall, and at least 80% of the voids have an aspect ratio of longitudinal length to transverse length greater than 2:

1.

25. The method according to any one of claims 18 to 24, wherein the foamed material has voids, and at least 10% of the voids are interconnected.

26. The method according to any one of claims 18 to 25, wherein the breathable foam material comprises a thermoplastic elastomer containing a polyether soft segment.

27. The method according to any one of claims 18 to 26, wherein the breathable foam material comprises a copolyester thermoplastic elastomer containing a polyether soft segment.

28. The method according to any one of claims 18 to 27, comprising forming the water vapor permeable component into a tube.

29. The method according to claim 28, wherein the processing of the mixture includes extruding the mixture into a tubular shape.

30. The method according to claim 29, wherein the processing of the mixture includes co-extruding a plurality of reinforcing ribs arranged circumferentially around the inner surface of the tubular object so that the plurality of ribs are generally aligned longitudinally along the length of the tubular object.

31. The method according to claim 28 or 29, wherein the processing of the mixture includes corrugating the extruded tubular object.

32. The method according to any one of claims 18 to 27, comprising molding the water vapor permeable component into a mask.

33. A tube for delivering humidifying gas to or from a patient, Entrance and exit, A foamed polymer conduit that is permeable to water vapor and substantially impermeable to liquid water and bulk gas flows, wherein a humidifying gas can flow from the inlet to the outlet within the space enclosed by the conduit, Here, the foamed polymer conduit comprises a solid thermoplastic elastomer material and voids distributed throughout the solid material, and the foamed polymer conduit has an inner surface facing the enclosed space and an internal volume facing the inner surface, The foamed polymer conduit is a tube having a diffusion coefficient greater than 3×10 －７ cm ２ / second.

34. The tube according to claim 33, wherein at least some of the bubble voids in the internal volume are connected to other bubble voids, thereby forming a continuous bubble passage that facilitates the movement of water vapor through the conduit.

35. The tube according to claim 34, wherein at least 10% of the air bubbles in the internal volume are connected to other air bubbles.

36. The tube according to claim 35, wherein at least 20% of the air bubbles in the internal volume are connected to other air bubbles.

37. The pipe according to any one of claims 33 to 36, wherein the conduit is extruded.

38. The pipe according to any one of claims 33 to 37, wherein the conduit is given a corrugated shape.

39. The tube according to any one of claims 33 to 38, further comprising a plurality of reinforcing ribs arranged circumferentially around the inner surface of the foamed polymer conduit and generally aligned longitudinally along the length of the foamed polymer conduit between the inlet and the outlet.

40. The tube according to any one of claims 33 to 39, further comprising a heating line generally aligned longitudinally along the length of the foamed polymer conduit between the inlet and the outlet.

41. The tube according to any one of claims 33 to 40, wherein the internal volume has a void ratio greater than 25%.

42. The tube according to any one of claims 33 to 41, wherein at least 80% of the void is flattened along the longitudinal axis of the conduit with an aspect ratio of longitudinal length to transverse length greater than 2:

1.

43. The tube according to claim 42, wherein at least 80% of the void is flattened along the longitudinal axis of the conduit with an aspect ratio of longitudinal length to transverse length greater than 3:

1.

44. The pipe according to any one of claims 33 to 43, wherein the foamed polymer conduit has a wall thickness between 0.1 mm and 3.0 mm.

45. The tube according to any one of claims 33 to 44, wherein the internal volume has an average lateral void size of less than 30% of the wall thickness of the foamed polymer conduit.

46. The tube according to claim 45, wherein the internal volume has an average lateral void size of less than 10% of the wall thickness of the foamed polymer conduit.

47. g-mm / m of pipe ２ The permeability P on a daily basis was measured according to ASTM E96 Procedure A (using the drying method at a temperature of 23°C and a relative humidity of 90%) and was at least 60 g-mm / m³. ２ The pipe according to any one of claims 33 to 46, which is / day and satisfies the following formula: [Math 3] (In the formula, M represents the elastic modulus of the foamed polymer in MPa, and M is between 30 and 1000 MPa.)

48. The tube according to any one of claims 33 to 47, wherein the foamed polymer conduit further has a skin layer facing the internal volume, and the voids in the internal volume are closed cells.

49. The tube according to any one of claims 33 to 48, wherein the foamed polymer conduit is sufficiently rigid so that it can be bent around a 25 mm diameter metal cylinder without kinking or crushing, as specified by a test for the increase in flow resistance with bending in accordance with ISO 5367:2000(E).

50. The tube according to any one of claims 33 to 49, wherein the tube is configured to be positioned between a ventilator and a patient and to deliver humidified gas from the ventilator to the patient.

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